UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)

For the quarterly period ended March 31, 2019

or

For the transition period from                      to                     

Commission File Number: 001-38295

X4 PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

(857) 529-8300

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  ☒    No  ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).    Yes  ☒    No  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☒

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ☐    No  ☒

As of May 5, 2019, the registrant had 12,420,778 shares of common stock outstanding.

X4 Pharmaceuticals, Inc.

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EXPLANATORY NOTE

On March 13, 2019, X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc), or the Company, completed its business combination in accordance with the terms of the Agreement and Plan of Merger, dated as of November 26, 2018, as amended on December 20, 2018 and March 8, 2019, or the Merger Agreement, by and among the Company, X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.) and Artemis AC Corp., a Delaware corporation and a wholly owned subsidiary of the Company, or the Merger Sub, pursuant to which, among other matters, Merger Sub merged with and into X4 Therapeutics, Inc., with X4 Therapeutics, Inc. continuing as a wholly owned subsidiary of the Company and the surviving corporation of the merger, or the Merger. Following the Merger, on March 13, 2019, the Company effected a 1-for-6 reverse stock split of its common stock, or the Reverse Stock Split, and changed its name to “X4 Pharmaceuticals, Inc.” Following the completion of the Merger, the business conducted by the Company became primarily the business conducted by X4 Therapeutics, Inc., which is a clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutics for the treatment of rare diseases.

Unless otherwise noted, all references to common stock share and per share amounts in this Quarterly Report on Form 10-Q have been retroactively adjusted to reflect the conversion of shares in the Merger based on an Exchange Ratio of 0.5702 and, the Reverse Stock Split. As used herein, the words “the Company,” “we,” “us,” and “our” refer to, for periods following the Merger, X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with is direct and indirect subsidiaries, and for periods prior to the Merger, X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.), and its direct and indirect subsidiaries, as applicable. In addition, the word “Arsanis” refers to the Company prior to the completion of the Merger, and we sometimes refer to X4 Therapeutics, Inc. as “X4.”

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This quarterly report includes forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, which we refer to as the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, which we refer to as the Exchange Act, that relate to future events or to our future operations or financial performance. Any forward-looking statement involves known and unknown risks, uncertainties and other factors that may cause our actual results, levels of activity, performance or achievements to differ materially from any future results, levels of activity, performance or achievements expressed or implied by such forward-looking statement. Forward-looking statements include statements, other than statements of historical fact, about, among other things:

Words such as, but not limited to, “believe,” “expect,” “anticipate,” “estimate,” “forecast,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “targets,” “likely,” “will,” “would,” “could,” “should,” “continue,” “scheduled” and similar expressions or phrases, or the negative of those expressions or phrases, are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Although we believe that we have a reasonable basis for each forward-looking statement contained in this report, we caution you that these statements are based on our estimates or projections of the future that are subject to known and unknown risks and uncertainties and other important factors that may cause our actual results, level of activity, performance, experience or achievements to differ materially from those expressed or implied by any forward-looking statement. These risks, uncertainties and other factors are described in greater detail under the caption “Risk Factors” contained in our Annual Report on Form 10-K for the fiscal year ended December 31, 2018, as updated by our Current Report on Form 8-K filed on April 11, 2019 and our subsequent filings under the Exchange Act, and in other filings that we make with the Securities and Exchange Commission, or SEC. As a result of the risks and uncertainties, the results or events indicated by the forward-looking statements may not occur. We caution you not to place undue reliance on any forward-looking statement.

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In addition, any forward-looking statement in this quarterly report represents our views only as of the date of this quarterly report and should not be relied upon as representing our views as of any subsequent date. We anticipate that subsequent events and developments may cause our views to change. Although we may elect to update these forward-looking statements publicly at some point in the future, we specifically disclaim any obligation to do so, except as required by applicable law. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments we may make.

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PART I: FINANCIAL INFORMATION

X4 PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

(In thousands, except share and per share amounts)

(Unaudited)

The accompanying unaudited notes are an integral part of these condensed consolidated financial statements.

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X4 PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except share and per share amounts)

(Unaudited)

The accompanying unaudited notes are an integral part of these condensed consolidated financial statements.

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X4 PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS

(In thousands)

(Unaudited)

The accompanying unaudited notes are an integral part of these condensed consolidated financial statements

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X4 PHARMACEUTICALS, INC

CONDENSED CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK, REDEEMABLE COMMON

STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT)

(In thousands, except share amounts)

(Unaudited)

The accompanying unaudited notes are an integral part of these condensed consolidated financial statements.

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X4 PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(In thousands)

(Unaudited)

The accompanying unaudited notes are an integral part of these condensed consolidated financial statements.

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X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with its subsidiaries (the “Company”), is a clinical-stage biotechnology research and development company focused on the development of novel therapeutics for the treatment of rare diseases. The Company is headquartered in Cambridge, Massachusetts.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with governmental regulations and the ability to secure additional capital to fund operations. Drug candidates currently under development will require extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel, and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

The accompanying condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Merger with Arsanis

On November 26, 2018, Arsanis, Inc., a publicly held Delaware corporation (“Arsanis”), Artemis AC Corp., a Delaware corporation and a wholly owned subsidiary of Arsanis (“Merger Sub”), and X4 Therapeutics, Inc. (“X4”) entered into an Agreement and Plan of Merger, as amended on December 20, 2018 and March 8, 2019 (the “Merger Agreement”), pursuant to which the Merger Sub merged with and into X4, with X4 surviving the merger as a wholly owned subsidiary of Arsanis. The transactions described in the foregoing sentence may be referred to in these condensed consolidated financial statements as “the Merger.”

The transaction was accounted for as a reverse merger in accordance with GAAP. Under this method of accounting, X4 was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the facts that, immediately following the Merger: (i) the Company’s stockholders own a substantial majority of the voting rights in the combined organization, (ii) the Company designated a majority of the members of the initial board of directors of the combined organization and (iii) the Company’s senior management hold all key positions in the senior management of the combined organization. Accordingly, for accounting purposes, the business combination was treated as the equivalent of X4 issuing stock to acquire the net assets of Arsanis. As a result, as of the closing date of the Merger, the net assets of Arsanis were recorded at their acquisition-date fair values in the financial statements of the Company and the reported operating results prior to the business combination will be those of the Company. In addition, transaction costs incurred by the Company in connection with the business combination will be expensed as incurred.

On March 13, 2019, Arsanis, X4 and Merger Sub completed the Merger pursuant to the terms of the Merger Agreement. Pursuant to the terms of the Merger Agreement, each outstanding share of X4’s common stock and preferred stock was exchanged for 0.5702 shares of Arsanis’s common stock (the “Exchange Ratio”). In addition, all outstanding options exercisable for common stock and warrants exercisable for convertible preferred stock of X4 became options and warrants exercisable for the same number of shares of common stock of Arsanis multiplied by the Exchange Ratio. In connection with the Merger, X4 changed its name to X4 Therapeutics, Inc. Following the closing of the Merger, X4 Therapeutics, Inc. is a wholly owned subsidiary of the Company. which changed its name to X4 Pharmaceuticals, Inc. As used herein, the words “the Company” refers to, for periods following the Merger, X4 Pharmaceuticals, Inc. (formerly Arsanis, Inc.), together with is direct and indirect subsidiaries, and for periods prior to the Merger, X4 Therapeutics, Inc. (formerly X4 Pharmaceuticals, Inc.), and its direct and indirect subsidiaries, as applicable.

Immediately following the Merger, stockholders of X4 owned approximately 63.7% of the combined organization’s outstanding common stock. On March 14, 2019, the combined organization’s common stock began trading on The Nasdaq Capital Market under the ticker symbol “XFOR.”

Reverse Stock Split

On March 13, 2019, immediately following the closing of the Merger, the Company effected a 6-for-1 reverse stock split of its common stock (the “Reverse Stock Split”). Accordingly, all share and per share amounts for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect the Reverse Stock Split. No fractional shares were issued in connection with the Reverse Stock Split. Unless otherwise noted, all references to common stock share and per share amounts have also been adjusted to reflect the exchange ratio of 0.5702.

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X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Going Concern Assessment

In accordance with Accounting Standards Update (“ASU”) No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40) , the Company has evaluated whether there are certain conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the consolidated financial statements are issued. As of May 14, 2019, the issuance date of these condensed consolidated financial statements, the Company expects that its cash and cash equivalents, including approximately $79 million of net proceeds from the public sale of common stock, pre-funded warrants and Class A warrants in April 2019, will be sufficient to fund its forecasted operating expenses, capital expenditure requirements and debt service payments for at least the next twelve months from the issuance of these financial statements. The future viability of the Company beyond that point is dependent on its ability to raise additional capital to finance its operations.

If the Company is unable to obtain funding, the Company will be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or pre-commercialization efforts, which could adversely affect its business prospects, or the Company may be unable to continue operations. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.

Unaudited Interim Financial Statements

The condensed balance sheet at December 31, 2018 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying condensed consolidated financial statements are unaudited. The accompanying unaudited interim consolidated financial statements have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial statements. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, the Company believes that the disclosures are adequate to make the information presented not misleading. These unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2018. In the opinion of management, all adjustments, consisting only of normal recurring adjustments as necessary, for the fair statement of the Company’s condensed financial position, condensed results of its operations and cash flows have been made. The results of operations for the three months ended March 31, 2019 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2019.

Use of Estimates

The preparation of the Company’s condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual of research and development expenses, the valuation of intangible assets acquired in business combinations, the valuations of common stock prior to the Merger, the valuation of stock options, preferred stock warrants (and the resulting preferred stock warrant liability), derivative instruments (and the resulting derivative liability), and the preferred stock repurchase liability, and valuation of lease liabilities. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates when there are changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.

Principles of Consolidation

The condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, including Arsanis Biosciences GmbH, which is incorporated in Vienna, Austria (“Arsanis GmbH”), and X4 Therapeutics, Inc. All significant intercompany accounts and transactions have been eliminated.

Foreign Currency and Currency Translation

Management has determined that the functional currency for the Company’s wholly owned foreign subsidiary, Arsanis Biosciences GmbH, is the Euro. Management’s assessment considered the currency environment in which the entity operates, including inflows of

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X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

cash from research and development incentive programs and outflows of cash for operating expenditure. Accordingly, the assets and liabilities of Arsanis Biosciences GmbH are translated from the Euro into United States dollars at the exchange rate in effect on the balance sheet date and income and expenses are translated at the average exchange rate in effect during the period. Unrealized translation gains and losses are recorded as a cumulative translation adjustment, which is included in the consolidated balance sheet as a component of accumulated other comprehensive income (loss). Adjustments that arise from exchange rate changes on transactions denominated in a currency other than the Euro are included in other income (expense), net in the consolidated statements of operations as incurred.

Concentrations of Credit Risk and Significant Suppliers

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and research and development incentive receivables. The Company generally maintains cash balances in various operating accounts at financial institutions that management believes to be of high credit quality, in amounts that may exceed federally insured limits. The Company has not experienced any losses related to its cash and cash equivalents.

The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. The Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in these manufacturing services or in the supply of active pharmaceutical ingredients and formulated drugs.

Cash and Cash Equivalents

The Company considers all highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents. Cash equivalents consisted of money market funds as of March 31, 2019 and December 31, 2018.

Restricted Cash

In connection with the Company’s lease agreement entered into January 2017 for its facility in Cambridge, Massachusetts, the Company maintains a letter of credit of $264 for the benefit of the landlord. As of March 31, 2019 and December 31, 2018, the underlying cash balance securing this letter of credit was classified as restricted cash (non-current) on its condensed consolidated balance sheets.

The Company also maintains letters of credit for the benefit of the landlords in connection with the Company’s office, laboratory, parking and storage space leases in Waltham, MA and Vienna, Austria and another letter of credit in connection with Company’s corporate credit cards. As of March 31, 2019, long term restricted cash consisted of letters of credit related to the Company’s leases of office, laboratory, parking and storage space lease in Vienna, Austria, of $283 and leased office space acquired from Arsanis located in Waltham, MA, which expires on December 31, 2023, of approximately $250.

As of March 31, 2019, the Company was also required to maintain a separate cash balance of $150 to collateralize corporate credit cards with a bank, which was classified as restricted cash (non-current) on its consolidated balance sheets.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset, as follows:

Estimated useful lives are periodically assessed to determine if changes are appropriate. Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost of these assets and related accumulated depreciation or amortization are eliminated from the consolidated balance sheet and any resulting gains or losses are included in the consolidated statements of operations and comprehensive loss in the period of disposal. Costs for capital assets not yet placed into service are capitalized as construction-in-progress and depreciated once placed into service.

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X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Right-of-Use Assets and Leases

Effective January 1, 2019, the Company adopted Accounting Standards Codification (“ASC”), Topic 842, Leases (“ASC 842”), using the modified retrospective approach through a cumulative-effect adjustment and utilizing the effective date as its date of initial application, with prior periods unchanged and presented in accordance with the guidance in Topic 840, Leases (“ASC 840”).

At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present. Leases with a non-cancellable term greater than one year are recognized on the balance sheet as right-of-use assets, lease liabilities and long-term lease liabilities. The Company has elected not to recognize on the balance sheet leases with terms of one year or less. Options to renew a lease are not included in the Company’s initial lease term assessment unless there is reasonable certainty that the Company will renew.

Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. However, certain adjustments to the right-of-use operating asset may be required for items, such as incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rates, which are the rates it incurs to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment.

In accordance with the guidance in ASC 842, components of a lease are split into lease components and non-lease components. A policy election is available pursuant to which an entity may elect to not separate lease and non-lease components. Rather, each lease component and the related non-lease components would be accounted for together as a single component. For new and amended leases beginning in 2019 and after, the Company has elected to account for the lease and non-lease components as a combined lease component for its office and laboratory building leases.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized in loss from operations when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value. To date, the Company has not recorded any impairment losses on long-lived assets.

Goodwill

Business combinations are accounted for under the acquisition method. The total purchase price of an acquisition is allocated to the underlying identifiable net assets, based on their respective estimated fair values as of the acquisition date. Determining the fair value of assets acquired and liabilities assumed requires management’s judgment and often involves the use of significant estimates and assumptions, including assumptions with respect to future cash inflows and outflows, probabilities of success, discount rates, and asset lives, among other items. Assets acquired and liabilities assumed are recorded at their estimated fair values. The excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill.

Goodwill is tested for impairment at the reporting unit level annually in the fourth quarter, or more frequently when events or changes in circumstances indicate that the asset might be impaired. Examples of such events or circumstances include, but are not limited to, a significant adverse change in legal or business climate, an adverse regulatory action or unanticipated competition. The Company has determined that it operates in a single operating segment and has a single reporting unit.

The Company assesses qualitative factors to determine whether the existence of events or circumstances would indicate that it is more likely than not that the fair value of the reporting unit was less than its carrying amount. If after assessing the totality of events or circumstances, the Company were to determine that it is more likely than not that the fair value of the reporting unit is less than its carrying amount, then the Company would perform a quantitative impairment test.

The Company compares the fair value of the reporting unit to its carrying value. If the fair value of the reporting unit exceeds the carrying value of the net assets, goodwill is not impaired, and no further testing is required. If the fair value of the reporting unit is less than the carrying value, the Company measures the amount of impairment loss, if any, as the excess of the carrying value over the fair value of the reporting unit. The Company has determined there were no indicators of goodwill impairment as of March 31, 2019.

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X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Intangible Assets

The Company acquired certain in-process research and development assets (“IPR&D”), which are classified as indefinite-lived intangible assets. Acquired IPR&D represents the fair value assigned to research and development assets that the Company acquires and have not been completed at the acquisition date. The fair value of IPR&D acquired in a business combination is capitalized on the Company’s consolidated balance sheets at the acquisition-date fair value and is determined by estimating the costs to develop the technology into commercially viable products, estimating the resulting revenue from the projects, and discounting the projected net cash flows to present value. IPR&D is not amortized, but rather is reviewed for impairment on an annual basis or more frequently if indicators of impairment are present, until the project is completed or abandoned. If the Company determines that IPR&D becomes impaired or is abandoned, the carrying value is written down to its fair value with the related impairment charge recognized in the Company’s consolidated statement of operations in the period in which the impairment occurs. Upon successful completion of each project and launch of the product, the Company will make a separate determination of the estimated useful life of the IPR&D intangible asset and the related amortization will be recorded as an expense prospectively over its estimated useful life.

The projected discounted cash flow models used to estimate the Company’s IPR&D reflect significant assumptions regarding the estimates a market participant would make in order to evaluate a drug development asset, including the following:

Additionally, to the extent the Company acquire other indefinite-lived intangible assets through its business combinations, these assets are reviewed for impairment on an annual basis or more frequently if indicators of impairment are present. If the Company determines that the asset becomes impaired, the carrying value is written down to its fair value with the related impairment charge recognized in its consolidated statements of operations in the period in which the impairment occurs.

Deferred Rent

The Company’s lease agreements include payment escalations and lease incentives (including a leasehold improvement tenant allowance). For periods prior to January 1, 2019, these payments were accrued or deferred as appropriate such that rent expense was recognized on a straight-line basis over the respective lease terms. Effective January 1, 2019, upon the adoption of ASC 842, deferred rent was reclassified as a reduction to the applicable right-of-use asset as further described in Note 8.

Fair Value Measurements

Certain assets and liabilities of the Company are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

Prior to the Merger, the Company’s preferred stock warrant liability, derivative liability and preferred stock repurchase liability were carried at fair value, determined according to Level 3 inputs in the fair value hierarchy described above (See Note 4). The Company’s cash equivalents, consisting of money market funds invested in U.S. Treasury securities, are carried at fair value, determined based on Level 2 inputs in the fair value hierarchy described above (see Note 4). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. The carrying value of the Company’s outstanding loan and security agreement (the “Hercules Loan Agreement”) with Hercules Capital, Inc. (“Hercules”) approximates its fair value at March 31, 2019 because the debt bears interest at a variable market rate and the Company’s credit risk has not materially

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X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

changed since the inception of the agreement. The carrying value of the Company’s loans under the funding agreements with Österreichische Forschungsförderungsgesellschaft mbH (“FFG”) were recorded at fair value on the opening balance sheet of Arsanis as of the date of the Merger, and approximates the fair value of the loans at March 31, 2019. (See Note 3).

Segment Information

The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. The Company’s focus is on the discovery, development and commercialization of novel therapeutics for the treatment of rare diseases.

Revenue Recognition

Effective January 1, 2018, the Company adopted ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”), using the modified retrospective transition method. The modified retrospective method requires that the cumulative effect of initially applying ASC 606 be recognized as an adjustment to the opening balance of retained earnings or accumulated deficit of the annual period that includes the date of initial application. The Company did not have any arrangements that were in the scope of ASC 606 on January 1, 2018 and thus there was no impact to the condensed consolidated financial statements as a result of the adoption. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as collaboration arrangements and leases. Prior to completion of the Merger, Arsanis entered into a single out-licensing agreement with Janssen Pharmaceuticals, Inc. (see Note 13) that was within the scope of ASC 606.

Research and Development Programs

Proceeds under the research and development incentive program from the Austrian government are recognized as other income in an amount equal to the qualifying expenses incurred in each period multiplied by the applicable reimbursement percentage. Incentive income recognized upon incurring qualifying expenses in advance of receipt of proceeds from research and development incentives is recorded in the consolidated balance sheet as research and development incentive receivables.

Research and Development Costs

Costs associated with internal research and development and external research and development services, including drug development and preclinical studies, are expensed as incurred. Research and development expenses include costs for salaries, employee benefits, subcontractors, facility-related expenses, depreciation and amortization, stock-based compensation, third-party license fees, laboratory supplies, and external costs of outside vendors engaged to conduct discovery, preclinical and clinical development activities and clinical trials as well as to manufacture clinical trial materials, and other costs. The Company recognizes external research and development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers.

Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. Such prepaid expenses are recognized as an expense when the goods have been delivered or the related services have been performed, or when it is no longer expected that the goods will be delivered or the services rendered.

Upfront payments, milestone payments and annual maintenance fees under license agreements are expensed in the period in which they are incurred.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Debt Issuance Costs

Debt issuance costs consist of payments made to secure commitments under certain debt financing arrangements. These amounts are recognized as interest expense over the period of the financing arrangement using the effective interest method. If the financing arrangement is canceled or forfeited, or if the utility of the arrangement to the Company is otherwise compromised, these costs are recognized as interest expense immediately. The Company’s consolidated financial statements present debt issuance costs related to a recognized debt liability as a direct reduction from the carrying amount of that debt liability.

Stock-Based Compensation

The Company measures all stock-based awards granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense for those awards, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award. The Company issues stock-based awards with only service-based vesting conditions and records the expense for these awards using the straight-line method. The Company has not issued any stock-based awards with performance-based vesting conditions.

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X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Effective January 1, 2019, the Company adopted ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”), which expands the scope of Topic 718 to include share-based payment awards to nonemployees. As a result, stock-based awards granted to consultants and non-employees are accounted for in the same manner as awards granted to employees and directors as described above. The impact of adoption this new guidance did not have a material impact on the Company’s consolidated financial statements. Prior to the adoption of ASU 2018-07, for stock-based awards granted to non-employee consultants, compensation expense was recognized over the period during which services were rendered by such non-employee consultants until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards was remeasured using the then-current fair value of the Company’s common stock and updated assumption inputs in the Black-Scholes option-pricing model.

The Company classifies stock-based compensation expense in its consolidated statement of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

The Company recognizes compensation expense for only the portion of awards that are expected to vest. In developing a forfeiture rate estimate, the Company has considered its historical experience to estimate pre-vesting forfeitures for service-based awards. The impact of a forfeiture rate adjustment will be recognized in full in the period of adjustment, and if the actual forfeiture rate is materially different from the Company’s estimate, the Company may be required to record adjustments to stock-based compensation expense in future periods.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. Prior to March 13, 2019, the Company had been a private company and lacked company-specific historical and implied volatility information for its stock. Therefore, the Company estimates its expected stock price volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The expected term of stock options granted to non-employee consultants is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future.

Preferred Stock Warrant Liability

Prior to the Merger with Arsanis, the Company classified warrants for the purchase of shares of its convertible preferred stock (see Note 10) as a liability on its consolidated balance sheets as these warrants are freestanding financial instruments that may have required the Company to transfer assets upon exercise. The warrant liability, which consisted of warrants for the purchase of Series A and Series B convertible preferred stock, was initially recorded at fair value upon the date of issuance of each warrant and is subsequently remeasured to fair value at each reporting date. Changes in the fair value of the warrant liability are recognized as a component of other income (expense), net in the consolidated statement of operations and comprehensive loss. Concurrent with the closing of the Merger, all X4 preferred stock was converted to Arsanis common stock and the X4 preferred stock warrants converted to warrants for the purchase of Arsanis common stock. The Company assessed the features of the warrants and determined that they qualify for classification as permanent equity. Accordingly, the Company remeasured the warrants to fair value upon the closing of the Merger and reclassified the resulting warrant liability to additional paid-in capital. (see Note 10).

Derivative Liability

The Company’s license agreement with Genzyme Corporation (“Genzyme”) (see Note 13) contained a contingent payment obligation that required the Company to make a cash payment to Genzyme upon a change of control event of the Company. The contingent payment obligation met the definition of a derivative instrument as the contingent payment obligation was not clearly and closely related to its host instrument and was a cash-settled liability. Accordingly, the Company classified this derivative as a liability within other liabilities (non-current) on its condensed consolidated balance sheet. The derivative liability was initially recorded at fair value on the date of entering into the license agreement and was subsequently remeasured to fair value at each reporting date. Changes in the fair value of this derivative liability were recognized as a component of other income (expense), net in the condensed consolidated statement of operations and comprehensive loss. The Merger with Arsanis (see Note 1) qualified as a change of control event, as defined in the license agreement, but resulted in no payment being due to Genzyme under the license agreement. As a result, on March 13, 2019, the closing date of the Merger with Arsanis, the derivative liability was remeasured to fair value, which was $0, and subsequent changes in fair value will no longer be recognized in the consolidated statements of operations and comprehensive loss because the contingent payment obligation to Genzyme expired at that time.

16

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

In addition, the Company’s Hercules loan (see Note 7) contains a redemption feature that, upon an event of default, provides Hercules the option to accelerate and demand repayment of the debt, including a prepayment premium. The redemption feature meets the definition of a derivative instrument as the repayment of the debt contains a substantial premium, resulting in the redemption feature not being clearly and closely related to its host instrument. Accordingly, the Company classifies this derivative as a liability within other liabilities (non-current) on its condensed consolidated balance sheet. The derivative liability was initially recorded at fair value on the date of entering into the Hercules Loan Agreement and is subsequently remeasured to fair value at each reporting date. Changes in the fair value of this derivative liability are recognized as a component of other income (expense), net in the condensed consolidated statement of operations and comprehensive loss. Changes in the fair value of this derivative liability will continue to be recognized until all amounts outstanding under the Hercules Loan Agreement are repaid or until the Hercules Loan Agreement is terminated.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. For the three months ended March 31, 2019, comprehensive loss included $23 of foreign currency translation gain adjustments.

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Net Income (Loss) per Share

The Company follows the two-class method when computing net income (loss) per share as the Company has issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed.

Basic net income (loss) per share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net income (loss) attributable to common stockholders is computed by adjusting net income (loss) attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares. For purpose of this calculation, outstanding stock options, convertible preferred stock and warrants to purchase shares of convertible preferred stock are considered potential dilutive common shares.

The Company’s convertible preferred stock contractually entitles the holders of such shares to participate in dividends but does not contractually require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss attributable to common stockholders, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the three months ended March 31, 2019 and 2018.

17

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Recently Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02” or “ASC 842”)), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors). The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less may be accounted for similar to prior guidance for operating leases. The Company adopted the new leasing standard as of the required effective date of January 1, 2019 using a modified retrospective transition approach to be applied to leases existing as of, or entered into after, January 1, 2019. The adoption had no impact on accumulated deficit. The new lease standard provides a number of optional practical expedients in transition. The Company applied the package of practical expedients to leases that commenced prior to the effective date, whereby it will elect to not reassess the following: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. The Company also elected the short-term lease recognition exemption for all leases that qualify, where a right-of-use asset or lease liability will not be recognized for short-term leases. Upon the adoption of ASC 842, the Company recorded $2.5 million of operating lease liabilities and $2.0 million of right-of-use assets on its consolidated balance. The adoption did not have a material impact on the Company’s statement of operations, statement of comprehensive loss or statement of cash flows.

In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment. The new standard simplifies the subsequent measurement of goodwill by eliminating the second step of the goodwill impairment test. This ASU will be applied prospectively and is effective for annual or interim goodwill impairment tests in fiscal years beginning after December 15, 2019 with early adoption permitted. The Company has adopted this guidance on January 1, 2019 and will apply it to its annual impairment test, and any interim impairment tests during the year ending December 31, 2019.

In April 2017, the FASB issued ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs (“Subtopic 310-20”). The new standard amends the amortization period for certain purchased callable debt securities held at a premium by shortening the amortization period for the premium to the earliest call date. Subtopic 310-20 calls for a modified retrospective application under which a cumulative-effect adjustment will be made to retained earnings as of the beginning of the first reporting period in which the guidance is adopted. The new standard will be effective beginning January 1, 2019 and early adoption is permitted for public entities. The Company adopted this guidance, effective January 1, 2019, and its adoption had no impact on the Company’s financial position, results of operations or cash flows.

In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815) (Part I) Accounting for Certain Financial Instruments with Down Round Features (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception (“ASU 2017-11”). Part I applies to entities that issue financial instruments such as warrants, convertible debt or convertible preferred stock that contain down-round features. Part II replaces the indefinite deferral for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities contained within ASC Topic 480 with a scope exception and does not impact the accounting for these mandatorily redeemable instruments. For public entities, ASU 2017-11 is effective for annual reporting periods beginning after December 15, 2018, including interim periods within those fiscal years. The Company adopted ASU 2017-11 as of the required effective date of January 1, 2019. The adoption of ASU 2017-11 had no impact on the Company’s financial position, results of operations or cash flows.

In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). These amendments expand the scope of Topic 718, Compensation—Stock Compensation (which previously only included share-based payments to employees) to include share-based payments issued to non-employees for goods or services. Consequently, the accounting for share-based payments to non-employees and employees will be substantially aligned. The ASU supersedes Subtopic 505-50, Equity—Equity-Based Payments to Non-Employees. The Company adopted ASU 2018-07 on January 1, 2019. The adoption of this standard had no impact on the Company’s financial statements.

Recently Issued Accounting Pronouncements

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), which removes, adds and modifies certain disclosure requirements for fair value measurements in Topic 820. The Company will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy as well as the valuation processes of Level 3 fair value

18

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

measurements. However, the Company will be required to additionally disclose the changes in unrealized gains and losses included in other comprehensive income for recurring Level 3 fair value measurements and the range and weighted average of assumptions used to develop significant unobservable inputs for Level 3 fair value measurements. ASU 2018-13 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The amendments relating to additional disclosure requirements will be applied prospectively for only the most recent interim or annual period presented in the initial year of adoption. All other amendments will be applied retrospectively to all periods presented upon their effective date. The Company is currently evaluating the impact that the adoption of ASU 2018-13 will have on its consolidated financial statements.

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, (“ASU 2018-15”). The amendments in this update align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by the amendments in this update. The new standard will be effective beginning January 1, 2020 and early adoption is permitted. The amendments in this update should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is currently evaluating the impact that the adoption of ASU 2018-15 will have on its consolidated financial statements.

Based on the Exchange Ratio of 0.5702, immediately following the Merger, former Arsanis stockholders, Arsanis option holders and other persons holding securities or other rights directly or indirectly convertible, exercisable or exchangeable for Arsanis common stock owned approximately 31.3% of the outstanding capital stock of the combined organization on a fully diluted basis, and former X4 stockholders, holders of options or warrants to acquire X4 capital stock and other persons holding securities and other rights directly or indirectly convertible, exercisable or exchangeable for X4 capital stock owned approximately 68.7% of the outstanding capital stock of the combined organization on a fully diluted basis. At the closing of the Merger, all shares of X4 common stock and X4 preferred stock then outstanding were exchanged for Arsanis common stock.

In addition, pursuant to the terms of the Merger Agreement, the Company, for accounting purposes, assumed all outstanding stock options to purchase shares of Arsanis common stock at the closing of the Merger. At the closing of the Merger, such stock options became options to purchase an aggregate of 271,230 shares of the Company’s common stock after giving effect to the Reverse Stock Split.

The total purchase price paid in the Merger has been allocated to the tangible and intangible assets acquired and liabilities assumed of Arsanis based on their fair values as of the completion of the Merger, with the excess allocated to goodwill. The following summarizes the preliminary estimate of the purchase price paid in the Merger:

19

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

The following summarizes the allocation of the purchase price to the net tangible and intangible assets acquired:

The goodwill of $27,407 is not tax deductible and represents the excess of the consideration paid over the fair value of assets acquired and liabilities assumed. Goodwill is mainly attributable to the enhanced value of the combined company, as reflected in the increase in market value of the Arsanis common shares following the announcement of the Merger with X4. The Company incurred costs directly related to the Merger of approximately $1 million for the three months ended March 31, 2019.

The preliminary allocation of the purchase price for the Merger was based on estimates of the fair value of the net assets acquired and is subject to adjustment upon finalization of the valuation of the acquired intangible assets, property, plant and equipment, right-of-use assets, lease obligations, fair value of debt and any related deferred taxes. Measurements of these items inherently require significant estimates and assumptions.

The following supplemental unaudited pro forma information presents the Company’s financial results as if the acquisition of Arsanis had occurred on January 1, 2018:

The above unaudited pro forma information was determined based on the historical GAAP results of the Company and Arsanis. The unaudited pro forma consolidated results are not necessarily indicative of what the Company’s consolidated results of operations would have been if the acquisition was completed on January 1, 2018. The unaudited pro forma consolidated net loss includes pro forma adjustments primarily relating to the reclassification of transaction costs and severance payments directly related to the closing of the Merger of $2.7 million from the three months ended March 31, 2019 to the three months ended March 31, 2018.

The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values:

20

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

As of March 31, 2019 and December 31, 2018, there were no transfers between Level 1, Level 2 and Level 3.

The Company’s cash equivalents consisted of a money market fund invested in U.S. Treasury securities. The money market fund was valued using inputs observable in active markets for similar securities, which represents a Level 2 measurement in the fair value hierarchy.

Valuation of Preferred Stock Warrant Liabilities

The preferred stock warrant liability in the table above consists of the fair values of (i) warrants to purchase shares of Series A convertible preferred stock that were issued in 2015 and shares of Series B convertible preferred stock that were issued in 2017 and 2018 in connection with the Company’s Series A and Series B convertible preferred stock financings, respectively (see Notes 10), (ii) warrants to purchase shares of Series A convertible preferred stock that were issued in 2016 in connection with the Company’s entering into a loan and security agreement with Silicon Valley Bank (see Note 7) and (iii) warrants to purchase shares of Series B convertible preferred stock that were issued or were issuable in 2018 in connection with the Company’s entering into the Hercules Loan Agreement (see Note 7). The liability associated with the warrants was recorded at fair value on the dates the warrants were issued and exercisable and was subsequently remeasured to fair value at each reporting date through December 31, 2018. Upon the closing of the Merger, all X4 preferred stock warrants were converted to warrants for Company’s common stock and, as a result, the warrants were adjusted to fair value and reclassified to permanent equity. The aggregate fair value of the warrant liability was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy.

The Company used various valuation methods, including the Monte Carlo method, the option-pricing method and the hybrid method (which is a combination of an option-pricing method and a probability-weighted expected return method), all of which incorporate assumptions and estimates, to value the preferred stock warrants. Estimates and assumptions impacting the fair value measurement include the fair value per share of the underlying shares of the Company’s Series A and Series B convertible preferred stock, risk free interest rate, expected dividend yield, expected volatility of the price of the underlying preferred stock, and either the remaining contractual term of the warrants (except for warrants that would be automatically exercised upon an initial public offering, in which case the remaining estimated term to automatic exercise was used). The most significant assumption in the Monte Carlo method, the option-pricing method and the hybrid method impacting the fair value of the preferred stock warrants is the fair value of the Company’s convertible preferred stock as of each remeasurement date. The Company determines the fair value per share of the underlying preferred stock by taking into consideration the most recent sales of its convertible preferred stock, results obtained from third-party valuations and additional factors that are deemed relevant. As of December 31, 2018, the fair value of the Series A convertible preferred stock was $1.70 per share the fair value of the Series B convertible preferred stock was $1.86 per share. There were no warrants for the purchase of convertible preferred shares as of March 31, 2019 as all such warrants were converted to warrants for the purchase of common stock upon the Merger. The Company has been a private company prior to the Merger and lacks company-specific historical and implied volatility information of its stock. Therefore, it estimates its expected stock volatility based on the historical volatility of publicly traded peer companies for a term equal to the estimated remaining term of the warrants. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve for time periods approximately equal to the estimated remaining term of the warrants. The Company estimated a 0% expected dividend yield based on the fact that the Company has never paid or declared dividends and does not intend to do so in the foreseeable future.

Valuation of Derivative Liability

The fair value of the derivative liability recognized in connection with the Company’s July 2014 license agreement with Genzyme (see Note 13) was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of this derivative liability is reported within other liabilities on the consolidated balance

21

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

sheets. The fair value of this derivative liability was estimated by the Company at each reporting date based, in part, on the results of third-party valuations, which were prepared using the option-pricing method or the hybrid method, each of which considered as inputs the type, timing and probability of occurrence of a change of control event, the potential amount of the payment under potential exit scenarios, the fair value per share of the underlying common stock and the risk-adjusted discount rate. As of December 31, 2018, the fair value of this derivative liability was $183. The Merger with Arsanis (see Note 1) qualified as a change of control event, as defined in the license agreement, but results in no payment being due to Genzyme under the license agreement. As a result, on March 13, 2019, the closing date of the Merger with Arsanis, this derivative liability was remeasured to fair value, which was $0, and subsequent changes in fair value will no longer be recognized in the consolidated statements of operations and comprehensive loss because the contingent payment obligation to Genzyme expired at that time.

The fair value of the derivative liability recognized in connection with the Hercules Loan Agreement (see Note 7) was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of this derivative liability is reported within other liabilities on the consolidated balance sheets. The fair value of this derivative liability was estimated by the Company at each reporting date based, in part, on the results of third-party valuations, which were prepared based on a discounted cash flow model that considered the timing and probability of occurrence of a redemption upon an event of default, the potential amount of prepayment upon an event of default and the risk-adjusted discount rate. As of March 31, 2019 and December 31, 2018, the fair value of this derivative liability was immaterial.

The following table provides a roll-forward of the aggregate fair values of the Company’s warrant liability, derivative liability and preferred stock repurchase liability, for which fair values are determined using Level 3 inputs:

Property and equipment, net consisted of the following:

Depreciation and amortization expense related to property and equipment was $20 and $26 for the three months ended March 31, 2019 and 2018, respectively.

22

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Accrued expenses consisted of the following:

Long-term debt consisted of the following:

SVB Loan Agreement

In October 2016, the Company entered into a loan and security agreement with Silicon Valley Bank (“SVB”), which the Company refers to as the SVB Loan Agreement, pursuant to which SVB made certain term loans available to the Company. The SVB Loan Agreement provided for a term loan of up to $6,000, which was borrowed by the Company in June 2017. Borrowings under the SVB Loan Agreement bore interest at a variable rate equal to 5.5% plus the greater of (i) 3.5% or (ii) The Wall Street Journal prime rate. In October 2018, in connection with entering into the Hercules Loan Agreement, the Company terminated the SVB Loan Agreement and repaid all amounts due under the SVB Loan Agreement, including unpaid principal of $4,333, a final payment of $270, a prepayment premium of $87 and accrued interest of $23. The Company accounted for the repayment of amounts as an extinguishment of the SVB Loan Agreement and recognized a loss on extinguishment of debt of $229 within other income (expense), net in the consolidated statement of operations and comprehensive loss. The loss on extinguishment of debt was calculated as the difference between the reacquisition price of the borrowings under the SVB Loan Agreement of $4,713 and the carrying value of the debt under the SVB Loan Agreement of $4,484. As of October 19, 2018, the date of repayment of all borrowings under the SVB Loan Agreement, the interest rate applicable to borrowings under the SVB Loan Agreement was 10.75%.

Hercules Loan Agreement

In October 2018, the Company entered into the Hercules Loan Agreement, which provided for aggregate borrowings of up to $13,000, consisting of (i) a term loan of up to $8,000, which was available upon entering into the agreement, (ii) subject to specified financing conditions, an additional term loan of up to $2,000, available for borrowing from January 1, 2019 to March 31, 2019, and (iii) subject to specified financing conditions and the receipt of the second tranche $2,000 term loan described above, an additional term loan of up to $3,000, available for borrowing until March 31, 2019. In October 2018, the Company borrowed $8,000 under the Hercules Loan Agreement.

In December 2018, the Company entered into the First Amendment to the Hercules Loan Agreement (the “First Amendment”), which amended the available borrowing dates of the second tranche from between January 1, 2019 and March 31, 2019 to between December 11, 2018 and December 14, 2018 and amended the term loan maturity date to November 1, 2021. In December 2018, the Company borrowed the additional $2,000 provided under the Hercules Loan Agreement, as amended by the First Amendment.

In March 2019, the conditions necessary for borrowing the remaining $3,000 under the Hercules Loan Agreement were not met and the borrowing capacity expired at that time.

23

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Borrowings under the Hercules Loan Agreement bear interest at variable rates, with the first tranche bearing interest at a variable rate equal to the greater of (i) 9.5% or (ii) 9.5% plus The Wall Street Journal prime rate minus 5.25%, the second tranche bearing interest at a variable rate, subject to completion of specified financing conditions, equal to either (A) the greater of (i) 9.5% or (ii) 9.5% plus The Wall Street Journal prime rate minus 5.25% or (B) the greater of (i) 8.75% or (ii) 8.75% plus The Wall Street Journal prime rate minus 5.25%, and the third tranche bearing interest at a variable rate equal to the greater of (i) 8.75% or (ii) 8.75% plus The Wall Street Journal prime rate minus 5.25%. In an event of default, as defined, and until such event is no longer continuing, the interest rate applicable to borrowings under the Hercules Loan Agreement would be increased by 4.0%. As of March 31, 2019 and December 31, 2018, the interest rate applicable to borrowings under the Hercules Loan Agreement was 9.80% and 9.75%.

Borrowings under the Hercules Loan Agreement are repayable in monthly interest-only payments through August 2019, or a later date upon achievement of specified conditions, and in equal monthly payments of principal and accrued interest from September 2019 until the maturity date of the loan, which is November 2021. At the Company’s option, the Company may prepay all, but not less than all, of the outstanding borrowings, subject to a prepayment premium of up to 2.0% of the principal amount outstanding as of the date of repayment. The Hercules Loan Agreement also provides for a final payment, payable upon maturity or the repayment in full of all obligations under the agreement, of up to $953. An aggregate final payment of $794 payable in connection with the $8,000 term loan and the $2,000 term loan is being accreted to interest expense to increase the carrying value of the debt over the term of the loan using the effective interest method.

In addition, the Hercules Loan Agreement contains a redemption feature that, upon an event of default, provides Hercules the option to accelerate and demand repayment of the debt, including a prepayment premium. The Company concluded that the redemption feature meets the definition of a derivative instrument as the repayment of the debt contains a substantial premium, resulting in the redemption feature not being clearly and closely related to the host instrument. The Company recorded the issuance-date fair value of the derivative liability of $18 as a debt discount and as a derivative liability on its consolidated balance sheet.

Borrowings under the Hercules Loan Agreement are collateralized by substantially all of the Company’s personal property and other assets, including its intellectual property until a specified financing condition is met. Under the Hercules Loan Agreement, the Company has agreed to affirmative and negative covenants to which the Company will remain subject until maturity or repayment in full. The covenants include maintaining a minimum liquidity amount of the lesser of (i) 125% of outstanding borrowings under the Hercules Loan Agreement and (ii) 100% of the Company’s cash and cash equivalents in an account in which Hercules has a first priority security interest as well as restrictions on the Company’s ability to incur additional indebtedness, pay dividends, encumber its intellectual property, or engage in certain fundamental business transactions, such as mergers or acquisitions of other businesses. Obligations under the Hercules Loan Agreement are subject to acceleration upon occurrence of specified events of default, including payment default, insolvency and a material adverse change in the Company’s business, operations or financial or other condition.

In connection with entering into the Hercules Loan Agreement in October 2018, the Company issued to Hercules warrants for the purchase of 210,638 shares of Series B convertible preferred stock at an exercise price of $1.88 per share. These warrants were immediately exercisable and expire in October 2028.

In connection with entering into the First Amendment in December 2018, the Company agreed to issue to Hercules warrants for the purchase of a specified number of shares of convertible preferred stock or, if issued following the Merger with Arsanis, a specified number of shares of common stock of the combined organization, at an aggregate exercise price of $99. The warrants were to be issued at the earliest of (i) June 30, 2019, (ii) the earlier to occur of (a) the date the Company prepays the outstanding borrowings or (b) the date the outstanding borrowings become due and payable, or (iii) on or before the fifth business day following the closing of or the announcement of the termination of the Company’s Merger with Arsanis. The number of shares of convertible preferred stock issuable upon exercise of these warrants was determined to be 52,659 shares, calculated by dividing $99 by the $1.88 price per share paid by investors that purchased shares of Series B convertible preferred stock in September 2018 (see Note 11). On March 18, 2019, as a result of the closing of the Merger with Arsanis on March 13, 2019, the Company issued to Hercules warrants for the purchase of 5,000 shares of common stock of the combined organization at an exercise price of $19.80 per share, each of which reflected the share Exchange Ratio of 1-for-0.5702 applied in the Merger as well as the Reverse Stock Split effected by the combined organization on March 13, 2019.

On October 19, 2018 and December 11, 2018, the dates the Company entered into the Hercules Loan Agreement and the First Amendment, respectively, the Company recorded the aggregate initial fair value of the warrants of $132 as a preferred stock warrant liability, with a corresponding amount recorded as a debt discount on the Company’s consolidated balance sheet. As of March 13, 2019 and December 31, 2018, the fair value of the warrants was $326 and $282, respectively. Upon the closing of the Merger, the warrants were converted to warrants for common stock and are no longer adjusted to fair value.

24

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

In connection with entering into the Hercules Loan Agreement and the First Amendment, the Company also paid Hercules $92 of upfront fees, including facility, due diligence and legal fees associated with entering into the agreement, which were also recorded as a debt discount. The debt discount is reflected as a reduction of the carrying value of long-term debt on the Company’s consolidated balance sheet and is being amortized to interest expense over the term of the loan using the effective interest method.

The Company recognized aggregate interest expense under the Hercules Loan Agreement of $357 and $0 during three months ended March 31, 2019 and 2018, respectively, which included non-cash interest expense of $113 related to the accretion of the debt discount and the final payment. As of March 31, 2019 and December 31, 2018, the unamortized debt discount was $182 and $226, respectively. The Company’s annual effective interest rate of the Hercules Loan Agreement as of March 31, 2019 and December 31, 2018 was approximately 14.2%, respectively.

There were no principal payments due or paid under the Hercules Loan Agreement during the three months ended March 31, 2019. Principal payments begin in September 2019.

FFG Loan Agreement

Between September 2011 and March 2017, Arsanis GmbH, a subsidiary of Arsanis, entered into a series of funding agreements with Österreichische Forschungsförderungsgesellschaft mbH (“FFG”) that provided for loans and grants to fund qualifying research and development expenditures of Arsanis GmbH on a project-by-project basis, as approved by FFG. Amounts due under the FFG loans bear interest at rates ranging from 0.75% to 2.0% per annum. As of March 31, 2019, giving effect to the Settlement Agreement (as defined below), the loans matured at various dates between March 31, 2019 and March 2021. Interest on amounts due under the loans is payable semi-annually in arrears, with all principal and remaining accrued interest due upon maturity.

As of March 31, 2019, the outstanding principal amount under loans from FFG was $9,546, including $2,914 of current portion.

On March 8, 2019, Arsanis, Merger Sub, X4 and Arsanis GmbH, a wholly owned subsidiary of Arsanis, entered into the Settlement Agreement with FFG (the “Settlement Agreement”) in respect to allegations by FFG in February 2019 that Arsanis and Arsanis GmbH breached certain reporting, performance and other obligations in connection with grants and loans made by FFG to Arsanis GmbH between September 2011 and March 2017 to fund qualifying research and development expenditures. Pursuant to the terms of the Settlement Agreement, in exchange for FFG’s waiver of all claims against Arsanis and Arsanis GmbH (except for its claims for repayment of the loans and regular interest but including its waiver of claims for repayment of grants and interest exceeding regular interest), subject to compliance by Arsanis and Arsanis GmbH with the terms of the Settlement Agreement, Arsanis GmbH agreed to repay the outstanding loan principal (plus regular interest accrued thereon) on an accelerated payment schedule of three years instead of five years, with the final accelerated installment due and payable on June 30, 2021. The parties also agreed, among other things, that (i) the portion of such loans to be repaid in 2019 is $2,914 on the first business day following March 31, 2019 and (ii) until all of the loans have been repaid and subject to other terms specified in the Settlement Agreement, commencing April 30, 2019, a minimum cash balance equal to 70% of the then-outstanding principal amount of the loans will be maintained at Arsanis GmbH in an account held with an Austrian bank.

As of March 31, 2019, future principal payments and the final payment due under the Company’s loan agreements were as follows:

Effective January 1, 2019, the Company adopted ASC 842 using the modified retrospective approach through a cumulative-effect adjustment and utilizing the effective date as its date of initial application, with prior periods unchanged and presented in accordance with the previous lease accounting guidance. Upon adoption, the Company recorded right-of-use assets of $2,026 and lease liabilities of $2,538, of which $1,925 was classified as non-current and $613 as current. The difference between the value of the right-of-use asset and the lease liabilities relates to $512 of net deferred, accrued and prepaid rent that was reclassified against the right-of-use asset upon adoption of ASC 842 on January 1, 2019. The Company has lease agreements for its facilities in Cambridge, Massachusetts, which is the Company’s global headquarters, Vienna, Austria, which is the Company’s research and development center, and Waltham, Massachusetts, which is the former headquarters of Arsanis. The Company plans to sublease its Waltham, Massachusetts facility. There are no restrictions or financial covenants associated with any of the lease agreements.

25

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Cambridge Lease

In August 2017, the Company entered into a lease agreement for office space of approximately thirteen thousand square feet in Cambridge, Massachusetts (“Cambridge Lease”) which expires on July 31, 2022. The Cambridge lease includes an annual rent escalation clause and the Company has the option to extend the lease for one period of five additional years. Base rent is approximately $810 annually and the monthly rent expense is being recognized on a straight-line basis over the term of the lease. In addition to the base rent, the Company is also responsible for its share of operating expenses, electricity and real estate taxes, in accordance with the terms of lease. These costs are classified as variable lease payments and are not included in the determination of the leases’ right-of-use operating assets or lease operating liabilities.

Waltham Lease

On March 13, 2019, as part of its Merger with Arsanis, the Company acquired an operating lease for approximately six thousand square feet of office space in Waltham, Massachusetts (“Waltham Lease”). The Waltham lease, as amended, commenced on January 1, 2019, and expires approximately 5 years from the commencement date. The base rent is approximately $459 annually. In addition to the base rent, the Company is also responsible for its share of operating expenses, electricity and real estate taxes, in accordance with the terms of the Amended Lease Agreement. These costs are classified as variable lease payments and are not included in the determination of the leases’ right-of-use assets or lease liabilities.

Vienna Lease

On March 13, 2019, as part of its Merger with Arsanis, the Company acquired an operating lease for approximately four hundred square meters of laboratory and office space in Vienna, Austria, which commenced on March 1, 2019, as amended, for a term of two years. The lease is cancellable by the Company upon three month’s notice with no penalty. The annual base rent is approximately $155. The Company has classified this lease as a short-term lease as it is not reasonably certain that the Company with not terminate the lease within one year and, accordingly, has not recorded a right-of-use asset. Accordingly, rent expense is recorded on a straight-line basis as incurred over the term of the lease.

As the Company’s leases do not provide an implicit rate, the Company estimated the incremental borrowing rate in calculating the present value of the lease payments. The Company utilizes its incremental borrowing rates, which are the rates incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment.

The components of lease expense for the three months ended March 31, 2019 were as follows:

26

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Maturities of lease liabilities due under these lease agreements as of March 31, 2019 are as follows:

The Company adopted ASU 2016-02 on January 1, 2019 as noted above, and as required, the following disclosure is provided for periods prior to adoption. Future annual minimum lease payments due under the Company’s operating leases as of December 31, 2018 were as follows:

Sponsored Research Agreement Commitments

In April 2017, the Company entered into a sponsored research agreement with a university that the Company refers to as the Sponsored Research Agreement, pursuant to which the Company and the university intend to conduct a research program related to understanding the mechanisms of failed long-term adaptive immunity in WHIM patients. Under the terms of the Sponsored Research Agreement, the Company agreed to provide funding for the research program of up to $499 over a three-year period. The Sponsored Research Agreement will remain in effect for three years, unless earlier terminated in the event that (i) either party materially breaches any representation, obligation or covenant and fails to remedy such breach within 30 days after receipt of notice or (ii) the Principal Investigator, as defined in the agreement, is unable or unwilling to conduct the research or perform his or her obligations under the agreement, at which time the Company may terminate the agreement upon 30 days’ prior written notice to the university. The Company may terminate the agreement at any time upon at least 60 days’ prior written notice.

During the three months ended March 31, 2019 and 2018, the Company incurred $42, respectively, of research and development expenses related to its payment obligations to the university under the Sponsored Research Agreement. As of March 31, 2019, the Company had non-cancelable purchase commitments under this agreement totaling $181, with $125 committed in 2019 and $56 committed in 2020.

Manufacturing Commitments

As of March 31, 2019, the Company entered into agreements with several contract manufacturing organizations to provide preclinical and clinical trial materials. As of March 31, 2019, and December 31, 2018, the Company had non-cancelable purchase commitments under these agreements totaling approximately $250, all committed in 2019.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements

27

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company to, among other things, indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnification obligations. The Company is not currently aware of any indemnification claims and has not accrued any liabilities related to such obligations in its consolidated financial statements as of March 31, 2019 or December 31, 2018.

License Agreements

Arsanis entered into an agreement (the “Adimab Option Agreement”) in February 2017, which was acquired by the Company as a result of the Merger, under which the Company is obligated to make contingent and non-contingent payments should the Company exercise its option to obtain rights to certain RSV antibodies. If the Company chose to exercise its option, it would be obligated to pay Adimab an option fee of approximately $250 and make clinical and regulatory milestone payments of up to approximately $25,000, as well as royalty payments on a product-by-product and country-by-country basis of a mid single-digit percentage based on net sales by the Company, its affiliates, licensees or sublicensees of products based on certain RSV antibodies during the applicable term for such product in that country. The Company may choose to exercise its option under the terms of the Adimab Option Agreement at any time on or before August 31, 2019. As of March 31, 2019, the Company had not exercised its option under the Adimab Option Agreement.

Legal Proceedings

The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings

As of March 31, 2019, the Company’s outstanding warrants to purchase shares of common stock consisted of the following:

28

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

As of December 31, 2018, the Company’s outstanding warrants to purchase shares of preferred stock (which converted into warrants to purchase common stock upon close of the Merger) consisted of the following (not adjusted for the Reverse Stock Split or Exchange Ratio):

Prior to the Merger, the Company classified its preferred stock warrants as a liability on its consolidated balance sheet because the warrants are freestanding financial instruments that may have required the Company to transfer assets upon exercise. The liability associated with each of these warrants was initially recorded at fair value upon the issuance date of each warrant and is subsequently remeasured to fair value as a component of other income (expense), net in the consolidated statement of operations and comprehensive loss. Upon the closing of the Merger with Arsanis (see Note 1), pursuant to the Merger Agreement, all of the outstanding X4 preferred stock was converted to Arsanis common stock and the X4 preferred stock warrants converted to warrants for the purchase of Arsanis common stock. The Company assessed the features of the warrants and determined that they qualify for classification as permanent equity upon the closing of the Merger. Accordingly, the Company remeasured the warrants to fair value upon the closing of the Merger, which was $5,235 at March 13, 2019, with $288 of expense recorded during the three months ended March 31, 2019. Upon the closing of the Merger, the warrant liability was reclassified to additional paid-in capital.    

Common Stock

As of March 31, 2019 and December 31, 2018, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue 33,333,333 shares and 11,070,776, shares, respectively, of $0.001 par value common stock. The voting, dividend and liquidation rights of the holders of the Company’s common stock are subject to and qualified by the rights, powers and preferences of the holders of the preferred stock.

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the board of directors, if any. Through March 31, 2019 and December 31, 2018, no cash dividends had been declared or paid.

Redeemable Common Stock

Pursuant to the requirements of the July 2014 license agreement with Genzyme (see Note 13), in August 2015, the Company issued to Genzyme for no additional consideration 107,371, as adjusted for the Reverse Stock Split and Exchange Ratio, shares of common stock, which had an aggregate fair value of $734 on the date of issuance. Genzyme had the right to require the Company to repurchase all, but not less than all, of these shares of common stock at any time during the term of the license agreement for a price of $0.01 per share. Because of this redemption feature, the shares of common stock issued to Genzyme were classified outside of stockholders’ deficit on the consolidated balance sheets. As a result of the Merger, these shares were exchanged for common stock.

29

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

Convertible Preferred Stock (converted to Common Stock)

The Company has issued Series Seed convertible preferred stock (the “Series Seed preferred stock”), Series A convertible preferred stock (the “Series A preferred stock”) and Series B convertible preferred stock (the “Series B preferred stock”). As of March 31, 2019 and December 31, 2018, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue a total of 10,000,000 shares and 59,413,523 shares, respectively, of preferred stock, with a par value of $0.001 per share.

The holders of Preferred Stock have liquidation rights in the event of a deemed liquidation that, in certain situations, are not solely within the control of the Company. Therefore, the Preferred Stock is classified outside of stockholders’ deficit on the consolidated balance sheet.

As of March 31, 2019, there were no preferred stock outstanding. As of December 31, 2018, the Preferred Stock consisted of the following:

Summary of Plans

Upon completion of the Merger with Arsanis on March 13, 2019, X4’s 2015 Employee, Director and Consultant Equity Incentive Plan, as amended (the “2015 Plan”), Arsanis’ 2017 Equity Incentive Plan (the “2017 Plan”) and Arsanis’ 2017 Employee Stock Purchase Plan (the “2017 ESPP”) (collectively, the “Plans”) were assumed by the Company. These Plans are administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or its committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the share of common stock on the date of grant and the term of the stock option may not be greater than ten years. Incentive stock options granted to employees and restricted stock awards granted to employees, officers, members of the board of directors, advisors, and consultants of the Company typically vest over four years. Non-statutory options granted to employees, officers, members of the board of directors, advisors, and consultants of the Company typically vest over three or four years. Shares that are expired, terminated, surrendered or canceled under the Plans without having been fully exercised will be available for future awards. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for the grant of awards.

2015 Employee, Director and Consultant Equity Incentive Plan

In 2015, the board of directors and shareholders of X4 adopted the 2015 Plan, which provided for the Company to grant incentive stock options or nonqualified stock options, restricted stock awards and other stock-based awards to employees, directors and consultants of the Company. Each stock option outstanding under the 2015 Plan at the effective time of the Merger was automatically converted into a stock option exercisable for a number of shares of the Company’s common stock calculated based on the Exchange Ratio and the exercise price per share of such outstanding stock option.

The total number of shares of common stock that may be issued under the 2015 Plan was 1,700,000 shares, adjusted for the reverse stock split as of December 31, 2018 and March 31, 2019. Shares that are expired, forfeited, canceled or otherwise terminated without having been fully exercised will be available for future grant under the 2015 Plan. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for future grants.

30

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

2017 Equity Incentive Plan

In 2017, the board of directors and shareholders of Arsanis adopted the 2017 Plan which provided for the Company to grant incentive stock options, non-qualified options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. Incentive stock options may be granted only to the Company’s employees, including officers and directors who are also employees. Awards other than incentive stock options may be granted to employees, officers, members of the board of directors, advisors and consultants of the Company. The number of shares of common stock reserved for issuance under this plan will automatically increase on January 1 of each year, through January 1, 2027, in an amount equal to the lowest of 1,025,490 shares of the Company’s common stock, 4% of the number of shares of the Company’s common stock outstanding on January 1 of each year and an amount determined by the Company’s board of directors.

2017 Employee Stock Purchase Plan

In 2017, the board of directors and shareholders of Arsanis adopted the 2017 ESPP. The 2017 ESPP provides participating employees with the opportunity to purchase shares of the Company’s common stock at defined purchase prices over six-month offering periods. For the three month period ended March 31, 2019, no shares of common stock were issued under the 2017 ESPP.

Stock Option Valuation

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The Company has historically been a private company prior to March 13, 2019, and as a result, lacked company-specific historical and implied volatility information. The Company estimated expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until it has adequate historical data regarding the volatility of its own traded stock price. For options with service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The expected term of stock options granted to non-employee consultants is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted to employees, directors and non- employees:

Stock Options

The following table summarizes the Company’s stock option activity since December 31, 2018:

31

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock. The aggregate intrinsic value of stock options exercised during the three months ended March 31, 2019 was $123. The weighted average grant-date fair value per share of stock options granted during the three months ended March 31, 2019 was $12.88.

Stock-Based Compensation

Effective January 1, 2019, the Company adopted ASU 2018-07 which required the Company to adjust compensation expense for the three months ended March 31, 2019 for an immaterial amount for the unvested non-employee share options outstanding. The Company no longer remeasures the fair value of options granted to non-employees at each reporting period end (see Note 2).

During the three months ended March 31, 2019, the Company granted options to purchase 136,913 shares of common stock. As of March 31, 2019, total unrecognized compensation expense related to unvested stock options award was $5,066, which is expected to be recognized over a weighted average period of 2.5 years.

Stock-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows:

Genzyme Agreement

In July 2014, the Company entered into a license agreement (the “Genzyme Agreement”) with Genzyme pursuant to which the Company was granted an exclusive license to certain patents and intellectual property owned or controlled by Genzyme related to the CXCR4 receptor to develop and commercialize products containing licensed compounds (including but not limited to X4P-001) for all therapeutic, prophylactic and diagnostic uses, with the exception of autologous and allogenic human stem cell therapy. Under the terms of the Genzyme Agreement, the Company is obligated to use commercially reasonable efforts to develop and commercialize licensed products for use in the field in the United States and at least one other major market country. The Company has the right to grant sublicenses of the licensed rights that cover X4P-001 to third parties.

In exchange for these rights, in August 2014, the Company made an upfront payment of $50 to Genzyme. The Company accounted for the acquisition of technology as an asset acquisition because it did not meet the definition of a business. The Company recorded the upfront payment as research and development expense in the consolidated statement of operations and comprehensive loss because the acquired technology represented in-process research and development and had no alternative future use. In August 2015, as a result of the closing of the Company’s Series A preferred stock financing, the Company made an additional cash payment of $300 to Genzyme and issued to Genzyme 107,371 shares of its common stock, as adjusted for the 6 for 1 Reverse Stock Split and Exchange Ratio (see Note 11), each as required by the Genzyme Agreement. The $300 payment and the $734 fair value of the 107,371 shares of common stock issued to Genzyme were recorded as research and development expense in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2015. Prior to the Merger with Arsanis, Genzyme has the right to require the Company to repurchase all, but not less than all, of these shares of common stock at any time during the term of the Genzyme Agreement for a price of $0.01 per share. Due to this redemption feature, the shares of common stock issued to Genzyme were classified outside of stockholders’ deficit on the consolidated balance sheets as of December 31, 2018. On March 13, 2019, the closing date of the Merger with Arsanis, these redeemable common shares were exchanged for common shares and, as a result, the fair value of the shares was reclassified to permanent equity.

Under the Genzyme Agreement, the Company is obligated to pay Genzyme milestone payments in the aggregate amount of up to $25,000, contingent upon the achievement by the Company of certain late-stage regulatory and sales milestones with respect to

32

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

licensed products. In addition, the Company may be required to make a one-time milestone payment to Genzyme upon the consummation by the Company of a change of control transaction, in an amount equal to 5.5% of the consideration paid to equity holders of the Company, other than Genzyme, in connection with such change of control transaction, after deducting outstanding debt obligations of the Company and the aggregate cash investments made by equity holders into the Company prior to the closing of the change of control transaction. The Merger with Arsanis qualifies as a change of control transaction, as defined in the license agreement, but results in no payment being due to Genzyme under the license agreement.

The Company concluded that this contingent payment obligation meets the definition of a derivative instrument as the contingent payment obligation is not clearly and closely related to its host instrument and is a cash-settled liability (see Note 2). Accordingly, the Company classifies this derivative as a liability within other liabilities (non-current) on its consolidated balance sheet (see Note 2), and changes in the fair value of the derivative liability are recognized as a component of other income (expense), net in the consolidated statement of operations and comprehensive loss (see Note 4). On March 13, 2019, the closing date of the Merger with Arsanis, this derivative liability was remeasured to fair value, which was $0, and subsequent changes in fair value will no longer be recognized in the consolidated statements of operations and comprehensive loss because the contingent payment obligation expired at that time.

Under the Genzyme Agreement, the Company is obligated to pay Genzyme tiered royalties based on net sales of licensed products that the Company commercializes under the agreement. The obligation to pay royalties for each licensed product expires on a country-by-country basis on the latest of (i) the expiration of licensed patent rights that cover that licensed product in that country, (ii) the expiration of regulatory exclusivity in that country and (iii) ten years after the first commercial sale of such licensed product in that country. Royalty rates are subject to reduction under the agreement in specified circumstances, including in any country if the Company is required to obtain a license from any third party to the extent the Company’s patent rights might infringe the third party’s patent rights, if a licensed product is not covered by a valid claim in that country or if sales of generic products reach certain thresholds in that country. If the Company enters into a sublicense under the agreement, the Company will be obligated to pay Genzyme a percentage of certain upfront fees, maintenance fees, milestone payments and royalty payments paid to the Company by the sublicensee.

Under the Genzyme Agreement, the Company will itself manufacture and supply, or enter into manufacturing or supply agreements with Genzyme or third parties to manufacture and supply, clinical and commercial supplies of licensed compounds and each licensed product. During the three months ended March 31, 2019 and 2018, the Company did not enter into any third-party manufacturing or supply agreements in connection with the Genzyme Agreement. The Company is also responsible for all costs related to the filing, prosecution and maintenance of the licensed patent rights.

The Genzyme Agreement will remain in effect until the expiration of the royalty term in all countries for all licensed products. The agreement may be terminated by either party with at least 90 days’ notice in the event of material breach by the other party that remains uncured for 90 days, by either party for insolvency or bankruptcy of the other party, immediately by Genzyme if the Company challenges the licensed patents, or immediately by the Company if a material safety issue arises.

During the three months ended March 31, 2019 and 2018, the Company did not incur any payment obligations to Genzyme under the Genzyme Agreement.

Georgetown Agreement

In December 2016, the Company entered into a license agreement (the “Georgetown Agreement”) with Georgetown University (“Georgetown”) pursuant to which the Company obtained an exclusive, worldwide license to make, have made, use, sell, offer for sale and import of products covered by patent rights co-owned by Georgetown. The rights licensed to the Company are for all therapeutic, prophylactic and diagnostic uses in all disease indications in humans and animals.

Under the terms of the Georgetown Agreement, the Company paid a one-time only, upfront fee of $50 and the Company may be required to pay milestone payments of up to an aggregate of $800 related to commercial sales of a product. The Company accounted for the acquisition of technology as an asset acquisition because it did not meet the definition of a business. The Company recorded the upfront payment as research and development expense in the consolidated statement of operations and comprehensive loss because the acquired technology represented in-process research and development and had no alternative future use.

Under the Georgetown Agreement, the Company is solely responsible for all development and commercialization activities and costs in its respective territories. The Company is also responsible for all costs related to the filing, prosecution and maintenance of the licensed patent rights.

33

X4 PHARMACEUTICALS, INC.

NOTES TO CONDENSED CONSOLIDATED FINANCIALS STATEMENTS

(Amounts in thousands, except share and per share amounts)

(Unaudited)

The term of the Georgetown Agreement will continue until the expiration of the last valid claim within the patent rights covering the product. Georgetown may terminate the agreement in the event (i) the Company fails to pay any amount and fails to cure such failure within 30 days after receipt of notice, (ii) the Company defaults in its obligation to obtain and maintain insurance and fails to remedy such breach within 45 days after receipt of notice, or (iii) the Company declares insolvency or bankruptcy. The Company may terminate the agreement at any time upon at least 60 days’ written notice.

During the three months ended March 31, 2019 and 2018, the Company did not incur any payment obligations to Georgetown under the Georgetown Agreement and no milestone payments were made or due under the Georgetown Agreement.

Beth Israel Deaconess Medical Center Agreement

In December 2016, the Company entered into a license agreement (the “BIDMC Agreement”) with Beth Israel Deaconess Medical Center (“BIDMC”), pursuant to which the Company obtained an exclusive, worldwide license to make, have made, use, sell, offer for sale and import of products covered by patent rights co-owned by BIDMC. The rights licensed to the Company are for all fields of use.

Under the terms of the BIDMC Agreement, the Company paid a one-time only, upfront fee of $20 and the Company is responsible for all future patent prosecution costs. The Company accounted for the acquisition of technology as an asset acquisition because it did not meet the definition of a business. The Company recorded the upfront payment as research and development expense in the consolidated statement of operations and comprehensive loss because the acquired technology represented in-process research and development and had no alternative future use.

The term of the BIDMC Agreement will continue until the expiration of the last valid claim within the patent rights covering the licensed products. BIDMC may terminate the agreement in the event (i) the Company fails to pay any amount and fails to cure such failure within 15 days after receipt of notice, (ii) the Company is in material breach of any material provision of the agreement and fails to remedy such breach within 60 days after receipt of notice, or (iii) the Company declares insolvency or bankruptcy. We may terminate the agreement at any time upon at least 90 days’ written notice.

The Company did not incur any payment obligations under the BIDMC Agreement during the months ended March 31, 2019 and 2018.

Adimab Option and License Agreement

In February 2017, Arsanis entered into an option and license agreement with Adimab, a related party (the “Adimab Option Agreement”). Under the Adimab Option Agreement, Adimab has provided to Arsanis certain proprietary antibodies against respiratory syncytial virus (“RSV antibodies”) for its evaluation during a specified option period and has granted Arsanis an exclusive, non-sublicensable license in a specified field under certain Adimab patent rights and know-how during the option period. Under the Adimab Option Agreement, the Company has an exclusive option, exercisable during the option period upon payment of an option fee to Adimab, to require Adimab to assign to the Company all rights in up to a specified number of RSV antibodies selected by the Company and certain patent rights owned by Adimab that cover these antibodies, and to obtain from Adimab a non-exclusive license in a specified field, with the right to grant sublicenses, under certain other patent rights and know-how owned by Adimab.

If the Company exercises its option under the Adimab Option Agreement, the Company is required to use commercially reasonable efforts to develop and commercialize at least one product based on a licensed RSV antibody in major markets and is obligated to pay Adimab an option fee of $0.3 million and make future milestone payments upon the achievement of specified clinical and regulatory milestones in the aggregate amount of up to $24.4 million. The Company is obligated to pay Adimab royalties at a mid single-digit percentage of net sales of products based on the initial RSV antibodies (including modified or derivative forms of those antibodies created by or for the Company) by the Company or any of its affiliates, licensees or sublicensees, regardless of whether these products practice any of the assigned or licensed patents or know-how. If the Company materially breaches these diligence obligations, Adimab will have the right to terminate the Adimab Option Agreement.

The Company has no payment obligations under the Adimab Option Agreement with respect to sales of products based on licensed RSV antibodies to the extent they are sold at cost in developing countries under the February 2017 Gates Foundation grant agreement, as amended and restated in August 2018, and the August 2018 Gates Foundation grant agreement (which are described in further detail below). However, if such products are sold in developing countries for an amount that exceeds cost, then the amount of such excess will be subject to the royalty payment obligations described in the preceding paragraph.

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(Unaudited)

If the Company does not exercise its option, the Adimab Option Agreement will expire on the Company’s achievement of specified preclinical milestones under the grant agreements with the Gates Foundation, but in any event no later than mid-2019. If the Company does exercise its option, the Adimab Option Agreement will expire on the last-to-expire royalty term (defined, on a product-by-product and country-by-country basis, as the period ending on the later of twelve years after the first commercial sale of such product in such country and the expiration of the last of a specified set of patents and patent applications covering such product in such country) for any and all products for which the Company is obligated to pay Adimab royalties under the Adimab Option Agreement. The Company has the right to terminate the Adimab Option Agreement for any reason by providing Adimab with a specified amount of prior written notice. Adimab has the right to terminate the Adimab Option Agreement if the Company materially breaches the agreement and fails to cure such breach within a specified cure period, including for the Company’s failure to use commercially reasonable efforts to develop and commercialize at least one product based on a licensed RSV antibody in major markets. If Adimab terminates the Adimab Option Agreement for the Company’s breach, if the Company terminates the agreement for convenience or if the agreement expires before the Company exercises its option, then the Company must return or destroy certain know-how, including all initial RSV antibodies, and all modified or derivative forms of those antibodies, in its possession other than those for which the Company has made all payments required under the Adimab Option Agreement, assign certain patents covering certain RSV antibodies to Adimab, grant Adimab a non-exclusive, royalty-free license under certain other patents, and grant Adimab a time-limited right of first negotiation to obtain an exclusive license to certain patents and know-how and the transfer and assignment of certain regulatory filings and approvals and other related assets related to products based on licensed RSV antibodies. Certain of the Company’s payment obligations relating to specified products and patents arising from the agreement survive expiration or termination of the agreement.

During the three months ended March 31, 2019, the Company recognized no research and development expense in connection with the Adimab Option Agreement.

Adimab Collaboration Agreement

In May 2011, Arsanis entered into a collaboration agreement with Adimab, LLC (“Adimab”) and together with certain applicable option exercise letters the Company has sent to Adimab, the “Adimab Collaboration Agreement”). Under the Adimab Collaboration Agreement, the Company and Adimab were required to use reasonable efforts to conduct certain research, which was funded by the Company, to discover and optimize antibodies directed against targets selected by the Company. With respect to each target that was the subject of the research, the Company had an exclusive option to obtain, with respect to a specified number of antibodies directed against such target and discovered or optimized by Adimab, (i) ownership of certain patent rights relating to such antibodies and (ii) exclusive and non-exclusive licenses in a specified field, with the right to grant sublicenses, under certain patent rights and know-how.

Under the Adimab Collaboration Agreement, for each target for which the Company has exercised an option, the Company is required to use commercially reasonable efforts to develop and commercialize at least one product in major markets. If the Company does not fulfill these diligence obligations, Adimab may consider it a material breach, allowing Adimab to terminate the Adimab Collaboration Agreement with respect to such target and all associated products.

The Company is obligated to pay Adimab royalties at a mid single-digit percentage of net sales made by the Company or its affiliates of products based on antibodies for which the Company exercised its option, or products that use or are based on any antibody discovered or optimized under the agreement, any derivative or modified version of any such antibody, or any sequence information as to any such antibody. In addition, if the Company sells or licenses to any third party, or otherwise grants rights to any third party to, any of the products for which the Company is obligated to pay Adimab royalties, either alone or as part of a package including specified patents not directed to these antibodies, the Company is obligated to pay Adimab either (i) the same royalties on net sales of such products by such third party or (ii) a percentage, ranging from the low double digits to a maximum of less than 30%, of the payments the Company receives from such third parties that are attributable to such grant of rights. In April 2017, the Company entered into a letter agreement with the Gates Foundation, pursuant to which the Company licensed to the Gates Foundation certain rights under its ASN100 program. The Company has no payment obligations under the Adimab Collaboration Agreement with respect to sales of certain antibody products if they are sold at cost in developing countries under its letter agreement with the Gates Foundation. However, if such products are sold in developing countries for an amount that exceeds cost, then the amount of such excess over cost will be subject to the royalty payment obligations described above.

If the Company (or one of its affiliates with rights under the agreement) undergoes a change in control and, at the time of such change in control, the Company has not sold or licensed to third parties all of its rights in antibodies for which the Company is obligated to pay Adimab royalties under the agreement, then the Company is obligated to either (i) pay Adimab a percentage, in the mid double digits, of the payments it receives from that change in control that are reasonably attributable to those rights and certain patents arising

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(Amounts in thousands, except share and per share amounts)

(Unaudited)

from the collaboration or (ii) require the Company’s acquirer and all of its future third-party collaborators to pay to Adimab the royalties at a mid single-digit percentage of net sales based on those rights. If the Company grants rights to a third party under certain patents that are not directed to the antibodies for which the Company is obligated to pay Adimab royalties (as described above), the Company is also obligated to pay Adimab, in place of royalties or a percentage of payments received from the third party, a lump sum in the high six digits.

The Adimab Collaboration Agreement will expire on a country-by-country basis twelve years after the first commercial sale in such country of the last product for which the Company is obligated to pay Adimab royalties in such country under the Adimab Collaboration Agreement. The Company has the right to terminate the Adimab Collaboration Agreement for any reason by providing Adimab with a specified amount of prior written notice. Adimab has the right to terminate the Adimab Collaboration Agreement if the Company materially breaches the agreement and fails to cure such breach within a specified cure period, including for its failure to use commercially reasonable efforts to develop and commercialize at least one product directed at a target for which the Company has exercised an option in major markets. If Adimab terminates the Adimab Collaboration Agreement for the Company’s breach, or if the Company terminates the agreement for convenience, then the Company must transfer or license to Adimab certain rights and assets relating to targets and antibodies for which the Company has exercised its option. Adimab is then obligated to make payments to the Company with respect to these targets and antibodies that are similar to the payments the Company is required to make to Adimab during the term of the agreement. Certain of the Company’s payment obligations relating to specified products and patents arising from the agreement survive expiration or termination of the agreement.

During the three months ended March 31, 2019, the Company did not recognize any research and development under the Adimab Collaboration Agreement.

Gates Foundation Grant Agreements

In February 2017, Arsanis entered into a grant agreement with the Gates Foundation (“Grant Agreement”), under which the Gates Foundation agreed to provide the Company up to approximately $9,300 to conduct preclinical development of monoclonal antibodies for the prevention of RSV infection in newborns (the “RSV project”).

In connection with this Grant Agreement, the Company has granted to the Gates Foundation a non-exclusive, perpetual, royalty-free, fully paid up, sublicensable license to make, use, sell, offer to sell, import, distribute, copy, modify, create derivative works, publicly perform and display the funded developments and, to the extent incorporated into a funded development or required to use a funded development, any other technology created outside of the RSV project that was used as part of the RSV project, for the benefit of people in developing countries. This license survives any expiration or termination of the grant agreement. The Grant Agreement expires on October 31, 2019. The Gates Foundation can modify, suspend or discontinue any payment under the grant agreement, or terminate the grant agreement, if it is not reasonably satisfied with the Company’s progress on the RSV project; if there are significant changes to the Company’s leadership or other factors that the Gates Foundation reasonably believes may threaten the RSV project’s success; if the Company undergoes a change in control; if there is a change in the Company’s tax status; if the RSV project is no longer aligned with the Gates Foundation’s programmatic strategy; or if the Company fails to comply with the grant agreement. Any grant funds that have not been used for, or committed to, the RSV project upon the expiration or termination of the grant agreement must be returned to the Gates Foundation or otherwise used as directed by the Gates Foundation. In August 2018, Arsanis entered into an amended and restated grant agreement which replaced the February 2017 grant agreement in its entirety. The amended and restated grant agreement includes amendments to conform to current Gates Foundation audit, reporting, and other administrative requirements, as well as to make the perpetual Gates Foundation license grant described below irrevocable.

During the three months ended March 31, 2019, the Company did not incur qualifying expenses under the letter agreement with the Gates Foundation.

Research and Development Incentive Program

The Company participates in a research and development incentive program provided by the Austrian government whereby the Company is entitled to reimbursement by the Austrian government for a percentage of qualifying research and development expenses incurred by the Company’s subsidiary in Austria. Under the program, the reimbursement rate for qualifying research and development expenses incurred by the Company through its subsidiary in Austria is 14% for the current year .

The Company recognizes incentive income from Austrian research and development incentives when qualifying expenses have been incurred, there is reasonable assurance that the payment will be received, and the consideration can be reliably measured. Management has assessed the Company’s research and development activities and expenditures to determine which activities and expenditures are likely to be eligible under the research and development incentive program described above. At each reporting date, management estimates the reimbursable incentive income available to the Company based on available information at the time.

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(Amounts in thousands, except share and per share amounts)

(Unaudited)

As of March 31, 2019, the Company recorded receivables for amounts due under the program of $1.6 million, which amounts were included in grant and incentive receivables in the consolidated balance sheet.

Janssen License and Option Agreement

On December 12, 2018, Arsanis entered into a patent license and option agreement with Janssen Pharmaceuticals, Inc. (“Janssen”), (the “Janssen License and Option Agreement”). Pursuant to the Janssen License and Option Agreement, Arsanis granted to Janssen (i) a non-exclusive license to specified patents in Arsanis’s portfolio related to the ASN200 E. coli program, and (ii) an option for Janssen to acquire these patents in the future if specified conditions are met. Janssen agreed to pay Arsanis $3.5 million within 15 business days after the December 12, 2018 effective date of the Janssen License and Option Agreement, in addition to a future $0.5 million payment in the event Janssen exercises its option to acquire the relevant patents. Arsanis received the $3.5 million payment from Janssen in December 2018 and recognized this amount as revenue. Such revenue is not reflected in the consolidated financial statements of the Company as it occurred prior to the Merger. Janssen’s option to the relevant patents will be recognized as revenue in full in the period in which the option exercise occurs.

The Company did not record a federal or state income tax benefit for its losses for the three months ended March 31, 2019 and 2018 due to the conclusion that a full valuation allowance is required against the Company’s deferred tax assets.

Basic and diluted net loss per share attributable to common stockholders was calculated as follow:

The Company has included 107,371 shares of redeemable common stock in its computation of basic and diluted weighted average common shares outstanding for the three months ended March 31, 2019 and 2018 as this class of stock participates in losses similarly to other common stockholders.

The Company’s potentially dilutive securities included outstanding stock options, convertible preferred stock, and warrants to purchase shares of convertible preferred stock for the three month period ended March 31, 2018 and included outstanding stock options and warrants to purchase common stock for the three month period ended March 31, 2019. These potentially dilutive securities have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share, and thus they are considered “anti-dilutive.” Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end and adjusted for the Exchange Ratio and Reverse Stock Split, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

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(Amounts in thousands, except share and per share amounts)

(Unaudited)