MUSTANG BIO, INC.

Note 1 - Organization and Description of Business

Mustang Bio, Inc. (the “Company” or “Mustang”) was incorporated in Delaware on March 13, 2015. Mustang is a clinical-stage biopharmaceutical company focused on translating today’s medical breakthroughs into potential cures for difficult-to-treat cancers and autoimmune diseases. The Company may acquire rights to these technologies by licensing the rights or otherwise acquiring an ownership interest in the technologies, funding their research and development and eventually either out-licensing or bringing the technologies to market.

The Company is a majority-controlled subsidiary of Fortress Biotech, Inc. (“Fortress” or “Parent”).

The Company’s common stock is listed on the Nasdaq Capital Market and trades under the symbol “MBIO.”

Reverse Stock Split

On January 15, 2025,* the Company filed an amendment (the “Reverse Split Amendment”) to its Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware to effect the 1-for-50 reverse stock split of the Company's shares of common stock ("Reverse Stock Split"). As a result of the Reverse Stock Split, every 50 shares of common stock outstanding immediately prior to effectiveness of the Reverse Stock Split were combined and converted intoone share of common stock without any change in the par value per share. The Reverse Stock Split became effective on January 15, 2025, and the common stock was quoted on the Nasdaq Stock Market on a post-split basis at the open of business on January 16, 2025. *No fractional shares were issued in connection with the Reverse Stock Split. Stockholders who would have otherwise been entitled to a fraction ofone share of common stock as a result of the Reverse Stock Split instead receiveda proportional cash payment.

All share and per share information has been retroactively adjusted to give effect to the Reverse Stock Split for all periods presented, unless otherwise indicated.

Liquidity and Capital Resources

The Company has incurred substantial operating losses and expects to continue to incur significant operating losses for the foreseeable future and may never become profitable. As of December 31, 2024, the Company had an accumulated deficit of $396.7 million.

The Company has funded its operations to date primarily through the sale of equity. During fiscal year 2024, the Company completed several financing transactions, including proceeds from the At-the-Market Offering (see Note 10), for aggregate net proceeds of approximately $11.2 million. Additionally, in February 2025, the Company completed a public offering for net proceeds of approximately $6.9 million (see Note 13).

In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern, the Company evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about its ability to continue as a going concern within one year after the date that these financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the Company’s ability to continue as a going concern. The mitigating effect of management’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that these financial statements are issued. In performing its evaluation, management excluded certain elements of its operating plan that cannot be considered probable. Under ASC 205-40, the future receipt of potential funding from future equity or debt issuances cannot be considered probable at this time because these plans are not entirely within the Company’s control.

The Company's expectation to generate operating losses and negative operating cash flows in the future, the need for additional funding to support its planned operations, and the continued listing requirements for Nasdaq raise substantial doubt regarding the Company’s ability to continue as a going concern for a period of one year after the date that these financial statements are issued. The Company made strategic decisions, including (i) a significant reduction in the workforce by approximately 81% in April 2024, and included the reversal of accrued annual bonuses, (ii) the termination of certain license agreements with St. Jude and Leiden University Medical Centre in April 2024, and with Mayo Clinic in June 2024, and (iii) closing the Mustang-sponsored Phase 1/2 study in Non-Hodgkin lymphoma and chronic lymphocytic leukemia (MB-106) to preserve capital and prioritize the allocation of resources. The Company continues to pursue raising additional cash resources through public or private equity or debt financings.

The accompanying financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that may be necessary if the Company is unable to continue as a going concern.

Note 2 - Significant Accounting Policies

Basis of Presentation

The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The Company hasno subsidiaries.

All inter-company transactions between Fortress and Mustang are classified as due from or due to related party in the financial statements.

Segment Reporting

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources in assessing performance. The Company views its operations and manages its business inone segment, which reflects the research and development of potential cures for difficult-to-treat cancers and autoimmune diseases. The Company’s chief operating decision maker (“CODM”) is its chief executive officer.

The CODM assesses performance for the research and development segment and decides how to allocate resources based on net loss, which is reported on the Statements of Operations. The CODM uses net loss to evaluate costs to develop its pipeline. The accounting policies of the segment are the same as those described in this Note 2. See Note 12 for segment information.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates.

Cash and Cash Equivalents

The Company considers highly liquid investments with a maturity of three months or less when purchased to be cash equivalents. Cash and cash equivalents at December 31, 2024 and 2023, consisted of cash and certificates of deposit in institutions in the United States. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are currently adequately protected against credit risk. At times, portions of the Company’s cash and cash equivalents may be uninsured or in deposit accounts that exceed Federal Deposit Insurance Corporation (FDIC) limits, though the Company customarily invests a significant portion of its cash in Insured Cash Sweep (“ICS”) accounts to maximize FDIC insurance coverage across its holdings. As of

December 31, 2024, the Company had not experienced losses on these accounts, and management believes the Company is not exposed to significant risk on such accounts.

Other Receivables – Related Party

Other receivables include amounts due to the Company from Fortress and is recorded at the invoiced amount.

Restricted Cash

The Company records cash held in an escrow account as a security deposit for the manufacturing facility in Worcester, Massachusetts, as restricted cash. The Company hadno restricted cash as of December 31, 2024, and $0.8 million in restricted cash as of December 31, 2023.

Property, plant and equipment, net

Property, plant and equipment, net, consists primarily of leasehold improvements, are carried at cost less accumulated depreciation. Depreciation for leasehold improvements is computed over the shorter of the estimated useful lives or the term of the respective leases. Depreciation for all other property and equipment assets is recorded over the useful lives of the respective assets, generally five years, using the straight-line method.

Property, plant and equipment, held for sale

Property, plant and equipment, held for sale represent assets that have met the criteria of “held for sale” accounting, as specified by Accounting Standards Codification (“ASC”) 360, “Long-lived Assets.” As of December 31, 2024, there were$1.2 million of lab and cell processing equipment, furniture and fixtures and computer equipment that are recorded as assets held for sale. The effect of suspending depreciation on the assets held for sale is immaterial to the results of operations. The assets held for sale were part of the repurchase of assets from uBriGene (see Note 5).

Impairment of Long-Lived Assets

The Company reviews long-lived assets, including tangible assets and other intangible assets with definitive lives, for impairment whenever events or changes in circumstances indicate that the asset’s carrying amount may not be recoverable. The Company conducts its long-lived asset impairment analyses in accordance with ASC 360-10, "Impairment or Disposal of Long-Lived Assets. ASC 360-10-15 requires the Company to group assets and liabilities at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities and evaluate the asset group against the sum of the undiscounted future cash flows. If the undiscounted cash flows do not indicate the carrying amount of the asset group is recoverable, an impairment charge is measured as the amount by which the carrying amount of the asset group exceeds its fair value based on discounted cash flow analysis or appraisals.

Research and Development Costs

Research and development costs are expensed as incurred. Advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. Upfront and milestone payments due to third parties that perform research and development services on the Company’s behalf will be expensed as services are rendered or when the milestone is achieved.

Research and development costs primarily consist of personnel related expenses, including salaries, benefits, travel, and other related expenses, stock-based compensation, payments made to third parties for license and milestone costs related to in-licensed products and technology, payments made to third party contract research organizations for preclinical and clinical studies, investigative sites for clinical trials, consultants, the cost of acquiring and manufacturing clinical trial materials, costs associated with regulatory filings, laboratory costs and other supplies.

In accordance with Accounting Standards Codification (“ASC”) 730-10-25-1,*Research and Development,*costs incurred in obtaining technology licenses are charged to research and development expense if the technology licensed has not reached commercial feasibility and has no alternative future use. The licenses purchased by the Company require

substantial completion of research and development, regulatory and marketing approval efforts to reach commercial feasibility and has no alternative future use. Accordingly, the total purchase price for the licenses acquired is reflected as research and development – licenses acquired in the Company’s Statements of Operations.

Annual Stock Dividend to Fortress

In July 2016, in connection with the Amended and Restated Articles of Incorporation, the Company issued 250,000 Class A preferred shares to Fortress. The Class A preferred shares entitle the holder to a stock dividend equal to 2.5% of the fully diluted outstanding equity of the Company (the “Annual Stock Dividend”). The Annual Stock Dividend was part of the consideration payable for formation of the Company and the identification of certain assets, including the license contributed to Mustang by Fortress (see Note 4). The Company considers the Annual Stock Dividend as contingent consideration for the license contributed to Mustang by Fortress. Since the ultimate amount of the Annual Stock Dividend is highly uncertain and cannot be reasonable estimable, in accordance with ASC 450-20,Loss Contingencies, the Company records the Annual Stock Dividend in Research and development expense – licenses acquired in the Company’s Statements of Operations, when the shares are issued.

Fair Value Measurement

The Company follows accounting guidance on fair value measurements for financial assets and liabilities measured at fair value on a recurring basis. Under the accounting guidance, fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability.

The accounting guidance requires fair value measurements be classified and disclosed in one of the following three categories:

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Observable inputs other than Level 1 prices, for similar assets or liabilities that are directly or indirectly observable in the marketplace.

Level 3: Unobservable inputs which are supported by little or no market activity and that are financial instruments whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment or estimation.

The fair value hierarchy also requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability.

Leases

Arrangements meeting the definition of a lease are classified as operating or financing leases and are recorded on the balance sheet as both a right of use asset and lease liability, calculated by discounting fixed lease payments over the lease term at the rate implicit in the lease or the Company's incremental borrowing rate. Lease liabilities are increased by interest and reduced by payments each period, and the right of use asset is amortized over the lease term. For operating leases, interest on the lease liability and the amortization of the right of use asset result in straight-line rent expense over the lease term. Variable lease expenses are recorded when incurred. In calculating the right of use asset and lease liability, the Company elects to combine lease and non-lease components. The Company excludes short-term leases having initial terms of 12 months or less from the new guidance as an accounting policy election and recognizes rent expense on a straight-line basis over the lease term.

Stock-Based Compensation

The Company expenses stock-based compensation to employees over the requisite service period based on the estimated grant-date fair value of the awards and forfeiture rates.

The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model. The assumptions used in calculating the fair value of stock-based awards represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment.

Income Taxes

The Company records income taxes using the asset and liability method. Deferred income tax assets and liabilities are recognized for the future tax effects attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective income tax bases, and operating loss and tax credit carryforwards. The Company establishes a valuation allowance if management believes it is more likely than not that the deferred tax assets will not be recovered based on an evaluation of objective verifiable evidence. For tax positions that are more likely than not of being sustained upon audit, the Company recognizes the largest amount of the benefit that is greater than 50% likely of being realized. For tax positions that are not more likely than not of being sustained upon audit, the Company does not recognize any portion of the benefit.

Net Loss per Share

Basic and diluted net loss per share is computed by dividing net loss by the weighted average number of common shares outstanding, including prefunded warrants and shares held in abeyance, during the period, without consideration of potential dilutive securities. For periods in which the Company generated a net loss, the Company does not include potential shares of common stock in diluted net loss per share when the impact of these items is anti-dilutive. The Company has generated a net loss for all periods presented, therefore diluted net loss per share is the same as basic net loss per share since the inclusion of potentially dilutive securities would be anti-dilutive.

The table below summarizes potentially dilutive securities that were not considered in the computation of diluted net loss per share because they would be anti-dilutive.

In connection with the exercise of certain existing warrants in October 2024 (see Note 10), the Company recorded a deemed dividend of approximately $7.8 million for the issuance of new warrants. For the year ended December 31, 2024, net loss attributable to common stockholders consisted of net loss, as adjusted for deemed dividends.

The Company considers Class A common stock and Class A preferred stock to be additional classes of common stock for the purpose of calculating net loss per share, as they do not have preferential rights when compared to the Company’s common stock, and therefore losses are allocated to these additional classes using the two-class method. The two-class method is an earnings allocation formula that treats participating securities as having rights that would otherwise have been available to common stockholders. At December 31, 2024, the Class A common stock and Class A preferred stock have rights to convert to a total of 1,461 common shares.

Comprehensive Loss

The Company hasno components of other comprehensive loss, and therefore, comprehensive loss equals net loss.

Recent Accounting Pronouncements

In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-07, “Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures.” The amendments in ASU 2023-07 improve reportable segment disclosure requirements through enhanced disclosures about significant segment expenses. The amendments introduce a new requirement to disclose significant segment expenses regularly provided to the chief operating decision maker (“CODM”), extend certain annual disclosures to interim periods, clarify single reportable segment entities must apply ASC 280 in its entirety, permit more than one measure of segment profit or loss to be reported under certain conditions, and require disclosure of the title and position of the CODM. This guidance is effective for fiscal years, beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption will be permitted. The Company adopted the ASU on its annual report on Form 10-K for the year ended December 31, 2024.

In December 2023, the FASB issued ASU 2023-09,Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which expands disclosures in an entity’s income tax rate reconciliation table and disclosures regarding cash taxes paid both in the U.S. and foreign jurisdictions. The update will be effective for annual periods beginning after December 15, 2024. The Company is currently evaluating the impact that this guidance will have on our financial statements and disclosures.

In November 2024, the FASB issued ASU 2024-03,*Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Topic 220-40).*The amendments in this update require new disclosures to disaggregate prescribed natural expenses underlying any income statement caption. ASU 2024-03 is effective for annual periods in fiscal years beginning after December 15, 2026, and interim periods thereafter. Early adoption is permitted. ASU 2024-03 applies on a prospective basis for periods beginning after the effective date. However, retrospective application to any or all prior periods presented is permitted. The Company is currently assessing the impact ASU 2024-03 will have on the financial statements and disclosures.

Note 3 - License, Clinical Trial and Sponsored Research Agreements

Research and Development Expenses – Licenses

For the year ended December 31, 2024, the Company recorded $0.3 million in Research and development – licenses acquired related to a clinical development milestone achieved related to its license agreement with Nationwide Children’s. For the year ended December 31, 2023, the Company recorded $50,000 in Research and development – licenses acquired in connection with Calimmune license. On August 14, 2023, the Company notified Calimmune that it was terminating the Calimmune license, which took effect 60 days following notification.

Research and Development Expenses - Sponsored Research and Clinical Trial Agreements

For the years ended December 31, 2024 and 2023, the Company recorded the following expense in research and development for sponsored research and clinical trial agreements:

Ongoing Clinical Trial and Sponsored Research Agreements

IL13Rα2 (MB-101) Clinical Research Support Agreements with City of Hope

Since February 2017, the Company has been party to a clinical research support agreement for the IL13Rα2-directed CAR T program (the “IL13Rα2 CRA”) with COH, whereby, the Company has agreed to contribute $0.1 million related to patient costs in connection with the on-going investigator-initiated study.

Since October 2020, the Company has been party to a clinical research support agreement for the IL13Rα2-directed CAR T program for adult patients with leptomeningeal glioblastoma, ependymoma or medulloblastoma (the “IL13Rα2 Leptomeningeal CRA”) with COH, whereby the Company has agreed to contribute $0.1 million per patient in connection with the ongoing investigator-initiated study. Further, the Company agreed to fund approximately $0.2 million annually pertaining to the clinical development of the IL13Rα2-directed CAR T program for this patient population.

Since October 2020, the Company has been party to a Sponsored Research Agreement (“SRA”) with COH to conduct combination studies of a potential IL13Rα2* *CAR (MB-101) and herpes simplex-1 oncolytic virus therapy (MB-108). Pursuant to the SRA, the Company funded research in the amount of $0.3 million for the program. In November 2022, the SRA was amended and the Company funded an additional $0.6 million.

CD20 (MB-106) Clinical Trial Agreement with Fred Hutchinson Cancer Center

Since July 3, 2017, in conjunction with the CD20 Technology License from Fred Hutchinson Cancer Center (“Fred Hutch”), the Company has been party to an investigator-initiated clinical trial agreement (the “CD20 CTA”) to provide partial funding for a Phase 1/2 clinical trial at Fred Hutch evaluating the safety and efficacy of the CD20 Technology in patients with relapsed or refractory B-cell non-Hodgkin lymphomas. In connection with the CD20 CTA, the Company agreed to fund up to $5.3 million of costs associated with the clinical trial, which commenced during the fourth quarter of 2017. In November 2020, the CD20 CTA was amended to include additional funding of approximately $1.8 million, which includes $0.8 million for the treatment of five patients with chronic lymphocytic leukemia. In January 2022, the CD20 CTA was amended to include additional funding of $2.2 million increasing the total payment obligation of the Company in connection with the CD20 CTA not to exceed $9.3 million.

Terminated Clinical Trial and Sponsored Research Agreements

In May 2023, the Company determined to discontinue development of certain programs, including CS1 (MB-104) and PSCA (MB-105), and terminated the associated CRA and license with COH. In April 2024, the Company terminated its license agreement and the associated Data Transfer Agreement with St. Jude, in exchange for a mutual release of liability and forgiveness by St. Jude of all amounts previously owed by the Company, which totaled approximately $0.6 million. Additionally, in April 2024, the Company delivered a termination notice to LUMC, pursuant to which it terminated the license agreement underpinning the MB-110 product candidate; the Company is currently in discussions with LUMC regarding the terms that will govern such termination In June 2024, the Company terminated its license agreement and associated SRA with the Mayo Clinic, in exchange for a mutual release of liability and forgiveness by Mayo Clinic of all amounts previously owed by the Company, which totaled approximately $0.3 million. The forgiven amounts, totaling approximately $0.9 million, were recognized as a reduction of research and development expenses in the Statements of Operations.

Note 4 - Related Party Agreements

Founders Agreement and Management Services Agreement with Fortress

Effective March 13, 2015, the Company entered a Founders Agreement with Fortress, which was amended and restated on May 17, 2016, and again on July 26, 2016 (the “Mustang Founders Agreement”). The Mustang Founders Agreement provides that, in exchange for the time and capital expended in the formation of Mustang and the identification of specific assets the acquisition of which result in the formation of a viable emerging growth life science company, Fortress loaned $2.0 million, representing the up-front fee required to acquire the Company’s license agreement with COH. The Mustang Founders Agreement has a term of 15 years, which upon expiration automatically renews for successiveone-year periods unless terminated by Fortress and the Company or a Change in Control (as defined in the Mustang Founders Agreement) occurs. Concurrently with the second amendment on July 26, 2016, to the Mustang Founders Agreement, Fortress entered into an Exchange Agreement whereby Fortress exchanged its 7.25 million Class B Common shares for 9,333 common shares and 250,000 Class A Preferred shares. Class A Preferred Stock is identical to common stock other than as to voting rights, conversion rights and the Annual Stock Dividend right (as described below). Each share of Class A Preferred Stock is entitled to vote the number of votes that is equal to one and one-tenth (1.1) times a fraction, the numerator of which is the sum of (A) the shares of outstanding Mustang common stock and (B) the whole shares of Mustang common stock into which the shares of outstanding Class A Common Stock and Class A Preferred Stock are convertible and the denominator of which is the number of shares of outstanding Class A Preferred Stock. Thus, the Class A Preferred Stock will at all times constitute a voting majority. Each share of Class A Preferred Stock is convertible, at Fortress’ option, intoone fully paid and nonassessable share of Mustang common stock, subject to certain adjustments. As holders of Class A Preferred Stock, Fortress will receive on each January 1 (each a “Annual Stock Dividend Payment Date”) until the date all outstanding Class A Preferred Stock is converted into common stock, pro rata per share dividends paid in additional fully paid and nonassessable shares of common stock (“Annual Stock Dividends”) such that the aggregate number of shares of common stock issued pursuant to such Annual Stock Dividend is equal to two and one-half percent (2.5%) of Mustang’s fully-diluted outstanding capitalization on the date that isone (1) business day prior to any Annual Stock Dividend Payment Date. The Company records the value of all shares issued for the Annual Stock Dividend as research and development – licenses expense in its Statements of Operations.

Pursuant to the Amended and Restated Articles of Incorporation, the Company issued 69,046 shares of common stock to Fortress for the Annual Stock Dividend, representing 2.5% of the fully-diluted outstanding equity of Mustang on January 1, 2025. The value of these shares is shown in the Statement of Stockholders’ Equity at December 31, 2024, as Common stock issuable – Annual Stock Dividend. The Company recorded an expense of approximately $0.6 million in research and development – licenses acquired related to these issuable shares during the year ended December 31, 2024.

Pursuant to the Amended and Restated Articles of Incorporation, the Company issued 7,061 shares of common stock to Fortress for the Annual Stock Dividend, representing 2.5% of the fully-diluted outstanding equity of Mustang on January 1, 2024. The value of these shares is shown in the Statement of Stockholders’ Equity at December 31, 2023, as Common stock issuable – Annual Stock Dividend. The Company recorded an expense of approximately $0.5 million in research and development – licenses acquired related to these issuable shares during the year ended December 31, 2023.

As additional consideration under the Mustang Founders Agreement, Mustang will also: (i) pay an equity fee in shares of common stock, payable within five (5) business days of the closing of any equity or debt financing for Mustang that occurs after the effective date of the Mustang Founders Agreement and ending on the date when Fortress no longer has majority voting control in the Company’s voting equity, equal to two and one-half (2.5%) of the gross amount of any such equity or debt financing, with the number of shares issuable based on the share price of the equity round or, in the instance of debt financing, the closing price of the Company’s common shares on the day prior to the closing; and (ii) pay a cash fee equal to four and one-half percent (4.5%) of the Company’s annual net sales, payable on an annual basis, within ninety (90) days of the end of each calendar year. In the event of a Change in Control, the Company will pay a one-time change in control fee equal tofive (5x) times the product of (A) net sales for thetwelve (12) months immediately preceding the change in control and (B) four and one-half percent (4.5%). The Company records the value of all shares issued for the equity fee component of the Mustang Founders Agreement as Stock-based compensation expense in its Statements of Operations.

For the year ended December 31, 2024, the Company issued 23,450 shares of common stock to Fortress, which equaled 2.5% of the sum of the gross proceeds of $2.6 million from the sale of shares of common stock under Mustang’s At-the-Market Offering, $4.0 million gross proceeds from the May 2024 Public Offering, $2.5 million from the June 2024 PIPE, and $4.0 million from the October 2024 warrant exercise. The Company recorded an expense of approximately $0.3 million in general and administrative expenses related to these shares for the year ended December 31, 2024.

For the year ended December 31, 2023, the Company did not issue any shares of common stock and recorded the value of 1,319 shares issuable to Fortress, which equaled 2.5% of the sum of the gross proceeds of $0.2 million from the sale of shares of common stock under Mustang’s At-the-Market Offering and $4.4 million gross proceeds on the Registered Direct Offering. The shares were subsequently issued on January 2, 2024. The Company recorded an expense of approximately $0.1 million in general and administrative expenses related to these shares for the year ended December 31, 2023.

Effective as of March 13, 2015, the Company entered into a Management Services Agreement (the “MSA”) with Fortress, pursuant to which Fortress renders advisory and consulting services to the Company. The MSA has an initial term offive years and is automatically renewed for successive five-year terms unless terminated in accordance with its provisions. Services provided under the MSA may include, without limitation, (i) advice and assistance concerning any and all aspects of the Company’s operations, clinical trials, financial planning and strategic transactions and financings and (ii) conducting relations on behalf of the Company with accountants, attorneys, financial advisors and other professionals (collectively, the “Services”). The Company is obligated to utilize clinical research services, medical education, communication and marketing services and investor relations/public relation services of companies or individuals designated by Fortress, provided those services are offered at market prices. However, the Company is not obligated to take or act upon any advice rendered from Fortress and Fortress shall not be liable for any of its actions or inactions based upon their advice. Pursuant to the MSA and the Company’s Certificate of Incorporation, Fortress and its affiliates, including all members of the Company’s Board of Directors, will have no fiduciary or other duty to communicate or present any corporate opportunities to the Company or to refrain from engaging in business that is similar to that of the Company. In consideration for the Services, the Company will pay Fortress an annual consulting fee of $0.5 million (the “Annual Consulting Fee”), payable in advance in equal quarterly installments on the first business day of each calendar quarter in each year, provided, however, that such Annual Consulting Fee shall be increased to $1.0 million for each calendar year in which the Company has net assets in excess of $100 million at the beginning of the calendar year. The Company records fifty percent of the Annual Consulting Fee in research and development expense andfifty percent in general and administrative expense in the Statement of Operations. For the years ended December 31, 2024 and 2023, the Company recorded expense of $0.5 million and $0.5 million, respectively, related to this agreement.

Payables and Accrued Expenses Related Party

In the normal course of business Fortress pays for certain expenses on behalf of the Company. Such expenses are recorded as payables and accrued expenses - related party.

Director Compensation

Dr. Rosenwald and David Jin

Pursuant to the terms of the Director Compensation Plan, Dr. Rosenwald and Mr. Jin will receive a cash fee of $50,000 per year paid quarterly and an annual stock award of the greater of (i) a number of shares of common stock having a fair market value on the grant date of $50,000 or (ii)200 shares of common stock, which shares shall vest and become non-forfeitable on the third anniversary of the grant date, subject to continued service on the Board on such date.

For the year ended December 31, 2024, the Company recognized $50,000 and $12,500 for Dr. Rosenwald and Mr. Jin, respectively, in expense in its Statements of Operations related to the director compensation. For the year ended December 31, 2023, the Company recognized $100,000 in expense in its Statements of Operations related to the director compensation, including approximately $50,000 in expense related to equity incentive grants. The Company issued Dr. Rosenwald 144 restricted stock awards for the year ended December 31, 2023. No restricted stock awards were granted in 2024. We recognized $12,500 in expense in our Statements of Operations related director compensation for Mr. Jin. We have not yet granted any equity awards to Mr. Jin.

Mr. Weiss - Advisory Agreement with Caribe BioAdvisors, LLC

The Board of the Company by unanimous written consent approved and authorized the execution of an advisory agreement dated January 1, 2017 (the “Advisory Agreement”), with Caribe BioAdvisors, LLC (the “Advisor”), owned by Michael S. Weiss, the Chairman of the Board, to provide the board advisory services of Mr. Weiss as Chairman of the Board. Pursuant to the Advisory Agreement, the Advisor will be paid an annual cash fee of $60,000, paid quarterly and an annual stock award of the greater of (i) a number of shares of common stock having a fair market value on the grant date of $50,000 or (ii)200 shares of common stock, which shares shall vest and become non-forfeitable on the third anniversary of the grant date, subject to continued service on the Board on such date.

For the year ended December 31, 2024, the Company recognized $60,000 in expense in its Statements of Operations related to the advisory agreement. For the year ended December 31, 2023, the Company recognized $110,000 in expense in its Statements of Operations related to the advisory agreement, including approximately $50,000 in expense related to equity incentive grants. The Company issued Mr. Weiss 144 shares of restricted stock for the year ended December 31, 2023. No restricted stock awards were granted in 2024.

Note 5 – Asset Purchase Agreements

Agreements with uBriGene

On May 18, 2023, the Company entered into an Asset Purchase Agreement (the “Original Asset Purchase Agreement”) with uBriGene (Boston) Biosciences, Inc., a Delaware corporation (“uBriGene”), pursuant to which the Company agreed to sell its leasehold interest in its cell processing facility located in Worcester, Massachusetts (the “Facility”), and associated assets relating to the manufacturing and production of cell and gene therapies at the Facility to uBriGene (the “Transaction”). The Company and uBriGene subsequently entered into Amendment No. 1 to the Original Asset Purchase Agreement, dated as of June 29, 2023 (“Amendment No. 1”), and Amendment No. 2 to the Original Asset Purchase Agreement, dated as of July 28, 2023 (“Amendment No. 2,” and together with the Original Asset Purchase Agreement and Amendment No. 1, the “Prior Asset Purchase Agreement”).

On July 28, 2023, pursuant to the Prior Asset Purchase Agreement, the Company completed the sale of all of its assets that primarily relate to the manufacturing and production of cell and gene therapies at the Facility (such operations, the “Transferred Operations” and such assets, the “Transferred Assets”) to uBriGene for upfront consideration of $6 million cash (the “Base Amount”). The Transferred Assets included all of the Company’s assets, except for the Company’s lease and related leasehold improvements of the Facility and contracts that are primarily used in the Transferred Operations. The Company recorded a gain of $1.4 million in connection with the sale of the Transferred Assets, and recorded approximately $0.3 million of the base consideration as deferred income, that was to be recognized upon the transfer of the lease.

In connection with the Prior Asset Purchase Agreement, the Company and uBriGene submitted a voluntary joint notice to the U.S. Committee on Foreign Investment in the United States (“CFIUS”). Following CFIUS’s review and subsequent investigation of the transactions related to the Prior Asset Purchase Agreement, on May 13, 2024, the Company, together with uBriGene and CFIUS, executed a National Security Agreement (the “NSA”), pursuant to which the Company and uBriGene agreed to abandon the transactions related to the Prior Asset Purchase Agreement and the agreements entered into in connection therewith. The NSA obligated uBriGene and the Company to terminate agreements between thetwo parties, including the Manufacturing Services Agreement, Quality Services Agreement, and Subcontracting CDMO Agreement. In addition, uBriGene must sell, or otherwise dispose of, the equipment assets purchased within 180 days after the execution of the NSA.

June 2024 Repurchase of Assets

On June 27, 2024 (the “Effective Date”), the Company entered into an Asset Purchase Agreement (the “Repurchase Agreement”) with uBriGene, pursuant to which the Company agreed, subject to the terms and conditions set forth therein, to repurchase the Transferred Assets, primarily lab equipment and supplies, (collectively, the “Repurchased Assets”). Pursuant to the terms of the Repurchase Agreement, the Company and uBriGene also terminated existing manufacturing and services agreements.

As consideration for the Repurchase Agreement, the Company agreed to pay to uBriGene a total purchase price (the “Purchase Price”) of $1.4 million, consisting of (i) an upfront payment of $0.1 million due within five (5) business days of the Effective Date and a (ii) subsequent amount of $1.3 million due on the date that is twelve (12) months after the closing date (the “Deferred Amount”). In the event that as of the original (or any extended) date on which the Deferred Amount is payable, the Company has, as of the date of the public reporting of its then-most recent quarterly audited or unaudited financial statements, net assets below $20 million, then the Company may, upon written notice to uBriGene, elect to delay its payment obligation of the Deferred Amount by an additional six (6) months, with no limit on the number of such extensions available to the Company. Notwithstanding the foregoing, if the Company has not paid the Deferred Amount in full as of the date that is twelve (12) months after closing of the Repurchase Agreement, any amounts that remain outstanding will accrue interest at a rate of 5% per annum beginning on the date that is twelve (12) months after closing and until the Deferred Amount is paid in full. Additionally, in connection with the termination of the agreements described above under the Repurchase Agreement, the Company agreed to forgive a net receivable from uBriGene of approximately $3.3 million, comprised of outstanding receivables of $6.9 million and payables of $3.6 million, resulting in total purchase consideration in the Repurchase Transactions of approximately $4.7 million. The upfront payment of $0.1 million was paid in July 2024, and as of December 31, 2024, the $1.3 million Deferred Amount was recorded in Accrued Other Expenses (see Note 7).

The Company allocated the total purchase consideration of $4.7 million to the Repurchased Assets on a relative fair value basis. The Company used a third party to perform a valuation of the repurchased equipment, which resulted in a fair value less costs to sell of approximately $2.2 million. The remaining purchase consideration of $2.5 million was allocated to the supplies repurchased. The supplies repurchased with no alternative future use were recognized as research and development expense in an amount of $2.2 million. Repurchased supplies with an alternative future use of $0.3 million were also recognized in research and development expense, as the Company does not have plans to resume operations in the facility, and it intends to dispose of the supplies in a single transaction with the equipment. The Company concluded that the disposal group, which includes the repurchased equipment assets and associated supplies, with an aggregate fair value less costs to sell of approximately $2.2 million met the criteria to be classified as held for sale at the date of acquisition. As of December 31, 2024, the disposal group had a fair value less costs to sell of approximately $1.2 million, based primarily on offers received by third parties for the equipment. As such, the Company recorded an adjustment to the fair value less costs to sell of approximately $1.0 million.

Note 6 – Property, Plant and Equipment, and Asset Impairment

For the years ended December 31, 2024 and 2023, property, plant and equipment consisted of the following:

Depreciation expense for the years ended December 31, 2024 and 2023, was approximately $0.7 million and $1.9 million, respectively, and was recorded in research and development expense in the Statements of Operations.

Fixed assets – construction in process primarily reflects buildout costs and equipment that have not yet been placed into service.

Impairment of Long-Lived Assets

During the second quarter of fiscal year 2024, the Company concluded it had a triggering event requiring assessment of impairment for certain leasehold improvements and the related right-of-use asset. The Company assessed the carrying value of the asset group consisting of the leasehold improvements and right-of-use asset in accordance with ASC 360, given the significant changes to the Company’s operations, operating cash and the repurchase of equipment. The assessment of the recoverability of the asset group concluded that there was impairment on the carrying value of the asset group of approximately $2.6 million, which was allocated on a pro rata basis using the relative carrying amounts of the assets. Approximately $2.2 million of the impairment loss was allocated to the leasehold improvements, with the remaining $0.4 million allocated to the right-of-use asset.

Note 7 - Accounts Payable and Accrued Expenses

At December 31, 2024 and 2023, accounts payable and accrued expenses consisted of the following:

(1) Other includes approximately $1.3 million of accrued consideration for the uBriGene Asset Purchase Agreement, see Note 5.

Note 8 - Commitments and Contingencies

Leases

On June 14, 2022, the Company entered into a sublease agreement with The Paul Revere Life Insurance Company. Pursuant to the terms of the sublease lease agreement, the Company agreed to lease 26,503 square feet, located at 1 Mercantile Street, Worcester, MA (the “Mercantile Street Facility”), through January 2030. The Company recorded a right of useasset and related operating lease liability of$2.2 million on the Balance Sheet at the lease inception.

On July 18, 2023, the Company executed, with a retroactive Effective Date of June 15, 2023, a Third Amendment to Sublease (the “Third Amendment”), with the Paul Revere Life Insurance Company, pursuant to which the Company relocated from the 26,503 square feet of rentable space on the fourth floor of the Mercantile Center to 11,916 square feet of rentable space on the second floor of the Mercantile Center. As a result of the modification, the Company recorded an adjustment to its right of use asset and related operating lease liability of $1.0 million and $1.2 million, respectively, and $0.2 million gain on the modification of the sublease, which is recorded in Other Income in the Statements of Operations. On June 28, 2024, the Company terminated the lease of its Mercantile Street Facility for a termination fee of $40,000.

On October 27, 2017, the Company entered into a lease agreement with WCS - 377 Plantation Street, Inc., a Massachusetts nonprofit corporation. Pursuant to the terms of the lease agreement, the Company agreed to lease 27,043 square feet from the landlord, located at 377 Plantation Street in Worcester, MA (the “Plantation Street Facility”), through November 2026, subject to additional extensions at the Company’s option (see Note 13). Base rent, net of abatements of $0.6 million over the lease term, totals approximately $3.6 million, on a triple-net basis.

The terms of the lease also require that the Company post an initial security deposit of $0.8 million, in the form of $0.5 million letter of credit and $0.3 million in cash, which increased to $1.3 million ($1.0 million letter of credit, $0.3 million in cash) on November 1, 2019. After the fifth lease year, the letter of credit obligation is subject to reduction. As of December 31, 2024, the letter of credit was cancelled.

The Company leases office space under an agreement classified as an operating lease that expires in October 2026. The Company’s lease liabilities result from the lease of its Plantation Street Facility in Massachusetts, which expires in 2026. Such leases do not require any contingent rental payments, impose any financial restrictions, or contain any residual value guarantees. Certain of the Company’s leases include renewal options and escalation clauses; renewal options have not been included in the calculation of the lease liabilities and right of use assets as the Company is not reasonably certain to exercise the options. The Company does not act as a lessor or have any leases classified as financing leases.

During the second quarter of fiscal year 2024, the Company identified triggering events that required an impairment of the asset group consisting of the right-of-use asset and associated leasehold improvements. The assessment concluded that impairment existed, and the impairment loss was allocated to the leasehold improvements and right-of-use assets based on the relative carrying amounts of the assets (see Note 6). At December 31, 2024, the Company had operating lease liabilities of $0.9 million and right of use assets of $0.1 million, which were included in the Balance Sheet. At December 31, 2023, the Company had operating lease liabilities of $2.5 million and right of use assets of $1.6 million, which were included in the Balance Sheet.

The following summarizes quantitative information about the Company’s operating leases:

Maturities of our operating leases, excluding short-term leases, are as follows:

Note 9 – Notes Payable

On April 11, 2023, the Company’s long-term debt facility (the “Term Loan”) with Runway Growth Finance Corp. (“Runway”), originally entered into on March 4, 2022, was terminated upon receipt by Runway of a payoff amount of $30.4 million from the Company comprised of principal, interest and the applicable final payment amount. The loss on extinguishment of $2.8 million was recorded in interest expense in the Statements of Operations. For the years December 31, 2024, and 2023, the Company recorded the following components in interest expense:

Note 10 - Stockholders’ Equity

Common Stock

The Company, in accordance with its certificate of incorporation, as amended in November 2020 and June 2021, which was retroactively applied, and July 2022, is authorized to issue (i)200,000,000 common shares with a par value of $0.0001 per share, of which 1,000,000 shares are designated as Class A Common Stock and the remainder are undesignated Common Stock, and (ii)2,000,000 shares of Preferred Stock,250,000 of which are designated as Class A Preferred Stock and the remainder are undesignated Preferred Stock (see below Stock Issuances to Fortress and Note 4).

In connection with the Company’s formation, Fortress subscribed for 7,000,000 shares of the Class B Common Stock and 2,666 shares of the Company’s Common Stock, pursuant to the Founders Agreement. Fortress paid the par value of $900 in 2016. The fair value of the Company’s common shares approximated par value as no licenses had been transferred at that time. In July 2016, the Class B Common Stock held by Fortress was exchanged for Class A Preferred Stock, and the Company amended and restated its Certificate of Incorporation to eliminate the Class B Common Stock and authorized a

new series of Class A Preferred Stock. Dividends, if and when declared, are to be distributed pro-rata to the Class A Common Stock, Common Stock and Class A Preferred Common Stock.

The holders of Common Stock are entitled toone vote per share of Common Stock held. The holders of Class A Common Stock are entitled to the number of votes equal to the number of whole shares of Common Stock into which the shares of Class A Common Stock held by such holder are convertible and for a period often years from its issuance, the holders of the Class A Common Stock have the right to appoint one member of the board of directors of Mustang; to date, the holders of Class A Common Stock have not yet appointed such director.

At-the-Market Offering of Common Stock

In July 2018, the Company entered into an At-the-Market Issuance Sales Agreement (the “Mustang ATM”) with B. Riley Securities, Inc. (formerly B. Riley FBR, Inc.), Cantor Fitzgerald & Co., National Securities Corporation (now B. Riley FBR, Inc.), and Oppenheimer & Co. Inc. (each an “Agent” and collectively, the “Agents”), relating to the sale of shares of common stock pursuant to a registration statement on Form S-3 (File No. 333-249657). Under the Mustang ATM, the Company pays the Agents a commission rate of up to 3.0% of the gross proceeds from the sale of any shares of common stock. On December 31, 2020, the Mustang ATM was amended to add H.C. Wainwright & Co., LLC (“Wainwright”) as an Agent. On April 14, 2023, the Mustang ATM was amended to add the limitations imposed by General Instruction I.B.6 to Form S-3 and remove Oppenheimer & Co., Inc. as an Agent. On May 31, 2024, the Company delivered notice to the Agents to terminate the Mustang ATM, which was effective June 5, 2024.

On May 31, 2024, the Company entered into an At-the-Market Offering Agreement (the “Offering Agreement”) with Wainwright (the “Manager”) under which the Company may offer and sell, from time to time at its sole discretion, shares of its common stock through or to the Manager pursuant to the 2024 S-3. Under the Offering Agreement, the Company pays the Manager a commission of 3.0% of the gross proceeds from the sales of any shares of common stock. The Company will also reimburse the Manager for certain expenses incurred in connection with the Offering Agreement. The Company and the Manager may each terminate the Sales Agreement at any time upon specified prior written notice.

During the year ended December 31, 2024, the Company issued approximately 140,000 shares of common stock at an average price of $18.78 per share for gross proceeds of $2.6 million under the Mustang ATM Agreement. In connection with these sales, the Company paid aggregate fees of approximately $0.1 million for net proceeds of approximately $2.5 million.

During the year ended December 31, 2023, the Company issued approximately 1,034 shares of common stock at an average price of $158.07 per share for gross proceeds of $163,000 under the ATM Agreement. In connection with these sales, the Company paid aggregate fees of approximately $3,000 for net proceeds of approximately $160,000.

Pursuant to the Founders Agreement, the Company issued 3,509 shares of common stock to Fortress at a weighted average price of $18.78 per share for the year ended December 31, 2024. For the year ended December 31, 2023, the Company did not issue any shares of its common stock to Fortress, and recorded the value of 25 shares issuable to Fortress in connection with the Mustang ATM.

May 2024 Equity Offering

On April 29, 2024, the Company commenced a best efforts equity offering with an institutional investor (the “Investor”) (the “May 2024 Offering”) of an aggregate of (i)23,200 shares of common stock, (ii) pre-funded warrants (the “May 2024 Pre-Funded Warrants”) to purchase up to an aggregate of 314,352 shares of common stock (the “May 2024 Pre-Funded Warrant Shares”), (iii) Series A-1 warrants (the “Series A-1 Warrants”) to purchase up to an aggregate of 337,552 shares of common stock (the “Series A-1 Warrant Shares”), (iv) Series A-2 warrants (the “Series A-2 Warrants”) to purchase up to an aggregate of 337,552 shares of common stock (the “Series A-2 Warrant Shares”), and (v) Series A-3 warrants (the “Series A-3 Warrants,” and together with the Series A-1 Warrants and Series A-2 Warrants, the “Warrants”) to purchase up to an aggregate of 337,552 shares of common stock (the “Series A-3 Warrant Shares”). Each share of common stock or May 2024 Pre-Funded Warrant was sold together withone Series A-1 Warrant to purchaseone share of common stock, one Series A-2 Warrant to purchaseone share of common stock, andone Series A-3 Warrant to purchaseone share of common stock. The public offering price for each share of common stock and accompanying Warrants was$11.85, and

the public offering price for each May 2024 Pre-Funded Warrant and accompanying Warrants was$11.845. The May 2024 Pre-Funded Warrants have an exercise price of$0.005 per share, were exercisable immediately and will expire when exercised in full. Each Warrant has an exercise price of$11.85 per share, will be exercisable beginning on the effective date of stockholder approval of the issuance of the shares upon exercise of the Warrants (the “Warrant Stockholder Approval”). The Series A-1 Warrant will expire on thefive-year anniversary of the Warrant Stockholder Approval. The Series A-2 Warrant will expire on thetwenty-four-month anniversary of the Warrant Stockholder Approval. The Series A-3 Warrant will expire on thenine-month anniversary of the Warrant Stockholder Approval. The Warrants contain customary anti-dilution adjustments to the exercise price, including for share splits, share dividends, rights offering and pro rata distributions.

The net proceeds of the May 2024 Offering, after deducting the fees and expenses of the Placement Agent (as defined below), described in more detail below, and other offering expenses payable by us, but excluding the net proceeds, if any, from the exercise of the Warrants, was approximately $3.2 million. The May 2024 Offering closed on May 2, 2024.

In connection with the May 2024 Offering, the Company also entered into a warrant amendment agreement (the “Warrant Amendment Agreement”) with the Investor. Under the Warrant Amendment Agreement, the Company agreed to amend certain existing warrants to purchase up to 51,764 shares of common stock that were previously issued in October 2023 to the Investor, with an exercise price of $79.00 per share (the “Existing Warrants”), in consideration for their purchase of the securities in the May 2024 Offering, as follows: (i) lower the exercise price of the Existing Warrants to $11.85 per share, (ii) provide that the Existing Warrants, as amended, will not be exercisable until the receipt of Warrant Stockholder Approval for the exercisability of the Warrants in the May 2024 Offering, and (iii) extend the original expiration date of the Existing Warrants byfive years following the receipt of such Warrant Stockholder Approval. The Warrant Amendment Agreement became effective on May 2, 2024.

June 2024 Registered Direct Offering and Concurrent Private Placement of Warrants (the “June 2024 Offering”)

On June 19, 2024, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with an institutional investor (the “June 2024 Investor”), pursuant to whichthe Company agreed to issue and sell, in a registered direct offering priced at-the-market under the rules of Nasdaq (the “Registered Direct Offering”), (i)60,500 shares of common stock, at a price per Share of $20.50 and (ii) pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to 62,100 shares of our common stock, at a price per Pre-Funded Warrant equal to $20.495, the price per share of common stock, less $0.005.

The Pre-Funded Warrants were sold in lieu of shares of common stockto the June 2024 Investor. The Pre-Funded Warrants have an exercise price of$0.005 per share, became exercisable upon issuance and remain exercisable until exercised in full.

The net proceeds from the June 2024 Offering, after deducting the fees and expenses of the Placement Agent andother offering expenses payable by us, but excluding the net proceeds, if any, from the exercise of the Warrants, wasapproximately$2.1 million. The June 2024 Offering closed on June 21, 2024.

In a concurrent private placement, pursuant to the terms of the Purchase Agreement, the Company also agreed to issue and sell to the June 2024 Investor unregistered warrants (the “Private Placement Warrants”) to purchase up to 122,600 shares of common stock, at an offering price of $20.50 per Private Placement Warrant to purchaseone share of common stock (the “Private Placement” and, together with the Registered Direct Offering, the “Offerings”) (which offering price was included in the purchase price per share of common stock or Pre-Funded Warrant). The Private Placement Warrants have an exercise price of $0.41 per share (subject to customary adjustments as set forth in the Private Placement Warrants), were exercisable upon issuance and will expire five years from the date of issuance. The Private Placement Warrants contain customary anti-dilution adjustments to the exercise price, including for share splits, share dividends, rights offering and pro rata distributions. The resale of the shares of common stock issuable upon the exercise of the Private Placement Warrants was subsequently registered in July 2024 on a Form S-1 (File No. 333-280927).

Wainwright acted as the exclusive placement agent in connection with the Offerings under an Engagement Letter, dated as of June 18, 2024, between us and Wainwright (the “Engagement Letter”). Pursuant to the Engagement Letter, the

Company issued to Wainwright (or its designees) warrants to purchase up to 7,355 shares of common stock (the “Wainwright Warrants” and, together with the Private Placement Warrants, the “2024 Warrants”). The Wainwright Warrants have substantially the same terms as the Private Placement Warrants, except that the Wainwright Warrants will expire five years from the commencement of the sales of the Offerings and have an exercise price of $25.625 per share (subject to customary adjustment as set forth in the Wainwright Warrants), representing 125% of the purchase price per share of common stock in the Registered Direct Offering.

On October 24, 2024, we entered into an inducement offer letter agreement (the “Inducement Letter”) with a certain investor (the “Holder”) that held outstanding Series A-3 warrants (the “Existing Warrants”) to purchase up to an aggregate of 337,552 shares of our common stock, originally issued to the Holder on May 2, 2024.

Pursuant to the Inducement Letter, the Holder agreed to exercise for cash the Series A-3 warrants at the exercise price of $11.85 per share in exchange for our agreement to issue in a private placement new Series B Common Stock purchase warrants to purchase up to (i)337,552 shares of common stock (the “New Series B-1 Warrant Shares”) and (ii)337,552 shares of common stock (the “New Series B-2 Warrant Shares” and collectively, the “New Warrants”). Each Warrant has an exercise price of $13.50 per share and will be exercisable beginning on the effective date of stockholder approval of the issuance of the shares upon exercise of the Warrants (the “Warrant Stockholder Approval”). The New Series B-1 Warrant will expire on thefive-year anniversary of the Warrant Stockholder Approval. The New Series B-2 Warrant will expire on thetwelve-month anniversary of the Warrant Stockholder Approval.

The closing of the transaction contemplated pursuant to the Inducement Letter occurred on October 25, 2024 (the “Closing Date”). We received aggregate gross proceeds of approximately $4.0 million from the exercise of the Existing Warrants by the Holder, before deducting placement agent fees and other expenses payable by us of approximately $0.4 million.

We engaged Wainwright to act as our exclusive agent in connection with the transaction summarized above and paid Wainwright a cash fee equal to 7.0% of the aggregate gross proceeds from the exercise of the Existing Warrants. In addition, we (i) reimbursed Wainwright for $50,000 of the fees and expenses of Wainwright’s legal counsel and other of its out-of-pocket expenses, (ii) reimbursed Wainwright for its non-accountable expenses in the amount of $25,000, and (iii) paid a management fee equal to 1.0% of the gross proceeds raised. We also issued to Wainwright or its designees (“PA Warrant Holders”) placement agent warrants (the “Wainwright Warrants”) to purchase up to 20,251 shares of Common Stock (the “Wainwright Warrant Shares”). The Wainwright Warrants have the same terms as the New Series B-1 Warrants, except that the Wainwright Warrants have an exercise price equal to $14.815 per share.

The issuance of the New Warrants was accounted for as an equity issuance cost associated with the exercise of the Existing Warrants, which had no net impact on equity as the New Warrants conveyed were determined to be equity classified.

Registration Statements

On April 23, 2021, the Company filed a shelf registration statement on Form S-3 (File No. 333-255476) (the “2021 S-3”), which was declared effective on May 24, 2021. Under the 2021 S-3, the Company was able to sell up to a total of $200.0 million of its securities. The 2021 S-3 expired on May 24, 2024. The Company sold approximately $4.4 million of securities under the 2021 S-3.

On May 31, 2024, the Company filed a shelf registration statement on Form S-3 (File No. 333-279891) (the “2024 S-3”), which was declared effective on June 12, 2024. Under the 2024 S-3, the Company may sell up to a total of $40.0 million of its securities. As of December 31, 2024, approximately $34.8 million of the 2024 S-3 remains available for sales of securities.

As of the filing of this Form 10-K, the Company is subject to the General Instruction I.B.6 to Form S-3, known as the “baby shelf rules,” which limit the number of securities it can sell under its registration statements on Form S-3.

Stock Issuances to Fortress

During the year, the Company issues shares of common stock to Fortress in connection with the Founders Agreement, see Note 4.

Stock Warrants

A summary of warrant activities for the years ended December 31, 2024 and 2023, is presented below:

Upon the exercise of warrants, the Company will issue new shares of common stock. In connection with the Company’s Registered Direct Offering on October 26, 2023, the Company issued pre-funded warrants to purchase up to 33,364 shares of common stock, and in a concurrent private placement, the Company issued unregistered warrants to purchase up to 51,764 shares of common stock, and the resale of the underlying shares of common stock were subsequently registered in April 2024 on Form S-1 (File No. 333-275997). In connection with these offerings, Wainwright received Placement Agent Warrants to purchase up to 3,104 shares of common stock. In connection with the Public Offering the Company completed in May 2024, the 51,764 unregistered warrants were repriced from the original exercise price of $79.00 per share to $11.85 per share.

In connection with the May 2024 Offering, the Company issued pre-funded warrants to purchase up to 314,352 shares of common stock and issued three series of warrants (the “Series A-1,” “Series A-2,” and “Series A-3”) to purchase up to 1,012,656 shares of common stock. In connection with these offerings, Wainwright received Placement Agent Warrants to purchase up to 20,251 shares of common stock.

In connection with the Registered Direct Offering, the Company issued pre-funded warrants to purchase up to 62,100 shares of common stock, and in the concurrent Private Placement, the Company issued unregistered warrants to purchase up to 122,600 shares of common stock. The resale of the underlying shares of common stock were subsequently registered in July 2024 on Form S-1 (File No. 333-280927). In connection with these offerings, Wainwright received Placement Agent Warrants to purchase up to 7,355 shares of common stock.

In connection with the induced warrant exercise in October 2024, the holder of the Series A-3 warrants from the May 2024 Offering agreed to exercise for cash 337,552 warrants in partial consideration for the Company to issued two series of unregistered warrants (the “New Series B-1” and “New Series B-2”) to purchase up to 675,104 shares of common stock. Upon exercise of the Series A-3 warrants, the Company issued to the holder 82,000 of the 337,552 shares of common stock. Due to beneficial ownership limitation provisions in the inducement letter agreement, the remaining 255,552 shares were initially unissued and held in abeyance for the benefit of the holder until notice from the holder that the shares may be issued in compliance with the agreement. As of December 31, 2024,185,880 shares remained in abeyance. In connection with the issuance of the New Series B-1 and New Series B-2 warrants, approximately $7.8 million of the aggregate fair value was deemed to be a dividend and recorded to additional paid-in-capital because the Company had an accumulated deficit on the exercise date. The deemed dividend was included in the net loss attributable to Class A common and common stockholders in the calculation of net loss per share in the Statements of Operations (see Note 2). The resale of the underlying shares of common stock were subsequently registered in November 2024 on Form S-3 (File No. 333-283420). In connection with these offerings, Wainwright received Placement Agent Warrants to purchase up to 20,251 shares of common stock.

The key inputs used for the Black-Scholes Model calculation on October 25, 2024, to measure the fair value of the New Warrants, were as follows:

As of December 31, 2024, all of the pre-funded warrants have been exercised.

Equity Incentive Plan

The Company has in effect the 2016 Incentive Plan (the “Incentive Plan”). The Incentive Plan was adopted in 2016 by our stockholders and the compensation committee of the Company’s board of directors and is authorized to grant stock-based awards to directors, officers, employees and consultants. The plan initially authorized grants to issue up to 2,666 shares of authorized but unissued common stock and expires 10 years from adoption and limits the term of each option to no more than 10 years from the date of grant.

In June 2018, the Company’s stockholders approved an amendment to the Incentive Plan to increase the number of authorized shares issuable by 4,000 shares, for a total of 6,666 shares. In June 2021, the Company’s stockholders approved an amendment to the Incentive Plan to increase the number of authorized shares issuable by 4,000 shares, for a total of 10,666 shares. In June 2022, the Company’s stockholders approved an amendment to the Incentive Plan to increase the number of authorized shares issuable by 4,000 shares, for a total of 14,666 shares

As of December 31, 2024,6,946 shares are available for issuance of stock-based awards under the Incentive Plan.

Stock Options

The following table summarizes stock option activities for the years ended December 31, 2024 and 2023:

As of December 31, 2024, the Company hadno unrecognized stock-based compensation expense related to options. The Company accounts for forfeited awards as they occur as permitted.

Restricted Stock Awards

Certain employees and directors have been awarded restricted stock. The restricted stock vesting consists of milestone and time-based vesting. The following table summarizes restricted stock award activities for the years ended December 31, 2024 and 2023:

As of December 31, 2024, the Company had unrecognized stock-based compensation expense related to restricted stock of $0.2 million, which is expected to be recognized over a weighted average period of approximately 1.1 years.

Restricted Stock Units

The following table summarizes restricted stock units’ activities for the year ended December 31, 2024 and 2023:

As of December 31, 2024, the Company had unrecognized stock-based compensation expense related to restricted stock units of approximately $25,000, which is expected to be recognized over a weighted average period of approximately 1.5 years.

The following table summarizes stock-based compensation expense for the years ended December 31, 2024 and 2023 (in thousands).

Employee Stock Purchase Plan

In connection with our Employee Stock Purchase Plan (“ESPP”), eligible employees of Mustang and Fortress can purchase the Company’s Common Stock at the end of a predetermined offering period at 85% of the lower of the fair market value at the beginning or end of the offering period.

As of December 31, 2024,2,562 shares have been purchased, and 6,771 shares are available for future sale under the Company’s ESPP.

Note 11 - Income Taxes

The Company has accumulated net losses since inception and has not recorded an income tax provision or benefit during the years ended December 31, 2024 and 2023.

A reconciliation of the statutory U.S. federal rate to the Company’s effective tax rate is as follows:

The components of the net deferred tax asset as of December 31, 2024 and 2023 are the following:

The Company has determined, based upon available evidence, that it is more likely than not that the net deferred tax asset will not be realized and, accordingly, has provided a full valuation allowance against its net deferred tax assets as of December 31, 2024 and 2023. A valuation allowance of approximately $152.1 million and $147.7 million, respectively, was recorded for the years ended December 31, 2024 and 2023.

As of December 31, 2024, the Company had federal and state net operating loss carryforwards of approximately $277.7 million and $568.2 million, respectively. Approximately $254.0 million and $0.5 million of the federal and state net operating loss carryforwards, respectively, can be carried forward indefinitely. As of December 31, 2024, the Company had federal and state income tax credits of approximately $15.0 million and $5.1 million, respectively, which will begin to expire in 2034. Under the provisions of Section 382 of the Internal Revenue Code, a corporation that undergoes an “ownership change”, as defined therein, is subject to limitations on its use of pre-change NOLs and income tax credits carryforwards to offset future tax liabilities. Certain tax attributes may be subject to an annual limitation as a result of the

Company’s January 2017 capital raise, as it appears to constitute an ownership change under Section 382. Additionally, under Section 382, annual use of the Company’s net operating loss carryforwards to offset taxable income may be limited based on cumulative changes in ownership. The Company has not completed an analysis to determine whether any such limitations have been triggered as of December 31, 2024. The Company has no income tax effect due to the recognition of a full valuation allowance on all of its deferred tax assets as it believes that it is more likely than not that the deferred tax assets will not be realized regardless of whether an “ownership change” has occurred.

There are no significant items determined to be unrecognized tax benefits taken or expected to be taken in a tax return, in accordance with ASC 740 “Income Taxes” (“ASC 740”), which clarifies the accounting for uncertainty in income taxes recognized in the financial statements, that have been recorded on the Company’s financial statements for the periods ended December 31, 2024 and 2023. The Company does not anticipate a material change to unrecognized tax benefits in the next twelve months.

Additionally, ASC 740 provides guidance on the recognition of interest and penalties related to income taxes. There wereno interest or penalties related to income taxes that have been accrued or recognized as of and for the periods ended December 31, 2024 and 2023.

The Company is subject to U.S. federal and various state taxes. As of December 31, 2024, the earliest federal tax year open for the assessment of income taxes under the applicable statutes of limitations is its 2021 tax year.

Beginning with the 2022 tax year, the Company is required to capitalize research and development expenses for tax purposes as defined under Internal Revenue Code Section 174. For expenses that are incurred for research and development in the U.S., the amounts will be amortized over 5 years, and for expenses that are incurred for research and development outside the U.S., the amounts will be amortized over 15 years. As a result of Section 174 capitalization, the Company recognized a deferred tax asset of $24.4 million.

In response to the COVID-19 pandemic, the Coronavirus Aid, Relief and Economic Security Act ("CARES Act") was signed into law on March 27, 2020. The CARES Act, among other things, includes tax provisions relating to refundable payroll tax credits, deferment of employer's social security payments, net operating loss utilization and carryback periods and modifications to the net interest deduction limitations. The CARES Act did not have a material impact on the Company’s income tax provision for 2024 and 2023. The Company will continue to evaluate the impact of the CARES Act on its financial position, results of operations and cash flows.

On December 27, 2020, the Consolidated Appropriations Act, 2021 (“Consolidated Appropriations Act”) was signed into law. The Consolidated Appropriations Act is intended to enhance and expand certain provisions of the CARES Act, allows for the deductions of expenses related to the Payroll Protection Program funds received by companies, and provides an update to meals and entertainment expensing for 2021. The Consolidated Appropriations Act did not have a material impact on the Company’s income tax provision for 2024 and 2023.

Note 12 – Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources in assessing performance. The Company views its operations and manages its business inone reportable segment, which reflects the research and development of potential cures for difficult-to-treat cancers and autoimmune diseases. The Company’s chief operating decision maker (“CODM”) is the chief executive officer. The primary financial measure by which the CODM evaluates the business is net loss. The CODM uses net loss to monitor budget versus actual results to assess performance of the segment.

The table below summarizes the significant segment expenses reported to the CODM for the years ended December 31, 2024 and 2023:

Note 13 – Subsequent Events

Reverse stock split

On January 15, 2025, the Company filed the Reverse Split Amendment to its Amended and Restated Certificate of Incorporation, as amended, with the Secretary of State of the State of Delaware to effect the Reverse Stock Split.

The Company’s stockholders previously approved the Reverse Stock Split within a range of between 1-for-10 and 1-for-50, with the final ratio to be determined by the board of directors of the Company (the “Board”). On January 6, 2025, the Board selected a final ratio of 1-for-50.

As a result of the Reverse Stock Split, every 50 shares of the Company’s pre-Reverse Stock Split common stock were combined and reclassified as one share of common stock. Proportionate voting rights and other rights of common stockholders were not affected by the Reverse Stock Split, other than as a result of the payment in lieu of issuance of fractional shares. No fractional shares were issued in connection with the Reverse Stock Split. Stockholders who would otherwise hold a fractional share of common stock received (upon surrender to the exchange agent of certificates representing such shares), a cash payment in lieu thereof, without interest or deduction, rounded to the nearest cent, in an amount equal to the product obtained by multiplying (a) the closing price per share of the Company’s common stock as reported on the Nasdaq Capital Market as of the effective date of the Reverse Stock Split, by (b) the fraction of one share owned by the stockholder.

The Reverse Stock Split became effective on January 15, 2025, and the common stock was quoted on the Nasdaq Capital Market on a post-Reverse Stock Split basis at the open of business on January 16, 2025. The Company’s post-Reverse Stock Split common stock has a new CUSIP number, 62818Q302, but the par value and other terms of the common stock were not affected by the Reverse Stock Split.

February 2025 Public Offering

On February 5, 2025, the Company commenced a best efforts public offering (the “Offering”) of an aggregate of (i)495,000 shares (the “Shares”) of its common stock, par value $0.0001 per share, (ii) pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to an aggregate of 2,162,807 shares of common stock (the “Pre-Funded Warrant Shares”), (iii) Series C-1 warrants (the “Series C-1 Warrants”) to purchase up to an aggregate of 2,657,807 shares of common stock (the “Series C-1 Warrant Shares”), and (iv) Series C-2 warrants (the “Series C-2 Warrants,” and together with the Series C-1 Warrants, the “Warrants”) to purchase up to an aggregate of 2,657,807 shares of common stock (the “Series C-2 Warrant Shares,” and together with the Series C-1 Warrant Shares, the “Warrant Shares”). Each Share or Pre-Funded Warrant was sold together withone Series C-1 Warrant to purchaseone share of common stock and one Series C-2 Warrant to purchaseone share of common stock. The combined public offering price for each Share and accompanying Warrants was $3.01, and the combined public offering price for each Pre-Funded Warrant and accompanying Warrants was $3.0099. The Pre-Funded Warrants have an exercise price of $0.0001 per share, are exercisable immediately upon issuance and will expire when exercised in full. Each Warrant has an exercise price of $3.01 per share and will be exercisable beginning on the effective date of stockholder approval of the issuance of the Warrant Shares (the “Warrant Stockholder Approval”). The Series C-1 warrants will expire five years from the Warrant Stockholder Approval and the Series C-2 warrants will expire twenty-four months from the Warrant Stockholder Approval.

The net proceeds of the Offering, after deducting the fees and expenses of the Placement Agent (as defined below), described in more detail below, and other offering expenses payable by the Company, but excluding the net proceeds, if any, from the exercise of the Warrants, is approximately $6.9 million. The Offering closed on February 10, 2025.

Pursuant to an Engagement Letter (the “Engagement Letter”) with Wainwright (the “Placement Agent”), the Company agreed to pay the Placement Agent in connection with the Offering (i) a cash fee equal to 7.0% of the aggregate gross proceeds raised in the Offering, (ii) a management fee equal to 1.0% of the aggregate gross proceeds raised in the Offering, (iii) up to $100,000 for fees and expenses of the Placement Agent’s counsel and other out of pocket expenses, (iv) a non-accountable expense allowance of $25,000, (v) up to $3,500 for road show expenses, and (vi) $15,950 for the clearing expenses.

Also pursuant to the Engagement Letter, the Company, in connection with the Offering, agreed to issue to the Placement Agent or its designees warrants (the “Placement Agent Warrants”) to purchase up to an aggregate of 159,468 shares of common stock (the “Placement Agent Warrant Shares”) (which represents 6.0% of the Shares and Pre-Funded Warrants sold in the Offering). The Placement Agent Warrants will become exercisable beginning on the effective date of the Warrant Stockholder Approval, have an exercise price of $3.7625 (125% of the combined public offering price per share of common stock and accompanying Warrants) and will terminate on thefive-year anniversary of commencement of sales in the Offering.

Termination of lease and sale of equipment

On February 10, 2025, the Company entered into a Bill of Sale and Surrender Agreement (the “Sale/Surrender Agreement”), effective as of January 31, 2025 (the “Effective Date”), with AbbVie Bioresearch Center Inc., a Delaware corporation (“AbbVie”). The Company was the tenant in the leased premises located at 377 Plantation Street, Worcester, Massachusetts (the “Premises”) under a Lease Agreement, dated as of October 27, 2017 (the “Lease”) with WCS - 377 Plantation Street, Inc., a Massachusetts nonprofit corporation (the “Landlord”). In connection with the entrance into the Sale/Surrender Agreement, the Company also entered into an Escrow Agreement, dated February 10, 2025 (the “Escrow Agreement”), with Bowditch & Dewey, LLP, as escrow agent (the “Escrow Agent”), pursuant to which the Escrow Agent would disburse the Purchase Price (defined herein) pursuant to the terms of the Escrow Agreement.

Pursuant to the terms of the Sale/Surrender Agreement, AbbVie agreed to purchase from the Company, and the Company agreed to sell and convey to AbbVie, certain furniture, fixtures and equipment (“FF&E”), which the Company classified as held for sale as of December 31, 2024, located in the Premises and other items as set forth in the Sale/Surrender Agreement for a purchase price of $1.0 million (the “Purchase Price”). AbbVie also agreed to lease the Premises from the Landlord following the termination of the Lease pursuant to a First Amendment to Lease Agreement (the “Amendment”), dated as of February 7, 2025.

The closing of the transactions described above occurred on February 21, 2025 (the “Closing”), with AbbVie’s issuance of an Acceptance Notice (as defined in the Sale/Surrender Agreement) to the Company stating that a Sufficient Percentage (as defined in the Sale/Surrender Agreement) of the FF&E items listed in the Sale/Surrender Agreement are present in the Premises and functional for their intended purpose without the need for repair or replacement. On February 25, 2025, as a result of the issuance of the Acceptance Notice, pursuant to the terms of the Escrow Agreement, the Escrow Agent released the Purchase Price to the Company.

Nasdaq Continued Listing Requirements

On May 16, 2024, the Company was notified by the Staff of the Listings Qualification Department (the “Staff”) of The Nasdaq Stock Market LLC (“Nasdaq”) that the Company’s closing bid price was below $1.00 per share for 30 consecutive business days, and that, therefore, the Company was not in compliance with Nasdaq Listing Rule 5550(a)(2) (the “Bid Price Rule”), which is the minimum bid price requirement for continued listing on the Nasdaq Capital Market. Under a decision by the Nasdaq Hearings Panel (the “Panel”), the Company was provided until January 31, 2025, to satisfy the Bid Price Rule for at least 10 consecutive trading days. The Company effected a 1-for-50 reverse stock split on January 15, 2025, which was intended to bring the Company into compliance with Nasdaq’s Bid Price Rule. On February 10, 2025, the Company was notified by the Staff that it had regained compliance with the Bid Price Rule.

On March 13, 2024, the Company was notified by the Staff that the Company was not in compliance with the minimum stockholders’ equity requirement under Nasdaq Listing Rule 5550(b)(1) (the “Equity Rule”) for continued listing on the Nasdaq Capital Market. Under a decision by the Panel, the Company was provided until February 18, 2025, to evidence compliance with the Equity Rule. The Company completed a best-efforts public offering for net proceeds of approximately $6.9 million, which closed on February 10, 2025. Following the closing, the Company provided an updated forecast to the Panel evidencing compliance with the Equity Rule. On February 26, 2025, the Company was notified by the Staff that it had regained compliance with the Equity Rule and is subject to mandatory monitoring by the Panel for one year.

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Pursuant to the requirements of the Securities Exchange Act of 1934, this Form 10-K has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.