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cas
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 10-K
(Mark One)
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ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 |
For the fiscal year ended December 31, 2025
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TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to |
Commission File Number 001-41259
ARCELLX, INC.
(Exact name of Registrant as specified in its Charter)
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Delaware |
47-2855917 |
(State or other jurisdiction of incorporation or organization) |
(I.R.S. Employer Identification No.) |
800 Bridge Parkway Redwood City, CA 94065 |
94065 |
(Address of principal executive offices) |
(Zip Code) |
Registrant’s telephone number, including area code: (240) 327-0630
Securities registered pursuant to Section 12(b) of the Act:
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Trading Symbol(s) |
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Name of each exchange on which registered |
Common Stock, $0.001 par value per share |
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ACLX |
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The Nasdaq Global Select Market |
Securities registered pursuant to Section 12(g) of the Act: None
Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☒ No ☐
Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. Yes ☐ No ☒
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.
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Large accelerated filer |
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Accelerated filer |
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Non-accelerated filer |
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Smaller reporting company |
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Emerging growth company |
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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 has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☒
If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐
Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐
Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes ☐ No ☒
The aggregate market value of the registrant's common stock, par value $0.001 per share, held by non-affiliates of the registrant on June 30, 2025, the last business day of the registrant's most recently completed second fiscal quarter, was approximately $3.2 billion based on the closing price of the registrant's common stock on the Nasdaq Global Select Market on that date. Exclusion of shares held by any person should not be construed to indicate that such person possesses the power, direct or indirect, to direct or cause the direction of management or policies of the registrant, or that such person is controlled by or under common control with the registrant.
The number of shares of Registrant’s Common Stock outstanding as of February 20, 2026 was 58,479,812.
DOCUMENTS INCORPORATED BY REFERENCE
Portions of the Registrant’s definitive Proxy Statement to be filed with the Securities and Exchange Commission in connection with the Registrant’s 2026 Annual Meeting of Stockholders, which will be filed subsequent to the date hereof, are incorporated by reference into Part III of this Form 10-K. Such Proxy Statement will be filed with the Securities and Exchange Commission not later than 120 days following the end of the Registrant’s fiscal year ended December 31, 2025. Except with respect to information specifically incorporated by reference, the Proxy Statement is not deemed to be filed as part of this Annual Report on Form 10-K.
Table of Contents
“Arcellx,” “we,” “us,” “our,” or “the Company” as used in this Annual Report on Form 10-K refer to Arcellx, Inc. and, where appropriate, our subsidiary, Subdomain, LLC.
Special Note Regarding Forward-Looking Statements
This Annual Report on Form 10-K (Annual Report) contains express or implied forward-looking statements which are made pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1933, as amended (the Securities Act), and Section 21E of the Securities Exchange Act of 1934, as amended (the Exchange Act), that are based on our management’s belief and assumptions and on information currently available to our management. Although we believe that the expectations reflected in these forward-looking statements are reasonable, these statements relate to future events or our future operational or financial performance, and involve known and unknown risks, uncertainties, and other factors that may cause our actual results, performance, or achievements to be materially different from any future results, performance, or achievements expressed or implied by these forward-looking statements. Forward-looking statements in this Annual Report include, but are not limited to, statements about:
•our proposed transaction with Gilead Sciences, Inc. (Gilead) and Ravens Sub, Inc., a wholly owned subsidiary of Gilead (Purchaser), consisting of a tender offer and subsequent merger of Purchaser with and into the Company, and other related matters;
•the expectation that the United States Food and Drug Administration (the FDA) may approve or make a decision regarding the Company's Biologics License Application (the BLA) for anito-cel for patients with relapsed or refractory multiple myeloma (rrMM) on or before the anticipated target Prescription Drug User Fee Act (PDUFA) date of December 23, 2026;
•our plans and ability to commercialize anito-cel for patients with rrMM, if approved, including the geographic areas of focus and sales strategy, ability to scale capacity to meet demand, and the expected number of available treatment centers;
•the size of the market opportunity for our product candidates and our ability to maximize those opportunities;
•the success of competing therapies that are or may become available, including clinical and/or commercial successes of potential competitors;
•the costs, margins, pricing and reimbursement of our product candidates, if approved;
•our ability to maintain our collaborative relationship with Kite Pharma, Inc., a Gilead company (Kite), in connection with the development, manufacturing and commercialization of certain of our product candidates, and obtain benefits therefrom, including Kite’s treatment centers, Kite Konnect, sales coverage and impact on financial metrics, and the speed, reliability, scalability and capacity of Kite’s manufacturing and expected availability of doses at launch and beyond;
•the expected benefits of potential strategic collaborations with third parties, including our collaboration with Kite and our ability to attract additional collaborators with development, regulatory and commercialization expertise;
•our plans relating to the clinical development of our product candidates, including the disease areas to be evaluated;
•the ability of our clinical trials to demonstrate safety and efficacy of our product candidates, and other potentially favorable results;
•the timing, progress, and results of preclinical studies and clinical trials for our programs and product candidates, including statements regarding the timing of initiation, enrollment and completion of studies or trials and related preparatory work, the period during which the results of the trials will become available, and our research and development programs;
•our ability to recruit and enroll suitable patients in our clinical trials;
•our estimates of the number of patients who suffer from the diseases we are targeting and the number of participants that will enroll in our clinical trials;
•the beneficial characteristics, safety, efficacy and therapeutic effects of our product candidates, including expected differentiation from other treatments, and the impact on treatment center operations;
•our plans relating to the further development and manufacturing of our product candidates, including for additional indications that we may pursue;
•our reliance on third parties to conduct clinical trials of our product candidates and manufacture of our product candidates for preclinical studies and clinical trials;
•the timing or likelihood of regulatory filings and approvals, including our expectation to seek special designations, such as orphan drug designation, for our product candidates for various diseases;
•our ability to obtain and maintain regulatory approval of our product candidates;
•our ability to adequately secure our information technology systems and the regulated data stored therein, as required by law;
•existing regulations and regulatory developments in the United States and other jurisdictions;
•our plans and ability to obtain or protect intellectual property rights, including extensions of existing patent terms where available;
•the need to hire additional personnel and our ability to attract and retain such personnel;
•the accuracy of our estimates regarding expenses, future revenue, margin profile or profitability, capital requirements and needs for additional financing;
•our financial performance and expected operational and cash efficiency;
•the sufficiency of our existing cash and cash equivalents and marketable securities to fund our future operating expenses, including our belief that our current cash and cash equivalents and marketable securities are adequate to fund operations into 2028;
•the impact of global economic and political developments on our business, including medical systems and drug pricing reforms, rising inflation and capital market disruptions, military conflicts in Ukraine, Israel, and the Middle East, tariffs, economic sanctions, political instability, pandemics, climate and/or public health emergencies and economic slowdowns or recessions that may result from such developments which could harm our people or business as well as the value of our common stock and our ability to access capital markets; and
•our anticipated use of our existing resources.
Forward-looking statements are not historical facts, but rather are based on current expectations, estimates, assumptions, and projections about the business and future financial results of the pharmaceutical industry, and other legal, regulatory, and economic developments. In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “intend,” “should,” “could,” “would,” “expect,” “plan,” “anticipate,” “believe,” “estimate,” “project,” “predict,” “potential,” “continue,” “likely,” and similar expressions (including their use in the negative) intended to identify forward-looking statements although not all forward-looking statements contain these identifying words. Actual results could differ materially from the results contemplated by these forward-looking statements due to a number of factors, including, but not limited to, those described in Part I, Item 1A (Risk Factors) of this Annual Report.
You should not place undue reliance on forward-looking statements because they involve known and unknown risks, uncertainties, and other factors, which are, in some cases, beyond our control and which could materially affect results. If one or more of these risks or uncertainties occur, or if our underlying assumptions prove to be incorrect, actual events or results may vary significantly from those implied or projected by the forward-looking statements. No forward-looking statement is a guarantee of future performance. You should read this Annual Report and the documents that we reference in this Annual Report and have filed with or furnished to the U.S. Securities and Exchange Commission (the SEC) completely and with the understanding that our actual future results may be materially different from any future results expressed or implied by these forward-looking statements.
The forward-looking statements in this Annual Report represent our views as of the date of this Annual Report. We anticipate that subsequent events and developments will cause our views to change. However, while we may elect to update these forward-looking statements at some point in the future, we have no current intention of doing so except to the extent required by applicable law. You should therefore not rely on these forward-looking statements as representing our views as of any date subsequent to the date of this Annual Report.
PART I
Item 1. Business.
Overview
We are a clinical-stage biotechnology company focused on delivering a new class of innovative immunotherapies for patients with cancer and other incurable diseases. We believe immunotherapies are one of the forward pillars of medicine, and our mission is to advance humanity by engineering immunotherapies that are safer, more effective and more broadly accessible. Although Chimeric Antigen Receptor T-cells (CAR-Ts) have shown benefits to date, they have primarily been constrained to existing biologic structures, which has limited their impact and opportunity. Our novel synthetic binding scaffold, the D-Domain, is designed to overcome the limitations of traditional CAR-Ts. Existing CAR-T therapy solutions, most of which use a biologic-based, single chain variable fragment (scFv) binding domain, tend to be difficult to manufacture, beneficial to a limited segment of patients, often result in high toxicity, and have narrow applicability in treatable indications. We believe we can address these limitations by engineering a new class of D-Domain powered immunotherapies, including classical single infusion CAR-Ts called “ddCARs” and dosable and controllable universal CAR-Ts called “ARC-SparX”, to address hematologic cancers, solid tumors, and indications outside of oncology, such as autoimmune diseases.
Our lead program is a BCMA-targeting ddCAR product candidate called anitocabtagene autoleucel or “anito-cel” (formerly, CART-ddBCMA), which is currently being evaluated in our pivotal Phase 2 iMMagine-1, Phase 3 iMMagine-3, and Phase 2 GEM-AnitoFIRST trials in patients with multiple myeloma (MM). We have partnered anito-cel with Kite Pharma Inc., a Gilead company (Kite), through our co-development/co-commercialization collaboration agreement, as described in more detail in “Licenses and Collaborations” below (the Kite Collaboration Agreement).
In 2024, we completed dosing in our pivotal Phase 2 clinical trial (iMMagine-1) of anito-cel in patients with fourth line or later relapsed or refractory MM (rrMM). In December 2025, we announced interim data from our pivotal iMMagine-1 study in patients with rrMM after three or more prior lines of therapy, which were presented during an oral presentation at the 67th ASH Annual Meeting and Exposition. In 2024, Kite initiated a global Phase 3 randomized controlled clinical trial (iMMagine-3) of anito-cel in patients with second through fourth line rrMM. Kite is manufacturing anito-cel for iMMagine-3 and expects the trial to be fully enrolled by mid-2026. This follows the completion of the technical transfer to Kite, which was announced in May 2024, as well as the transfer of the Investigational New Drug (IND) application for anito-cel in MM, which has been cleared by the U.S. Food and Drug Administration (FDA).
On December 23, 2025, we submitted a BLA for anito-cel to treat patients with fourth line or later rrMM to the FDA. On February 20, 2026, the FDA notified us that it has accepted our BLA with an anticipated PDUFA action date of December 23, 2026. On February 22, 2026, we entered into an Agreement and Plan of Merger (the Merger Agreement) with Gilead and Purchaser, as described in more detail in "Pending Acquisition by Gilead" below (the Merger).
Outside of our collaboration with Kite, we intend to evaluate anito-cel for the treatment of certain non-oncology indications, including some autoimmune disorders. We began dosing patients in a Phase 1 trial in generalized Myasthenia Gravis (gMG) in the second half of 2025. We also are advancing several ARC-SparX programs: ACLX-001, which targets BCMA in rrMM and for which Kite exercised its option under the Kite Collaboration Agreement to negotiate a license in November 2023; our wholly-owned ACLX-002, which targets CD123 in relapsed or refractory acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS); and our wholly-owned ACLX-004, which targets CD33 and CD123 in relapsed or refractory AML.
In December 2025, at the American Society of Hematology (ASH) Annual Meeting, we presented interim data from our pivotal Phase 2 iMMagine-1 trial evaluating anito-cel, in patients with rrMM after three or more prior lines of therapy. We believe these results further demonstrate that our D-Domain technology can potentially provide meaningful clinical benefits. As of the October 7, 2025 data cutoff date for the iMMagine-1 ASH presentation, the 117 patients dosed in the study had a median follow-up of 15.9 months. All patients received a single infusion of anito-cel (target dose of 115×106 CAR+ T cells). Within the study population, 102 of 117 patients (87%) were triple refractory, 48 of 117 patients (41%) were penta refractory, 21 of 117 patients (18%) had extramedullary disease, and 47 of 117 patients (40%) had high risk cytogenetics. Patients received a median of three prior lines of
therapy, with 65 of 117 patients (56%) having received three prior lines. Efficacy was assessed by an Independent Review Committee (IRC) using the 2016 International Myeloma Working Group (IMWG) uniform response criteria for MM.
Key highlights from the interim data presented for iMMagine-1 as of the October 7, 2025 data cutoff date are as follows:
•For the 117 patients with median follow-up of 15.9 months:
•96% (112 of 117) overall response rate (ORR) achieved;
•86 of 117 (74%) patients achieved complete response (CR) or a stringent complete response (sCR); and
•103 of 117 (88%) patients achieved very good partial response (VGPR) or higher.
•Of the overall MRD evaluable group, 91 of 96 patients (94.8%) were MRD-negative at a minimum of 10-5 sensitivity and 68 of 87 patients (78.2%) were MRD-negative at a minimum of 10-6 sensitivity. Of the MRD evaluable group with sufficient follow up, 54 of 65 patients (83.1%) were MRD-negative for at least 6 months at a minimum of 10-5 sensitivity.
•Median progression free survival (PFS), and overall survival (OS) were not reached, as less than half of all dosed subjects had experienced an event of progression or death.
•Using the Kaplan-Meier analysis, which calculates the cumulative survival probability in any given length of time through analysis of subjects who have had an event (death or progression) within specified time intervals:
•PFS rates, which reflect the percentage of patients who are alive and have not progressed, at 6, 12, 18, and 24 months were 93%, 82% and 67%, and 62%, respectively;
•OS rates, which reflect the percentage of patients who are alive at 6, 12, 18 and 24 months were 96%, 94%, 88%, and 83%, respectively.
To date, no delayed neurotoxicities, including no Parkinsonism, no cranial nerve palsies, no Guillain-Barré syndrome, and no immune effector cell-associated enterocolitis have been observed with anito-cel with all patients dosed more than 12 months ago.
Additionally, in December 2024, at the ASH Annual Meeting, we had presented updated data from our ongoing Phase 1 clinical trial for anito-cel for the treatment of rrMM. As of the October 3, 2024, data cutoff date, 38 patients were evaluable for safety and efficacy analysis using IMWG uniform response criteria for MM. These evaluable patients comprised the dose escalation cohorts for the first dose level (DL1) (n=6), the second dose level (DL2) (n=6), and a dose expansion cohort of DL1 (n=26).
Key highlights from the data presented are as follows:
•For the 38 efficacy evaluable patients with median follow-up of 38.1 months, per IMWG criteria:
•30 of 38 (79%) patients achieved CR or sCR; and
•35 of 38 (92%) patients achieved VGPR or higher.
•Of those evaluable for MRD testing (n=28), 25 (89%) were MRD-negative at a minimum of 10-5 sensitivity.
•With a median follow-up of 38.1 months, median OS was not reached and the estimated Kaplan-Meier median PFS for the study population was 30.2 months.
•The safety profile was manageable and consistent with prior data presentations, including no delayed or non-ICANS neurotoxicities observed, including no Parkinsonism, no cranial nerve palsies, and no Guillain-Barré syndrome.
Overall, patients enrolled in the Phase 1 trial had poor prognostic factors with 26 of 38 (68%) patients being penta-refractory and all 38 patients being triple refractory, with a median of four prior lines of therapy. 20 of 38 (53%) patients were aged 65 or older at time of dosing. 26 of 38 (68%) patients had at least one high-risk prognostic feature, defined as a patient with extramedullary disease (EMD); International Staging System (ISS) Stage III (defined as serum ß2 micro globulin value that is greater than or equal to 5.5 mg/L); High Risk Cytogenetics (Del17p, t(14;16), or t(4;14)); or greater than or equal to 60% bone marrow plasma cells (BMPC). Patients with these high-risk prognostic features have been reported to experience lower CR rates and shorter duration of response (DOR) in clinical trials of other BCMA-targeting CAR-T therapies. All patients enrolled scored 0 or 1 on the Eastern Cooperative Oncology Group Performance Status Scale and the subtypes of MM were representative of the natural distribution of MM subtypes.
We believe these results from our pivotal Phase 2 iMMagine-1 trial along with the Phase 1 trial of anito-cel, which together supported the filing of a BLA to the FDA in December 2025, demonstrate the potential for anito-cel to become a best-in-class treatment for patients suffering from rrMM, including those considered high risk. MM is the third most common hematological malignancy in the United States and Europe, with approximately 36,000 new cases diagnosed per year in the United States. Although changes in the treatment landscape for MM have increased the rates of and depth of response (antitumor activity), MM is currently considered incurable; and patients typically have a life expectancy of just over five years. We estimate that the size of the global MM market was approximately $26 billion in 2025 and that the current total addressable global CAR-T market for rrMM to be $12 billion or more based on the number of patients who are receiving second line treatments and beyond.
We are also rapidly pursuing clinical development of anito-cel in earlier lines of therapy through our Phase 3 iMMagine-3 clinical trial in second through fourth line rrMM in collaboration with Kite, which is expected to complete enrollment in mid-2026. As described in more detail in “Licenses and Collaborations” below, we are collaborating with Kite to co-develop and co-commercialize anito-cel as well as other autologous and non-autologous CAR-T cell therapies that use the same D-domain BCMA binder for the treatment of MM, pursuant to the Kite Collaboration Agreement.
We have summarized our preclinical and clinical programs in the pipeline chart below and indicated where such programs are subject to the Kite Collaboration Agreement, which is described in “Licenses and Collaborations” below. Except for such partnered programs, we have worldwide rights to all our programs.

* Kite exercised its option to negotiate a license for ACLX-001 and retains one remaining option for a select ARC-SparX program in multiple myeloma and lymphoma
Outside our collaboration with Kite, we are also advancing anito-cel into select autoimmune disorders. In the second half of 2025, we began dosing patients in our Phase 1 clinical trial of anito-cel in gMG, a rare autoimmune disease characterized by severe muscle weakness. In gMG, the body’s immune system mistakenly attacks proteins in the neuromuscular junction, disrupting neuromuscular signaling and preventing muscle contraction. We believe anito-cel's mechanism in targeting plasma cells through BCMA may be a relevant mechanism to address the underlying pathogenesis of disease. We estimate that gMG affects over 100,000 people in the United States and there is no known cure.
We are also advancing our novel ARC-SparX programs. ARC-SparX are adaptable versions of ddCARs where the antigen-targeting region is located on a SparX protein that can be dosed separately from the ARC-T cells, our proprietary D-Domain based universal CAR-T-cells that are designed to activate only when bound to a SparX protein that is bound to an antigen on a cell. We initiated our Phase 1 clinical trial of ACLX-001, the first product candidate developed under our ARC-SparX platform, for the treatment of rrMM in 2022. ACLX-001 is an immunotherapeutic combination composed of our ARC-T-cells and SparX proteins that target BCMA. This trial is intended to establish an ARC-SparX dosing regimen and prepare for ARC-SparX trials in expanded indications. In 2023, Kite exercised its option under the Kite Collaboration Agreement to negotiate a license for ACLX-001. Our lead wholly-owned ARC-SparX indication is AML/MDS, for which we have multiple SparX in development targeting different antigens. We initiated the Phase 1 clinical trial for ACLX-002, an ARC-SparX product candidate targeting CD123, for the treatment of AML/MDS in 2022 and received FDA clearance of an IND application for ACLX-004, which targets CD33 and CD123, for the treatment of AML in 2025.
We believe we are building a broad and scalable pipeline that positions us to capitalize on the potential of our proprietary platform technologies to potentially achieve long-term growth and sustainability within the field of immunotherapy. We believe our therapeutic approaches, ddCAR and ARC-SparX, will enable us to select mechanisms that are most appropriate for each target and indication we may choose to pursue based on underlying disease biology and patient need, such as in solid tumors, including small cell lung cancer (SCLC) and hepatocellular carcinoma (HCC). We are also integrating AI-powered discovery and computational tools to expand the applicability of our platforms.

Our D-Domain platform has broad potential utility for additional cell modalities, targets, therapeutic areas and applications and we plan to expand our pipeline beyond hematologic and solid cancers to autoimmune disease, as well as to allogeneic and other cell types, including through our collaboration with Kite. We believe our preliminary clinical data for anito-cel have demonstrated that D-Domains can potentially provide meaningful clinical benefits. Our D-Domain platform consists of structurally unique binders that are small and stable, which can be consistently manufactured. They can also be modified to generate diverse libraries of proprietary target- binding domains. The small size and structure of our D-Domain binders compared to other antigen binding domains used in CAR constructs, such as scFvs, are illustrated above. In our preclinical studies, we have demonstrated that CARs with D-Domains exhibit higher transduction efficiency, higher surface expression, and lower tonic signaling than CARs with scFvs, which we believe can lead to cell therapies with improved therapeutic benefit and reduced toxicity. From our clinical trials of anito-cel, we reported preliminary data that we believe supports efficacy and safety benefits, as well as potential manufacturability advantages associated with our D-Domain technology.
The recent availability of CAR-T products introduces an unprecedented “living therapeutic” modality that offers benefits well beyond what previous oncology modalities offered. For the first time, these therapeutics directly harness the strength of the patient’s own immune system to significantly reduce, even potentially eradicate, tumors. While CAR-Ts have shown significant progress in extending or improving the lives of patients who often have no other treatment options, there remain limitations to their broader use, including variable long-term efficacy, significant adverse effects, narrow applicability, and limited access. Our mission is to advance humanity by engineering immunotherapies that are safer, more effective, and broadly accessible. We plan to achieve this goal by maximizing the impact of our proprietary D-Domain binders, which may enable CAR-Ts to have distinct advantages that address these limitations, including achieving promising preliminary clinical data with high ORR and durable responses, potentially differentiated safety profile, opportunity to treat a broader group of patients, and potential manufacturability advantages through our D-Domain technology and the partnership with an experienced CAR-T company (see Kite Collaboration Agreement), as detailed in the section entitled “CAR-T Background & Current Limitations” below.
The foundation of our competitive advantage is our proprietary technology, clinical evidence, track record of execution, manufacturing success, and assembly of a proven management team. We believe these advantages, and our recent partnership around our lead program anito-cel with global CAR-T leader, Kite, position us to achieve significant market share in a large and attractive market and to ultimately transform the CAR-T market, contributing to a significant advancement in medicine.
Pending Acquisition by Gilead
Merger Agreement
On February 22, 2026, we entered into the Merger Agreement with Gilead and Purchaser. The Merger Agreement provides for the acquisition of the Company by Gilead in a two-step transaction, consisting of a tender offer (the Offer) followed by a subsequent merger of Purchaser with and into the Company (the Merger and together with the Offer and the other transactions contemplated by the Merger Agreement, the Transactions), with the Company continuing as the surviving corporation.
Pursuant to the Merger Agreement, and upon the terms and subject to the conditions thereof, Purchaser will commence a tender offer, to acquire all of our issued and outstanding shares of common stock, par value $0.001 per share (the Shares), other than any Shares owned immediately prior to the effective time of the Merger by the Company (including shares held in our treasury) and any Shares owned both as of the date of the commencement of the Offer and immediately prior to the effective time of the Merger by Gilead, Purchaser or any other direct or indirect wholly owned subsidiary of Gilead, for (x) $115.00 per Share (the Closing Amount), net to the seller in cash, without interest and subject to any required withholding of taxes, and (y) one contractual contingent value right (a CVR), which will represent the right to receive one contingent payment of $5.00 per CVR, in cash, without interest and subject to any required withholding of taxes, payable upon the achievement of a specified milestone in accordance with the terms and subject to the conditions of a contingent value rights agreement (the CVR Agreement), to be entered into with a rights agent selected by Gilead and reasonably acceptable to us (the Rights Agent) (the Closing Amount plus one (1) CVR together, the Offer Price). The Offer will initially remain open for a minimum of 20 business days from the date of commencement of the Offer, subject to possible extension pursuant to the terms of the Merger Agreement.
The obligation of Purchaser to consummate the Offer is subject to the satisfaction or waiver of customary closing conditions set forth in the Merger Agreement, including that there will have been validly tendered, and not validly withdrawn, in the Offer a number of Shares that, considered together with all other Shares owned by Purchaser and its affiliates, represent one more Share than 50% of the total number of Shares outstanding at the time of the expiration of the Offer. In addition, the obligation of Purchaser to consummate the Offer is conditioned upon, among other things, the accuracy of the representations and warranties of the Company contained in the Merger Agreement (subject to certain materiality exceptions), material compliance by us with our covenants under the Merger Agreement, the expiration or termination of the waiting period applicable to the Offer under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, other specified notices, approvals or clearances in accordance with foreign antitrust laws having been given and obtained, the absence of any law or order prohibiting the consummation of the Offer or the Merger in any jurisdiction in which Gilead or the Company has material business operations, and other customary closing conditions set forth in the Merger Agreement. Consummation of the Offer is not subject to a financing condition.
As soon as practicable following the consummation of the Offer, subject to the terms and conditions of the Merger Agreement, the Merger will be effected under Section 251(h) of the Delaware General Corporation Law, as amended (DGCL), without a meeting or vote of our stockholders.
At the effective time of the Merger (the Effective Time), each Share (other than (i) Shares owned by the Company (including shares held in our treasury), (ii) Shares owned both as of the date of the commencement of the Offer and immediately prior to the Effective Time of the Merger by Gilead, Purchaser, or any other direct or indirect wholly owned subsidiary of Gilead, (iii) Shares irrevocably accepted for purchase pursuant to the Offer and (iv) Shares held by stockholders who have properly exercised and perfected their demands for appraisal of such Shares in accordance with the DGCL and have neither withdrawn nor lost such rights prior to the Effective Time of the Merger) will be converted into the right to receive (A) the Closing Amount in cash, in each case without any interest thereon, subject to any withholding of taxes, plus (B) one (1) CVR (the Merger Consideration).
At the Effective Time, each option to purchase Shares (each, a Company Option) that is then outstanding and unexercised, whether or not vested, and which has a per share exercise price that is less than the Closing Amount, will be canceled and converted into the right of the holder to receive (x) (subject to any applicable withholding taxes) a lump-sum cash payment equal to (i) the excess (if any) of (a) the Closing Amount over (b) the per Share exercise price subject to such Company Option, multiplied by (ii) the total number of Shares subject to such Company Option immediately prior to the Effective Time, plus (y) one (1) CVR for each Share subject to such Company Option immediately prior to the Effective Time. At the Effective Time, each Company Option that is then outstanding and unexercised, whether or not vested, and which has a per share exercise price that is equal to or greater than the Closing Amount, will be canceled with no additional consideration payable therefor.
At the Effective Time, each award of restricted stock units with respect to Shares (each, a Company RSU) that is then outstanding, whether or not vested, will be canceled and converted into the right of the holder to receive (x) (subject to any applicable withholding taxes) a lump-sum cash payment equal to (i) the Closing Amount, multiplied by (ii) the total number of Shares subject to such Company RSU immediately prior to the Effective Time (with the number of Shares underlying any Company RSUs that are subject to performance-based vesting conditions determined based on achievement of actual performance in connection with the Merger, as determined by our board of directors or a committee thereof) and (y) one (1) CVR for each Share subject to such Company RSU immediately prior to the Effective Time.
The Merger Agreement contains certain termination rights for the Company and Gilead, including, among others, the right of (i) the Company to terminate the Merger Agreement in order to enter into a Specified Agreement (as defined in the Merger Agreement) and (ii) Gilead to terminate the Merger Agreement as a result of the board of directors changing its recommendation with respect to the Offer. Upon termination of the Merger Agreement under specified circumstances, we will be required to pay Gilead a termination fee in the amount of $260.0 million.
Contingent Value Rights Agreement
At or prior to the Offer Acceptance Time, Gilead and the Rights Agent will enter into the CVR Agreement. Pursuant to and subject to the terms and conditions of the Merger Agreement, holders of Shares (other than certain exceptions detailed in the Merger Agreement), will be entitled to one (1) CVR for each Share outstanding (A) that Purchaser accepts for payment from such holder pursuant to the Offer or (B) owned by or issued to such holder as of immediately prior to the Effective Time and converted into the right to receive the Merger Consideration from Purchaser pursuant to the Merger Agreement. Each holder of Company Options and Company RSUs will be entitled to one (1) CVR for each Share subject to such Company Option or Company RSU immediately prior to the Effective Time. The CVRs are contractual rights only and not transferable except under certain limited circumstances, will not be certificated or evidenced by any instrument, and will not be registered with the SEC or listed for trading. The CVRs will not have any voting or dividend rights and will not represent any equity or ownership interest in Gilead, Purchaser, the Company or any of their affiliates.
Each CVR will represent a non-tradable contractual contingent right to receive one contingent payment in an amount equal to $5.00 per CVR, in cash, without interest (except deemed interest for tax purposes, as applicable), payable if, after the closing of the Merger, the cumulative worldwide Sales (as defined in the CVR Agreement) of the anito-cel product exceed $6.0 billion on or prior to December 31, 2029.
There can be no assurance that any CVR Payment will be received.
Tender and Support Agreements
On February 22, 2026, in connection with the execution and delivery of the Merger Agreement, entities affiliated with New Enterprise Associates, entities affiliated with SR One Capital Fund I Aggregator, L.P., each of our directors and executive officers and certain other members of our management team (collectively, the Support Stockholders), solely in their respective capacities as stockholders of the Company, each entered into a tender and support agreement (collectively, the Support Agreements) with Gilead and Purchaser, pursuant to which each Support Stockholder agreed, among other things, (i) to tender all of its, his or her Shares, (ii) to vote against other proposals to acquire the Company and for any proposal for the Merger and (iii) to certain other restrictions on its, his or her respective ability to take actions with respect to the Company and its or his or her Shares. The Support Stockholders collectively own or control an aggregate of approximately 10.3% of the outstanding Shares as of February 19, 2026. Each of the Support Agreements will terminate upon the first to occur of (a) the valid termination of the Merger Agreement in accordance with its terms, (b) the Effective Time, (c) the termination thereof by written notice from Gilead to the Support Stockholders or (d) any amendment or change to the Merger Agreement or the Offer that is effected without the Stockholder’s consent that decreases the amount, or changes the form, of consideration payable to all stockholders of the Company pursuant to the terms of the Merger Agreement.
For additional information related to the Merger Agreement and the transactions contemplated thereby, please refer to the relevant materials that we have filed and will file with the SEC and that will contain important information about the Company and the Transactions.
Our Strategy
Our strategy to achieve our mission is as follows:
•In collaboration with Kite, advance anito-cel to treat MM patients in the United States and abroad;
•Evaluate anito-cel for the treatment of certain non-oncology indications, including selected autoimmune disorders;
•Enable greater access to CAR-T therapy through clinical trials in broader patient populations that support improved market access;
•Invest in building out infrastructure and technologies that lower customer friction, increase capacity and improve responsiveness;
•Develop a comprehensive ARC-SparX AML/MDS program;
•Expand our pipeline, including to select solid tumor indications and indications outside of oncology;
•Apply our D-Domain technology outside of autologous CAR-T solutions, including through our collaboration with Kite;
•Leverage AI, machine learning, and other novel technologies to drive our discovery efforts; and
•Opportunistically pursue strategic partnerships and collaborations, such as our collaboration with Kite, to maximize the full potential of our platform.
Our Team
Our team and culture are critical to realizing our vision of reimagining immunotherapies as one of the future pillars of medicine.
We are led by a diverse team of executives with significant experience in business, discovery, development, manufacturing, and commercialization of differentiated and novel therapies specifically in the fields of oncology, CAR-T and rare diseases. Rami Elghandour, our Chairman and Chief Executive Officer, previously served as President and Chief Executive Officer at Nevro where he grew the company from a small private company to a publicly traded commercial organization with nearly $400 million in revenue.
Prior to Nevro, Mr. Elghandour was an investor with Johnson & Johnson Development Corporation where he led several investments, including Nevro’s Series B financing. Our Chief Medical Officer, Christopher Heery, M.D., an oncologist by training, was the former Head of Clinical Trials Group for the Laboratory of Tumor Immunology and Biology at the National Cancer Institute, and previously served as Chief Medical Officer at Precision Biosciences and Bavarian Nordic. Our Chief Financial Officer, Michelle Gilson, was previously a senior equity research analyst covering the biotechnology sector, most recently as a Managing Director at Canaccord Genuity.
We have attracted a diverse and talented group of innovators and company builders to help us execute our strategy and to build a transformative CAR-T platform company. Collectively, we are driven by our shared purpose and our values.
As of December 31, 2025, we had 209 full-time employees and we are committed to continuing to build and maintain a diverse and inclusive organization. We believe focusing on diversity and inclusion is not only the right thing to do but is also a competitive advantage. We also believe talent is equally distributed across gender, ethnicity and is not overly represented in any single group. As such, we believe focusing on building high performance teams naturally leads to building diverse teams. We are purposeful in our efforts to create a culture and environment that attracts and retains top talent, including talent from underrepresented groups as reflected in the diversity throughout our organization:
•Total Company: 54% female; 76% diverse (gender, racial & ethnic representation);
•Board of Directors: 50% female; 75% diverse;
•Executive Leadership: 60% female; 90% diverse;
•Directors roles: 50% female; 66% diverse;
•Managers and senior scientists with managerial responsibilities: 46% female; 66% diverse; and
•Technical and Scientific roles: 48% female; 71%diverse.
Demographics are self-reported and diversity numbers are representative of both gender and ethnic diversity. Our commitment to diversity does not stop within the walls of our organization. With our mission of advancing humanity, we believe in equitable access to healthcare. Inclusive research programs that encompass real-world patient populations can contribute to addressing racial inequality in healthcare. We are dedicated to expanding representation within our clinical trials. We also believe deeply in corporate social responsibility and being conscious stewards in our society. We are devoted to leveraging our science to make a positive impact for the patient and local communities we serve. As our organization expands, we intend to grow our community involvement and outreach efforts and establish our corporate brand as a force for good through corporate philanthropy, patient advocacy, and employee volunteerism.
CAR-T Background & Current Limitations
Background
T-cells are a key component of the immune system that can target diseased cells for elimination through the recognition of cell surface antigens. A growing understanding of the immune system over the years and advances in cell, gene and protein engineering have led to approved genetically modified CAR-T products.
Genetically modified CAR-T involves isolating immune cells, modifying them outside of the patient’s body and then reintroducing them into the patient to destroy diseased cells. Such cell therapies have largely focused on using the patient’s own T-cells (autologous approach) to express engineered antigen receptor complexes, such as TCRs or CARs. The extracellular binding domain of the TCR or CAR recognizes the antigen, and, after the T cell binds with the cell expressing the antigen, the intracellular signaling domain induces cell killing and activates pathways specific for the T cell’s proliferation and survival.
The recent availability of CAR-T products introduced an unprecedented “living therapeutic” modality that offers benefits well beyond what previous oncology modalities offered. For the first time, these therapeutics directly harness the strength of the patient’s own immune system to significantly reduce, even potentially eradicate, tumors. Initially evaluated in indications where patients were refractory to multiple lines of therapy and had generally exhausted their therapeutic options, CAR-Ts have shown response rates that exceed many other available modalities, and are now being evaluated in earlier line settings. Particularly striking is that these responses are achieved with a single, personalized administration of the CAR-T, generally achieving rapid and durable responses with
toxicities resolving in days to weeks. This transformative therapy results in extended quality of life benefits without maintenance or additional treatment.
As of December 31, 2025, there are seven FDA approved CAR-T cell therapies:
•Carvykti (ciltacabtagene autoleucel), which has been approved by the FDA for treatment of adult patients with rrMM after one or more prior line of therapy including a proteasome inhibitor and an immunomodulatory agent, and are refractory to lenalidomide;
•Abecma (idecabtagene vicleucel), which has been approved by the FDA for treatment of adult patients with rrMM after two or more prior lines of therapy, including an immunomodulatory agent, a proteasome inhibitor, and an anti-CD38 monoclonal antibody;
•Breyanzi (lisocabtagene maraleucel), which has been approved by the FDA for treatment of adult patients with large B-cell lymphoma (LBCL) that is refractory to first-line chemoimmunotherapy or relapse after first-line chemoimmunotherapy within 12 months or are also ineligible for stem cell transplantation, and relapsed or refractory LBCL after two or more lines of systemic therapy; adult patients with relapsed or refractory chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL) after two or more prior lines of therapy, including a Bruton tyrosine kinase (BTK) inhibitor and B-cell lymphoma 2 (BCL-2) inhibitor under accelerated approval; adult patients with relapsed or refractory follicular lymphoma (FL) after two or more prior lines of systemic therapy under accelerated approval; adult patients with relapsed or refractory mantle cell lymphoma (MCL) after two or more prior lines of systemic therapy including a BTK inhibitor; and adult patients with relapsed or refractory marginal zone lymphoma (MZL) after two or more prior lines of systemic therapy.
•Kymriah (tisagenlecleucel), which has been approved by the FDA for treatment of patients up to 25 years of age with relapsed or refractory B-cell precursor acute lymphoblastic leukemia (ALL) that is refractory or in second or later relapse; adult patients with relapsed or refractory LBCL after two or more lines of systemic therapy; and adult patients with relapsed or refractory follicular lymphoma after two or more lines of systemic therapy;
•Tecartus (brexucabtagene autoleucel), which has been approved by the FDA for treatment of adult patients with relapsed or refractory mantle cell lymphoma under accelerated approval; and adult patients with relapsed or refractory B-cell precursor ALL;
•Yescarta (axicabtagene ciloleucel), which has been approved by the FDA for treatment of adult patients with LBCL that is refractory to first-line chemoimmunotherapy or relapse within 12 months of first-line chemoimmunotherapy, and relapsed or refractory LBCL after two or more lines of systemic therapy; and adult patients with relapsed or refractory follicular lymphoma after two or more lines of systemic therapy under accelerated approval; and
•Aucatzyl (obecabtagene autoleucel), which has been approved by the FDA for treatment of adults with relapsed or refractory B-cell precursor ALL.
Hematologic cancers represent a robust and growing market opportunity for CAR-T cell therapies. These cancers, which include leukemia, lymphoma and myeloma, account for approximately 10% of all cancer incidences in 2025. Sales of CAR-T therapies in hematologic cancers exceeded $5.9 billion in 2025, representing year over year growth of 30%.
Current Limitations
While CAR-T and other genetically modified cell therapies have shown significant progress in extending the lives of patients who often have no other treatment options, there are limitations to their broader use, including:
•Variable Long-Term Efficacy: FDA-approved CAR-Ts may offer higher response rates compared to other available therapies, but efficacy as measured by the DOR is highly variable between different CAR-T programs and also within the same program for different patients. Further, unmet need remains for patients with high-risk prognostic features, who often do not achieve deep, durable responses with other modalities and other CAR-Ts.
•Significant Adverse Effects: Some cell therapies also have the potential to cause several adverse effects. Uncontrolled cellular expansion and off-target binding, and the potentially related side effects such as non-ICANS/delayed neurotoxicities (Parkinsonism, cranial nerve palsies, and Guillain-Barré syndrome) and Immune Effector Cell-associated (IEC-EC) as well as other potential toxicities may stifle the broader use of these therapies in several key ways. Specifically, they may limit the number of patients that are eligible for treatment, complicate adoption into earlier lines of treatment,
preclude the use of these therapies in the non-academic and outpatient settings, and increase costs to patients, payers and providers due to the need for intensive care unit access when they are used.
•Narrow Applicability: Currently, CAR-T and other genetically modified cell therapies are utilized in only a few hematological oncology indications. Their activity in most tumors is primarily driven by a limited number of tumor specific antigen targets. Their utility is further limited by secondary resistance mechanisms arising in the relapsed or refractory settings, as well as the antigen heterogeneity that is characteristic of some of these diseases.
•Limited Access: Due to the potential for severe toxicities, the limited number of treatment centers, supply constraints due to manufacturing complexity and scalability of processes, length of the regulatory process, and the substantial capital requirements for bringing cell therapies to market at scale, CAR-Ts are still not widely available for oncology patients. Further, FDA-approved CAR-Ts are primarily administered and managed in authorized treatment centers, which represent approximately 7-8% of oncology/hematology practices in the United States.
Our Solution
Our mission is to advance humanity by engineering cell therapies that are safer, more effective, and broadly accessible. We plan to achieve this goal by maximizing the impact of our proprietary D-Domain binders, which enable CAR-Ts to have distinct advantages including:
•Promising Clinical Data–High ORR and Durable Responses: In our iMMagine-1 clinical trial of anito-cel in the 117 patients with rrMM, we reported an ORR of 96%, a complete response/stringent complete response (CR/sCR) rate of 74%, and 12-month PFS rate of 82% with a median follow up of 15.9 months. In our Phase 1 trial of anito-cel in 38 patients with rrMM, we reported an ORR of 100%, a CR/sCR rate of 79%, and median PFS of 30 months with a median follow up of 38 months. We believe these results demonstrate the capability of D-Domains not only to effectively bind target antigens and drive CAR-T cell proliferation but also to enable efficient killing of a substantial proportion of tumor cells. High cell surface expression, low propensity for tonic signaling, and fast off-rate of D-Domains may enable more effective interactions between the CAR and the antigen as well as reduced T-cell exhaustion, which may explain the rapid and long-term responses currently observed in our Phase 1 and iMMagine-1 clinical trials. Notably, the durable responses also provide patients a treatment-free interval unique to CAR-T therapies versus other therapeutic modalities in MM.
•Potentially Differentiated Safety Profile: In our clinical trials of anito-cel, we did not observe any non-ICANS/delayed neurotoxicities, including no Parkinsonism, no cranial nerve palsies, and no Guillain-Barré syndrome, and no IEC-EC in the entire population through the follow-up period. Our D-Domains have a low propensity for tonic signaling, high target specificity, and a fast off-rate, which are differentiating characteristics vs. biologics-based CAR-Ts. Additionally, we believe the small and stable structure of the D-Domain enables a high transduction rate, resulting in a high proportion of cells expressing the CAR construct on the cell surface (CAR+ cells), as we observed in our clinical trials of anito-cel. A high proportion of CAR+ cells lowers the total number of T-cells required to be administered which we believe may yield a therapy with an improved toxicity profile, consistent with currently available results of the clinical trials of anito-cel. A 2022 cross-trial safety analysis on CAR-Ts by the FDA supports this concept, finding lower transduction frequency in the CAR-T product was significantly associated with higher rates of severe CRS. Additionally, the lower rates of Grade 3+ infections and non-relapse mortality observed in the iMMagine-1 clinical trial as compared to other late-line rrMM pivotal trials may provide a safety advantage versus other therapeutic options in MM such as bispecifics. Although anito-cel has not been compared in any head-to-head studies to evaluate this potential advantage.
•Opportunity to Treat a Broader Group of Patients: We believe the preliminary positive results of our clinical trials of anito-cel underscores the advantages conferred by our D-Domain binders. The potential safety profile may allow for increased access through outpatient dosing and ability to discharge patients sooner. This may expand access to be more similar to other therapeutic options such as bispecifics. Additionally, we plan to continue to expand our pipeline of D-Domain based CAR-Ts to a wider variety of indications in the future. Based on the differentiation of the D-Domain, and the breadth and depth of our D-Domain libraries, we believe we can expand to a broader group of patients, including those with heterogeneous tumor antigen expression and antigen targets that might be difficult to target. We are currently developing therapies within both our ddCAR and ARC-SparX platforms to treat a broad variety of indications, starting with rrMM, AML/MDS, gMG and, in the future, solid tumors.
•Potential Advantages from D-Domain Manufacturability and Experienced CAR-T Partner: We believe the manufacturing data from our clinical trials of anito-cel demonstrate the potential manufacturing advantages conferred by D-Domains vs. scFv and biologics-based constructs used in CAR-T therapies. Along with the experience and established global CAR-T infrastructure offered by our Kite Collaboration Agreement, which has resulted in high success rates and
reliability in delivering their currently marketed products; we are encouraged by our combined potential to mitigate the supply constraints to support our launch of anito-cel in rrMM. Further, we believe the Kite Collaboration Agreement and the associated economic terms substantially limit our need for additional capital to build out commercial manufacturing infrastructure.
The foundation of our proprietary platform is our D-Domain technology, that has generated promising initial clinical data. We believe our D-Domain technology is a transformational platform that enables us to take the right approach for the right indication within CAR-T. The strengths of the D-Domains are its size, stability, and structure which make it a unique and essential building block for making next generation CAR-Ts to unlock the potential of this therapeutic category which is poised to be one of the forward pillars of medicine. Our method of generating D-Domains, and the individual binders themselves are protected in our patent portfolio, which as of December 31, 2025, includes 51 U.S. and foreign patents and over 100 U.S. and foreign pending applications.
We are generating D-Domains against multiple targets which can then be deployed to create a new class of D-Domain powered CAR-Ts, including ddCAR and ARC-SparX CAR-T therapies, to address hematologic cancers, solid tumors, and indications outside of oncology such as autoimmune diseases. ddCARs are single infusion CAR-Ts enhanced with our D-Domains as the antigen recognition motif. ARC-SparX are adaptable versions of ddCARs where the SparX protein is dosed separately from the ARC-T cell. Our ARC-T-cells are dosable, controllable, universal CAR-Ts designed to activate only when combined with a SparX protein that is bound to an antigen on a cell.

ddCAR Platform
We use our ddCAR platform to generate single infusion therapies where our D-Domain binder replaces the scFvs. The ddCAR is composed of an intracellular T cell signaling domain similar to traditional CARs fused to our D-Domain, which functions as the extracellular antigen binding region. Upon engagement with the antigen on a target cell, the ddCAR signals to activate the T cell to kill the target cell.

The D-Domain was developed to overcome limitations of existing CAR-T therapies by employing a novel synthetic binding domain as a replacement to the traditionally used antigen binding domains for conventional CAR-T therapies, known as scFvs. The result is a structurally unique binder that is small, stable, and can be modified to generate a diverse library of proprietary target-binding domains.
Structurally Unique D-Domains: The unique structural features of our D-Domain may confer the unique combination of properties we observe in our ddCAR product candidates, such as high cell surface expression, high proportion of CAR+ cells (high transduction rate), and low tonic signaling, which we believe have contributed to the efficacy, safety, and manufacturability profile observed in our clinical trials of our lead program anito-cel. D-Domains are short polypeptides that spontaneously fold into a stable triple alpha-helical structure. The D-Domain is derived from a 73 amino acid synthetic protein, α-3D, that has no known homolog in nature or apparent function as first described in a paper by Walsh, et al. that appeared in the Proceedings of the National Academy of Sciences in 1999. This domain is devoid of post-translational glycosylation or disulfide bonds leading to consistent manufacturability via microbial, fungal or mammalian protein expression. Additional key structural features of the D-Domain are as follows:
•Small Size: The figure below showcases the small size of the 8kDa D-Domain compared to other antigen binding domains used in CAR constructs such as the scFv and bi-valent camelid VHh structure of approximately 25kDa. A smaller antigen binding domain will decrease the overall lentiviral construct size which may improve transduction efficiency. The small antigen binding domain may also function to improve the immunological synapse formation and thus CAR-T cell killing.

•Hydrophobic Core: The figure below depicts the three-dimensional structure of the D-Domain highlighting the triple alpha helical bundle with the tight hydrophobic core (in red). The hydrophobic core results in ultrafast folding kinetics of the D-Domain creating a stable structure when expressed in cells.

•Stability: D-Domains are highly stable proteins compared to scFvs which facilitates the high expression of CARs on T-cells and manufacturing of SparX proteins. As shown in the middle panels of the figure below, using size exclusion chromatography, we have demonstrated that a higher level of monomeric protein content can be purified from human embryonic kidney (HEK) 293 cells expressing D-Domain-based SparX proteins compared to scFv, indicating lower levels of aggregation of the D-Domain based SparX proteins and thus greater stability. In addition, we have tested the thermal stability of D-Domains as compared to a PD-L1 binding scFv by heating them to temperatures about 100 degrees Celsius and measuring the retention of PD-L1 binding. As shown in the panels on the far right, D-Domains that were heated to the indicated temperatures retained greater PD-L1 binding as compared to the PD-L1-binding scFv, demonstrating the thermal stability of the D-Domains.

When utilized in CARs, we believe the structural properties of the D-Domain translate into unique benefits of high transduction rates, high cell surface expression, and low tonic signaling. To modify the binding properties of the D-Domain, we can vary the amino acids on the D-Domain scaffold. In the context of ddCARs, we believe the D-Domain structure creates an efficient and scalable cell manufacturing process, as demonstrated by our high CAR+ rate, yield, and viability of cell product made to date. See “Manufacturing and Delivery—anito-cel Cell and ARC-T Cell.”
•High Transduction Rate: In the manufacturing of 38 lots of anito-cel in our Phase 1 clinical trial, the median transduction rate was 70%. In the manufacturing of 117 lots of anito-cel in iMMagine-1, the median transduction rate was 62%. We believe this high transduction efficiency may improve product consistency and reduce the number of untransduced T-cells administered to patients that do not contribute to efficacy but may contribute to toxicity. Our high transduction rate compares favorably with previously published Phase 1 data regarding the transduction rates for Abecma (then known as bb2121) and Carvykti (then known as JNJ-4528), as shown in the left panel of the figure below. While we believe these data suggest that anito-cel has a meaningful advantage in transduction efficiency over existing CAR-T therapies, these data are based on a cross-trial comparison and not a head-to-head clinical trial and may not be directly comparable due to differences in trial designs and methodologies. As manufacturing processes and vectors can also be vastly different across cell products, we also engineered a vector where the D-Domain was replaced by an scFv targeting BCMA while leaving all other conditions identical to isolate the effects on transduction from using a D-Domain as compared to scFv. As shown in the right panel of the figure below, our anito-cel transduced T-cells demonstrated superior transduction efficiency when compared to scFv transduced T-cells derived from multiple normal human donors.

•High Cell Surface Expression: Coincident with higher transduction rates, the expression of the CAR on the surface of the T cell is higher with CARs employing a D-Domain compared with an scFv. As shown in the figure below, when transduced with different CAR constructs, the CAR expression on the surface of T-cells of six normal human donors was uniformly higher using a BCMA-binding D-Domain as compared to a BCMA-binding scFv. We believe that higher CAR cell surface density may help drive activation against low antigen-expressing target cells.
CAR Surface Expression on T Cell

•Low Tonic Signaling: Tonic signaling occurs in CAR-T-cells when the CAR construct signals without engaging an antigen on a target cell, which can exhaust a T cell prematurely. T cell exhaustion has been associated with suboptimal outcomes for CAR-T therapies. Tonic signaling has been described in the literature for several scFv-based CARs. To determine the percentage of D-Domains that induce tonic signaling, we examined 42 D-Domains isolated from two different screening campaigns for their ability to signal without antigen stimulation when incorporated into a CAR construct. Pooled data indicated that only 3 out of the 42 D-Domains exhibited a level of tonic signaling above background, as measured by relative luciferase units, a signal detecting CAR activation, as represented by the blue dots in the left-hand column of the figure below. In contrast, the 42 D-Domains exhibited a much higher level of CAR activation in the presence of the CAR antigen, as illustrated by the right hand column of the figure below. We believe the low propensity for tonic signaling of D-Domain-based CARs may lower T cell exhaustion.

•Engineered D-Domain Scaffolds: The structural features of the D-Domain make it particularly well suited as a scaffold protein that can be modified by inserting selected amino acids to generate diverse libraries of proprietary target-binding domains. We create highly diverse libraries of variants of α-3D by randomly replacing 12-14 amino acid residues on the outward facing surface of α-3D with one of 18 amino acids.

We screen the resulting libraries for potential target-binding domains and engineer further variants with the appropriate target binding profiles to enhance target specificity, optimize binding affinity, and remove potentially immunogenic sequences, a process we refer to as “deimmunization”. We use rigorous target selection criteria applied to genomic and proteomic datasets generated from public, collaborator, and internal sources. We internally validate expression profiles for all antigens under evaluation to select the best targets. At the same time, all the reagents needed to screen our proprietary D-Domain libraries for specific binders to the antigen are generated and qualified. D-Domain binders to a variety of tumor antigens have already been generated to date. We have also identified and characterized several target-binding domains for certain therapeutic targets, such as BCMA, CD123, CS1, HER2, and PD-L1, among others. AI-based approaches are employed to assist in optimization and continue to be developed to enhance our discovery process. Applying all these discovery methods, the engineered D-Domains are incorporated into our genetically modified T-cells in our ddCAR and ARC-SparX platform.
ARC-SparX Platform
Our ARC-SparX platform is a controllable and adaptable modular therapy that builds on our ddCARs platform by replacing the antigen binding domain of the T cell with a novel synthetic binding domain that recognizes only SparX proteins, which contain the antigen binding domain. When the SparX protein’s antigen binding domain recognizes and binds to the antigen on a diseased cell, it recruits the ARC-T cell to kill the diseased cell.

Our ARC-T-cells are designed to remain in an inactive state, or silenced, and activate only when combined with a SparX protein that is bound to an antigen on a cell. We believe that controlling ARC-T activation with SparX protein effectively separates the antigen-recognition and killing functions. By separating these functions, our approach renders the killing function of the ARC-T cell dependent on the antigen specificity and dose of the SparX protein enabling a differentiated CAR-T expansion and proliferation profile as compared to conventional CAR-T therapy. The separation of the CAR-T from the antigen binding domain allows for a more controlled, modular approach to CAR-T therapy, as SparX dosing can be modified over the course of treatment, multiple SparX proteins may be incorporated, and additional functionality (i.e., logic-gating) may be designed to expand the utility of CAR-T therapy. Further, the approach may simplify the manufacturing of multiple CAR-T programs and the regulatory path, as the ARC-T programs can utilize the same vector to express binding domain. We also believe unregulated killing, which induces severe toxicities, may be mitigated with our approach by adjusting the dose and schedule of SparX protein administration, which may expand the antigens that can be targeted safely with CAR-T therapy. Additionally, stopping the dose of the SparX protein periodically can allow the ARC-T-cells to rest after activation lowering the risk of T-cell exhaustion, which is a common cause of rapid decline of genetically modified T-cells.
Our Pipeline Approach
We are leveraging the full breadth of our platform by matching ddCARs and ARC-SparX with the indications in which they would be most effective based on the biology, patients, and market dynamics.
In MM, we plan to:
•In collaboration with Kite, seek regulatory approval of our lead product candidate, anito-cel, with results from our Phase 1 clinical trial and our pivotal Phase 2 iMMagine-1 clinical trial in rrMM;
•In collaboration with Kite, pursue expanded access to anito-cel through other label expansion clinical trials, including iMMagine-3, GEM-AnitoFIRST and others;
•Through our ex-U.S. partner, Kite, pursue clinical development of anito-cel in other key geographies, such as Europe and Asia; and
•Evaluate the potential of our ARC-SparX technology through our ongoing Phase 1 clinical trial of ACLX-001 in rrMM.
In AML/MDS, we plan to:
•Pursue AML/MDS with a library of SparX proteins beginning with our wholly-owned ACLX-002 program, which is currently in a Phase 1 clinical trial, and continuing with our ACLX-004 program; and
•Explore trials that evaluate the use of a single administration of ARC-T-cells together with a combination of SparX proteins engineered to target different AML and MDS antigens, to extend the power of the platform.
In additional indications, we plan to:
•Evaluate the efficacy of anito-cel in indications outside of oncology, including in some autoimmune indications such as gMG.
•Extend benefits of our D-Domain platform by applying ddCARs and ARC-SparXs to additional hematological and solid tumor indications, including SCLC and HCC.
Our Pipeline
We have built a broad and scalable pipeline that has positioned us to capitalize on the potential of our proprietary platform technologies and achieve long-term growth and sustainability within the field of CAR-T. We have summarized our preclinical and clinical programs in the pipeline chart below and indicated where such programs are subject to the Kite Collaboration Agreement, which is described in “Licenses and Collaborations” below. Except for such partnered programs, we have worldwide rights to all of our programs:

* Kite exercised its option to negotiate a license for ACLX-001 and retains an option for additional select ARC-SparX programs in multiple myeloma and lymphoma
Our Multiple Myeloma Program
Our MM program is led by our anito-cel product candidate, which is an autologous CAR-T comprised of D-Domain powered T-cells that have been genetically modified to recognize and kill specific cells expressing BCMA, a target antigen for multiple myeloma. In collaboration with Kite, we are advancing our anito-cel product through our pivotal Phase 2 iMMagine-1 trial in patients with rrMM, which we initiated in 2022 and are currently pursuing U.S. regulatory approval. We and Kite are also evaluating anito-cel in our global Phase 3 iMMagine-3 trial in second through fourth line patients with rrMM which began dosing patients in 2024. Anito-cel has been granted Fast Track and Orphan Drug by the FDA. In 2021, we also received Regenerative Medicine Advanced Therapy (RMAT) designation for anito-cel for the treatment of multiple myeloma. In collaboration with Kite, we plan to continue to enroll more patients into additional clinical trials, to support label expansion to enter into earlier lines of therapy and include patients who have had prior BCMA-targeted therapies. For example, in 2025 we initiated the GEM-AnitoFIRST study in frontline MM which serves as the safety lead-in to future pivotal trials in the frontline MM setting. Additionally, pursuant to the Kite Collaboration Agreement, as further described in “Licenses and Collaborations” below, Kite will pursue international clinical trials to expand into geographic locations in Europe and Asia-Pacific. We are also advancing our initial ARC-SparX program, ACLX-001, an immunotherapeutic combination composed of ARC-T-cells and bi-valent SparX proteins targeting BCMA, to treat rrMM. In December 2023, Kite exercised its option under the Kite Collaboration Agreement to negotiate a license for ACLX-001.
Market Opportunity
MM is a type of hematological cancer in which diseased plasma cells proliferate and accumulate in the bone marrow, crowding out healthy blood cells and causing bone lesions, loss of bone density and bone fractures. These abnormal plasma cells also produce excessive quantities of an abnormal immunoglobulin fragment called a myeloma protein (M protein) causing kidney damage and impairing the patient’s immune function.
MM is the third most common hematological malignancy in the United States and Europe, representing approximately 10% of all hematological cancer cases, 20% of deaths due to hematological malignancies and, by our estimate, impacting over 175,000 patients globally each year. The Surveillance, Epidemiology, and End Results (SEER) Program database projects that approximately 35,000 new cases of MM in the United States and over 36,000 new cases in six select markets within Europe and Asia.
The median age of MM patients at diagnosis is 69 years with one-third of patients diagnosed at an age of at least 75 years. Because MM tends to afflict patients at an advanced stage of life, patients often have multiple co-morbidities and toxicities that can quickly escalate and become life-endangering. Despite the development and use of multiple new therapies, including second generation proteasome inhibitors (PI) and immunomodulatory drugs (IMiD), stem cell transplantation and CD38-binding monoclonal antibodies, the five-year survival rate is still approximately 60% and MM remains incurable in most patients.
Currently, multiple BCMA-targeting therapies are approved, in development or under regulatory review, including T cell engagers (TCEs), antibody drug conjugates (ADCs) and other CAR-T therapies.
We estimate that the size of the global MM market was approximately $26 billion in 2025 and that the current total addressable CAR-T market for rrMM to be $12 billion or more based on the number of patients who are receiving second line treatments and beyond.
As of December 31, 2025, the two CAR-T therapies targeting BCMA that have been approved by the FDA are Abecma and Carvykti, developed and marketed by 2seventy bio/Bristol Myers Squibb and Legend/Johnson & Johnson, respectively. Currently, Abecma is approved for the treatment of adult patients with rrMM after two or more prior lines of therapy including an immunomodulatory agent (IMiD), a proteasome inhibitor (PI), and an anti-CD38 monoclonal antibody. Carvykti is approved for the treatment of adult patients with rrMM who have received at least 1 prior line of therapy, including a PI and an IMiD and are refractory to lenalidomide. In addition to its current approval in rrMM, Carvykti is currently enrolling additional clinical trials to expand into front-line multiple myeloma treatment.
Carvykti, developed by Legend/Johnson & Johnson, has demonstrated an ORR of 97.9%, a CR/sCR rate of 82%, an estimated median progression-free survival (mPFS) of 34.9 months, and an estimated median overall survival (mOS) of 60.7 months in the Phase 1b/2 CARTITUDE-1 trial in patients with rrMM that had received 3 or more prior lines of therapy. Abecma developed by 2seventy bio/Bristol Myers Squibb, has demonstrated an ORR of 73.4%, and an sCR/CR rate of 33% with an estimated mPFS of 8.8 months in the Phase 2 KarMMa trial in patients with rrMM that had received 3 or more prior lines of therapy.
Although approved BCMA-targeting CAR-T therapies represent a step forward, there remains a need for improved overall response, durability, safety, and accessibility, especially in difficult to treat patient populations. For example, Carvykti has a Black Box warning for Parkinsonism, Guillain-Barré syndrome, and IEC-EC, and its label contains Warnings and Precautions for
Neurologic Toxicities, including those not considered ICANS such as Parkinsonism, Guillain-Barré Syndrome, Immune Mediated Myelitis, Peripheral Neuropathy, Cranial Nerve Palsies, and IEC-EC. Additionally, across the clinical trials of Abecma and Carvykti, several poor prognostic factors have been identified including the presence of extra-medullary disease (EMD) and more broadly plasmacytomas, ISS stage 3, high tumor burden, and high-risk cytogenetics. In clinical trials in rrMM, these patients demonstrated shorter PFS rates. For example, in the Phase 1b/2 trial of Carvykti (CARTITUDE-1), patients with plasmacytomas (of which ~2/3 had EMD) demonstrated a mPFS of 13.8 months, patients with ISS stage 3 disease demonstrated a mPFS of 15.0 months, patients with BMPC ≥60% demonstrated a mPFS of 24.1 months, and patients with high risk cytogenetics demonstrated a mPFS of 21.1 months.
In addition to the FDA-approved CAR-T therapies targeting BCMA, several other BCMA-targeting therapies have been approved by the FDA for treatment of rrMM, these include BCMA-targeting TCEs and ADCs.
•In October 2022, the BCMA-targeting bispecific antibody, Tecvayli developed by Johnson & Johnson, received accelerated approval for treatment of adults with rrMM who have received at least four prior lines of therapy. Tecvayli has reported an ORR of 63% and a CR/sCR rate of 46%, with a mPFS of 11.4 months. However, Tecvayli is dosed weekly or biweekly, and is administered under a Risk Evaluation and Mitigation Strategy (REMS) program and requires hospitalization through the initial titration period. Tecvayli has also been studied in rrMM patients with one to three prior lines of therapy for which two positive trials were announced, the MajesTEC-3 trial in combination with Darzalex and the MajesTEC-9 trial as monotherapy, and is expected to receive earlier line approval in the first half of 2026.
•In August 2023, the BCMA-targeting bispecific antibody, Elrexfio, developed by Pfizer, received accelerated approval for treatment of adults with rrMM who have received at least four prior lines of therapy. Elrexfio has reported an ORR of 61% and a CR/sCR rate of 37%, with a mPFS of 17.2 months. However, Elrexfio is dosed weekly or biweekly, and is administered under a REMS, and requires hospitalization following administration of the initial doses. Additional trials for Elrexfio in earlier lines are ongoing.
•In July 2025, the BCMA-targeting bispecific antibody, Lynozyfic, developed by Regeneron, received accelerated approval for treatment of adults with rrMM who have received at least four prior lines of therapy. Lynozyfic has reported an ORR of 70% and a CR/sCR rate of 45%. However, Lynozyfic is dosed weekly, biweekly, or monthly, and is administered under a REMS, and requires hospitalization following administration of the initial doses. Additional trials for Lynozyfic in earlier lines are ongoing.
•In October 2025, the BCMA-targeting antibody drug conjugate (ADC), Blenrep (belantamab mafodotin), developed by GSK, received approval in combination with bortezomib and dexamethasone (BelaVd) for treatment of adults with rrMM who have received at least two prior lines of therapy. This Blenrep regimen has reported an ORR of 81.5% and a CR/sCR rate of 31.5%, with a mPFS of 31.3 months. However, Blenrep is dosed every three weeks, and is administered under a REMS, and requires ophthalmic exams at baseline, before each dose, promptly for new or worsening symptoms, and as clinically indicated.
anito-cel: Phase 1 Trial in rrMM
The anito-cel Phase 1 multi-center, open label, trial is the first involving one of our proprietary D-Domains and was designed to test anito-cel in rrMM patients to evaluate the safety profile of escalating dose levels (DL) and to expand enrollment at a selected dose to further characterize the efficacy and safety profile of that dose. To be eligible, patients must have had at least 3 prior lines of treatment, which had to include an immunomodulatory drug (IMiD), a proteosome inhibitor (PI), and an anti-CD38 antibody, be refractory to the most recent line of therapy, have an ECOG performance status of 0 or 1, have measurable disease, and have adequate function of vital organs. If eligible, patients were enrolled, underwent leukapheresis (apheresis), and could receive bridging therapy while cell manufacturing occurred. When anito-cel cell manufacturing was complete, patients received lymphodepleting (LD) chemotherapy with fludarabine (Flu) and cyclophosphamide (Cy) on days -5, -4, and -3. On day 0, patients received an intravenous infusion of anito-cel. After infusion, patients were evaluated at fixed intervals for assessment of AEs and evidence of objective response using PET/CT scan, serum measurement of M-protein (including heavy or light chain measurement), and measurement of number of malignant plasma cells in bone marrow aspirates. Safety data are assessed for dose limiting toxicity in the first 28 days following infusion and will be collected throughout the trial. Long-term safety data will be collected for up to 15 years per health authority guidelines. Efficacy data are assessed pursuant to the IMWG criteria on a monthly basis for the first 6 months and then quarterly for up to two years, or upon symptomatic relapse.

The IMWG uniform response criteria have been utilized in registration trials of approved myeloma drugs. The IMWG uniform response criteria assess efficacy of treatment options for myeloma and allow for a comparison of efficacy between treatment strategies in clinical trials, strict definitions for responses, as shown in the table below, and classifications to improve detail and clarify inconsistent interpretations across clinical trials. The IMWG criteria for sCR, CR, VGPR, and PR are summarized below.
•stringent Complete Response (sCR): Complete Response (as defined below) plus normal free light chain (FLC) ratio and absence of clonal cells in bone marrow biopsy by immunohistochemistry (kappa to lambda light chain ratio (k/l) ≤4:1 or ≥1:2 for k or l patients, respectively, after counting ≥100 plasma cells).
•Complete Response (CR): Negative immunofixation in the serum and urine; and disappearance of any soft tissue plasmacytomas; and <5% plasma cells in bone marrow aspirates.
•Very Good Partial Response (VGPR): Serum and urine M protein, detectable by immunofixation but not on electrophoresis; or ≥90% reduction in serum M protein plus urine M protein level <100 mg/24 hr.
•Partial Response (PR): ≥50% reduction of serum M protein plus reduction in 24-hour urinary M protein by ≥90% or to <200 mg/24 h; or if the serum and urine M protein are unmeasurable, a ≥50% decrease in the difference between involved and uninvolved FLC levels is required in place of the M protein criteria and if serum-free light assay is also unmeasurable, ≥50% reduction in plasma cells is required in place of M protein, provided baseline BMPC percentage was ≥30%. In addition to these criteria, if present at baseline, a ≥50% reduction in the size (SPD) of soft tissue plasmacytomas is also required.
Overall Response Rate (ORR) includes patients that achieved sCR, CR, VGPR or PR. sCR and CR do not indicate that the patient was cured of the condition, as multiple myeloma is currently considered incurable.
The clinical trial began enrollment in December 2019 and the first patient was dosed in February 2020. Four clinical trial sites participated in the Phase 1 trial. We completed the dose escalation component with 6 patients each enrolled in DL1 (100 (+/-20%) x 106 cells) and DL2 (300 (+/- 20%) x 106 cells) and enrolled additional patients (n=26) at DL1 for further characterization of safety and preliminary efficacy. The median dose administered in DL1 was 115 million cells (range, 112-120 million cells), and the recommended Phase 2 dose (RP2D) is 115 (+/- 10) x 106 CAR+ cells. The data from the dose escalation and expansion were most recently presented at the 2024 Annual Meeting of the ASH. In the safety and efficacy analysis, 38 patients were evaluable, 32 in the DL1 and 6 in DL2.

Median administered dose at DL1, 115 million cells (range, 112-120 million cells)
Patient and Disease Characteristics are demonstrated in the table below. Taken together, these demographic data indicate the patient population enrolled in this trial had poor prognosis with expected median OS in the range of 6-8 months based on published analyses of patients with similar characteristics.

As of the October 3, 2024 data cutoff date, the ORR was 100%, the CR/sCR rate was 79%, the VGPR rate was 13%, and the PR rate was 8%. As previously presented (ASH Presentation 2022), the likelihood of achieving CR/sCR increased with longer follow-up. This observation is consistent with other rrMM studies, especially in BCMA-targeted CAR-T cell trials, primarily related to the IMWG criteria for CR/sCR. Additionally, 89% (n=25 of 28) of all subjects who are evaluable for minimal residual disease testing (MRD) were negative at the depth of 10-5. Evaluable patients had identifiable malignant clone in the baseline bone marrow aspirate.
As of the October 3, 2024 data cutoff date, with a median follow up of 38.1 months, the mPFS for all patients (N=38) was 30.2 months. For those subjects with CR/sCR (n=30), the mPFS was 34.3 months. Median OS was Not Reached.

A Kaplan-Meier analysis of all subjects demonstrated a PFS rate at 6, 12, 18, 24, and 30 months of 92%, 76%, 65%, 57%, and 50%, respectively. A subgroup analysis of subjects with high risk clinical features (defined as presence of EMD, BMPC ≥ 60%, High Risk Cytogenetics or ISS Stage III) indicated similar PFS rates at 12, 24, and 30 months of 72%, 60%, and 60%, respectively.
