BioAtla’s Mecbotamab Vedotin (Mec-V), an AXL-targeting ADC, Demonstrates a Median Overall Survival (OS) of 21.5 months in Subtypes of Refractory Soft Tissue Sarcomas

— Mec-V demonstrates median OS of 21.5 months in patients with treatment-refractory leiomyosarcoma, liposarcoma, and undifferentiated pleomorphic sarcoma compared with approximately 12 months with approved agents

— Mec-V safety profile as monotherapy, and in combination with anti-PD-1 antibody, was manageable and consistent with conditional binding of the AXL target restricted to the tumor microenvironment

SAN DIEGO, Nov. 07, 2025 (GLOBE NEWSWIRE) -- BioAtla, Inc. (Nasdaq: BCAB), a global clinical-stage biotechnology company focused on the development of Conditionally Active Biologic (CAB) antibody therapeutics for the treatment of solid tumors, today announced clinical data in a poster titled “Median OS of 21.5 months among 44 patients with treatment-refractory leiomyosarcoma, liposarcoma, and undifferentiated pleomorphic sarcoma treated with mecbotamab vedotin, an AXL-targeting ADC,” at the Society for Immunotherapy of Cancer (SITC) 2025 Annual Meeting, being held November 5–9, 2025, in National Harbor, Maryland.

Mec-V is a CAB antibody–drug conjugate (ADC) targeting AXL, a receptor tyrosine kinase overexpressed in various solid tumors including sarcoma. Mec-V, developed using BioAtla’s proprietary CAB technology, conditionally binds to AXL under acidic-pH conditions, enabling tumor-specific delivery of its cytotoxic payload while minimizing off-tumor toxicity.

In the Phase 2 clinical trial, 79 patients with advanced soft tissue sarcomas were treated with Mec-V either as monotherapy (n=54) or in combination with anti–PD-1 antibody (n=25). A focused efficacy analysis of OS was performed among the subset of 44 patients who had treatment-refractory leiomyosarcoma, liposarcoma, or undifferentiated pleomorphic sarcoma.

"The data presented at SITC 2025 underscore the potential of Mec-V to meaningfully extend survival in patients with treatment-refractory soft tissue sarcomas—a population with few effective options,” said Jay M. Short, Ph.D., Chairman, Chief Executive Officer and co-founder of BioAtla. “The prolonged overall survival observed suggests that early exposure to Mec-V may change the long-term clinical outcome among patients suffering from these advanced sarcomas, potentially by helping to selectively eliminate AXL-expressing cancer cells that contribute to subsequent treatment resistance and poor outcomes."

Data highlights from the poster include:

• Patients (n=44) with leiomyosarcoma, liposarcoma, and undifferentiated pleomorphic sarcoma were heavily pretreated, having received a median of 2 prior lines of therapy (range 0–10).
• Mec-V was administered every two weeks either as monotherapy (n=33) or in combination with anti–PD-1 antibody (n=11); data reflect a March 25, 2025 cutoff.
• Median overall survival was 21.5 months across all patients, with 22.9 months observed in the combination arm and 18.4 months in the monotherapy arm.
• In addition, the 12-month OS rate was 73%, compared to approximately 50% historically reported for approved agents in similar populations.
• Two patients also achieved partial responses: one with leiomyosarcoma (combination therapy) and one with undifferentiated pleomorphic sarcoma (monotherapy).
• Disease control rate (DCR) was 52% across all patients.
• Adverse events were generally low-grade, transient, and manageable; no treatment-related deaths were reported.
• Grade 3/4 treatment-related adverse events included neutropenia (21%), hepatic transaminase elevations (16%), and hyperglycemia (3%); no ocular or pulmonary toxicities were observed.

Presentation details:
Title: Median OS of 21.5 Months Among 44 Patients with Treatment-Refractory Leiomyosarcoma, Liposarcoma, and Undifferentiated Pleomorphic Sarcoma Treated with Mecbotamab Vedotin, an AXL-Targeting ADC
Presenter: Mihaela Druta, MD, Moffitt Cancer Center
Abstract Number: 523
Date & Time: Friday, November 7, 2025 | 12:15–1:45 p.m. ET & 5:35–7 p.m. ET
Location: Gaylord National Resort and Convention Center Lower-Level Atrium Prince George's ABC

A copy of the presentation materials can be accessed on the “Publication” section of the Company’s website at www.bioatla.com once the presentation has concluded.

About Mecbotamab Vedotin
Mecbotamab Vedotin (Mec-V) is a CAB-platform antibody–drug conjugate (ADC) targeting AXL, a receptor tyrosine kinase overexpressed in many solid tumors that has been shown to be associated with treatment resistance and poor clinical outcomes. Engineered using BioAtla’s proprietary CAB technology, Mec-V selectively binds to AXL in the acidic tumor microenvironment while sparing healthy tissue. This pH-dependent binding mechanism reduces off-tumor toxicity and improves the therapeutic index. Mec-V is a Phase 2 stage clinical asset targeting multiple solid tumor indications, including the treatment of patients with mKRAS NSCLC who have previously experienced progression on or after PD-1/L1, epidermal growth factor receptor and/or ALK inhibitor therapies. In this population, Mec-V achieved landmark overall survival rate of 66% and 58%, at one-year and two-years, respectively.

About BioAtla^®, Inc.
BioAtla is a global clinical-stage biotechnology company with operations in San Diego, California, and in Beijing, China through its contractual relationship with BioDuro-Sundia, a provider of preclinical development services. Utilizing its proprietary CAB platform technology, BioAtla develops novel, reversibly active monoclonal and bispecific antibodies and other protein therapeutic product candidates. CAB product candidates are designed to have more selective targeting, greater efficacy with lower toxicity, and more cost-efficient and predictable manufacturing than traditional antibodies. BioAtla has extensive and worldwide patent coverage for its CAB platform technology and products with greater than 780 active patent matters, more than 500 of which are issued patents. Broad patent coverage in all major markets includes methods of making, screening and manufacturing CAB product candidates in a wide range of formats and composition of matter coverage for specific products. To learn more about BioAtla, Inc., visit www.bioatla.com.

Forward-looking Statements
Statements in this press release contain "forward-looking statements" that are subject to substantial risks and uncertainties. Forward-looking statements contained in this press release may be identified by the use of words such as "anticipate," "expect," "believe," "will," "may," "should," "estimate," "project," "outlook," "forecast" or other similar words. Examples of forward-looking statements include, among others, statements we make regarding the potential of Mec-V to extend survival in patients with treatment-refractory soft tissue sarcomas based on recent clinical data; the safety and efficacy profile of Mec-V as monotherapy and in combination with anti–PD-1 antibody; the ability of Mec-V to selectively eliminate AXL-expressing cancer cells and impact treatment resistance and outcomes; BioAtla’s business plans and prospects and whether our clinical trials will support registration; achievement of milestones; results, progress and timing of our research and development programs and clinical trials; expectations with respect to enrollment and dosing in our clinical trials, plans and expectations regarding future data updates, clinical trials, regulatory meetings and regulatory submissions; the timing of and the ability to establish collaborations or other strategic partnerships for selected assets; and the potential regulatory approval path for our product candidates. Forward-looking statements are based on BioAtla's current expectations and are subject to inherent uncertainties, risks and assumptions, many of which are beyond our control, difficult to predict and could cause actual results to differ materially from what we expect. Further, certain forward-looking statements are based on assumptions as to future events that may not prove to be accurate. Factors that could cause actual results to differ include, among others: factors that raise substantial doubt about our ability to continue as a going concern and that we will need additional funding to continue development of our CAB technology platform and our CAB product candidates; the risk that preliminary or interim clinical results may not be indicative of results from later cohorts or larger populations; potential delays in clinical and preclinical trials; the uncertainties inherent in research and development, including the ability to meet anticipated clinical endpoints, commencement and/or completion dates for clinical trials, regulatory submission dates, or regulatory approval dates, as well as the possibility of unfavorable new clinical data and further analyses of existing clinical data; whether regulatory authorities will be satisfied with the design of and results from the clinical studies or take favorable regulatory actions based on results from the clinical studies; our dependence on the success of our CAB technology platform; our ability to enroll patients in our ongoing and future clinical trials; our ability to form collaborations and partnerships with third parties and the success of such collaborations and partnerships; our reliance on third parties for the manufacture and supply of our product candidates for clinical trials; our reliance on third parties to conduct our clinical trials and some aspects of our research and preclinical testing; potential adverse impacts due to geopolitical or macroeconomic events outside of our control, including health epidemics or pandemics; and those other risks and uncertainties described in the section titled "Risk Factors" in our Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on March 27, 2025, our Quarterly Reports on Form 10-Q filed with the SEC on May 6, 2025 and August 7, 2025 and our other reports as filed with the SEC. Forward-looking statements contained in this press release are made as of this date, and BioAtla undertakes no duty to update such information except as required under applicable laws.

Internal Contact:
Richard Waldron
Chief Financial Officer
BioAtla, Inc.
rwaldron@bioatla.com
858.356.8945

External Contact:
Joyce Allaire
LifeSci Advisors, LLC
jallaire@lifesciadvisors.com

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