CD3ε

Observed additional clinical responses and FDA feedback supports path forward for CAB-AXL-ADC (BA3011) non-small cell lung cancer (NSCLC) registrational study; detailed interim Phase 2 data to be presented at upcoming IASLC conference in early December and discussed at KOL event on December 4, 2023Observed new PRs with CAB-ROR2-ADC (BA3021) Q2W dosing regimen in the Phase 2 melanoma study and a new PR with BA3021 2Q3W in the Phase 2 head and neck studyInitiated Phase 2 CAB-CTLA-4 (BA3071) study; First Patient In (FPI) completed; Phase 1 data to be presented at upcoming R&D Day on December 13, 2023Phase 1 study for CAB-EpCAM x CAB-CD3 bispecific T-cell engager (TCE), BA3182, ongoing; data readout remains on track in 2024Cash balance of $141.3 million now expected to fund operations into 2H 2025 Management to host conference call and webcast today at 4:30 PM Eastern Time SAN DIEGO, Nov. 07, 2023 (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 its financial results for the third quarter ended September 30, 2023, and provided an update on its clinical programs. “At BioAtla, our highest priority is to deliver innovative, life-changing therapies to cancer patients with significant unmet medical needs. We have consistently observed multiple clinical responses in treatment-refractory NSCLC populations with CAB-AXL-ADC, BA3011. In addition, we recently have observed new PRs with CAB-ROR2-ADC, BA3021 in melanoma and head and neck cancer as we continue to dose patients, further underscoring our promising CAB-ADC opportunities,” said Jay M. Short, Ph.D., Chairman, Chief Executive Officer and co-founder of BioAtla, Inc. “We are also advancing our CAB-CTLA-4, BA3071, and now have initiated the Phase 2 study and will provide an update at our upcoming R&D day in December. As we have obtained data to support several value inflection points across our CAB portfolio, we believe that forming one or more strategic collaborations with major pharmaceutical partners can accelerate development of selected assets and maximize their market opportunities.” CAB-ADC Clinical-Stage Programs Phase 2 Trial of Mecbotamab Vedotin, BA3011: NSCLC In treatment-refractory patients (median 3 prior lines of therapy) receiving BA3011 Q2W monotherapy who previously experienced PD-1 treatment failure and were evaluable for efficacy at 12 weeks, the observed objective response rate was 27.8%In treatment-refractory patients with epidermal growth factor receptor (EGFR) wild-type, non-squamous NSCLC who previously experienced PD-1 treatment failure, 33.3% had a partial response (PR) to BA3011 monotherapyContinue to observe clinical benefit in patients, including multiple PRs at a TmPS score of 1% and exploring the potential clinical benefits in AXL TmPS negative patientsBased upon our meeting with the FDA in October, we believe the FDA is supportive of our registrational path forward; details forthcoming at IASLC conference and KOL event in early December Undifferentiated Pleomorphic Sarcoma (UPS) Phase 2 potentially registrational study ongoing Bone and soft tissue sarcomas All cohorts completed with additional subtypes achieving the predefined efficacy and safety criteriaPlanned submission of data to medical meeting in 2024 Phase 2 Trials of Ozuriftamab Vedotin, BA3021: All dosing to be completed before year-end 2023Melanoma Completed enrollment Q2W targeted cohort who previously progressed on PD-1/L1 therapyTo date, eight melanoma monotherapy patients are evaluable with reported first scan data across Phase 1 and Phase 2. Among these, we observed four responses, two stable disease and two progressive disease with at least one response observed in a ROR2 TmPS negative patient. The remainder of patients in the targeted cohort will have had the opportunity to have first scan by year end.Continue to collect data in ongoing study Squamous Cell Carcinoma of Head and Neck (SCCHN) On track to complete all dosing regimens enrollment by year-end 2023; new PR observed in the first Phase 2 patient scanned at 2Q3W (ROR2 TmPS negative)Continue to collect data in ongoing study NSCLC Clinical benefit observed and tumor volume reduction in Q2W dosing regimen but did not meet our internal criteria for advancing at this dose; currently no plans to internally explore additional dosing regimens Phase 2 Investigator-initiated Trial of platinum-resistant ovarian cancer Interim analysis of n=10 patients in each BA3011 and BA3021 Q2W cohorts demonstrated modest disease control, but did not meet our internal criteria for advancing at this dose; currently no plans to internally explore additional dosing regimensData disclosure planned for future medical meeting at investigator’s discretion CAB-CTLA-4 I/O Clinical-Stage Program Phase 1/2 dose-escalation trial of CAB-CTLA-4, BA3071 basket trial: Phase 1 data readout and path forward at upcoming R&D Day on December 13Initiated Phase 2; FPI completed CAB-T-Cell Engager Clinical-Stage Program Phase 1/2 dose-escalation for CAB-EpCAM x CAB-CD3 TCE, BA3182: Progressing Phase 1 study for the treatment of advanced adenocarcinomaAnticipated completion of Phase 1 and data readout remains on track in 2024 Presentations Upcoming poster presentation at the IASLC North America Conference on Lung Cancer (NACLC), titled “Phase 2 Trial of Mecbotamab Vedotin (BA3011), a CAB-AXL-ADC, Alone or in Combination With Nivolumab in Patients With Non-Squamous NSCLC”, in early DecemberKOL event planned for December 4 following conclusion of the IASCL conference, to discuss detailed interim Phase 2 data on CAB-AXL-ADC, BA3011, in NSCLCR&D Day planned for December 13 to discuss CAB-CTLA-4 (BA3071) Phase 1/2 basket trial Third Quarter 2023 Financial Results Cash and cash equivalents as of September 30, 2023 were $141.3 million, compared to $215.5 million as of December 31, 2022. We expect current cash and cash equivalents will be sufficient to fund planned operations including prioritized CAB programs into second half of 2025. Research and development (R&D) expenses were $28.4 million for the quarter ended September 30, 2023 compared to $19.8 million for the same quarter in 2022. The increase of $8.6 million was primarily driven by a $6.3 million increase in our clinical product development expenses primarily related to the launch of our AXL UPS potentially registrational trial, and a $1.8 million increase in preclinical product development expenses primarily related to our CAB B7H3 x CD3 bispecific T-cell engager. We expect our R&D expenses to remain variable from quarter to quarter as we continue to advance our clinical programs, then decreasing after we complete enrollment and focus development on selected high potential indications. General and administrative (G&A) expenses were $6.6 million for the quarter ended September 30, 2023 compared to $6.3 million for the same quarter in 2022. The $0.3 million change was attributable to an increase in professional services and consulting expenses for the 2023 period. We expect our G&A expenses to remain flat to moderately increasing to support development of our prioritized CAB programs. Net loss for the third quarter ended September 30, 2023 was $33.3 million compared to a net loss of $25.8 million for the same quarter in 2022. Net cash used in operating activities for the nine months ended September 30, 2023 was $74.1 million compared to net cash used in operating activities of $66.1 million for the same period in 2022. The increase in net cash used in operating activities for the first nine months of 2023 is primarily due to an increase in research and development expenses related to our program development efforts as compared to the first nine months of 2022. Third Quarter 2023 Conference Call and Webcast Details The management of BioAtla, Inc. will host a conference call and webcast for the investment community today, November 7, 2023, at 4:30 pm Eastern Time. A live webcast may be accessed here: https://viavid.webcasts.com/starthere.jsp?ei=1635568&tp_key=63f5901bb0. The conference call can be accessed by dialing toll-free (888) 886-7786 or (416) 764-8658 (international). The passcode for the conference call is 05202391. A replay of the webcast and slides with topline interim clinical data referenced on the call will be available through “Events & Presentations” in the Investors section of the company’s website after the conclusion of the presentation and will be archived on the BioAtla website for one year. About Mecbotamab Vedotin (BA3011) Mecbotamab vedotin, CAB-AXL-ADC, is a conditionally and reversibly active antibody drug conjugate targeting the receptor tyrosine kinase AXL. This Phase 2 stage clinical asset is targeting multiple solid tumor types, including soft tissue and bone sarcoma and non-small cell lung cancer (NSCLC) that have previously progressed on PD-1/L1, EGFR or ALK inhibitor therapies. The Office of Orphan Drug Products (OODP) at FDA granted Orphan Drug Designation to mecbotamab vedotin for the treatment of soft tissue sarcoma. About Ozuriftamab Vedotin (BA3021) Ozuriftamab vedotin, CAB-ROR2-ADC, is a conditionally and reversibly active antibody drug conjugate directed against ROR2, a receptor tyrosine kinase that is overexpressed across many different solid tumors including breast, lung, head and neck and melanoma. This Phase 2 stage clinical asset is targeting multiple solid tumor types, including NSCLC that have previously progressed on PD-1/L1, EGFR or ALK inhibitor therapies, melanoma that have previously progressed on PD-1/L1 therapy and SCCHN that have previously progressed on PD-1/L1 therapies with or without platinum chemotherapy. About BA3071 BA3071, is a CAB anti-CTLA-4 antibody that is being developed as an immuno-oncology agent with the goal of delivering efficacy at least comparable to the approved anti-CTLA-4 antibodies, but with lower toxicities due to the CAB's tumor microenvironment-restricted activity. This may enable safer anti-CTLA-4 antibody combination therapies, such as with anti-PD-1 antibody checkpoint inhibitors, and potentially broaden the patient population tolerant to combination therapy and deliver greater efficacy. Like our other CAB candidates, this Phase 2 clinical asset is designed to be conditionally and reversibly active in the tumor microenvironment. BA3071 is being developed as a potential therapeutic for multiple solid tumor indications that are known to be responsive to CTLA-4 treatment in combination with a PD-1 blocking agent. About BA3182 BioAtla is developing BA3182 as a potential anticancer therapy for patients with advanced adenocarcinoma. BA3182 is a conditionally active biologic (CAB) EpCAM/CD3 bispecific T cell engager antibody that contains two binding sites for EpCAM and two binding sites for CD3ε. The binding sites for EpCAM and CD3ε have been designed to bind their respective targets specifically and reversibly under the conditions found in the TME and to have reduced binding outside of the TME. The CAB selective binding to both the CAB EpCAM and CAB CD3ε arms are required to activate the T cell engagement against the tumor, thus enabling the combined selectivity of each CAB binding arm in the bispecific antibody. BioAtla continues to advance the ongoing Phase 1 study to evaluate the safety, pharmacokinetics, and efficacy of BA3182 in advanced adenocarcinoma patients. About EpCAM EpCAM is involved in the maintenance of epithelial integrity, and its expression is associated with proliferation during morphogenesis, tissue regeneration, and stem cell maintenance. Expression levels of EpCAM vary amongst different organs and cell types, with epithelia of colon, small intestine, lung, pancreas, liver and gall bladder expressing the highest levels of EpCAM protein. Given the functions and properties of EpCAM protein, high levels of EpCAM expression have been found in many carcinomas. EpCAM is highly and frequently expressed in the vast majority of carcinomas and their metastases and has been considered as a potential prognostic and therapeutic marker for many carcinomas. About BioAtla®, Inc. BioAtla is a global clinical-stage biotechnology company with operations in San Diego, California, and in Beijing, China through our contractual relationship with BioDuro-Sundia, a provider of preclinical development services. Utilizing its proprietary Conditionally Active Biologics (CAB) 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 technology and products with greater than 700 patents filed, more than 400 of which have been issued. Broad patent coverage in all major markets include methods of making, screening and manufacturing CAB product candidates in a wide range of formats and composition of matter coverage for specific products. BioAtla has two first-in-class CAB programs currently in Phase 2 clinical testing, mecbotamab vedotin, BA3011, a novel conditionally active AXL-targeted antibody-drug conjugate (CAB-AXL-ADC), and ozuriftamab vedotin, BA3021, a novel conditionally active ROR2-targeted antibody-drug conjugate (CAB-ROR2-ADC). The Phase 2 stage CAB-CTLA-4 antibody, BA3071, is a novel CTLA-4 inhibitor designed to reduce systemic toxicity and potentially enable safer combination therapies with checkpoint inhibitors such as anti-PD-1 antibody. The company’s first bispecific T-cell engager antibody, BA3182, is currently in Phase 1 development. BA3182 targets EpCAM, which is highly and frequently expressed on many adenocarcinomas while engaging human CD3 expressing T cells. 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 our business plans and prospects and whether our clinical trials will support registration; achievement of milestones; results, conduct, 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; plans to form collaborations or other strategic partnerships for selected assets; the potential regulatory approval path for our product candidates; expectations about the sufficiency of our cash and cash equivalents to fund planned operations, which includes plans to not explore additional dosing regimens, delaying certain pre-clinical development programs and to prioritize and focus development on selected assets and indications; and expected R&D and G&A expenses. 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: potential delays in clinical and pre-clinical 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; the successful selection and prioritization of assets to focus development on selected product candidates and indications; 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 any resurgence of COVID-19 and its variants 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 (SEC) on March 23, 2023, in our Quarterly Report on Form 10-Q filed with the SEC on May 11, 2023, August 1, 2023 and November 7, 2023 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 law. Internal Contact: Richard Waldron Chief Financial Officer BioAtla, Inc. rwaldron@bioatla.com 858.356.8945 External Contact: Bruce Mackle LifeSci Advisors, LLC bmackle@lifesciadvisors.com BioAtla, Inc. Unaudited Condensed Statements of Operations and Comprehensive Loss(in thousands) Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Operating expenses: Research and development expense$28,400 $19,839 $81,057 $57,473 General and administrative expense 6,620 6,340 20,094 22,107 Total operating expenses 35,020 26,179 101,151 79,580 Loss from operations (35,020) (26,179) (101,151) (79,580)Other income (expense): Interest income 1,734 370 4,674 601 Other income (expense) (39) 30 (60) 40 Total other income (expense) 1,695 400 4,614 641 Net loss and comprehensive loss$(33,325)$(25,779) $(96,537)$(78,939) BioAtla, Inc.Condensed Consolidated Balance Sheets Data(in thousands) September 30,2023 December 31,2022 Cash and cash equivalents $141,282 $215,507Total assets 151,362 225,736Total current liabilities 35,602 23,131Total liabilities 56,659 45,397Total stockholders’ equity 94,703 180,339Total liabilities and stockholders’ equity 151,362 225,736

Achieved first patient in (FPI) and continuing to enroll CAB-AXL BA3011 in a Phase 2 potentially registrational study in Undifferentiated Pleomorphic Sarcoma (UPS) Submitted Food & Drug Administration (FDA) meeting request for potentially registrational study of BA3011 in non-small cell lung cancer (NSCLC) study; FDA feedback and initiation of study remain on track for 2H23 Continuing to enroll BA3021 Phase 2 NSCLC, melanoma and squamous cell carcinoma of the head & neck (SSCHN) studies; anticipate data across indications to prioritize and make a 'go' decision in 2H2023 Cleared fifth cohort at 5 mg/kg monotherapy and in combination with PD-1 in Phase 1 dose-escalation CAB-CTLA-4 (BA3071) study with no dose-limiting toxicities (DLTs) reported; currently enrolling patients in sixth cohort at 10 mg/kg; anticipated Phase 1 data readout and initiation of Phase 2 remain on track for 2H23 Cash balance of $168.7 million expected to provide funding into 2025 Management to host conference call and webcast today at 4:30 PM Eastern Time SAN DIEGO, Aug. 01, 2023 (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 its financial results for the second quarter ended June 30, 2023, and provided highlights on its clinical programs. “BioAtla continues to progress our robust CAB pipeline, including the recent clearance of the fifth cohort with no DLTs observed in our Phase 1 BA3071 CTLA-4 study,” said Jay M. Short, Ph.D., Chairman, Chief Executive Officer and co-founder of BioAtla, Inc. “BioAtla has several important near-term value inflection points, including data readouts in the second half of this year. Additionally, we anticipate FDA feedback for our Phase 2, part 2 potentially registrational BA3011 trial in NSCLC, and initiation of our Phase 2 CAB-CTLA-4 BA3071 trial in multiple indications. We continue to work diligently to progress our programs while managing our resources to preserve cash into 2025.” Key Developments, Operational Updates and Upcoming Milestones Phase 2 Trial of Mecbotamab Vedotin in Patients with: AXL-positive Soft Tissue and Primary Bone Sarcomas (BA3011, NCT03425279) Phase 2, part 1: Continuing to enroll remaining cohortsLMS cohort data readout remains on track for 2H23 using a more frequent, dose-intensive regimens Phase 2, part 2: Continuing to enroll and dose patients in potentially registrational Phase 2 UPS study AXL-positive NSCLC (BA3011, NCT04681131) Phase 2, part 1: Continuing to enroll more frequent, dose-intensive regimens; anticipated data for all dosing regimens to enable decision on selected dose for Phase 2, part 2 remains on track for 2H23 Phase 2, part 2 (potentially registrational): Submitted meeting request to the FDA for the study design; anticipate FDA feedback in 2H23Initiation of study on track for 2H23 AXL-positive platinum-resistant ovarian cancer (BA3011, NCT04918186) Phase 2 investigator-initiated trial is on track with interim data (n=10) anticipated in 2H23 Phase 2 Trials of Ozuriftamab Vedotin in Patients with: ROR2-positive NSCLC (BA3021, NCT03504488) Continuing to enroll in the more frequent, dose-intensive regimen ROR2-positive melanoma (BA3021, NCT03504488) Identified ROR2-positive tumors using liquid biopsy assayAnticipate dosing patients in 2H23 ROR2-positive SCCHN (BA3021, NCT05271604) Multiple patients dosed and continuing to enroll patients ROR2-positive platinum-resistant ovarian cancer (BA3021, NCT04918186) Phase 2 investigator-initiated trial is on track with interim data (n=10) anticipated in 2H23 Anticipated data across indications to prioritize and make a 'go' decision for indications to further pursue remains on track for 2H23 Phase 1/2 dose-escalation trial of CAB-CTLA-4 (BA3071, NCT05180799) across multiple solid tumor types responsive to CTLA-4 DLT observation period cleared for fifth cohort (350 mg [5 mg/kg]) as monotherapy and in combination with nivolumab 3 mg/kg every three weeks (Q3W)Enrolling 700 mg (10mg/kg) as sixth dose cohort as monotherapy and in combination with nivolumab 3mg/kg Q3WAnticipated Phase 1 data readout remains on track for 2H23 Initiation of the Phase 2 part of the study remains on track for 2H23 Phase 1/2 dose-escalation for CAB-EpCAM x CAB-CD3 TCE (BA3182) Enrolling Phase 1 study for the treatment of advanced adenocarcinomaAnticipated completion of Phase 1 data readout remains on track in 2024 Since the first quarter, two additional accepted and upcoming poster presentations for trials in progress (for BA3011 and BA3021) at the upcoming World Conference on Lung Cancer (WCLC), to be held September 9-12, titled: “A Phase 2 Study of Mecbotamab Vedotin (BA3011), a CAB-AXL-ADC, Alone or in Combination with Nivolumab”“A Phase 1/2 Dose Escalation and Dose Expansion Study of Ozuriftamab Vedotin (BA3021) Alone and in Combination with Nivolumab” Second Quarter 2023 Financial Results Cash and cash equivalents as of June 30, 2023 were $168.7 million, compared to $215.5 million as of December 31, 2022. We expect current cash and cash equivalents will be sufficient to fund planned operations including all ongoing CAB product development programs into 2025. Research and development (R&D) expenses were $31.0 million for the quarter ended June 30, 2023 compared to $20.7 million for the same quarter in 2022. The increase of $10.3 million was primarily driven by our preclinical and clinical product development efforts. We expect our R&D expenses to remain variable from quarter to quarter and generally increase as we continue to invest in R&D activities to advance our product candidates and our clinical programs. General and administrative (G&A) expenses were $6.2 million for the quarter ended June 30, 2023 compared to $8.3 million for the same quarter in 2022. The $2.1 million change was attributable to a decrease in various administrative expenses for the 2023 period. We expect our G&A expenses to moderately increase to support development of our product candidates, advance our intellectual property portfolio, support focused pre-commercialization activities for our product candidate mecbotamab vedotin (BA3011) and satisfy requirements as a public company. Net loss for the second quarter ended June 30, 2023 was $35.8 million compared to a net loss of $28.9 million for the same quarter in 2022. Net cash used in operating activities for the months ended June 30, 2023 was $46.7 million compared to net cash used in operating activities of $42.1 million for the same period in 2022. The increase in net cash used in operating activities for the first six months of 2023 is primarily due to an increase in research and development expense related to our program development efforts as compared to the first six months of 2022. Second Quarter 2023 Conference Call and Webcast Details The management of BioAtla, Inc. will host a conference call and webcast for the investment community today, August 1, 2023, at 4:30 pm Eastern Time. A live webcast may be accessed here: https://viavid.webcasts.com/starthere.jsp?ei=1619442&tp_key=871a8141a7. The conference call can be accessed by dialing toll-free (877) 425-9470 or (201) 389-0878 (international). The passcode for the conference call is 13739244. A replay of the webcast and slides with topline interim clinical data referenced on the call will be available through “Events & Presentations” in the Investors section of the company’s website after the conclusion of the presentation and will be archived on the BioAtla website for one year. About Mecbotamab Vedotin (BA3011) Mecbotamab vedotin, CAB-AXL-ADC, is a conditionally and reversibly active antibody drug conjugate targeting the receptor tyrosine kinase AXL. This Phase 2 stage clinical asset is targeting multiple solid tumor types, including soft tissue and bone sarcoma and non-small cell lung cancer (NSCLC) that have previously progressed on PD-1/L1, EGFR or ALK inhibitor therapies. We are also supporting a multi-center investigator-initiated clinical trial in combination with durvalumab, a PD-L1-blocking antibody, in patients with platinum-resistant ovarian cancer, in addition to other potential indications in the future. The Office of Orphan Drug Products (OODP) at FDA granted Orphan Drug Designation to mecbotamab vedotin for the treatment of soft tissue sarcoma. About Ozuriftamab Vedotin (BA3021) Ozuriftamab vedotin, CAB-ROR2-ADC, is a conditionally and reversibly active antibody drug conjugate directed against ROR2, a receptor tyrosine kinase that is overexpressed across many different solid tumors including lung, head and neck and melanoma. We are advancing this Phase 2 stage clinical asset for multiple solid tumor types, including NSCLC that have previously progressed on PD-1/L1, EGFR or ALK inhibitor therapies, melanoma that have previously progressed on PD-1/L1 therapy and SCCHN that have previously progressed on PD-1/L1 therapies with or without platinum chemotherapy. We are also supporting a multi-center investigator-initiated clinical trial in combination with durvalumab, a PD-L1-blocking antibody, in patients with platinum-resistant ovarian cancer, in addition to other potential indications in the future. About BA3071 BA3071, is a CAB anti-CTLA-4 antibody that is being developed as an immuno-oncology agent with the goal of delivering efficacy at least comparable to the approved anti-CTLA-4 antibodies, but with lower toxicities due to the CAB's tumor microenvironment-restricted activity. This may enable safer anti-CTLA-4 antibody combination therapies, such as with anti-PD-1 antibody checkpoint inhibitors, and potentially broaden the patient population tolerant to combination therapy and deliver greater efficacy. Like our other CAB candidates, BA3071 is designed to be conditionally and reversibly active in the tumor microenvironment. BA3071 is being developed as a potential therapeutic for multiple solid tumor indications that are known to be responsive to CTLA-4 treatment in combination with a PD-1 blocking agent. About BA3182 BioAtla is developing BA3182 as a potential anticancer therapy for patients with advanced adenocarcinoma. BA3182 is a conditionally active biologic (CAB) EpCAM/CD3 bispecific T cell engager antibody that contains two binding sites for EpCAM and two binding sites for CD3ε. The binding sites for EpCAM and CD3ε have been designed to bind their respective targets specifically and reversibly under the conditions found in the TME and to have reduced binding outside of the TME. The CAB selective binding to both the CAB EpCAM and CAB CD3ε arms are required to activate the T cell engagement against the tumor, thus enabling the combined selectivity of each CAB binding arm in the bispecific antibody. BioAtla recently received FDA IND clearance to conduct a first-in-human, Phase 1 study to evaluate the safety, pharmacokinetics, and efficacy of BA3182 in advanced adenocarcinoma patients. About EpCAM EpCAM is involved in the maintenance of epithelial integrity, and its expression is associated with proliferation during morphogenesis, tissue regeneration, and stem cell maintenance. Expression levels of EpCAM vary amongst different organs and cell types, with epithelia of colon, small intestine, lung, pancreas, liver and gall bladder expressing the highest levels of EpCAM protein. Given the functions and properties of EpCAM protein, high levels of EpCAM expression have been found in many carcinomas. EpCAM is highly and frequently expressed in the vast majority of carcinomas and their metastasis and has been considered as a potential prognostic and therapeutic marker for many carcinomas. About BioAtla®, Inc. BioAtla is a global clinical-stage biotechnology company with operations in San Diego, California, and in Beijing, China through our contractual relationship with BioDuro-Sundia, a provider of preclinical development services. Utilizing its proprietary Conditionally Active Biologics (CAB) 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 technology and products with greater than 700 patents filed, more than 400 of which have been issued. Broad patent coverage in all major markets include methods of making, screening and manufacturing CAB product candidates in a wide range of formats and composition of matter coverage for specific products. BioAtla has two first-in-class CAB programs currently in Phase 2 clinical testing, mecbotamab vedotin, BA3011, a novel conditionally active AXL-targeted antibody-drug conjugate (CAB-AXL-ADC), and ozuriftamab vedotin, BA3021, a novel conditionally active ROR2-targeted antibody-drug conjugate (CAB-ROR2-ADC). The Phase 1 stage CAB-CTLA-4 antibody, BA3071, is a novel CTLA-4 inhibitor designed to reduce systemic toxicity and potentially enable safer combination therapies with checkpoint inhibitors such as anti-PD-1 antibody. The company’s first bispecific antibody, BA3182, targets EpCAM, which is highly and frequently expressed on many adenocarcinomas while engaging human CD3 expressing T cells. To learn more about BioAtla, Inc. visit www.bioatla.com. Forward-looking statementsStatements 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 our business plans and prospects, including our plans to initiate and advance a Phase 1 dose-escalation and expansion clinical study for BA3182, whether our clinical trials will support registration; achievement of milestones; results, conduct, 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 potential regulatory approval path for our product candidates; expectations about the sufficiency of our cash and cash equivalents; and expected R&D and G&A expenses. 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: potential delays in clinical and pre-clinical trials due to the global COVID-19 pandemic; other potential adverse impacts due to the global COVID-19 pandemic such as delays in regulatory review, manufacturing and supply chain interruptions, adverse effects on healthcare systems and disruption of the global economy; 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; the success of our current and future collaborations with third parties; 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; 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 (SEC) on March 23, 2023, in our Quarterly Report on Form 10-Q filed with the SEC on May 11, 2023 and August 1, 2023 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 law. Internal Contact: Richard Waldron Chief Financial Officer BioAtla, Inc. rwaldron@bioatla.com 858.356.8945 External Contact: Bruce Mackle LifeSci Advisors, LLC bmackle@lifesciadvisors.com BioAtla, Inc. Unaudited Condensed Statements of Operations and Comprehensive Loss(in thousands) Three Months Ended June 30, Six Months Ended June 30, 2023 2022 2023 2022 Operating expenses: Research and development expense 30,960 20,711 $52,657 $37,634 General and administrative expense 6,241 8,344 13,474 15,767 Total operating expenses 37,201 29,055 66,131 53,401 Loss from operations (37,201) (29,055) (66,131) (53,401)Other income (expense): Interest income 1,460 146 2,940 231 Other income (expense) (11) 3 (21) 10 Total other income (expense) 1,449 149 2,919 241 Net loss and comprehensive loss$(35,752)$(28,906) $(63,212)$(53,160) BioAtla, Inc.Condensed Consolidated Balance Sheets Data(in thousands) June 30,2023 December 31,2022 Cash and cash equivalents $168,693 $215,507Total assets 179,637 225,736Total current liabilities 33,653 23,131Total liabilities 55,121 45,397Total stockholders’ equity 124,516 180,339Total liabilities and stockholders’ equity 179,637 225,736

Advancing CAB-AXL BA3011 in ongoing sarcoma Phase 2 studies including a potentially registrational study in Undifferentiated Pleomorphic Sarcoma (UPS); expect Leiomyosarcoma (LMS) cohort readout in 2H23On track for submitting a meeting request to the Food & Drug Administration (FDA) for the potentially registrational BA3011 Phase 2, part 2 non-small cell lung cancer (NSCLC) study in 1H23; FDA feedback and initiation of Phase 2, part 2 remain on track for 2H23 Enrolling BA3021 Phase 2 NSCLC study including more frequent, dose-intensive regimen; anticipated interim readout remains on track for 2H23 Enrolling CAB-ROR2 BA3021 Phase 2 squamous cell carcinoma of the head & neck (SCCHN) study as anticipatedPhase 1 dose-escalation CAB-CTLA-4 (BA3071) study ongoing including with PD-1 combination; anticipated data readout and initiation of Phase 2 remain on track for 2H23 FPI anticipated for CAB-EpCAM x CAB-CD3 bispecific T-cell engager (TCE) (BA3182) Phase 1 study in 1H23Cash balance of $192.7 million expected to provide funding into 2025 Management to host conference call and webcast today at 4:30 PM Eastern Time SAN DIEGO, May 11, 2023 (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 its financial results for the first quarter ended March 31, 2023, and provided highlights on its clinical programs. “BioAtla continues to progress our robust CAB pipeline, including our Phase 2, part 2 potentially registrational BA3011 UPS study and successful identification of ROR2-positive tumors using our validated CTC assay in metastatic melanoma patients,” said Jay M. Short, Ph.D., Chairman, Chief Executive Officer and co-founder of BioAtla, Inc. “BioAtla has several important milestones and value inflection points that remain on track for this year, including initiation of our Phase 2, part 2 potentially registrational BA3011 trial in NSCLC following anticipated FDA feedback, Phase 2 interim readout for BA3021 in NSCLC, Phase 1 data readout for our CAB-CTLA-4 basket trial and initiation of our Phase 2 BA3071 trial in multiple indications. In addition, we are opening centers for our first CAB bispecific antibody, BA3182 for the potential treatment of adenocarcinomas, while continuing to manage our resources to carry the company into 2025. Importantly, all of our programs are focused on providing novel cancer therapies for patients with high unmet medical need.” Key Developments, Operational Updates and Upcoming Milestones Phase 2 Trial of Mecbotamab Vedotin in Patients with: AXL-positive Soft Tissue and Primary Bone Sarcomas (BA3011, NCT03425279) Phase 2, part 1: Continue to enroll multiple cohortsAnticipated LMS cohort data readout remains on track for 2H23 using the more frequent, dose-intensive regimen Phase 2, part 2: Continue to enroll in potentially registrational Phase 2 UPS study AXL-positive NSCLC (BA3011, NCT04681131) Phase 2, part 1: Continuing to enroll more frequent, dose-intensive regimen; anticipated data readout remains on track for 2H23 Phase 2, part 2: On-track to submit study design in 1H23; anticipate FDA feedback in 2H23Initiate potentially registrational study; anticipated 2H23 AXL-positive platinum-resistant ovarian cancer (BA3011, NCT04918186) Phase 2 investigator-initiated trial is on-track with interim data (n=10) anticipated in 2H23 Phase 2 Trials of Ozuriftamab Vedotin in Patients with: ROR2-positive NSCLC (BA3021, NCT03504488) Continuing to enroll in the more frequent, dose-intensive regimen; anticipated interim data readout remains on-track for 2H23 ROR2-positive melanoma (BA3021, NCT03504488) Identifying ROR2-positive tumors using liquid biopsy assayAnticipate increased enrollment in 2H23 ROR2-positive SCCHN (BA3021, NCT05271604) Continuing to enroll patients; ROR2 positivity rate remains high as anticipated ROR2-positive platinum-resistant ovarian cancer (BA3021, NCT04918186) Phase 2 investigator-initiated trial is on track with interim data (n=10) anticipated in 2H23 Phase 1/2 dose-escalation trial of CAB-CTLA-4 (BA3071, NCT05180799) across multiple solid tumor types responsive to CTLA-4 Enrolling 350mg (5mg/kg) dose cohort as monotherapy and in combination with nivolumab 3mg/kg Q3WAnticipated Phase 1 data readout remains on track for 2H23 Initiation of the Phase 2 part of the study remains on track for 2H23 FDA clearance of IND for CAB-EpCAM x CAB-CD3 TCE (BA3182) FPI for Phase 1 study anticipated for 1H23 for the treatment of advanced adenocarcinoma Potential additional IND submissions for pre-clinical CAB bispecific and next generation ADC candidates in 2023 through 2024 Several accepted and upcoming poster presentations, including online publication and Trials in Progress (TiP) poster presentation at the upcoming American Society of Clinical Oncology (ASCO) Annual Meeting, to be held June 2-6, titled: Online publication, “Population Pharmacokinetic and Exposure-Response Safety Analyses of Mecbotamab Vedotin (BA3011) in Patients with Advanced Solid Tumors”TiP poster, “A Phase 2 Open-Label Study of Conditionally Active Biologic, Ozuriftamab Vedotin (BA3021) in PD-1/L1 Failure Patients with Recurrent or Metastatic Squamous Cell Carcinoma of the Head and Neck” First Quarter 2023 Financial Results Cash and cash equivalents as of March 31, 2023 were $192.7 million, compared to $215.5 million as of December 31, 2022. We expect current cash and cash equivalents will be sufficient to fund planned operations including all ongoing CAB product development programs into 2025. Research and development (R&D) expenses were $21.7 million for the quarter ended March 31, 2023 compared to $16.9 million for the same quarter in 2022. The increase of $4.8 million was primarily driven by our preclinical and clinical product development efforts. We expect our R&D expenses to remain variable from quarter to quarter and generally increase as we continue to invest in R&D activities to advance our product candidates and our clinical programs. General and administrative (G&A) expenses were $7.2 million for the quarter ended March 31, 2023 compared to $7.4 million for the same quarter in 2022. The $0.2 million change was attributable to a decrease in various administrative expenses for the 2023 period. We expect our G&A expenses to moderately increase to support development of our product candidates, advance our intellectual property portfolio, support focused pre-commercialization activities for our product candidate mecbotamab vedotin (BA3011) and satisfy requirements as a public company. Net loss for the first quarter ended March 31, 2023 was $27.5 million compared to a net loss of $24.3 million for the same quarter in 2022. Net cash used in operating activities for the first quarter ended March 31, 2023 was $22.7 million compared to net cash used in operating activities of $25.1 million for the same period in 2022. First Quarter 2023 Conference Call and Webcast Details The management of BioAtla, Inc. will host a conference call and webcast for the investment community today, May 11, 2023, at 4:30 pm Eastern Time. A live webcast may be accessed here: https://viavid.webcasts.com/starthere.jsp?ei=1609324&tp_key=f982141e9d. The conference call can be accessed by dialing toll-free (877) 425-9470 or (201) 389-0878 (international). The passcode for the conference call is 13737960. A replay of the webcast and updated slides referenced on the call will be available through “Events & Presentations” in the Investors section of the company’s website after the conclusion of the presentation and will be archived on the BioAtla website for one year. About Mecbotamab Vedotin (BA3011) Mecbotamab vedotin, CAB-AXL-ADC, is a conditionally and reversibly active antibody drug conjugate targeting the receptor tyrosine kinase AXL. This Phase 2 stage clinical asset is targeting multiple solid tumor types, including soft tissue and bone sarcoma and non-small cell lung cancer (NSCLC) that have previously progressed on PD-1/L1, EGFR or ALK inhibitor therapies. We are also supporting a multi-center investigator-initiated clinical trial in combination with durvalumab, a PD-L1-blocking antibody, in patients with platinum-resistant ovarian cancer and for other potential indications in the future. The Office of Orphan Drug Products (OODP) at FDA granted Orphan Drug Designation to mecbotamab vedotin for the treatment of soft tissue sarcoma. About Ozuriftamab Vedotin (BA3021) Ozuriftamab vedotin, CAB-ROR2-ADC, is a conditionally and reversibly active antibody drug conjugate directed against ROR2, a receptor tyrosine kinase that is overexpressed across many different solid tumors including lung, head and neck and melanoma. We are advancing this Phase 2 stage clinical asset for multiple solid tumor types, including NSCLC that have previously progressed on PD-1/L1, EGFR or ALK inhibitor therapies, melanoma that have previously progressed on PD-1/L1 therapy and SCCHN that have previously progressed on PD-1/L1 therapies with or without platinum chemotherapy. We are also supporting a multi-center investigator-initiated clinical trial in combination with durvalumab, PD-L1-blocking antibody, in patients with platinum-resistant ovarian cancer, with other potential indications in the future. About BA3071 BA3071, is a CAB anti-CTLA-4 antibody that is being developed as an immuno-oncology agent with the goal of delivering efficacy at least comparable to the approved anti-CTLA-4 antibodies, but with lower toxicities due to the CAB's tumor microenvironment-restricted activity. This may enable safer anti-CTLA-4 antibody combination therapies, such as with anti-PD-1 antibody checkpoint inhibitors, and potentially broaden the patient population tolerant to combination therapy and deliver greater efficacy. Like our other CAB candidates, BA3071 is designed to be conditionally and reversibly active in the tumor microenvironment. BA3071 is being developed as a potential therapeutic for multiple solid tumor indications that are known to be responsive to CTLA-4 treatment in combination with a PD-1 blocking agent. About BA3182 BioAtla is developing BA3182 as a potential anticancer therapy for patients with advanced adenocarcinoma. BA3182 is a conditionally active biologic (CAB) EpCAM/CD3 bispecific T cell engager antibody that contains two binding sites for EpCAM and two binding sites for CD3ε. The binding sites for EpCAM and CD3ε have been designed to bind their respective targets specifically and reversibly under the conditions found in the TME and to have reduced binding outside of the TME. The CAB selective binding to both the CAB EpCAM and CAB CD3ε arms are required to activate the T cell engagement against the tumor, thus enabling the combined selectivity of each CAB binding arm in the bispecific antibody. BioAtla recently received FDA IND clearance to conduct a first-in-human, Phase 1 study to evaluate the safety, pharmacokinetics, and efficacy of BA3182 in advanced adenocarcinoma patients. About EpCAM EpCAM is involved in the maintenance of epithelial integrity, and its expression is associated with proliferation during morphogenesis, tissue regeneration and stem cell maintenance. Expression levels of EpCAM vary amongst different organs and cell types, with epithelia of colon, small intestine, lung, pancreas, liver and gall bladder expressing the highest levels of EpCAM protein. Given the functions and properties of EpCAM protein, high levels of EpCAM expression have been found in many carcinomas. EpCAM is highly and frequently expressed in the vast majority of carcinomas and their metastasis and has been considered as a potential prognostic and therapeutic marker for many carcinomas. About BioAtla®, Inc.BioAtla is a global clinical-stage biotechnology company with operations in San Diego, California, and in Beijing, China through our contractual relationship with BioDuro-Sundia, a provider of preclinical development services. Utilizing its proprietary Conditionally Active Biologics (CAB) 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 technology and products with 716 patents (440 issued, 7 allowed, and 269 pending). Broad patent coverage in all major markets include methods of making, screening and manufacturing CAB product candidates in a wide range of formats and composition of matter coverage for specific products. BioAtla has two first-in-class CAB programs currently in Phase 2 clinical testing, mecbotamab vedotin, BA3011, a novel conditionally active AXL-targeted antibody-drug conjugate (CAB-AXL-ADC), and ozuriftamab vedotin, BA3021, a novel conditionally active ROR2-targeted antibody-drug conjugate (CAB-ROR2-ADC). The Phase 1 stage CAB-CTLA-4 antibody, BA3071, is a novel CTLA-4 inhibitor designed to reduce systemic toxicity and potentially enable safer combination therapies with checkpoint inhibitors such as anti-PD-1 antibody. The company’s first bispecific antibody, BA3182, targets EpCAM, which is highly and frequently expressed on many adenocarcinomas while engaging human CD3 expressing T cells. To learn more about BioAtla, Inc. visit www.bioatla.com. Forward-looking statementsStatements 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 our business plans and prospects, including our plans to initiate and advance a Phase 1 dose-escalation and expansion clinical study for BA3182, plans to advance our clinical trials for mecbotamab vedotin, BA3011, for ozuriftamab vedotin, BA3021, and for CAB-CTLA-4, BA3071, in multiple indications, whether our clinical trials will support registration; results, conduct, progress and timing of our research and development programs and clinical trials; expectations with respect to enrollment and dosing in our clinical trials, plans regarding future data updates, clinical trials, regulatory meetings and regulatory submissions; the potential regulatory approval path for our product candidates; expectations about the sufficiency of our cash and cash equivalents; and expected R&D and G&A expenses. 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: potential delays in clinical and pre-clinical trials due to the global COVID-19 pandemic; other potential adverse impacts such as delays in regulatory review, manufacturing and supply chain interruptions, adverse effects on healthcare systems and disruption of the global economy; 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; the success of our current and future collaborations with third parties; 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; 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 (SEC) on March 23, 2023, in our Quarterly Report on Form 10-Q filed with the SEC on May 11, 2022 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 law. Internal Contact: Richard Waldron Chief Financial Officer BioAtla, Inc. rwaldron@bioatla.com 858.356.8945 External Contact: Bruce Mackle LifeSci Advisors, LLC bmackle@lifesciadvisors.com BioAtla, Inc. Unaudited Condensed Statements of Operations and Comprehensive Loss(in thousands) Three Months Ended March 31, 2023 2022 Operating expenses: Research and development expense$21,697 $16,923 General and administrative expense 7,233 7,423 Total operating expenses 28,930 24,346 Loss from operations (28,930) (24,346)Other income (expense): Interest income 1,480 85 Other income (expense) (10) 7 Total other income (expense) 1,470 92 Consolidated net loss and comprehensive loss$(27,460) $(24,254) BioAtla, Inc.Condensed Balance Sheets Data(in thousands) March 31, 2023 December 31, 2022 Cash and cash equivalents$192,687 $215,507Total assets 204,552 225,736Total current liabilities26,256 23,131Total liabilities 48,125 45,397Total stockholders’ equity 156,427 180,339Total liabilities and stockholders’ equity 204,552 225,736