#1First Quarter Earnings 2022 Supplemental Slides May 4, 2022 bicatla 1#2Important Notices & Disclaimers This presentation (the "Presentation") by BioAtla, Inc. ("we", "us", "our", "BioAtla", or the "Company") contains "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995 relating to our business, operations and financial conditions, including but not limited to current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, results of clinical trials and other future conditions. Words such as, but not limited to, "anticipate", "believe", "could", "estimate", "expect", "intend", "may", "plan", "potential", "predict", "project", "should", "will", "would" or the negative of those terms, and similar expressions that convey uncertainty of future events or outcomes, identify forward-looking statements. These forward-looking statements reflect management's beliefs and views with respect to future events and are based on estimates and assumptions as of the date of this Presentation and are subject to risks and uncertainties, including those described in the Company's filings with the SEC, including but not limited to the Company's latest Annual Report on Form 10-K. Moreover, the Company operates in a very competitive and rapidly changing environment. New risks emerge from time to time. It is not possible for management to predict all risks, nor can the Company assess the impact of all factors on its business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements we may make. Given these uncertainties, you should not place undue reliance on these forward-looking statements. The Company qualifies all the forward-looking statements in this Presentation by these cautionary statements. Except as required by law, the Company undertakes no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise. Statements contained herein are made as of the date of this Presentation unless stated otherwise, and this Presentation shall not under any circumstances create an implication that the information contained herein is correct as of any time after such date or that the information will be updated or revisited to reflect information that subsequently becomes available or changes occurring after that date hereof. Certain information contained in this Presentation relates to or is based on statistical and other industry and market data obtained from independent industry publications and research, surveys and studies conducted by independent third parties as well as the Company's own estimates of the prevalence of certain diseases and conditions. The market data used in this Presentation involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such data. Industry publications and third-party research, surveys and studies generally indicate that their information has been obtained from sources believed to be reliable, although they do not guarantee the accuracy or completeness of such information. The Company's estimates of the patient population with the potential to benefit from treatment with any product candidates the Company may develop include several key assumptions based on its industry knowledge, industry publications and third-party research, which may be based on a small sample size and may fail to accurately reflect the addressable patient population. While the Company believes that its internal assumptions are reasonable, no independent source has verified such assumptions. This Presentation may contain trademarks, trade names, or service marks belonging to other entities. The Company does not intend the use or display of other parties' trade names, trademarks or service marks to imply a relationship with, or endorsement or sponsorship of, or by these other parties. None of the Company or any of its directors, officers, employees, contractors, agents, consultants, advisors or other representatives makes any representation or warranty, express or implied, as to the accuracy or completeness of the information contained in this Presentation. bicatla 2#3Sarcoma Phase 2 Part 1 Design: Predefined Interim Analysis Decision Tree PHASE 2 - SARCOMA STS Monotherapy Bone Combo with PD-1 LMS Syn Lipo Others Osteo Ewing Others ~10 patients w TmPS>=70 ~10 patients w TmPS>=70 ~10 patients w TmPS>=70 ~10 patients w TmPS>=70 ~10 patients w TmPS>=70 ~10 patients w TmPS>=70 ~10 patients w TmPS>=70 ~10 patients w CD20 pos ~10 patients w CD20 neg For each Subgroup up to 10 patients No Go if 0 CR/PR and PFR12 week < 40% Go if ≥ 1 CR/PR or PFR12 week ≥ 40% bicatla Mecbotamab vedotin - BA3011 3#4Sarcoma: Phase 2 Part 1 Topline Interim Analysis Results PHASE 2 - SARCOMA STS Bone LMS Syn. Monotherapy Others / UPS Combo with PD-1 Lipo Osteo Ewing Others (chondro/chordo) Part 1 (Actual*) 17 patients 3 patients 4 patients 8/5 patients 6 patients 0 patients 7 (4/3) CD20 pos: 14 patients CD20 neg: 4 patients Predefined Criteria For each Subgroup up to 10 patients No Go if 0 CR/PR and PFS 3months < 40% Go if ≥ 1 CR/PR or PFS 3months > 40% * As of data cut-off of Apr 28, 2022; Cohorts in grey continuing enrollment until sufficient sample size is achieved Interim Results ● • LMS not moving forward O PFS = 27% (pending confirmation) • UPS moving forward O PR = 2/6 • Osteosarcoma moving forward O PFS = 67% bicatla Mecbotamab vedotin - BA3011 *Included in UPS cohort Combo w PD-1 moving forward O PR = 1/ 1 (UPS)* o PFS (combo overall) = 51% All other cohorts (in grey) – continue enrollment 4#5Undifferentiated Pleomorphic Sarcoma (UPS): Phase 1 & 2 (1.8mg/kg; n=8) Change in Target Lesion and Progression Free Survival 100 80 60 40 20 0 -20 -40 -60 -80 -100 Baseline PHASE 1/2 - UPS Change Target Lesion From Baseline (%) Week 6 Week 20 Week 12 Interim data- Data cut-off of April 28, 2022 Week 28 Combo Week 36 Week 44 Week 52 Week 60 Week 68 Week 76 Week 84 Week 92 Week 100 Progression Free Survival Probability Number at Risk All Patients 0.8 0.6 0.4- 0.2 0.0- 0 T 1 2 3 Progression-free Survival Events n(%) 5(62.5) 4 8 8 7 3 3 All Patients 5 3 T 6 7 8 9 10 11 12 13 Months from First Dose 3 3 2 2 2 1 1 1 Mecbotamab vedotin - BA3011 Median (mos) (95% CI) 6.8 (1.4-NE) 14 15 16 bicatla 1 1 1 17 18 PFS 3mo % (95% CI) 50.0 (15.2, 77.5) 19 20 21 1 1 0 5#650 40 30 20 10 0 -10 -20 -30 -40 -50 Osteosarcoma: Phase 1 & 2 (1.8mg/kg; n=7) Change in Target Lesion and Progression Free Survival Week 0 PHASE 1/2 - Osteosarcoma Change in target lesion from baseline (%) week 6 Interim data- Data cut-off of April 28, 2022 week 12 week 18 week 24 Progression Free Survival Probability 1.0 0.8 0.6 0.4 0.2 0.0 Number at Risk All Patients 0 7 1 7 2 4 All Patients Progression-free Survival) Events n(%) 4(57.1) 4 3 5 Months from First Dose 2 1 1 Mecbotamab vedotin - BA3011 Median (mos) (95% CI) 3.8 (1.2-NE) 1 bicatla PFS 3mo % (95% CI) 57.1 (17.2, 83.7) 7 0 Recent independent phase 2 study demonstrated placebo PFS rate at 2 months for 1st and 2nd line metastatic osteosarcoma of ~0% (www.thelancet.com/oncology Vol 20 January 2019) 8 6#7Oo Stage IV Multi-Refractory Melanoma: Phase 1 & 2 Complete Response Observed in Two of Two ROR2+ Patients Phase 1/2 - MELANOMA Data on file. % Change in Target Lesions from Baseline 100 80 60 40 20 0 -20 -40 -60 -80 -100 0 Phase 2 Patient Details: Prior treatment failure: nivolumab followed by Dacarbazine ✓ Complete Response on 1st scan (3 doses) 20 ROR2 + Phase 2 Patient 40 60 80 Time (weeks) 100 120 140 Phase 1 Patient Details: ✓ Prior treatment failure: nivolumab followed by nivolumab + ipilimumab combination Clearance of pulmonary metastases followed by normalization of adenopathy Continued CR Off treatment for over 2 yrs ROR2 + Phase 1 Patient bicatla 160 Ozuriftamab vedotin - BA3021 7#8Continued Promising Safety and Tolerability Profile in Phase 2 at the RP2D PHASE 2 AEs Overview ■ ■ ■ AEs consistent with MMAE-based toxicity, including: Reversible myelosuppression Transient liver enzyme elevation Metabolic disturbances Few related SAEs Few related AEs leading to treatment discontinuation Mecbo - BA3011 CAB AXL-ADC Dosing 1.8mg/kg Q2W (safety population Phase 2) Characteristic Any Adverse Events (AES) Related AEs with CTCAE¹ Grade 3 or 4²2 Any related serious AEs² Related AEs leading to death² Related AEs leading to treatment discontinuation² BA3011 (N=68) 61 (90%) 16 (23%) 6 (9%) Mecbo - BA3011 Peripheral Neuropathy ● Constipation ● Constipation is believed to be an on-target mediated effect Diarrhea Grade 1-2 (18%) Grade 3-4 (0%) All Grade 1-2 (23%) Grade 1-2 (19%) Grade 3-4 (0%) bicatla No clinically meaningful on-target toxicity observed over background Differentiated profile due to advantageous pharmacokinetic characteristics of CAB ADCs 2 (3%) Note: ¹CTCAE: Common Terminology Criteria for Adverse Events. The NCI Common Terminology Criteria for Adverse Events is a descriptive terminology which is utilized for Adverse Event (AE) reporting. A grading (severity) scale is provided for each AE term. 2As assessed by the investigator. Missing responses are counted as related. §Grade 2 peripheral neuropathy Interim data- Data cut-off of March 31, 2022 8#9● Significant Unmet Need and Commercial Opportunity Across Multiple Solid Tumors Types • ~17K newly diagnosed metastatic cases / yr (US) ● Sarcoma 5-year survival rate (~20% for advanced metastatic disease) UPS is one of the largest and most aggressive sarcoma subtypes Osteosarcoma represents nearly 1/3 of all bone sarcoma cases aggressive tumors - high recurrence - with limited treatment options ● NSCLC ~200K newly diagnosed NSCLC patients/yr (US) J 5-year survival rate (~25% for advanced metastatic disease) • While relatively crowded market, there is a lack of efficacious therapies for refractory patients Sources: www.cancer.net; www.cancer.org; Clarivate, Disease Landscape and Forecast: NSCLC, Melanoma, SCCHN (2022) Melanoma ● ~200K newly diagnosed cases / yr (US) - 50% invasive • 5-year survival rate (~25% for advanced metastatic disease) ~1.3mm people in the US living with melanoma Head & Neck • ~66K newly diagnosed cases / yr (US) ● ● bicatla 5-year survival rate (~40% for recurrent or advanced metastatic disease) Deficit of 2nd line treatments 9