BioAtla Investor Presentation Deck

Osteosarcoma: Phase 1 & 2 Change in Target Lesion and Progression Free Survival (1.8mg/kg; n=7) 50 40 30 20 10 0 -10 -20 -30 -40 -50 Week 0 Change in target lesion from baseline (%) ■ week 6 week 12 week 18 week 24 Progression Free Survival Probability Number at Risk 1.0- 0.8 Interim data- Data cut-off of April 28, 2022 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) 0.6 0.4 0.2- 0.0- All Patients 0 7 Progression-free Survival 7 All Patients 2 3 4 Events n(%) 4(57.1) 4 Median (mos) (95% CI) 3.8 (1.2 - NE) 5 Of 7 patients enrolled, PFS rate at 3 months was 57% When combining all Phase 1 & 2 bone sarcoma patients, a total of 7 patients were enrolled and observed a PFS rate at 3 months of 56% Interim results satisfied the pre-defined Go criteria of osteosarcoma cohort into part 2 of the Phase 2 study bicatla Months from First Dose 2 1 6 1 PFS 3mo % (95%CI) 57.1 (17.2, 83.7) 1 7 8 0 BioAtla| Overview 13

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