BioAtla Results Presentation Deck

50 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

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