BioAtla Results Presentation Deck

Sarcoma: 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

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