BioAtla Investor Presentation Deck

Sarcoma update ● ● Initiated UPS Phase 2, part 2 potentially registrational study Based on safety and exposure-response of our CAB-ADCs, we believe that we can further maximize benefit while maintaining an acceptable and differentiated safety profile with more frequent dosing - Enrolling total of ~80 AXL-expressing UPS patients in Phase 2, part 2 o FDA supportive of investigating a more frequent dosing regimen (3Q4W 44% and 2Q3W 38% increased exposure over Q2W) o First 40 patients with a TmPS >= 50% will be randomized 1:1 to 3Q4W or 2Q3W dosing regimen O o Additional 40 patients will be enrolled at the selected dose Primary efficacy endpoint is objective response rate (ORR) per RECIST v1.1 o Primary efficacy analysis will be based on ~60 patients treated at the selected dosing regimen Prior systemic regimens limited to <3 Currently studying 3Q4W dosing regimen in LMS / UPS Phase 2, part 1 cohorts (combined n = ~10-15) First 6 patients cleared DLT period using the more frequent dosing (3Q4W) - completed Q1'23 - bicatla UPS = Undifferentiated Pleomorphic Sarcoma; LMS = Leiomyosarcoma BioAtla| Overview 13

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