IDEAYA Biosciences Interim IDE397 Phase 1 Clinical Data and Q1 2022 Corporate Update

14 IDE397 Clinical Phase 1 Interim Tumor Pharmacodynamic Data 95% Reduction in Tumor SDMA Tumor SDMA in Cohort 5 NSCLC Patient Predose 95% Reduction of Tumor SDMA Tumor SDMA IHC, 20X H-score: 280 % of total number of cells scored 100 80 60 40 20 8620 0 Cohort 5 NSCLC Patient IHC Scores Observed AUC ss value in Cohort 5 NSCLC patient within predicted target efficacious exposure range# Plasma SAM Reduction of 79% Tumor SDMA Reduction of 95% #Based on preclinical PK/PD analysis On Treatment H-score: 13 IDEAYA Data: % Reduction of Tumor SDMA measured by IHC H-Score Pre-Dose Post-Dose 3+ 2+ 1+ 0 Staining Intensity - High (+3) to Low (0) gsk IDEAA IDEAYA BIOSCIENCES

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