We have confirmed that Bcl-xL inhibitor A-1331852 enhances antitumor activity of genotoxic payloads by combining B7-H3- seco-DUBA ADC with unconjugated A-1331852 using in vivo C4-2B and C4-2B TP53 KO tumor models. The gene discussed is TP53; the disease is neoplasm.