MD-4251: A First-in-Class Oral MDM2 Degrader Inducing Complete Tumor Regression with Single-Dose Administration

MDM2 is a key negative regulator of the tumor suppressor p53 and an attractive target for cancer therapy. We report the discovery of MD-4251, the first orally efficacious MDM2 degrader developed using PROTAC technology. MD-4251 induces potent and rapid MDM2 degradation in RS4;11 cells (DC₅₀ = 0.2 nM; D_max = 96% at 2 h), leading to robust p53 activation. It selectively inhibits the growth of acute leukemia cell lines with wild-type p53, with minimal activity in p53 mutant lines. MD-4251 shows excellent oral bioavailability in mice, favorable metabolic stability, and no CYP or hERG liabilities. A single oral dose induces sustained MDM2 depletion and attains complete tumor regression in vivo. These results support MD-4251 as a promising therapeutic candidate for cancers through depletion of MDM2.