SPH420

SPH420 is an investigational, orally bioavailable small molecule inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), developed by Shanghai Pharmaceuticals. It is designed to selectively target the CDK4/6-cyclin D-retinoblastoma (Rb) signaling pathway, which is frequently dysregulated in various cancers, particularly hormone receptor-positive (HR+) breast cancer. By inhibiting CDK4 and CDK6, SPH420 prevents the phosphorylation of the Rb protein, thereby arresting the cell cycle in the G1 phase and inhibiting tumor cell proliferation. The drug is currently undergoing clinical evaluation to determine its safety, tolerability, and preliminary efficacy in patients with advanced solid tumors and breast cancer.