We recently reported an orally bioavailable CDK12/13 inhibitor, SR-4835, that selectively targets the CDK12/13 ATP binding site with high affinity.22,23 SR-4835 sensitizes triple-negative breast cancer cells to PARP inhibitors and DNA-damaging chemotherapeutics by reducing expression of the genes in the DNA damage response pathway and stimulates rapid tumor regression in multiple patient-derived xenograft mouse models. The gene discussed is CDK12; the disease is triple-negative breast carcinoma.