Rintodestrant (G1T48) is an orally active, non-steroidal, selective estrogen receptor degrader (SERD) and CDK4/6 inhibitor.

Rintodestrant (G1T48) serves as a potent and effective inhibitor, targeting estrogen-mediated transcription and proliferation specifically in ER-positive breast cancer cells, mirroring the efficacy of the pure antiestrogen agent fulvestrant. Its activity is exclusive to ER-positive breast cancer cells, showing no effect on ER-negative cell types. In a Cell Viability Assay utilizing MCF7 cells at concentrations ranging from 1 pM to 1 μM over an incubation period of 18 hours, Rintodestrant demonstrated a significant downregulation of the estrogen receptor, markedly inhibiting estrogen-stimulated growth in these cells with a potency approximately threefold greater than that of Fulvestrant. Notably, this inhibition does not influence apoptosis within MCF7 breast cancer cells.

Rintodestrant (G1T48, 30 or 100 mg/kg) effectively suppresses estrogen signaling in models of endocrine-resistant breast cancer, specifically in MCF7 xenograft tumors[1]. Administered orally at doses of 30 or 100 mg/kg daily for 28 days, it exhibits a dose-dependent reduction in TamR tumor growth.