PARP1, also called as Poly(ADP-ribose) polymerase, is involved in the signaling of DNA damage. It can recognize and bind DNA single or double-strand breaks, thus possessing various cellular function, including regulation of apoptosis and chromosome stability, gene amplification and transcription, as well as cell division and differentiation. PARP-2 is the closest homolog of PARP1 (~62% similarity in catalytic domain) and compensates for PARP-1 activity in DNA single-strand break. BMN 673 is a potent PARP1/2 inhibitor with IC50 value of 0.57nM for PARP1 (measured by PARP1 enzyme activity). BMN673 showed EC50 value of 2.5nM for inhibition of cellular PAR synthesis in LoVo cells, IC50 value of 5nM for single-agent cytotoxicity of Capan-1 cell survival reduction and GI50 value of 3nM for Temozolomide potentiation assay in LoVo cells. BMN 673 selectivity inhibited BRCA-deficient cells and delivered a therapeutic window between BRCA-proficient and –deficient models at much lower concentrations compared with the other PARP inhibitor, veliparib, rucaparib and olaparib. BMN 673 possessed good pharmacodynamics, as a single oral administration of 1 mg/kg BMN 673 caused drastically decreased intratumoral PAR levels at 2 and 8 hours following drug administration with partial recovery observed at 24 hours after dosing. Oral administration of BMN 673 at dose of 0.33mg/kg, daily, for 28 days caused significant growth inhibition of MX-1 xenografts in mice[1]. BMN 673 showed ~100-fold more potent at trapping PARP-DNA complexes and more cytotoxic as single agent than olaparib[2].
作用机制
BMN 673 is anchored to the nicotinamide-binding pocket of PARP and extends the binding interactions towards the outer edges of the pocket, which exhibit the least sequence homology among PARP enzymes.[3]
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