Poly(ADP-ribose)polymerase (PARP) inhibition and anticancer activity of simmiparib, a new inhibitor undergoing clinical trials.

Poly(ADP-ribose)polymerase (PARP)1/2 inhibitors have been proved to be clinically effective anticancer drugs. Here we report a new PARP1/2 inhibitor, simmiparib, displaying apparently improved preclinical anticancer activities relative to the first approved inhibitor olaparib. Simmiparib inhibited PARP1/2 approximately 2-fold more potently than olaparib, with more than 90-fold selectivity over the other tested PARP family members. Simmiparib and olaparib caused similar cellular PARP1-DNA trapping. Simmiparib selectively induced the accumulation of DNA double-strand breaks, G2/M arrest and apoptosis in homologous recombination repair (HR)-deficient cells. Consistently, simmiparib showed 26- to 235-fold selectivity in its antiproliferative activity against HR-deficient cells over the corresponding isogenic HR-proficient cells. Notably, its antiproliferative activity was 43.8-fold more potent than that of olaparib in 11 HR-deficient cancer cell lines. Simmiparib also potentiated the proliferative inhibition of several conventional anticancer drugs. Simmiparib reduced the poly(ADP-ribose) formation in HR-deficient cancer cells and xenografts. When orally administered to nude mice bearing xenografts, simmiparib revealed excellent pharmacokinetic properties. Simmiparib caused approximately 10-fold greater growth inhibition than olaparib against HR-deficient human cancer cell- or tissue-derived xenografts in nude mice. Collectively, these findings support the undergoing clinical trials of simmiparib.

Yuan B ，Ye N ，Song SS ，Wang YT ，Song Z ，Chen HD ，Chen CH ，Huan XJ ，Wang YQ ，Su Y ，Shen YY ，Sun YM ，Yang XY ，Chen Y ，Guo SY ，Gan Y ，Gao ZW ，Chen XY ，Ding J ，He JX ，Zhang A ，Miao ZH ... -  《-》

Pharmacologic characterization of fluzoparib, a novel poly(ADP-ribose) polymerase inhibitor undergoing clinical trials.

Poly(ADP-ribose) polymerase (PARP) enzymes play an important role in repairing DNA damage and maintaining genomic stability. Olaparib, the first-in-class PARP inhibitor, has shown remarkable clinical benefits in the treatment of BRCA-mutated ovarian or breast cancer. However, the undesirable hematological toxicity and pharmacokinetic properties of olaparib limit its clinical application. Here, we report the first preclinical characterization of fluzoparib (code name: SHR-3162), a novel, potent, and orally available inhibitor of PARP. Fluzoparib potently inhibited PARP1 enzyme activity and induced DNA double-strand breaks, G2 /M arrest, and apoptosis in homologous recombination repair (HR)-deficient cells. Fluzoparib preferentially inhibited the proliferation of HR-deficient cells and sensitized both HR-deficient and HR-proficient cells to cytotoxic drugs. Notably, fluzoparib showed good pharmacokinetic properties, favorable toxicity profile, and superior antitumor activity in HR-deficient xenografts models. Furthermore, fluzoparib in combination with apatinib or with apatinib plus paclitaxel elicited significantly improved antitumor responses without extra toxicity. Based on these findings, studies to evaluate the efficacy and safety of fluzoparib (phase II) and those two combinations (phase I) have been initiated. Taken together, our results implicate fluzoparib as a novel attractive PARP inhibitor.

Wang L ，Yang C ，Xie C ，Jiang J ，Gao M ，Fu L ，Li Y ，Bao X ，Fu H ，Lou L ... -  《-》

Discovery of potent 2,4-difluoro-linker poly(ADP-ribose) polymerase 1 inhibitors with enhanced water solubility and in vivo anticancer efficacy.

Chen WH ，Song SS ，Qi MH ，Huan XJ ，Wang YQ ，Jiang H ，Ding J ，Ren GB ，Miao ZH ，Li J ... -  《-》

Histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), enhances anti-tumor effects of the poly (ADP-ribose) polymerase (PARP) inhibitor olaparib in triple-negative breast cancer cells.

Min A ，Im SA ，Kim DK ，Song SH ，Kim HJ ，Lee KH ，Kim TY ，Han SW ，Oh DY ，Kim TY ，O'Connor MJ ，Bang YJ ... -  《-》

Discovery, mechanism and metabolism studies of 2,3-difluorophenyl-linker-containing PARP1 inhibitors with enhanced in vivo efficacy for cancer therapy.

Poly (ADP-ribose) polymerase 1 (PARP1) is overexpressed in a variety of cancers, especially breast and ovarian cancers, and tumor cell lines deficient in breast cancer gene 1/2 (BRCA1/2) are highly sensitive to PARP1 inhibition. In this study, with the help of molecular docking, we identified a novel series of 2,3-difluorophenyl-linker analogues (15-54) derived from olaparib (1) as PARP1 inhibitors. Lead optimization led to the identification of 47, which showed high selectivity and high potency against PARP1 enzyme (IC50 = 1.3 nM), V-C8 cells (IC50 = 0.003 nM), Capan-1 cells (IC50 = 7.1 nM) and MDA-MB-436 cells (IC50 = 0.2 nM). Compound 47 had more potent PARP1-DNA trapping and double-strand breaks (DSBs)-induction activities than 1 and induced G2/M arrest and caspase-dependent apoptosis. Compound 47 (50 mg/kg, 94.2%) had a more beneficial effect on tumor growth inhibition than 1 (100 mg/kg, 65.0%) in a BRCA1-mutated xenograft model and significantly inhibited tumor growth (40 mg/kg, 48.1%) in a BRCA2-mutated xenograft model, with no negative influence on the body weight of the mice. Collectively, these data demonstrated that 47 might be an excellent drug candidate for the treatment of cancer, especially for BRCA-deficient tumors.

Chen W ，Guo N ，Qi M ，Dai H ，Hong M ，Guan L ，Huan X ，Song S ，He J ，Wang Y ，Xi Y ，Yang X ，Shen Y ，Su Y ，Sun Y ，Gao Y ，Chen Y ，Ding J ，Tang Y ，Ren G ，Miao Z ，Li J ... -  《-》