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

A Genetically Encoded Sensor for Real-Time Monitoring of Poly-ADP-Ribosylation Dynamics In Vitro and in Cells

ADP-ribosylation, the transfer of ADP-ribose (ADPr) from nicotinamide adenine dinucleotide (NAD+) groups to proteins, is a conserved post-translational modification (PTM) that occurs most prominently in response to DNA damage. ADP-ribosylation is a dynamic PTM regulated by writers (PARPs), erasers (ADPr hydrolases), and readers (ADPR binders). PARP1 is the primary DNA damage-response writer responsible for adding a polymer of ADPR to proteins (PARylation). Real-time monitoring of PARP1-mediated PARylation, especially in live cells, is critical for understanding the spatial and temporal regulation of this unique PTM. Here, we describe a genetically encoded FRET probe (pARS) for semiquantitative monitoring of PARylation dynamics. pARS feature a PAR-binding WWE domain flanked with turquoise and Venus. With a ratiometric readout and excellent signal-to-noise characteristics, we show that pARS can monitor PARP1-dependent PARylation temporally and spatially in real-time. pARS provided unique insights into PARP1-mediated PARylation kinetics in vitro and high-sensitivity detection of PARylation in live cells, even under mild DNA damage. We also show that pARS can be used to determine the potency of PARP inhibitors in vitro and, for the first time, in live cells in response to DNA damage. The robustness and ease of use of pARS make it an important tool for the PARP field.

Development of UPLC-MS/MS method for studying the pharmacokinetic interactions of fuzuloparib with curcumin in rats

Fuzuloparib is a novel orally bioactive poly-ADP-ribose polymerase inhibitor (PARPi), which was approved by the Chinese Regulatory Agency (CRA) in 2020 for the treatment of platinum-sensitive recurrent ovarian, fallopian tube, and primary peritoneal cancers. This study firstly presents a rapid and accurate ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for analyzing the levels of fuzuloparib and its major metabolite (SHR165202), and to investigate drug-drug interaction between fuzuloparib and curcumin in vitro and in vivo studies. After protein precipitation with acetonitrile, mobile phase consisted of acetonitrile and 0.1 % formic acid with a gradient elution was used to successfully separate fuzuloparib, SHR165202 and talazoparib (internal standard, IS). The results indicated that fuzuloparib and SHR165202 had good linearity over the calibration range of 2-50 ng/mL and 1-20 ng/mL, respectively. The precision, accuracy, stability, matrix effect, and extraction recovery required for methodological validation all complied with the requirements of the Bioanalytical Method Validation Guidelines. In vitro microsome incubation experiments, curcumin exhibited inhibitory effect on fuzuloparib in both rat liver microsomes (RLM) and human liver microsomes (HLM) with half-maximal inhibitory concentration (IC50) value of 10.54 μM and 47.64 μM, respectively, and the corresponding mechanism was non-competitive. Furthermore, the inhibitory mechanism of curcumin on fuzuloparib was validated through molecular docking. In pharmacokinetic experiments in rats, curcumin significantly altered the plasma exposure of fuzuloparib, resulting in significant increases in AUC(0-t) and Cmax of fuzuloparib and a significant decrease in CLz/F. Moreover, the metabolite SHR165202 showed significant increases in AUC(0-t), AUC(0-∞), Tmax and Cmax and a significant decrease in CLz/F. This further supports the notion that curcumin could inhibit the metabolism of fuzuloparib. Therefore, when co-administering fuzuloparib and curcumin in clinic, it is recommended to monitor plasma levels of fuzuloparib and pay close attention to adverse effects. If necessary, the dose of fuzuloparib needs to be reduced.

Design, synthesis and antitumor activities of phthalazinone derivatives as PARP-1 inhibitors and PARP-1/HDAC-1 inhibitors

In recent years, poly(ADP-ribose)polymerase-1 (PARP-1) and histone deacetylase (HDAC) have emerged as significant targets in tumor therapy, garnering widespread attention. In this study, we designed and synthesized two novel phthalazinone PARP-1 inhibitors and dual PARP-1/HDAC-1 inhibitors, named DLC-1-46 containing dithiocarboxylate fragments and DLC-47-63 containing hydroxamic acid fragments, and evaluated their inhibitory activities on enzymes and cells. Among the PARP-1 inhibitors, most compounds exhibited high inhibitory activity against the PARP-1 enzyme, with DLC-1-6 being particularly notable, showing IC50 values <0.2 nM. Notably, DLC-1 demonstrated significant anti-proliferative activity, with IC50 values for inhibiting the proliferation of MDA-MB-436, MDA-MB-231, and MCF-7 cells reaching 0.08, 26.39, and 1.01 μM, respectively. Further investigation revealed that DLC-1 arrested MDA-MB-231 cells in the G1 phase and induced apoptosis in a dose-dependent manner. Among the designed dual PARP-1/HDAC-1 inhibitors, several compounds exhibited potent dual-target inhibitory activity, with DLC-49 displaying IC50 values of 0.53 nM and 17 nM for PARP-1 and HDAC-1, respectively. DLC-50 demonstrated the most potent anti-proliferative activity, with IC50 values for inhibiting the proliferation of MDA-MB-436, MDA-MB-231, and MCF-7 cells at 0.30, 2.70, and 2.41 μM, respectively. Cell cycle arrest and apoptosis assays indicated that DLC-50 arrested the cell cycle in the G2 phase and induced apoptosis in HCT-116 cells. Our findings present a novel avenue for further exploration of PARP-1 inhibitors and dual PARP-1/HDAC-1 inhibitors.

Phase 1b study of first-line fuzuloparib combined with modified FOLFIRINOX followed by fuzuloparib maintenance monotherapy in pancreatic adenocarcinoma

BACKGROUND

Chemotherapy remains the standard first-line treatment for pancreatic adenocarcinoma, but with limited efficacy. We aimed to explore the feasibility of adding the PARP inhibitor fuzuloparib to mFOLFIRINOX in the locally advanced/metastatic (LA/M) setting.

METHODS

This was the dose-escalation and -expansion, phase 1b portion of a phase 1b/2 study. Patients were given oral fuzuloparib at escalating doses starting at 30 mg twice daily (BID) plus intravenous mFOLFIRINOX q2w for 8-12 cycles, followed by maintenance fuzuloparib at 150 mg BID. Cohorts at the maximal tolerated dose (MTD) and lower dose of fuzuloparib were expanded. Primary endpoints were dose-limiting toxicity (DLT), MTD, and recommended phase 2 dose (RP2D).

RESULTS

As of data cutoff on Jan 15, 2023, 39 patients were recruited. 12 patients were enrolled during dose escalation (30 mg [n = 4]; 60 mg [n = 6]; 100 mg [n = 2]). DLT occurred in 1 patient in 60 mg cohort and 1 patient in 100 mg cohort. 60 mg BID was determined to be the MTD, and then 60 and 30 mg cohorts were expanded to 22 and 15 patients, respectively. The most common grade ≥ 3 treatment-related adverse events were hematologic toxicities. Efficacy in 60 mg cohort seemed to be most favorable, with an objective response rate of 50.0% (95% CI, 26.0-74.0) and disease control rate of 94.4% (95% CI, 72.7-99.9).

CONCLUSIONS

First-line fuzuloparib plus mFOLFIRINOX followed by maintenance fuzuloparib was generally safe and showed encouraging anti-tumor activity in patients with LA/M pancreatic adenocarcinoma. The RP2D of fuzuloparib combination was 60 mg BID.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04228601.

Proteasome and PARP1 dual-target inhibitor for multiple myeloma: Fluzoparib

One of the current mainstream treatments for multiple myeloma (MM) is chemotherapy. However, due to the high clonal heterogeneity and genomic complexity of MM, single-target drugs have limited efficacy and are prone to drug resistance. Therefore, there is an urgent need to develop multi-target drugs against MM. We screened drugs that simultaneously inhibit poly(ADP-ribose) polymerase 1 (PARP1) and 20S proteasome through computer-aided drug discovery (CADD) techniques, and explored the binding mode and dynamic stability of selected inhibitor to proteasome through Molecular biology (MD) simulation method. Thus, the dual-target inhibition effect of fluzoparib was proposed for the first time, and the ability of dual-target inhibition and tumor killing was explored at the enzyme, cell and animal level, respectively. This provides a theoretical and experimental basis for exploring multi-target inhibitory drugs for cancers.

Design of Selective PARP-1 Inhibitors and Antitumor Studies

Designing selective PARP-1 inhibitors has become a new strategy for anticancer drug development. By sequence comparison of PARP-1 and PARP-2, we identified a possible selective site (S site) consisting of several different amino acid residues of α-5 helix and D-loop. Targeting this S site, 140 compounds were designed, synthesized, and characterized for their anticancer activities and mechanisms. Compound I16 showed the highest PARP-1 enzyme inhibitory activity (IC50 = 12.38 ± 1.33 nM) and optimal selectivity index over PARP-2 (SI = 155.74). Oral administration of I16 (25 mg/kg) showed high inhibition rates of Hela and SK-OV-3 tumor cell xenograft models, both of which were higher than those of the oral positive drug Olaparib (50 mg/kg). In addition, I16 has an excellent safety profile, without significant toxicity at high oral doses. These findings provide a novel design strategy and chemotype for the development of safe, efficient, and highly selective PARP-1 inhibitors.

A genetically encoded sensor for real-time monitoring of poly-ADP-ribosylation dynamics in-vitro and in cells

ADP-ribosylation, the transfer of ADP-ribose (ADPr) from nico-tinamide adenine dinucleotide (NAD+) groups to proteins, is a conserved post-translational modification (PTM) that occurs most prominently in response to DNA damage. ADP-ribosylation is a dynamic PTM regulated by writers (PARPs), erasers (ADPr hy-drolases), and readers (ADPR binders). PARP1 is the primary DNA damage-response writer responsible for adding a polymer of ADPR to proteins (PARylation). Real-time monitoring of PARP1-mediated PARylation, especially in live cells, is critical for under-standing the spatial and temporal regulation of this unique PTM. Here, we describe a genetically encoded FRET probe (pARS) for semi-quantitative monitoring of PARylation dynamics. pARS feature a PAR-binding WWE domain flanked with turquoise and Venus. With a ratiometric readout and excellent signal-to-noise characteristics, we show that pARS can monitor PARP1-dependent PARylation temporally and spatially in real-time. pARS provided unique insights into PARP1-mediated PARylation kinetics in vitro and high-sensitivity detection of PARylation in live cells, even under mild DNA damage. We also show that pARS can be used to determine the potency of PARP inhibitors in vitro and, for the first time, in live cells in response to DNA damage. The robustness and ease of use of pARS make it an important tool for the PARP field.

Synthetically accessible de novo design using reaction vectors: Application to PARP1 inhibitors

De novo design has been a hotly pursued topic for many years. Most recent developments have involved the use of deep learning methods for generative molecular design. Despite increasing levels of algorithmic sophistication, the design of molecules that are synthetically accessible remains a major challenge. Reaction-based de novo design takes a conceptually simpler approach and aims to address synthesisability directly by mimicking synthetic chemistry and driving structural transformations by known reactions that are applied in a stepwise manner. However, the use of a small number of hand-coded transformations restricts the chemical space that can be accessed and there are few examples in the literature where molecules and their synthetic routes have been designed and executed successfully. Here we describe the application of reaction-based de novo design to the design of synthetically accessible and biologically active compounds as proof-of-concept of our reaction vector-based software. Reaction vectors are derived automatically from known reactions and allow access to a wide region of synthetically accessible chemical space. The design was aimed at producing molecules that are active against PARP1 and which have improved brain penetration properties compared to existing PARP1 inhibitors. We synthesised a selection of the designed molecules according to the provided synthetic routes and tested them experimentally. The results demonstrate that reaction vectors can be applied to the design of novel molecules of biological relevance that are also synthetically accessible.

Design and synthesis of novel chloropyridazine hybrids as promising anticancer agents acting by apoptosis induction and PARP-1 inhibition through a molecular hybridization strategy

Guided by the molecular hybridization principle, a novel series of 4-chloropyridazinoxyphenyl conjugates (3a-h, 4a-e, and 5) was designed and synthesized as proposed apoptotic inducers and PARP-1 inhibitors. The growth inhibition % of the designed hybrids was investigated in eleven cancer cell lines, where the anticancer activities were found to be in the following order: 4-chloropyridazinoxyphenyl-aromatic ketones hybrids (3a-h) > 4-chloropyridazinoxyphenyl-benzyloxyphenylethan-1-one hybrids (4a-e) > 4-chloropyridazinoxyphenyl-thiazolidine-2,4-dione hybrid (5). Further, the most sensitive three cancer cell lines (HNO97, FaDu, and MDA-MB-468) were selected to measure the IC50 values of the new hybrids. Moreover, the frontier three members (3c, 3e, and 4b) were selected for the measurements of apoptotic protein markers (p53, BAX, caspase 3, caspase 6, BCL-2, and CK 18). Besides, the impact of compounds 3a-e and 4b on the activity of PARP-1 was investigated, where 3c, 3d, and 3e demonstrated comparable efficiencies to olaparib. Furthermore, γ-H2Ax, a well-established marker for double-strand DNA breaks, was examined and the occurrence of DNA damage was observed. In addition, a significant inhibition of cell proliferation and a remarkable 15 to 50-fold reduction in the number of colonies compared to the control group were recorded. Finally, the PARP-1 inhibitory potential of the novel hybrids was compared to the co-crystal of the target receptor (PDB ID: 6NTU) using molecular docking.

Alkaloids from Corydalis saxicola and their antiproliferative activity against cancer cells

Eight undescribed alkaloids named corydalisine D-K (1-7), including one isoquinoline benzopyranone alkaloid (1), one benzocyclopentanone alkaloid (2), four benzofuranone alkaloids (3, 4, and 5a/5b) and two protoberberine alkaloids (6 and 7), along with fourteen known ones, were isolated from the Corydalis saxicola. Their structures, including absolute configurations, were unambiguously identified using spectroscopic techniques, single-crystal X-ray diffraction and electron circular dichroism calculation. Compounds 2, 14 and 21 exhibit antiproliferative activity against five cancer cell lines. The aporphine alkaloid demethylsonodione (compound 14), which exhibited the best activity (IC50 = 3.68 ± 0.25 μM), was subjected to further investigation to determine its mechanism of action against the T24 cell line. The molecular mechanism was related to the arrest of cell cycle S-phase, inhibition of CDK2 expression, accumulation of reactive oxygen species (ROS), induction of cell apoptosis, inhibition of cell migration, and activation of p38 MAPK signaling pathway. The results indicated that 14 could be used as a potential candidate agent for further development of anti-bladder transitional cell carcinoma.

Targeting BRCA and PALB2 in Pancreatic Cancer

OPINION STATEMENT

An important subgroup of pancreatic ductal adenocarcinomas (PDACs) harbor pathogenic variants in BRCA1, BRCA2, or PALB2. These tumors are exquisitely sensitive to platinum-based chemotherapy and patients may experience deep and durable responses to this treatment. PARP inhibitors offer potential respite from the cumulative toxicities of chemotherapy as they significantly extend progression-free survival compared to a chemotherapy holiday. Given the lack of proven survival benefit, the decision to use a maintenance PARP inhibitor rather than continue chemotherapy should be individualized. Interestingly, in both published clinical trials of maintenance PARP inhibitors, there is a striking range of interpatient benefit: Even in the platinum-sensitive setting, roughly 25% of tumors appear to be PARP inhibitor refractory (progressive disease within 2 months of starting treatment), 50% sustain moderate benefit (up to 2 years), and 25% are hyper-responsive (more than 2 years of benefit). This finding highlights the need to refine our understanding of which patients will respond to maintenance PARP inhibitors, both by being able to identify biallelic loss and by deepening our knowledge of resistance mechanisms and who develops them. Recent data supports that reversion mutations are common in PARP inhibitor refractory patients, but we have little understanding of the mechanisms that drive delayed resistance and long-term responses. Identifying which patients are more prone to certain mechanisms of resistance and tackling them with specific treatment strategies are areas of active investigation. Additionally, given that PARP inhibitors have limited overall efficacy for most patients, upfront combination strategies are an important future strategy.

Discovery of a potent and selective PARP1 degrader promoting cell cycle arrest via intercepting CDC25C-CDK1 axis for treating triple-negative breast cancer

PARP1 is a multifaceted component of DNA repair and chromatin remodeling, making it an effective therapeutic target for cancer therapy. The recently reported proteolytic targeting chimera (PROTAC) could effectively degrade PARP1 through the ubiquitin-proteasome pathway, expanding the therapeutic application of PARP1 blocking. In this study, a series of nitrogen heterocyclic PROTACs were designed and synthesized through ternary complex simulation analysis based on our previous work. Our efforts have resulted in a potent PARP1 degrader D6 (DC50 = 25.23 nM) with high selectivity due to nitrogen heterocyclic linker generating multiple interactions with the PARP1-CRBN PPI surface, specifically. Moreover, D6 exhibited strong cytotoxicity to triple negative breast cancer cell line MDA-MB-231 (IC50 = 1.04 µM). And the proteomic results showed that the antitumor mechanism of D6 was found that intensifies DNA damage by intercepting the CDC25C-CDK1 axis to halt cell cycle transition in triple-negative breast cancer cells. Furthermore, in vivo study, D6 showed a promising PK property with moderate oral absorption activity. And D6 could effectively inhibit tumor growth (TGI rate = 71.4 % at 40 mg/kg) without other signs of toxicity in MDA-MB-321 tumor-bearing mice. In summary, we have identified an original scaffold and potent PARP1 PROTAC that provided a novel intervention strategy for the treatment of triple-negative breast cancer.

Identification of [1,2,4]Triazolo[4,3-a]pyrazine PARP1 inhibitors with overcome acquired resistance activities

Poly(ADP-ribose) polymerase 1 (PARP1) inhibitors can selectively kill homologous recombination (HR) deficient cancer cells and elicit anticancer effect through a mechanism of synthetic lethality. In this study, we designed, synthesized and pharmacologically evaluated a series of [1,2,4]triazolo[4,3-a]pyrazine derivatives as a class of potent PARP1 inhibitors. Among them, compounds 17m, 19a, 19c, 19e, 19i and 19k not only displayed more potent inhibitory activities (IC50s < 4.1 nM) than 9 and 1 against PARP1, but also exhibited nanomolar range of antiproliferative effects against MDA-MB-436 (BRCA1-/-, IC50s < 1.9 nM) and Capan-1 (BRCA2-/-, IC50s < 21.6 nM) cells. Notably, 19k significantly inhibited proliferation of resistant Capan-1 cells (IC50s < 0.3 nM). Collectively, the newly discovered PARP1 inhibitors act as a useful pharmacological tool for investigating the mechanism of acquired resistance to PARP1 inhibitors, and may also represent promising therapeutic agents for the treatment of HR deficient cancers with the potential to overcome the acquired resistance.

Discovery of a novel dual-target inhibitor of CDK12 and PARP1 that induces synthetic lethality for treatment of triple-negative breast cancer

Triple negative breast cancer (TNBC) is one of the most aggressive breast tumors, with a high rate of recurrence and metastasis as well as a poor prognosis. Consequently, it is urgent to find new targeted therapeutic strategies and development of corresponding drugs. Previous studies have shown that CDK12 inhibitors in combination with PARP1 inhibitors is able to induce synthetic lethality in TNBC cells. Here, we reported simultaneously inhibition of CDK12 and PARP1 by genetic or pharmacological approaches synergistically inhibited the proliferation of TNBC cells. Then, a series of small molecule inhibitors targeting both CDK12 and PARP1 were designed and synthesized. The new dual-target inhibitor (12e) showed potent inhibitory activity against CDK12 (IC50 = 285 nM) and PARP1 (IC50 = 34 nM), as well as good anti-proliferative effects in TNBC cell lines. Meanwhile, compound 12e showed favorable synergistic anti-tumor efficacy in cells and xenografts by inhibiting DNA damage repair, promoting cell cycle arrest and apoptosis. Taken together, we successfully synthesized the first effective CDK12-PARP1 dual inhibitor, which is expected to be an attractive therapeutic strategy for TNBC.

Discovery of novel 2,3,4,5-tetrahydrospiro[benzo[c]azepine-1,1'-cyclohexan]-5-ol derivatives as PARP-1 inhibitors

As an essential marker of cancer treatment, PARP-1 inhibitors could effectively kill tumor cells through a mechanism known as synthetic lethality and are used to treat a variety of cancers. In order to explore novel PARP-1 inhibitors, a series of 22 novel erythrina derivatives were reported and preliminarily explored their mechanism of action. The antitumor activities against four human cancer cell lines including A549, OVCAR-3, HCT-116, and MCF-7 were evaluated, and the preliminary SARs were summarized. Among them, compound 11b exhibited better anti-proliferative effects against A549 cells (IC50 = 1.95 µM). The SI results showed that compound 11b had low toxicity. Moreover, compound 11b displayed excellent PARP-1 inhibitory activities with IC50 values of 19.24 nM. In addition, molecular docking studies provided the rational binding modes of compound 11b in complexes with PARP-1. The flow cytometry assays revealed that compound 11b could induce apoptosis of A549 cells (P < 0.001). Simultaneously, compound 11b could effectively reduce the formation of PAR (P < 0.001). The ADMET prediction results indicated compound 11b had similar properties to rucaparib. Collectively, compound 11b has potential research value for further investigation.

Discovery of Quinazoline-2,4(1H,3H)-dione Derivatives Containing a Piperizinone Moiety as Potent PARP-1/2 Inhibitors─Design, Synthesis, In Vivo Antitumor Activity, and X-ray Crystal Structure Analysis

PARP-1/2 inhibitors have become an important therapeutic strategy for the treatment of HR-deficient tumors. However, discovery of new inhibitors with an improved and distinct pharmacological file still need enormous explorations. Herein, a series of novel highly potent PARP-1/2 inhibitors bearing an N-substituted piperazinone moiety were achieved. In particular, Cpd36 was identified as a distinct PARP inhibitor, showing remarkable enzymatic activity not only toward PARP-1 (IC50 = 0.94 nM) and PARP-2 (IC50 = 0.87 nM) but also toward PARP-7 (IC50 = 0.21 nM), as well as high selectivity over other PARP isoforms. Furthermore, Cpd36 was orally bioavailable and significantly repressed the tumor growth in both breast cancer and prostate cancer xenograft model. The crystal structures of Cpd36 within PARP-1 and PARP-2 together with the predicted binding mode within PARP-7 revealed its binding features and provided insightful information for further developing highly potent and selective PARP-1 and/or PARP-7 inhibitors.

Enhanced efficacy of combined fluzoparib and chidamide targeting in natural killer/T-cell lymphoma

The treatment of natural killer/T-cell lymphoma (NKTCL) presents an onerous challenge, and a search for new therapeutic targets is urgently needed. Poly ADP-ribose polymerase inhibitors (PARPi) were initially used to treat breast and ovarian cancers with BRCA1/2 mutations. Their excellent antitumor efficacy led to a series of clinical trials conducted in other malignancies. However, the exploration of PARPi and their potential use in combination treatments for NKTCL remains unexplored. We treated NKTCL cell lines with fluzoparib (a novel inhibitor of PARP) and chidamide (a classical inhibitor of HDACs) to explore their cytotoxic effects in vitro. Then, their antitumor efficacy in vivo was confirmed in YT-luciferin xenograft mouse models. Fluzoparib or chidamide alone inhibited NKTCL cell proliferation in a dose-dependent manner. Cotreatment with both drugs synergistically induced excessive accumulation of DNA double-strand breaks and massive apoptotic cell death by inhibiting the DNA damage repair pathway, as shown by the decreased protein levels of p-ATM, p-BRCA1, p-ATR, and Rad51. Moreover, the combination treatment apparently increased the level of intracellular reactive oxygen species (ROS) to enhance apoptosis, and pretreatment with an ROS scavenger reduced the proapoptotic effect by 30-60% in NKTCL cell lines. In vivo, this combined regimen also showed synergistic antitumor effects in xenograft mouse models. The combination of fluzoparib and chidamide showed synergistic effects against NKTCL both in vitro and in vivo and deserves further exploration in clinical trials.

Potential agnostic role of BRCA alterations in patients with several solid tumors: One for all, all for one?

Germline BRCA1/2 alterations in the Homologous Recombination (HR) pathway are considered as main susceptibility biomarkers to Hereditary Breast and Ovarian Cancers (HBOC). The modern molecular biology technologies allowed to characterize germline and somatic BRCA1/2 alterations in several malignancies, broadening the landscape of BRCA1/2-alterated tumors. In the last years, BRCA genetic testing, beyond the preventive value, also assumed a predictive and prognostic significance for patient management. The approval of molecules with agnostic indication is leading to a new clinical model, defined "mutational". Among these drugs, the Poly (ADP)-Ribose Polymerase inhibitors (PARPi) for BRCA1/2-deficient tumors were widely studied leading to increasing therapeutic implications. In this Review we provided an overview of the main clinical studies describing the association between BRCA-mutated tumors and PARPi response, focusing on the controversial evidence about the potential agnostic indication based on BRCA1/2 alterations in several solid tumors.

A phase 1 trial of fuzuloparib in combination with apatinib for advanced ovarian and triple-negative breast cancer: efficacy, safety, pharmacokinetics and germline BRCA mutation analysis

BACKGROUND

The effect of the combination of an anti-angiogenic agent with a poly (ADP-ribose) polymerase (PARP) inhibitor in cancer treatment is unclear. We assessed the oral combination of fuzuloparib, a PARP inhibitor, and apatinib, a VEGFR2 inhibitor for treating advanced ovarian cancer (OC) or triple-negative breast cancer (TNBC).

METHODS

This dose-escalation and pharmacokinetics-expansion phase 1 trial was conducted in China. We used a standard 3 + 3 dose-escalation design, with 7 dose levels tested. Patients received fuzuloparib orally twice daily, and apatinib orally once daily. The study objectives were to determine the safety profile, recommended phase 2 dose (RP2D), pharmacokinetics, preliminary efficacy, and efficacy in relation to germline BRCA mutation (gBRCAmut).

RESULTS

Fifty-two pre-treated patients were enrolled (30 OC/22 TNBC). 5 (9.6%) patients had complete response, 14 (26.9%) had partial response, and 15 (28.8%) had stable disease. Objective response rate (ORR) and disease control rate were 36.5% (95% CI 23.6-51.0) and 65.4% (95% CI 50.9-78.0), respectively. At the highest dose level of fuzuloparib 100 mg plus apatinib 500 mg, the ORR was 50.0% (4/8; 95% CI 15.7-84.3); this dose was determined to be the RP2D. Patients with gBRCAmut had higher ORR and longer median progression-free survival (PFS) than those with gBRCAwt, both in OC (ORR, 62.5% [5/8] vs 40.9% [9/22]; PFS, 9.4 vs 6.7 months) and TNBC (ORR, 66.7% [2/3] vs 15.8% [3/19]; PFS, 5.6 vs 2.8 months). Two dose-limiting toxicities occurred: grade 4 febrile neutropenia (fuzuloparib 100 mg plus apatinib 250 mg) and thrombocytopenia (fuzuloparib 100 mg plus apatinib 375 mg). Maximum tolerated dose was not reached. The most common treatment-related grade ≥ 3 toxicities in all patients were hypertension (19.2%), anaemia (13.5%), and decreased platelet count (5.8%). Exposure of apatinib increased proportionally with increasing dose ranging from 250 to 500 mg, when combined with fuzuloparib 100 mg.

CONCLUSIONS

Fuzuloparib plus apatinib had acceptable safety in patients with advanced OC or TNBC. Fuzuloparib 100 mg bid plus apatinib 500 mg qd was established as the RP2D. With the promising clinical activity observed, this combination is warranted to be further explored as a potential alternative to chemotherapy.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03075462 (Mar. 9, 2017).

YCH1899, a Highly Effective Phthalazin-1(2H)-one Derivative That Overcomes Resistance to Prior PARP Inhibitors

Poly(ADP-ribose) polymerase inhibitors (PARPi) have significant efficacy in treating BRCA-deficient cancers, although resistance development remains an unsolved challenge. Herein, a series of phthalazin-1(2H)-one derivatives with excellent enzymatic inhibitory activity were designed and synthesized, and the structure-activity relationship was explored. Compared with olaparib and talazoparib, compound YCH1899 exhibited distinct antiproliferation activity against olaparib- and talazoparib-resistant cells, with IC50 values of 0.89 and 1.13 nM, respectively. Studies of the cellular mechanism revealed that YCH1899 retained sensitivity in drug-resistant cells with BRCA1/2 restoration or 53BP1 loss. Furthermore, YCH1899 had acceptable pharmacokinetic properties in rats and showed prominent dose-dependent antitumor activity in olaparib- and talazoparib-resistant cell-derived xenograft models. Overall, this study suggests that YCH1899 is a new-generation antiresistant PARPi that could provide a valuable direction for addressing drug resistance to existing PARPi drugs.

Efficacy and safety of fluzoparib combined with anlotinib in extensive stage small cell lung cancer after first-line platinum-based chemotherapy: a multi-center, single-arm prospective phase II clinical study (STAMP study)

BACKGROUND

Small-cell lung cancer (SCLC) is a highly aggressive and lethal malignancy that accounts for 10-15% of lung cancers, and it is generally divided into limited and extensive stage. The standard of care for patients with newly diagnosed extensive-stage SCLC (ES-SCLC) is still platinum-based chemotherapy and as maintenance therapy scheme. Although most parts of patients experience a significant tumor response to first-line therapy, the disease recurs invariably. Anlotinib hydrochloride, a novel oral multitarget tyrosine kinase inhibitor, has significant inhibitory activity against angiogenesis-related kinases, such as VEGFR, FGFR, PDGFR, and c-Kit kinase associated with tumor cell proliferation. Fluzoparib is a type of inhibitor of poly ADP ribose polymerase (PARP, including PARPl, PARP2 and PARP3). Previous studies have shown that Fluzoparib has a strong inhibitory effect on PARP1 activity at the molecular and cellular levels.

METHODS

This is a multi-center, prospective, single-arm phase II clinical study. A total of 50 ES-SCLC patients who experienced disease progression after first-line standard platinum-based chemotherapy with/without immune checkpoint inhibitors scheme, or within 6 months after the completion of treatment will be recruited. Those who had prior treatment with any PARP inhibitor or antiangiogenic agent includes anlotinib, bevacizumab, sorafenib, and thalidomide are excluded. Eligible patients will receive oral anlotinib 8 mg once daily and oral fluzoparib 150 mg twice daily until disease progression or intolerable toxicity. The primary endpoint is objective response rate (ORR).

DISCUSSION

The addition of fluzoparib to anlotinib is expected to increase the clinical benefit in ES-SCLC patients after platinum-based chemotherapy.

TRIAL REGISTRATION

This study protocol was prospectively registered on June 17, 2021.

CLINICALTRIALS

gov Identifier: NCT04933175 .

Privileged Scaffolds for Potent and Specific Inhibitors of Mono-ADP-Ribosylating PARPs

The identification of new targets to address unmet medical needs, better in a personalized way, is an urgent necessity. The introduction of PARP1 inhibitors into therapy, almost ten years ago, has represented a step forward this need being an innovate cancer treatment through a precision medicine approach. The PARP family consists of 17 members of which PARP1 that works by poly-ADP ribosylating the substrate is the sole enzyme so far exploited as therapeutic target. Most of the other members are mono-ADP-ribosylating (mono-ARTs) enzymes, and recent studies have deciphered their pathophysiological roles which appear to be very extensive with various potential therapeutic applications. In parallel, a handful of mono-ARTs inhibitors emerged that have been collected in a perspective on 2022. After that, additional very interesting compounds were identified highlighting the hot-topic nature of this research field and prompting an update. From the present review, where we have reported only mono-ARTs inhibitors endowed with the appropriate profile of pharmacological tools or drug candidate, four privileged scaffolds clearly stood out that constitute the basis for further drug discovery campaigns.

PARP-1: a critical regulator in radioprotection and radiotherapy-mechanisms, challenges, and therapeutic opportunities

Background: Since its discovery, poly (ADP-ribose) polymerase 1 (PARP-1) has been extensively studied due to its regulatory role in numerous biologically crucial pathways. PARP inhibitors have opened new therapeutic avenues for cancer patients and have gained approval as standalone treatments for certain types of cancer. With continued advancements in the research of PARP inhibitors, we can fully realize their potential as therapeutic targets for various diseases. Purpose: To assess the current understanding of PARP-1 mechanisms in radioprotection and radiotherapy based on the literature. Methods: We searched the PubMed database and summarized information on PARP inhibitors, the interaction of PARP-1 with DNA, and the relationships between PARP-1 and p53/ROS, NF-κB/DNA-PK, and caspase3/AIF, respectively. Results: The enzyme PARP-1 plays a crucial role in repairing DNA damage and modifying proteins. Cells exposed to radiation can experience DNA damage, such as single-, intra-, or inter-strand damage. This damage, associated with replication fork stagnation, triggers DNA repair mechanisms, including those involving PARP-1. The activity of PARP-1 increases 500-fold on DNA binding. Studies on PARP-1-knockdown mice have shown that the protein regulates the response to radiation. A lack of PARP-1 also increases the organism's sensitivity to radiation injury. PARP-1 has been found positively or negatively regulate the expression of specific genes through its modulation of key transcription factors and other molecules, including NF-κB, p53, Caspase 3, reactive oxygen species (ROS), and apoptosis-inducing factor (AIF). Conclusion: This review provides a comprehensive analysis of the physiological and pathological roles of PARP-1 and examines the impact of PARP-1 inhibitors under conditions of ionizing radiation exposure. The review also emphasizes the challenges and opportunities for developing PARP-1 inhibitors to improve the clinical outcomes of ionizing radiation damage.

Itraconazole interferes in the pharmacokinetics of fuzuloparib in healthy volunteers

OBJECTIVE

Fuzuloparib is an orally administered poly [ADP-ribose] polymerase 1 (PARP1) inhibitor and has potential anti-tumor effect on ovarian cancer (such as fallopian tube cancer and primary peritoneal cancer) in China. As fuzuloparib is metabolized mainly by CYP3A4, we explored the effect of itraconazole, a strong CYP3A4 inhibitor, on a single oral dose of fuzuloparib in healthy male subjects.

METHODS

An open-label, single-arm, fixed sequence study was conducted. Twenty healthy adult males received one single dose of fuzuloparib (20 mg) with one dose administered alone and the other dose coadministered with itraconazole. Subjects received 200 mg QD itraconazole for 6 days during the study. Serials of blood samples were collected pre-dose of each fuzuloparib capsule administration and 48 h post-dose, and were used to analyze the PK parameters of fuzuloparib.

RESULTS

Coadministration of repeated 200 mg QD oral doses of itraconazole for 6 days increased fuzuloparib exposure by 1.51-fold and 4.81-fold for peak plasma concentration and area under the plasma concentration-time curve (AUC), respectively. Oral administration of 20 mg fuzuloparib alone or together with itraconazole was safe and tolerable in healthy male subjects.

CONCLUSION

The CYP3A4 inhibitor itraconazole has a significant influence on the PK behavior of fuzuloparib, suggesting to avoid using strong CYP3A4 inhibitors simultaneously with fuzuloparib. If it is necessary to use a strong CYP3A4 inhibitor, fuzuloparib would be discontinued and be restored to the original dose and frequency of administration after 5-7 half lives of CYP3A4 inhibitor stopped.

TRIAL REGISTRATION

http://www.chinadrugtrials.org.cn/index.html , CTR20191271.

Recent advances in EZH2-based dual inhibitors in the treatment of cancers

The enhancer of zeste homolog 2 (EZH2) protein is the catalytic subunit of one of the histone methyltransferases. EZH2 catalyzes the trimethylation of lysine 27 of histone H3 (H3K27me3) and further alters downstream target levels. EZH2 is upregulated in cancer tissues, wherein its levels correlate strongly with cancer genesis, progression, metastasis, and invasion. Consequently, it has emerged as a novel anticancer therapeutic target. Nonetheless, developing EZH2 inhibitors (EZH2i) has encountered numerous difficulties, such as pre-clinical drug resistance and poor therapeutic effect. The EZH2i synergistically suppresses cancers when used in combination with additional antitumor drugs, such as PARP inhibitors, HDAC inhibitors, BRD4 inhibitors, EZH1 inhibitors, and EHMT2 inhibitors. Typically, the use of dual inhibitors of two different targets mediated by one individual molecule has been recognized as the preferred approach for overcoming the limitations of EZH2 monotherapy. The present review discusses the theoretical basis for designing EZH2-based dual-target inhibitors, and also describes some in vitro and in vivo analysis results.

Targeting PARP for the optimal immunotherapy efficiency in gynecologic malignancies

Gynecologic cancer, which includes ovarian, cervical, endometrial, vulvar, and vaginal cancer, is a major health concern for women all over the world. Despite the availability of various treatment options, many patients eventually progress to advanced stages and face high mortality rates. PARPi (poly (ADP-ribose) polymerase inhibitor) and immune checkpoint inhibitor (ICI) have both shown significant efficacy in the treatment of advanced and metastatic gynecologic cancer. However, both treatments have limitations, including inevitable resistance and a narrow therapeutic window, making PARPi and ICI combination therapy a promising approach to treating gynecologic malignancies. Preclinical and clinical trials have looked into the combination therapy of PARPi and ICI. PARPi improves ICI efficacy by inducing DNA damage and increasing tumor immunogenicity, resulting in a stronger immune response against cancer cells. ICI, conversly, can increase PARPi sensitivity by priming and activating immune cells, consequently prompting immune cytotoxic effect. Several clinical trials in gynecologic cancer patients have investigated the combination therapy of PARPi and ICI. When compared to monotherapy, the combination of PARPi and ICI increased progression-free survival and overall survival in ovarian cancer patients. The combination therapy has also been studied in other types of gynecologic cancer, including endometrial and cervical cancer, with promising results. Finally, the combination therapeutic strategy of PARPi and ICI is a promising approach in the treatment of gynecologic cancer, particularly advanced and metastatic stages. Preclinical studies and clinical trials have demonstrated the safety and efficacy of this combination therapy in improving patient outcomes and quality of life.

Effect of a moderate CYP3A inducer efavirenz on the pharmacokinetics of fuzuloparib: An open-label, fixed sequence study in Chinese healthy male subjects

To evaluate the potential drug-drug interaction (DDI), safety and tolerability of fuzuloparib co-administered with a moderate CYP3A inducer efavirenz in healthy male subjects. Eighteen healthy male subjects were enrolled in a single-center, single-arm, open-label, fixed-sequence study. Fuzuloparib was administered as a single oral 50 mg under a fasting state on day 1, efavirenz (600 mg once daily) was given on days 4-17 before bed time, concomitantly with fuzuloparib on day 18, and for the follow-up 3 additional days (days 19-20). Pharmacokinetic sampling was performed following each fuzuloparib dose. Safety and tolerability were assessed during the whole process via clinical laboratory tests. Ratios of least-squares means (GMRs) and 90% geometric confidence interval (90% CI) of maximum plasma concentration (C_max), the area under the curve of plasma concentration-time from zero to the last measurable concentration (AUC_0 - t) and the area under the curve of blood concentration from zero to infinity (AUC_0-∞) for fuzuloparib combined with efavirenz to fuzuloparib alone were 0.473 (0.394, 0.568), 0.220 (0.185, 0.263) and 0.221 (0.185, 0.263), respectively. Co-administration with efavirenz led to 53% and 78% decreases in fuzuloparib C_max and AUC_0-∞. All 18 subjects enrolled in this study were included in the safety analysis set. A total of 16 subjects had 62 AEs during the study period. No serious adverse events (SAE) were reported. Most treatment-emergent adverse events were grade 1 or 2 based on CTCAE. Only one grade 3 adverse event was observed. Concomitant intake of fuzuloparib with the moderate CYP3A inhibitor efavirenz resulted in a decrease in fuzuloparib AUC_0-∞ and C_max of 78% and 53% respectively. The results suggested that concomitant moderate CYP3A inducers should be avoided during the administration of fuzuloparib, or else the dosage adjustments should be required. (This trial was registered at http://www.chinadrugtrials.org.cn . The registration No. is CTR20211022, and the date of registration is 2021-05-13).

Targeted therapy and immunotherapy: Diamonds in the rough in the treatment of epithelial ovarian cancer

Currently, for ovarian cancer, which has the highest mortality rate among all gynecological cancers, the standard treatment protocol is initial tumor cytoreductive surgery followed by platinum-based combination chemotherapy. Although the survival rate after standard treatment has improved, the therapeutic effect of traditional chemotherapy is very limited due to problems such as resistance to platinum-based drugs and recurrence. With the advent of the precision medicine era, molecular targeted therapy has gradually entered clinicians' view, and individualized precision therapy has been realized, surpassing the limitations of traditional therapy. The detection of genetic mutations affecting treatment, especially breast cancer susceptibility gene (BRCA) mutations and mutations of other homologous recombination repair defect (HRD) genes, can guide the targeted drug treatment of patients, effectively improve the treatment effect and achieve a better patient prognosis. This article reviews different sites and pathways of targeted therapy, including angiogenesis, cell cycle and DNA repair, and immune and metabolic pathways, and the latest research progress from preclinical and clinical trials related to ovarian cancer therapy.

Synthesis and in vitro biological evaluation of 3-ethyl-1,5-naphthyridin-2(1H)-one derivatives as potent PARP-1 selective inhibitors and PARP-1 DNA trappers

Inhibition of poly (ADP-ribose) polymerase (PARP) has been applied with great success in the clinical treatment of homologous recombination-deficient malignancy. Recent study demonstrated that not only PARP-1 inhibition but also DNA trapping contributes to the efficacy in BRCA mutant tumors and the toxicities results from the poor selectivity of PARP-1 over PARP-2 as well as their DNA trapping. Herein, a series of 3-ethyl-1,5-naphthyridin-2(1H)-one derivatives (7a-7l, 8a-8n) were synthesized and identified as PARP-1 selective inhibitors and PARP-1 DNA trappers. Among them, compound 8m was found to be highly potent and selective. It inhibited PARP-1 activity and BRCA mutant DLD-1 cell activity with IC₅₀ values of 0.49 nM and 4.82 nM, and the in vitro DNA trapping efficacy of compound 8m was 1.85 nM. Compared with AZD5305, compound 8m significantly improved the selectivity of PARP-1 over PARP-2 as well. Compound 8m was>1000-fold selective for PARP-1 DNA trapping over PARP-2.

The Role of PARP Inhibitors in Patients with Primary Malignant Central Nervous System Tumors

OPINION STATEMENT

Primary malignant central nervous (CNS) tumors are a devastating group of diseases with urgent need for improved treatment options. Surgery, radiation, and cytotoxic chemotherapy remain the primary standard treatment modalities, with molecularly targeted therapies having proven efficacy in only small subsets of cases. Poly(ADP-ribose) polymerase (PARP) inhibitors, which have had immense success in the treatment of extracranial cancers with homologous recombination deficiency (HRD), are emerging as a potential targeted treatment for various CNS tumors. Although few primary CNS tumors display canonical BRCA gene defects, preclinical evidence suggests that PARP inhibitors may benefit certain CNS tumors with functional HRD or elevated replication stress. In addition, other preclinical studies indicate that PARP inhibitors may synergize with standard therapies used for CNS tumors including radiation and alkylating agents and may prevent or overcome drug resistance. Thus far, initial clinical trials with early-generation PARP inhibitors, typically as monotherapy or in the absence of selective biomarkers, have shown limited efficacy. However, the scientific rationale remains promising, and many clinical trials are ongoing, including investigations of more CNS penetrant or more potent inhibitors and of combination therapy with immune checkpoint inhibitors. Early phase trials are also critically focusing on determining active drug CNS penetration and identifying biomarkers of therapy response. In this review, we will discuss the preclinical evidence supporting use of PARP inhibitors in primary CNS tumors and clinical trial results to date, highlighting ongoing trials and future directions in the field that may yield important findings and potentially impact the treatment of these devastating malignancies in the coming years.

Overview of fuzuloparib in the treatment of ovarian cancer: background and future perspective

Over the last decade, clinical trials using various poly ADP ribose polymerase (PARP) inhibitors on patients with ovarian cancer have shown promising results. The introduction of PARP inhibitors has changed the treatment landscape and improved outcomes for patients with ovarian cancer. Fuzuloparib, developed by Jiangsu Hengrui Pharmaceuticals Co., Ltd., is a novel orally available small molecule PARP inhibitor. By introducing the trifluoromethyl group into chemical structure, fuzuloparib exhibits higher stability and lower inter-individual variability than other PARP inhibitors. Several clinical trials (FZOCUS series and others) have been carried out to assess the efficacy and safety of fuzuloparib through different lines of treatments for advanced or recurrent ovarian cancer in both treatment and maintenance. Here, we present the most recent data from these studies, discuss current progress and potential future directions.

Combination of ligand and structure based virtual screening approaches for the discovery of potential PARP1 inhibitors

Poly (ADP-ribose) polymerase 1 (PARP1) has high therapeutic value as biomolecular target for research and development of small molecules with antineoplastic activity, since it is upregulated in many cancers, especially in ovarian and BRCA 1/2 mutated breast cancers. Decades of investigation of PARP inhibitors (PARPi) have led to the approval of several drug compounds, however clinical application of PARPi in cancer therapy is limited due to a number of factors, including low selectivity, weak affinity and undesired side effects. Thus, identification of novel drug-like chemical compounds with alternatives to the known PARPi chemical scaffolds, binding modes and interaction patterns with amino acid residues in the active site is of high therapeutic importance. In this study we applied a combination of ligand- and structure-based virtual screening approaches with the goal of identification of novel potential PARPi.

Case Report: Fluzoparib for multiple lines of chemotherapy refractory in metastatic cutaneous squamous cell carcinoma with BRCA2 pathogenic mutation

Background: Poly ADP-ribose polymerase inhibitors (PARPis) are widely used for patients with BRCA1/2 mutations. However, until now, there is no available evidence reported for the efficiency of PARPis in cutaneous squamous cell carcinoma (cSCC).

Case presentation: We presented a case of a 40-year-old man diagnosed with metastatic cSCC, relapsing after multiple lines of chemotherapy. Liquid biopsy detected a BRCA2 pathogenic germline mutation (c.3109C > T), indicating PARPis might be effective for this patient. The patient achieved tumor stability, and progression-free survival was five months without severe adverse effects after taking fluzoparib.

Conclusion: This result confirmed that PARPis were effective for metastatic cSCC patients with germline BRCA2 pathogenic mutations and provided a new treatment option for this group of patients.

Tolerability, safety, and preliminary antitumor activity of fuzuloparib in combination with SHR-1316 in patients with relapsed small cell lung cancer: a multicenter, open-label, two-stage, phase Ib trial

Background

Second-line treatment options for small cell lung cancer (SCLC) are limited. Preclinical research shows that inhibition of poly (ADP-ribose) polymerase (PARP) could upregulate programmed death-ligand 1 (PD-L1), and thus render cancer cells more sensitive to immune checkpoint inhibitors. This study investigated the tolerability, safety, and preliminary antitumor activity of fuzuloparib (a PARP inhibitor) plus SHR-1316 (a PD-L1 inhibitor) for relapsed SCLC.

Methods

Patients with SCLC who failed previous first-line platinum-based therapy were enrolled in this two-stage phase Ib trial. In stage 1, 2 dose levels were designed: fuzuloparib 100 mg or 150 mg twice daily plus SHR-1316 600 mg every 2 weeks, with 6 patients in each dose level. Based on the tolerability during the first 28-day cycle and the preliminary antitumor activity in stage 1, a recommended phase II dose (RP2D) was determined and introduced in the stage 2 expansion phase. The primary endpoints were safety and RP2D in stage 1 and objective response rate (ORR) in stage 2.

Results

A total of 23 patients were enrolled, with 16 receiving fuzuloparib 100 mg plus SHR-1316 and 7 receiving fuzuloparib 150 mg plus SHR-1316. At data cutoff on April 23, 2021, the median follow-up duration was 6.4 months (IQR, 3.0–9.7 months). All patients discontinued study treatment. One patient receiving fuzuloparib 150 mg plus SHR-1316 had clinically significant toxicities, and fuzuloparib 100 mg plus SHR-1316 was considered as the RP2D. In the RP2D cohort, the confirmed ORR was 6.3% (95% CI: 0.2–30.2%), and the disease control rate was 37.5% (95% CI: 15.2–64.6%). The median progression-free survival was 1.4 months (95% CI: 1.3–2.8 months), and the median overall survival was 5.6 months (95% CI: 3.0–16.7 months). Grade ≥3 treatment-related adverse events (TRAE) occurred in 8 patients (34.8%). No treatment-related death occurred, and no patients discontinued treatment due to TRAEs.

Conclusions

Fuzuloparib combined with SHR-1316 failed to improve the outcomes in unselected patients with relapsed SCLC. Future studies with biomarker analysis are warranted to select patients most likely to benefit from this combination treatment. Fuzuloparib 100 and 150 mg plus SHR-1316 were both tolerable with no new signals observed.

Fuzuloparib Maintenance Therapy in Patients With Platinum-Sensitive, Recurrent Ovarian Carcinoma (FZOCUS-2): A Multicenter, Randomized, Double-Blind, Placebo-Controlled, Phase III Trial

PURPOSE

This phase III trial aimed to explore the efficacy and safety of fuzuloparib (formerly fluzoparib) versus placebo as a maintenance treatment after response to second- or later-line platinum-based chemotherapy in patients with high-grade, platinum-sensitive, recurrent ovarian cancer.

PATIENTS AND METHODS

Patients with platinum-sensitive, recurrent ovarian cancer previously treated with at least two platinum-based regimens were assigned (2:1) to receive fuzuloparib (150 mg, twice daily) or matching placebo for 28-day cycles. The primary end points were progression-free survival (PFS) assessed by blinded independent review committee (BIRC) in the overall population and PFS by BIRC in the subpopulation with germline BRCA 1/2 mutation.

RESULTS

Between April 30, 2019, and January 10, 2020, 252 patients were randomly assigned to the fuzuloparib (n = 167) or placebo (n = 85). As of July 1, 2020, the median PFS per BIRC assessment in the overall population was significantly improved with fuzuloparib treatment (hazard ratio [HR], 0.25; 95% CI, 0.17 to 0.36; one-sided P < .0001) compared with that with placebo. The HR derived from a prespecified subgroup analysis showed a consistent trend of benefit in patients with germline BRCA 1/2 mutations (HR, 0.14; 95% CI, 0.07 to 0.28) or in those without mutations (HR, 0.46; 95% CI, 0.29 to 0.74). The most common grade ≥ 3 treatment-emergent adverse events reported in the fuzuloparib group were anemia (25.1%), decreased platelet count (16.8%), and decreased neutrophil count (12.6%). Only one patient (0.6%) discontinued fuzuloparib because of treatment-related toxicity (concurrent decreased white blood cell count and neutrophil count).

CONCLUSION

Fuzuloparib as maintenance therapy achieved a statistically significant and clinically meaningful improvement in PFS for patients with platinum-sensitive, recurrent ovarian cancer versus placebo, regardless of germline BRCA 1/2 mutation, and showed a manageable safety profile.

Combined use of 177 Lu-DOTATATE peptide receptor radionuclide therapy and fluzoparib for treatment of well-differentiated neuroendocrine tumors: A preclinical study

Peptide receptor radionuclide therapy (¹⁷⁷ Lu-DOTATATE) causes DNA strand breaks and has been validated for well-differentiated neuroendocrine tumor treatment. Poly-(ADP-ribose)-polymerase inhibitors have also been used for malignant tumors with deficient DNA repair. We aimed to determine whether the poly-(ADP-ribose)-polymerase inhibitor fluzoparib could enhance the anti-tumor effects of ¹⁷⁷ Lu-DOTATATE in neuroendocrine tumor cells and xenografts. The neuroendocrine characteristics of NCI-H727 bronchial carcinoid cells were evaluated by immunofluorescence staining. The synergistic effects of fluzoparib and ¹⁷⁷ Lu-DOTATATE were evaluated by cell proliferation and flow cytometry assays. Tumor response and the side effects of combination therapy were also assessed in xenograft mice treated with ⁷⁷ Lu-DOTATATE and fluzoparib alone or in combination. Somatostatin receptors were specifically expressed in NCI-H727 cells and tumor xenografts. ¹⁷⁷ Lu-DOTATATE (22.20 MBq mL^-1 ) and fluzoparib (50 µm) inhibited cell proliferation by 16.6% and 35.6%, respectively, compared to 73.2% in cells treated with their combination. Tumor cell proliferation was significantly suppressed by ¹⁷⁷ Lu-DOTATATE (22.20 MBq mL^-1 , 4.4-fold) and fluzoparib (50 µm, 2.1-fold). ¹⁷⁷ Lu-DOTATATE caused cell cycle arrest mainly at G1 phase, whereas fluzoparib caused arrest at G2/M phase, and combined treatment with both agents caused cell cycle arrest at G1 phase, similar to ¹⁷⁷ Lu-DOTATATE alone. The volume of tumor xenografts was reduced by 18.6% in mice receiving combined treatment, compared to 4.9% and 11.4% in mice treated with ¹⁷⁷ Lu-DOTATATE or fluzoparib alone. Fluzoparib can potentiate the anti-tumor effect of ¹⁷⁷ Lu-DOTATATE in NCI-H727 cells in a synergistic manner by arresting the cell cycle at G1 phase. Further preclinical and clinical studies are warranted to validate these findings.

Design and synthesis of benzodiazepines as brain penetrating PARP-1 inhibitors

The poly (ADP-ribose) polymerase (PARP) inhibitors play a crucial role in cancer therapy. However, most approved PARP inhibitors cannot cross the blood-brain barrier, thus limiting their application in the central nervous system. Here, 55 benzodiazepines were designed and synthesised to screen brain penetrating PARP-1 inhibitors. All target compounds were evaluated for their PARP-1 inhibition activity, and compounds with better activity were selected for further assays in vitro. Among them, compounds H34, H42, H48, and H52 displayed acceptable inhibition effects on breast cancer cells. Also, computational prediction together with the permeability assays in vitro and in vivo proved that the benzodiazepine PARP-1 inhibitors we synthesised were brain permeable. Compound H52 exhibited a B/P ratio of 40 times higher than that of Rucaparib and would be selected to develop its potential use in neurodegenerative diseases. Our study provided potential lead compounds and design strategies for the development of brain penetrating PARP-1 inhibitors.

HIGHLIGHTS

Structural fusion was used to screen brain penetrating PARP-1 inhibitors.

55 benzodiazepines were evaluated for their PARP-1 inhibition activity.

Four compounds displayed acceptable inhibition effects on breast cancer cells.

The benzodiazepine PARP-1 inhibitors were proved to be brain permeable.

Chidamide Reverses Fluzoparib Resistance in Triple-Negative Breast Cancer Cells

Poly (ADP-ribose) polymerase inhibitor (PARPi) resistance is a new challenge for antitumor therapy. The purpose of this study was to investigate the reversal effects of chidamide on fluzoparib resistance, a PARPi, and its mechanism of action. A fluzoparib-resistant triple-negative breast cancer (TNBC) cell line was constructed, and the effects of chidamide and fluzoparib on drug-resistant cells were studied in vitro and in vivo. The effects of these drugs on cell proliferation, migration, invasiveness, the cell cycle, and apoptosis were detected using an MTT assay, wound-healing and transwell invasion assays, and flow cytometry. Bioinformatics was used to identify hub drug resistance genes and Western blots were used to assess the expression of PARP, RAD51, MRE11, cleaved Caspase9, and P-CDK1. Xenograft models were established to analyze the effects of these drugs on nude mice. In vivo results showed that chidamide combined with fluzoparib significantly inhibited the proliferation, migration, and invasiveness of drug-resistant cells and restored fluzoparib sensitivity to drug-resistant cells. The combination of chidamide and fluzoparib significantly inhibited the expression of the hub drug resistance genes RAD51 and MRE11, arrested the cell cycle at the G2/M phase, and induced cell apoptosis. The findings of this work show that chidamide combined with fluzoparib has good antineoplastic activity and reverses TNBC cell resistance to fluzoparil by reducing the expression levels of RAD51 and MRE11.

Metabolite profiles and mass balance of fuzuloparib, a novel poly (ADP-ribose) polymerase (PARP) inhibitor, in subjects with advanced solid cancers

AIM

This trial (NCT04013048) investigated the metabolite profiles, mass balance and pharmacokinetics of fuzuloparib, a novel poly (ADP-ribose) polymerase (PARP) inhibitor, in subjects with advanced solid cancers.

METHODS

A single dose of 150 mg [¹⁴ C]fuzuloparib was administered to five subjects with advanced solid cancers. Blood, urine and fecal samples were collected, analyzed for radioactivity, unchanged fuzuloparib and profiled for metabolites. The safety of the medicine was assessed during the study.

RESULTS

The maximum concentration (C_max ) of the total radioactivity (TRA) and unchanged fuzuloparib in plasma was 5.39 μg eq/mL and 4.19 μg/mL, respectively, at approximately 4 h post dose. The exposure (AUC_0-t ) of fuzuloparib accounted for 70.7% of the TRA in plasma, and no single metabolite was observed accounting for more than 10% of the plasma TRA. The recovery of TRA in excreta was 103.3±3.8% in 288 h, including 59.1±9.9% in urine and 44.2±10.8% in feces. Sixteen metabolites of fuzuloparib were identified, including mono-oxidation (M1), hydrogenation (M2), di-oxidation (M3), trioxidation (M4), glucuronidation (M5, M7, M8) and de-ethylation (M6) products, and there was no specific binding between these metabolites and blood cells. Aliphatic hydroxylated fuzuloparib (M1-1) was the primary metabolite in the excreta, accounting for more than 40% of the dose for subjects. There were no serious adverse events observed in the study.

CONCLUSION

Fuzuloparib was widely metabolized and excreted completely through urine and feces in subjects with advanced solid cancer. Unchanged fuzuloparib was indicated to be the primary drug-related compound in circulation. [¹⁴ C]fuzuloparib was well-tolerated at the study dose.

Structure-based design, synthesis, and evaluation of inhibitors with high selectivity for PARP-1 over PARP-2

The poly (ADP-ribose) polymerase (PARP) inhibitors play a crucial role in cancer therapy. However, most approved PARP inhibitors have lower selectivity to PARP-1 than to PARP-2, so they will inevitably have side effects. Based on the different catalytic domains of PARP-1 and PARP-2, we developed a strategy to design and synthesize highly selective PARP-1 inhibitors. Compounds Y17, Y29, Y31 and Y49 showed excellent PARP-1 inhibition, and their IC₅₀ values were 0.61, 0.66, 0.41 and 0.96 nM, respectively. Then, Y49 (PARP-1 IC₅₀ = 0.96 nM, PARP-2 IC₅₀ = 61.90 nM, selectivity PARP-2/PARP-1 = 64.5) was proved to be the most selective inhibitor of PARP-1. Compounds Y29 and Y49 showed stronger inhibitory effect on proliferation in BRCA1 mutant MX-1 cells than in other cancer cells. In the MDA-MB-436 xenotransplantation model, Y49 was well tolerated and showed remarkable single dose activity. The design strategy proposed in this paper is of far-reaching significance for the further construction of the next generation of selective PARP-1 inhibitors.

Effect of fluconazole on the pharmacokinetics of fuzuloparib: an open-label, crossover study in Chinese healthy male volunteers

PURPOSE

Fuzuloparib (AiRuiYiTM, formerly fluzoparib, SHR3162) is a new orally active poly adenosine diphosphate ribose polymerase (PARP) inhibitor. It has multiple pharmacological activities in breast, ovarian, and prostatic cancer. Fuzuloparib is mainly metabolized through the enzyme CYP3A4 may slow fuzuloparib metabolism and increase its concentrations in blood. We evaluated the pharmacokinetics and tolerability of fuzuloparib by fluconazole, which is a broad antifungal agent and a moderate inhibitor of CYP3A4.

METHODS

In this study, the effects of CYP3A4 inhibition on the pharmacokinetics of fuzuloparib were assessed in a total of 20 healthy Chinese male subjects in an open-label, two-period, single-sequence, crossover study.

RESULTS

Pharmacokinetic parameters, including the maximal plasma concentration (Cmax), the plasma concentration-time curve from time 0 to last measurable area under concentration (AUC0-t), and from time 0 to infinity (AUC0-∞), were increased by 32.4%, 104.5%, and 109.6%, with corresponding 90% confidence intervals of (23-43%), (93-116%), and (98-122%), respectively, when fluconazole was combined with fuzuloparib compared to fuzuloparib alone. There was also a slight increase in the incidence of treatment emergent adverse events, including hyperlipidemia and elevated aspartate transaminase.

CONCLUSION

The fuzuloparib is 150 mg b.i.d in clinics use. Our results suggest that fuzuloparib could well be tolerated when administered as a single 20 mg oral dose alone or co-administered with 400 mg fluconazole in healthy male subjects. It is recommended to avoid using moderate CYP3A4 inhibitors together with fuzuloparib or instead of 50 mg when necessary.

Understanding and overcoming resistance to PARP inhibitors in cancer therapy

Developing novel targeted anticancer therapies is a major goal of current research. The use of poly(ADP-ribose) polymerase (PARP) inhibitors in patients with homologous recombination-deficient tumours provides one of the best examples of a targeted therapy that has been successfully translated into the clinic. The success of this approach has so far led to the approval of four different PARP inhibitors for the treatment of several types of cancers and a total of seven different compounds are currently under clinical investigation for various indications. Clinical trials have demonstrated promising response rates among patients receiving PARP inhibitors, although the majority will inevitably develop resistance. Preclinical and clinical data have revealed multiple mechanisms of resistance and current efforts are focused on developing strategies to address this challenge. In this Review, we summarize the diverse processes underlying resistance to PARP inhibitors and discuss the potential strategies that might overcome these mechanisms such as combinations with chemotherapies, targeting the acquired vulnerabilities associated with resistance to PARP inhibitors or suppressing genomic instability.

Discovery of Quinazoline-2,4(1H,3H)-dione Derivatives Containing 3-Substituted Piperizines as Potent PARP-1/2 Inhibitors─Design, Synthesis, In Vivo Antitumor Activity, and X-ray Crystal Structure Analysis

Inhibiting PARP-1/2 offered an important arsenal for cancer treatments via interfering with DNA repair of cancer cells. Novel PARP-1/2 inhibitors were designed by capitalizing on methyl- or ethyl-substituted piperizine ring to capture the characteristics of adenine-ribose binding site (AD site), and their unique binding features were revealed by the cocrystal structures of compounds 4 and 6 in PARP-1. The investigation on structure-activity relationship resulted in compounds 24 and 32 with high enzymatic potency, binding selectivity, and significantly longer residence time for PARP-1 over PARP-2 (compound 24, PARP-1: IC₅₀ = 0.51 nM, PARP-2: IC₅₀ = 23.11 nM; compound 32, PARP-1: IC₅₀ = 1.31 nM, PARP-2: IC₅₀ = 15.63 nM). Furthermore, compound 24 was determined to be an attractive candidate molecule, which possessed an acceptable pharmacokinetic profile and produced remarkable antitumor activity in both breast cancer xenograft model and glioblastoma orthotopic model in mice, either alone or in combination treatment.

Therapeutic Potential of PARP Inhibitors in the Treatment of Gastrointestinal Cancers

Gastrointestinal (GI) malignancies are a major global health burden, with high mortality rates. The identification of novel therapeutic strategies is crucial to improve treatment and survival of patients. The poly (ADP-ribose) polymerase (PARP) enzymes involved in the DNA damage response (DDR) play major roles in the development, progression and treatment response of cancer, with PARP inhibitors (PARPi) currently used in the clinic for breast, ovarian, fallopian, primary peritoneal, pancreatic and prostate cancers with deficiencies in homologous recombination (HR) DNA repair. This article examines the current evidence for the role of the DDR PARP enzymes (PARP1, 2, 3 and 4) in the development, progression and treatment response of GI cancers. Furthermore, we discuss the role of HR status as a predictive biomarker of PARPi efficacy in GI cancer patients and examine the pre-clinical and clinical evidence for PARPi and cytotoxic therapy combination strategies in GI cancer. We also include an analysis of the genomic and transcriptomic landscape of the DDR PARP genes and key HR genes (BRCA1, BRCA2, ATM, RAD51, MRE11, PALB2) in GI patient tumours (n = 1744) using publicly available datasets to identify patients that may benefit from PARPi therapeutic approaches.

A randomized, open-label, two-period crossover bridging study on fuzuloparib capsules of different specifications in healthy Chinese volunteers

AIMS

Fuzuloparib, also known as fluzoparib or SHR3162, is a poly ADP-ribose polymerase (PARP) inhibitor developed for the treatment of malignant tumours. Three specifications of fuzuloparib capsules (10 mg, 40 mg and 100 mg) were originally developed for clinical trials. After the recommended dose was determined, a new specification of fuzuloparib capsule (50 mg) was produced for clinical use. This bridging study was conducted to determine the bioequivalence of the new specification to the three other specifications at the recommended dose.

METHODS

A single-centre, randomized, open-label, two-period, crossover bridging study was conducted in 40 healthy Chinese subjects under fed conditions. Enrolled subjects received a single oral dose of test or reference preparations according to a randomization list in the first period and crossed over to receive the other preparations in the second period after a 6-day washout interval. Blood samples were collected pre-dose and post-dose at specified time intervals. Plasma fuzuloparib concentrations were analysed by liquid chromatography-mass spectroscopy (LC-MS). A non-compartment model was adopted to calculate pharmacokinetic parameters of investigational preparations. Primary PK parameters including area under the concentration-time curve (AUC) from administration to the last sampling time (AUC_0-t ), AUC extrapolated to infinity (AUC_0-∞ ) and C_max of test and reference preparations were compared to evaluate their bioequivalence.

RESULTS

The 90% confidence intervals (CIs) of geometric mean ratios of AUC_0-t , AUC_0-∞ and C_max were 96.99-104.95%, 97.03-104.93% and 96.53-108.98%, respectively, all of which were within the bioequivalence range of 80-125%. No serious adverse events were observed in this study and no subjects withdrew from the study due to adverse events.

CONCLUSIONS

The test preparations were bioequivalent to the reference preparations. All investigational products were well tolerated.

The evolving role of PARP inhibitors in advanced ovarian cancer

The field of ovarian cancer has been revolutionized with the use of poly (ADP-ribose) polymerase (PARP) inhibitors, which present greater inhibition effect in epithelial subtype due to high rates of homologous recombination deficiency. PARP inhibition exploits this cancer pitfall by disrupting DNA repair, leading to genomic instability and apoptosis. Three PARP inhibitors (olaparib, niraparib, and rucaparib) are now approved for use in women with epithelial ovarian cancer, while others are under development. Among women with BRCA1/2 mutations, maintenance PARP therapy has led to a nearly fourfold prolongation of PFS, while those without BRCA1/2 mutations experience an approximately twofold increase in PFS. Differences in trial design, patient selection and primary analysis population affect the conclusions on PARP inhibitors. Limited OS data have been published and there is also limited experience regarding long-term safety. With regard to toxicity profile, there are no differences in serious adverse events between the experimental and control groups. However, combining adverse event data from maintenance phases, a trend towards more events in the experimental group, compared with controls, has been shown. The mechanisms of PARP-inhibitor resistance include restoration of HR through reversion mutations in HR genes, leading to resumed HR function. Other mechanisms that sustain sufficient DNA repair are discussed as well. PARP inhibitors play a pivotal role in the management of ovarian cancer, affecting the future treatment choices. Defining exactly which patients will benefit from them is a challenge and the need for HRD testing to define ‘BRCA-ness’ will add additional costs to treatment.

Fuzuloparib: First Approval

Fuzuloparib (AiRuiYi®, ; formerly fluzoparib) is a small molecule, orally active PARP inhibitor being developed by Jiangsu Hengrui Pharmaceuticals Co., Ltd. (formerly Jiangsu Hengrui Medicine Co., Ltd.) for the treatment of solid cancers. Fuzuloparib has been approved in China for the treatment of ovarian cancer (including fallopian tube cancer or primary peritoneal cancer), and phase II and III trials are investigating fuzuloparib for the treatment of other solid cancers, including cancers of the pancreas, breast, prostate and lungs. This article summarizes the milestones in the development of fuzuloparib leading to this first approval for the treatment of platinum-sensitive recurrent ovarian cancer, fallopian tube cancer or primary peritoneal cancer in patients with germline BRCA mutation who have undergone second-line or above chemotherapy.

Design, synthesis and biological evaluation of novel molecules as potent PARP-1 inhibitors

Two series of novel compounds with inhibition activity against PARP-1 were designed and synthesized. All target compounds were evaluated for their PARP-1 inhibition activity, and compounds with high PARP-1 inhibition activity were selected to assess for cellular assays in vitro. Among them, compound II-4 displayed impressive results in both PARP-1 enzyme inhibition with IC₅₀ value of 0.51 nM and anti-proliferation activity against HCT116 and HCC1937 cell lines with IC₅₀ values of 6.62 nM and 12.65 nM, respectively. Also, II-4 exhibited good metabolic stability in vitro with t_1/2 of 173.25 min and CL_int of 0.04 mL/min/mg. Prediction of molecular properties and protein docking were applied to structure design. Our study provides potential lead compounds and design directions for the development of PARP-1 inhibitors.

Pharmacokinetic effects of proton pump inhibitors on the novel PARP inhibitor fluzoparib: a single-arm, fixed-sequence trial in male healthy volunteers

Purpose To assess the pharmacokinetic (PK) effect of proton pump inhibitors on the novel poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor fluzoparib, and observe the safety of its co-administration with omeprazole. Patients and methods Sixteen male healthy volunteers (HVs) were enrolled in a single-center, single-arm, open-label, fixed-sequence study. HVs took fluzoparib (100 mg, p.o.) after meal consumption on day-1, took omeprazole 40 mg (p.o.) under a fasting condition from day-5 to day-9, and took fluzoparib (100 mg, p.o.) after meal consumption on day-9. Blood samples were collected at predetermined timepoints for PK analyses. Safety was assessed via clinical laboratory tests. The study was registered with the Clinical Trials Registry on 30 September 2019 (NCT04108676). Results The peak plasma concentrations (Cmax) after fluzoparib administration was 2395.17 ± 418.27 ng/mL, the area under the curve (AUC) within 72 h (AUC0 - 72 h) was 26669.09 ± 7320.12 h·ng/mL, and AUC0-∞ was 26897.44 ± 7573.61 h·ng/mL. The Cmax after co-administration of fluzoparib and omeprazole was 2489.43 ± 423.72 ng·mL, AUC0 - 72 h was 30300.49 ± 8350.08 h·ng/mL, and AUC0-∞ was 30678.74 ± 8595.55 h·ng/mL. The geometric mean ratio of Cmax, AUC0 - 72 h and AUC0-∞ was 104.0% (90%CI: 94.8-114.0%), 113.6% (104.2-123.9%) and 104.1% (104.5-124.6%). The number of HVs with adverse reactions was identical (eight) for administration of fluzoparib and co-administration of fluzoparib and omeprazole. Conclusions The proton pump inhibitor omeprazole did not have a significant influence on the PK behavior of fluzoparib, and its safety profile was good upon co-administration with omeprazole. (NCT04108676, 30 September 2019).

PARP Inhibitors Talazoparib and Niraparib Sensitize Melanoma Cells to Ionizing Radiation

(1) Background: Niraparib and Talazoparib are poly (ADP-ribose) polymerase (PARP) 1/2 inhibitors. It is assumed that combining PARP inhibitors with radiotherapy could be beneficial for cancer treatment. In this study, melanoma cells were treated with Niraparib and Talazoparib in combination with ionizing radiation (IR). (2) Methods: The effects of Talazoparib and Niraparib in combination with IR on cell death, clonogenicity and cell cycle arrest were studied in healthy primary fibroblasts and primary melanoma cells. (3) Results: The melanoma cells had a higher PARP1 and PARP2 content than the healthy fibroblasts, and further increased their PARP2 content after the combination therapy. PARP inhibitors both sensitized fibroblasts and melanoma cells to IR. A clear supra-additive effect of KI+IR treatment was detected in two melanoma cell lines analyzing the surviving fraction. The cell death rate increased in the healthy fibroblasts, but to a larger extent in melanoma cells after combined treatment. Finally, a lower percentage of cells in the radiosensitive G2/M phase is present in the healthy fibroblasts compared to the melanoma cells. (4) Conclusions: Both PARP inhibitors sensitize melanoma cells to IR. Healthy tissue seems to be less affected than melanoma cells. However, the great heterogeneity of the results suggests prior testing of the tumor cells in order to personalize the treatment.