Discovery of 2-{4-[(3S)-piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide (MK-4827): a novel oral poly(ADP-ribose)polymerase (PARP) inhibitor efficacious in BRCA-1 and -2 mutant tumors

Duplexed CeTEAM drug biosensors reveal determinants of PARP inhibitor selectivity in cells

Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) targeting PARP1 and PARP2 have revolutionized cancer therapy by selectively killing cancer cells with defective DNA repair. However, achieving PARP1 or PARP2-selective inhibitors is difficult due to structural homology. Selectivity profiling is typically done with purified proteins, but these lack the complexity of intracellular environments and could therefore be inaccurate. Here, we duplex PARP1 L713F-GFP and PARP2 L269A-mCherry cellular target engagement by accumulation of mutant (CeTEAM) drug biosensors to systematically characterize binding and cell cycle alterations of 27 PARPi. Our results reveal that most PARPi are equipotent for both PARPs, including the next-generation drug, senaparib. However, benzimidazole carboxamide (niraparib) derivatives demonstrated PARP1-selective tendencies, while pthalazinones (olaparib) favored PARP2. AZD5305, a reported PARP1-selective inhibitor with characteristics of both series, was the exception and appears ∼1600-fold more potent towards PARP1. In agreement with current understanding, we see that trapping-associated S/G2-phase transitions positively correlate with PARP1/2 binding potency, while some potent binders, such as veliparib, did not - likely reflecting their allosteric influence on DNA retention. We also assessed the effect of the PARP1/2 active site component, histone PARylation factor 1 (HPF1), on intracellular PARPi binding and see that HPF1 depletion elicits slight deviations in apparent binding potency, while contributing additively to trapping-like phenotypes. The PARP1/2 CeTEAM platform thus provides a structural roadmap for the development of selective PARPi and should facilitate the discovery of targeted therapies. Furthermore, our results highlight that multiplexing CeTEAM biosensors and layered genetic perturbations can systematically profile determinants of intracellular drug selectivity.

Development of 99mTc-Labeled Complexes with a Niraparib HYNIC Derivative for PARP-Positive Tumor Imaging

As an enzyme that plays an important role in DNA repair, poly(ADP-ribose) polymerase-1 (PARP-1) has become a popular target for cancer therapy. Nuclear medicine molecular imaging technology, supplemented by radiolabeled PARP-1 inhibitors, can accurately determine the expression level of PARP-1 at lesion sites to help patients choose an appropriate treatment plan. In this work, niraparib was modified with a hydrazinonicotinamide (HYNIC) group to generate the ligand NPBHYNIC, which has an in vitro affinity (IC50) of 450.90 nM for PARP-1. The ligand NPBHYNIC was labeled with technetium-99m and six different coligands to yield [99mTc]Tc-(X/tricine)-NPBHYNIC (X = TPPTS, TPPMS, PSA, PDA, NIC and ISONIC). These complexes were hydrophilic and exhibited good stability in vitro, and low levels of these complexes were taken up by nontarget organs and tissues in Kunming mice. Among these complexes, [99mTc]Tc-(TPPTS/tricine)-NPBHYNIC and [99mTc]Tc-(NIC/tricine)-NPBHYNIC were selected for biodistribution in HeLa tumor-bearing BALB/c nude mice at 2 h post injection. The results revealed that the tumor uptake of [99mTc]Tc-(TPPTS/tricine)-NPBHYNIC (1.02 ± 0.07% ID/g) was greater than that of [99mTc]Tc-(NIC/tricine)-NPBHYNIC (0.36 ± 0.05% ID/g). Additionally, in biodistribution, single-photon emission computed tomography/computed tomography (SPECT/CT) and radioautography experiments, the tumor uptake of [99mTc]Tc-(TPPTS/tricine)-NPBHYNIC was significantly reduced in the blocked group, indicating PARP-1 specificity. Therefore, it has potential for use as a niraparib-based tumor imaging agent that targets PARP-1.

Design, Synthesis, and Pharmacodynamic Evaluation of Highly Selective PARP1 Inhibitors with Brain Penetrance

Selective poly(ADP-ribose) polymerase 1 (PARP1) inhibitors not only exhibit antitumor efficacy but also offer the potential to mitigate the toxicities typically associated with broader PARP inhibition. In this study, we designed and synthesized a series of small molecules targeting highly selective PARP1 inhibitors. Among these, T26 demonstrated excellent selectivity to PARP1 along with the capability to effectively cross the blood-brain barrier (BBB). T26 exhibited an IC50 of 0.2 nM against PARP1, with a remarkable 610-fold selectivity over PARP2 and high antiproliferative activity in BRCA mutant MDA-MB-436 cells with an IC50 of 2.6 nM. T26 also displayed excellent oral bioavailability (F = 87.74%) and long half-life (T1/2 = 76.07 h) in mice, supporting once every other day administration. Oral administration of T26 at 0.3 mg/kg and 3 mg/kg resulted in significant tumor growth inhibition in both subcutaneous and intracranial xenograft models of MDA-MB-436, suggesting T26 significant potential for the treatment of breast cancer metastases.

The recent advance and prospect of poly(ADP-ribose) polymerase inhibitors for the treatment of cancer

Chemotherapies are commonly used in cancer therapy, their applications are limited to low specificity, severe adverse reactions, and long-term medication-induced drug resistance. Poly(ADP-ribose) polymerase (PARP) inhibitors are a novel class of antitumor drugs developed to solve these intractable problems based on the mechanism of DNA damage repair, which have been widely applied in the treatment of ovarian cancer, breast cancer, and other cancers through inducing synthetic lethal effect and trapping PARP-DNA complex in BRCA gene mutated cancer cells. In recent years, PARP inhibitors have been widely used in combination with various first-line chemotherapy drugs, targeted drugs and immune checkpoint inhibitors to expand the scope of clinical application. However, the intricate mechanisms underlying the drug resistance to PARP inhibitors, including the restoration of homologous recombination, stabilization of DNA replication forks, overexpression of drug efflux protein, and epigenetic modifications pose great challenges and desirability in the development of novel PARP inhibitors. In this review, we will focus on the mechanism, structure-activity relationship, and multidrug resistance associated with the representative PARP inhibitors. Furthermore, we aim to provide insights into the development prospects and emerging trends to offer guidance for the clinical application and inspiration for the development of novel PARP inhibitors and degraders.

Synthesis and bioevaluation of a new 68Ga-labelled niraparib derivative that targets PARP-1 for tumour imaging

Poly ADP-ribose polymerase (PARP) inhibitors prevent the repair of DNA single-strand breaks in cancer cells with abnormal homologous recombination, producing a synthetic lethal effect. Thus, PARP inhibitors have become clinically effective anticancer drugs. Labelling with radionuclides may extend the use of PARP inhibitors as tracers in nuclear medicine diagnostics, helping to stratify patients. In the present study, niraparib was selected as a skeleton molecule modified with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and labelled with gallium-68 to obtain [68Ga]Ga-DOTANPB with high radiochemical purity (>95 %). To verify the accuracy of the [68Ga]Ga-DOTANPB structure, [natGa]Ga-DOTANPB was also synthesized, and in vitro affinity experiments were performed, which revealed a high affinity for PARP-1 (IC50 = 82.21 nM). [68Ga]Ga-DOTANPB is hydrophilic and has good in vitro stability within 3 h. In in vitro experiments, [68Ga]Ga-DOTANPB has a high uptake in HeLa cells and can enter the cell to target PARP-1. In coronal PET imaging of HeLa tumour-bearing mice, [68Ga]Ga-DOTANPB showed significant radioconcentration at the tumour site at 0.5 h, 1 h, and 2 h. Biodistribution and autoradiography experiments revealed that [68Ga]Ga-DOTANPB has obvious tumour uptake and can be significantly inhibited (3.37 ± 0.33 % ID/g vs. 2.50 ± 0.27 % ID/g, **P < 0.01), suggesting that it has PARP-1 specificity. Thus, these findings suggested that [68Ga]Ga-DOTANPB may be a potential niraparib-based PET tracer for targeting PARP-1.

Discovery of 6-Fluoro-5-{4-[(5-fluoro-2-methyl-3-oxo-3,4-dihydroquinoxalin-6-yl)methyl]piperazin-1-yl}-N-methylpyridine-2-carboxamide (AZD9574): A CNS-Penetrant, PARP1-Selective Inhibitor

PARP inhibitors have attracted considerable interest in drug discovery due to the clinical success of first-generation agents such as olaparib, niraparib, rucaparib, and talazoparib. Their success lies in their ability to trap PARP to DNA; however, first-generation PARP inhibitors were not strictly optimized for trapping nor for selectivity among the PARP enzyme family. Previously we described the discovery of the second-generation PARP inhibitor AZD5305, a selective PARP1-DNA trapper. AZD5305 maintained the antitumor efficacy of first-generation PARP inhibitors while exhibiting lower hematological toxicity. Recently, there has been interest in central nervous system (CNS)-penetrant PARP inhibitors for CNS malignancies and other neurological conditions; however, AZD5305 is not CNS penetrant. Herein we describe the discovery and optimization of a series of CNS-penetrant, PARP1-selective inhibitors and PARP1-DNA trappers, culminating in the discovery of AZD9574, a compound that maintains the PARP1 selectivity of AZD5305 with improved permeability, reduced efflux, and increased CNS penetration.

Drug repurposing screen targeting PARP identifies cytotoxic activity of efavirenz in high-grade serous ovarian cancer

Drug repurposing has potential to improve outcomes for high-grade serous ovarian cancer (HGSOC). Repurposing drugs with PARP family binding activity may produce cytotoxic effects through the multiple mechanisms of PARP including DNA repair, cell-cycle regulation, and apoptosis. The aim of this study was to determine existing drugs that have PARP family binding activity and can be repurposed for treatment of HGSOC. In silico ligand-based virtual screening (BLAZE) was used to identify drugs with potential PARP-binding activity. The list was refined by dosing, known cytotoxicity, lipophilicity, teratogenicity, and side effects. The highest ranked drug, efavirenz, progressed to in vitro testing. Molecularly characterized HGSOC cell lines, 3D hydrogel-encapsulated models, and patient-derived organoid models were used to determine the IC50 for efavirenz, cell death, apoptosis, PARP1 enzyme expression, and activity in intact cancer cells following efavirenz treatment. The IC50 for efavirenz was 26.43-45.85 μM for cells in two dimensions; 27.81 μM-54.98 μM in three dimensions, and 14.52 μM-42.27 μM in HGSOC patient-derived organoids. Efavirenz decreased cell viability via inhibition of PARP; increased CHK2 and phosphor-RB; increased cell-cycle arrest via decreased CDK2; increased γH2AX, DNA damage, and apoptosis. The results of this study suggest that efavirenz may be a viable treatment for HGSOC.

Synthetic routes and clinical application of new drugs approved by EMA during 2023

In 2023, the European Medicines Agency (EMA) granted approval to 77 new molecular entities (NMEs), consisting of 45 new chemical entities (NCEs) and 32 new biological entities (NBEs). These pharmacological agents encompass a broad spectrum of therapeutic domains, including oncology, cardiology, dermatology, diagnostic medicine, endocrinology, gastroenterology and hepatology, metabolic disorders, and neurology. Among the 77 approved pharmaceuticals, three received accelerated review status, and 17 (22 %) were granted orphan drug designation for the treatment of rare diseases. This review provides an overview of the clinical applications and synthetic routes of 42 newly approved NCEs by the EMA in 2023. The objective is to offer a comprehensive understanding of the synthetic approaches used in the development of these drug molecules, thereby inspiring the creation of novel, efficient, and applicable synthetic methodologies.

Dual Targeting of CX3CR1 and PARP in Models of High-Grade Serous Ovarian Carcinoma

BACKGROUND/OBJECTIVES

Clinical use of poly(ADP-ribose) polymerase inhibitors (PARPis) against metastatic high-grade serous ovarian carcinoma (HGSOC) is limited to cases with deficient a homologous recombination (HR). Our objective was to determine whether the impairment of the fractalkine receptor (CX3CR1) could sensitize HR-proficient cases to PARPis.

METHODS

The efficacy of a dual drug combination, including AZD8797, an inhibitor of CX3CR1, and several PARPis was examined using cell lines and xenograft models.

RESULTS

The effectiveness of PARPis and AZD8797 drug combinations ranged from additive to strongly synergistic. Olaparib was synergistic with AZD8797 in OVCAR-4, Caov-3, and OHSAHO. Niraparib and AZD8797 produced synergy in OVCAR-4 and ES2. Rucaparib and AZD8797 were strongly synergistic in Caov-3 and OVSAHO. Veliparib was strongly synergistic with AZD8797 in OVCAR-4 and Caov-3. Notably, a combination of veliparib and AZD8797 produced a strong synergistic effect in a xenograft model.

CONCLUSIONS

While the exact mechanisms determining the nature of the PARPis and AZD8797 interaction remain to be uncovered, our data indicate that, in a subset of models, selected PARPis strongly synergize with the inhibition of CX3CR1, suggesting a potential therapeutic opportunity.

Clinical Outcomes of Poly(ADP-Ribose) Polymerase Inhibitors as Maintenance Therapy in Patients with Ovarian Cancer in the Southeastern Region of Korea

PURPOSE

In this study, we aimed to retrospectively investigate the real-world clinical efficacy and adverse events of poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitors in real-world clinical practice among patients with newly diagnosed epithelial ovarian cancer.

METHODS

We retrospectively reviewed the medical records from hospitals. Patients with epithelial ovarian cancer treated with olaparib or niraparib as frontline maintenance treatment between 1 January 2014 and 31 December 2022 were included. Progression-free survival (PFS) was analyzed using the Kaplan-Meier method, and adverse events associated with PARP inhibitor treatment were investigated.

RESULTS

Ninety-six patients treated with PARP inhibitors were identified. The median follow-up period was 21.8 months (95% confidence interval [CI] 19.4-24.0). Twenty (20.1%) patients experienced disease progression, and two patients died. The median PFS was 45.3 months (95% CI 39.4-NA). BRCA1 or BRCA2 gene mutations and primary cytoreductive surgery were associated with better PFS. Adverse events of any grade occurred in 74 (77.1%) patients. Nineteen (19.8%) patients experienced PARP inhibitor therapy interruptions, and 35 (36.5%) patients experienced dose reductions. Only three patients discontinued the drug due to adverse events.

CONCLUSIONS

In a real-world setting, PARP inhibitors showed efficacy comparable to that reported in published randomized controlled trials and had acceptable safety profiles.

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.

A First-in-Class High-Throughput Screen to Discover Modulators of the Alternative Lengthening of Telomeres (ALT) Pathway

Telomeres are a protective cap that prevents chromosome ends from being recognized as double-stranded breaks. In somatic cells, telomeres shorten with each cell division due to the end replication problem, which eventually leads to senescence, a checkpoint proposed to prevent uncontrolled cell growth. Tumor cells avoid telomere shortening by activating one of two telomere maintenance mechanisms (TMMs): telomerase reactivation or alternative lengthening of telomeres (ALT). TMMs are a viable target for cancer treatment as they are not active in normal, differentiated cells. Whereas there is a telomerase inhibitor currently undergoing clinical trials, there are no known ALT inhibitors in development, partially because the complex ALT pathway is still poorly understood. For cancers such as neuroblastoma and osteosarcoma, the ALT-positive status is associated with an aggressive phenotype and few therapeutic options. Thus, methods that characterize the key biological pathways driving ALT will provide important mechanistic insight. We have developed a first-in-class phenotypic high-throughput screen to identify small-molecule inhibitors of ALT. Our screen measures relative C-circle level, an ALT-specific biomarker, to detect changes in ALT activity induced by compound treatment. To investigate epigenetic mechanisms that contribute to ALT, we screened osteosarcoma and neuroblastoma cells against an epigenetic-targeted compound library. Hits included compounds that target chromatin-regulating proteins and DNA damage repair pathways. Overall, the high-throughput C-circle assay will help expand the repertoire of potential ALT-specific therapeutic targets and increase our understanding of ALT biology.

Niraparib Population Pharmacokinetics and Exposure-Response Relationships in Patients With Newly Diagnosed Advanced Ovarian Cancer

PURPOSE

Niraparib is a poly(adenosine diphosphate [ADP]-ribose) polymerase inhibitor approved for the maintenance treatment of advanced ovarian cancer (OC). Niraparib was originally approved in recurrent OC at a fixed starting dose (FSD) of 300 mg once daily (QD). This analysis characterized the population pharmacokinetics (PK) of niraparib and evaluated the relationships between exposure, efficacy, and safety to support clinical use of an individualized dosing strategy, in which the starting dose of niraparib was adjusted based on patient characteristics to improve the benefit-risk profile.

METHODS

A population PK model was developed by pooling data from four niraparib clinical trials (PN001 [n = 104], QUADRA [n = 455], NOVA [n = 403], and PRIMA [n = 480]) in patients with solid tumors, including OC. Exposure-response analyses were conducted to explore the relationships of niraparib exposure with progression-free survival (PFS) and adverse events in the PRIMA study. A multivariate logistic regression model was also developed to estimate the probability of grade ≥3 thrombocytopenia, using data from patients enrolled in PRIMA and NOVA. The impact of an individualized starting dose (ISD) regimen (200 mg QD in patients with body weight [BW] <77 kg or platelet count [PLT] <150,000/µL, or 300 mg QD in patients with BW ≥77 kg and PLT ≥150,000/µL) on systemic exposure, efficacy, and safety was assessed.

FINDINGS

Niraparib disposition was best described by a 3-compartment model with linear elimination. Key covariates included baseline creatinine clearance, BW, albumin, and age, all of which had minor effects on niraparib exposure. Comparable model-predicted exposure up to the time of disease progression/death or censoring in the 300-mg FSD and 200-/300-mg ISD groups was consistent with the lower rate of dose reduction in the ISD groups. No consistent niraparib exposure-response relationship was observed for efficacy in all PRIMA patients (first-line OC), and no statistically significant difference was seen in PFS curves for patients receiving a niraparib dose of 200 mg versus 300 mg. In the multivariate regression model, performed using combined data from PRIMA and NOVA, higher niraparib exposure (area under the concentration-time curve at steady-state [AUCss]), lower BW, and lower PLT were associated with an increased risk of grade ≥3 thrombocytopenia.

IMPLICATIONS

Population PK and exposure-response analyses support use of an ISD to improve the safety profile of niraparib, including reducing the rate of grade ≥3 thrombocytopenia, without compromising efficacy.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT01847274 (NOVA), NCT00749502 (PN001), NCT02655016 (PRIMA), NCT02354586 (QUADRA), www.

CLINICALTRIALS

gov.

A validated LC-MS/MS method for determination of neuro-pharmacokinetic behavior of niraparib in brain tumor patients

Niraparib is a potent and orally bioavailable inhibitor of poly (ADP-ribose) polymerase (PARP) with high specificity for isoforms 1 and 2. It has been approved by the U.S. Food and Drug Administration for ovarian cancer maintenance therapy and is currently under development for various cancers, including glioblastoma. To assess central nervous system (CNS) penetration of niraparib in glioblastoma patients, a novel bioanalytical method was developed to measure total and unbound niraparib levels in human brain tumor tissue and cerebrospinal fluid (CSF). The method was validated using plasma as a surrogate matrix over the concentration range of 1-10,000 nM on an LC-MS/MS system. The MS/MS detection was conducted in positive electrospray ionization mode, while chromatography was performed using a Kinetex™ PS C18 column with a total 3.5-minute gradient elution run time. The maximum coefficient of variation for both intra- and inter-day precision was 10.6%, with accuracy ranging from 92.8% - 118.5% across all matrices. Niraparib was stable in human brain homogenate for at least 6 hours at room temperature (RT) and 32 days at -20°C, as well as in stock and working solutions for at least 21 hours (RT) and 278 days (4°C). Equilibrium dialysis experiments revealed the fractions unbound of 0.05 and 0.16 for niraparib in human brain and plasma, respectively. The validated method is currently employed to assess niraparib levels in human glioblastoma tissue, CSF, and plasma in an ongoing trial on newly diagnosed glioblastoma and recurrent IDH1/2(+) ATRX mutant glioma patients (NCT05076513). Initial results of calculated total (Kp) and unbound (Kp,uu) tumor-to-plasma partition coefficients indicate significant brain penetration ability of niraparib in glioblastoma patients.

Preparation and Evaluation of a Novel 99mTc-Labeled Niraparib Isonitrile Complex as a Potential PARP-1 Imaging Agent

Poly ADP-ribose polymerase (PARP) plays an important role in the DNA repair process and has become an attractive target for cancer therapy in recent years. Given that niraparib has good clinical efficacy as a PARP inhibitor, this study aimed to develop radiolabeled niraparib derivatives for tumor imaging to detect PARP expression and improve the accuracy of stratified patient therapy. The niraparib isonitrile derivative (CNPN) was designed, synthesized, and radiolabeled to obtain the [99mTc]Tc-CNPN complex with high radiochemical purity (>95%). It was lipophilic and stable in vitro. In HeLa cell experiments, the uptake of [99mTc]Tc-CNPN was effectively inhibited by the ligand CNPN, indicating the binding affinity for PARP. According to the biodistribution studies of HeLa tumor-bearing mice, [99mTc]Tc-CNPN has moderate tumor uptake and can be effectively inhibited, demonstrating its specificity for targeting PARP. The SPECT imaging results showed that [99mTc]Tc-CNPN had tumor uptake at 2 h postinjection. All of the results of this study indicated that [99mTc]Tc-CNPN is a promising tumor imaging agent that targets PARP.

Design, synthesis, biological evaluation of novel piperidine-based derivatives as potent poly(ADP-ribose) polymerase-1 (PARP-1) inhibitors

Poly(ADP-ribose) polymerase-1 (PARP-1) is a crucial member of DNA repair enzymes responsible for repairing DNA single-strand breaks. Developing PARP inhibitors based on synthetic lethality strategies is an effective approach for treating breast cancer and other diseases. In this study, a series of novel piperidine-based benzamide derivatives were designed and synthesized using structure-based drug design principles. The anticancer activities of these compounds were evaluated against five human cancer cell lines (MDA-MB-436, CAPAN-1, SW-620, HepG2, SKOV3, and PC3) and the preliminary structure-activity relationships were delineated. Among the compounds, 6a and 15d demonstrated potent antiproliferative effects against MDA-MB-436 cells with IC50 values of 8.56 ± 1.07 μM and 6.99 ± 2.62 μM, respectively. Furthermore, both compounds exhibited excellent inhibitory activity against PARP-1, with IC50 values of 8.33 nM and 12.02 nM, respectively. Mechanistic investigations revealed that 6a and 15d effectively inhibited colony formation and cell migration of HCT116 cells. Moreover, they induced apoptosis by upregulating the expression of Bax and cleaved Caspase-3, while downregulating the expression of Caspase-3 and Bcl-2 in HCT116 cells. Based on its impressive pharmacodynamic data in vitro, we conducted a study to evaluate the efficacy of 15d in a xenograft tumor model in mice when used in combination with cytotoxic agents. Collectively, these findings suggest that 15d could be promising drug candidates worthy of further investigation.

Synthesis of 2-Aryl Indazole: Synthesis, Biological Evaluationand In-Silico Studies

In this work, a highly effective synthesis technique for obtaining aryl indazole under mild circumstances is provided, using trimethyl phosphine as a powerful reagent. The procedure shows that a wide range of substrates can be investigated, yielding various 2-aryl indazole derivatives with acceptable to exceptional yields and a wide range of functional group tolerance. Additionally, based on In Silico studies tests were conducted to determine the anticancer activity In Vitro for all produced compounds (3 a-3 j) against A549, HT-29 and HepG2 cell lines. Compounds 3 c and 3 d, with IC50 values of 15, 53.55, 7.34, 7.10, 56.28, and 17.87 (μM) against A549, HT-29 and HepG2 respectively, showed significant anticancer activity.

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.

Multi-functionalization of reduced graphene oxide nanosheets for tumor theragnosis: Synthesis, characterization, enzyme assay, in-silico study, radiolabeling and in vivo targeting evaluation

BACKGROUND

In this study, a combination of nanotechnology, organic synthesis and radiochemistry were utilized in order to design an efficient nano-system conjugated with a suitable radionuclide and an antitumor agent for possible application as tumor theragnostic agent.

METHOD

Four novel compounds (3 and 4a-c) bearing tetrahydroquinazoline-7-sulfonohydrazide or 1,2,3,4-tetrahydroquinazoline-7-sulfonamide scaffold were designed. Then, docking study predicted that the compounds can be considered as potential inhibitors for PARP-1. Following that; the four compounds were synthesized and properly characterized using 1HNMR, 13CNMR, IR and Mass spectroscopy. The cytotoxic effect of the four compounds was evaluated against breast cancer cell line (MDA-MB-436), where compound 3 showed the most promising cytotoxic effect. The inhibitory effect of the four compounds was evaluated in vitro against PARP-1.

RESULT

Carboxylated graphene oxide nanosheets (NGO-COOH) were synthesized by a modified Hummer's method and has size of range 40 nm. The NGO-COOH nanosheets were proven to be safe and biocompatible when tested in vitro against normal human lung fibroblast cells (MRC-5). The prepared NGO-COOH nanosheets were conjugated with compound 3 then radiolabeled with 99mTc to yield 99mTc-NGO-COOH-3 with a radiochemical yield of 98.5.0 ± 0.5%. 99mTc-NGO-COOH-3 was injected intravenously in solid tumor bearing mice to study the degree of localization of the nano-system at tumor tissue. The results of the study revealed, excellent localization and retention of the designed nano-system at tumor tissues with targeting ratio of 9.0.

CONCLUSION

Stirred a new candidate tumor theragnostic agent that is safe, selective and stable.

Real world data of niraparib in platinum sensitive relapsed ovarian cancer: A multicenter experience of the MITO group

OBJECTIVE

PARP (poly adenosine diphosphate [ADP]-ribose polymerase) inhibitors are approved as maintenance therapy in platinum sensitive ovarian cancer (OC), in first line and in the recurrent setting, regardless of BRCA mutational status. Real-world data after the introduction of these agents are needed to evaluate whether the benefit observed in phase III randomized clinical trials can be translated into clinical practice. The aim of our study was to provide real-life data on efficacy and safety of niraparib administered as maintenance in platinum sensitive relapsed OC patients (PSROC).

METHODS

This retrospective/prospective observational study included relapsed OC patients that received niraparib as maintenance, at the time of platinum sensitive recurrence within the Italian expanded-access program. Clinical data at the time of diagnosis and at the time of recurrence were collected and analyzed. Median progression free survival (PFS) and overall survival (OS) were calculated as the time from start of niraparib treatment to subsequent radiologically confirmed relapse and death or last contact, respectively.

RESULTS

Among 304 eligible patients, 260 (85%) had BRCA wild-type tumor and 36. (11.9%) were BRCA mutated. Median PFS was 9.1 months (95% CI: 6.9-11.2) and 10.3 months (95% CI: 7.0-13.5) in the BRCAwt and BRCAmut cohorts, respectively. Furthermore, median OS was 41.7 months (95% CI: 31.6-41.9) and 34.6 months (95% CI: N.E.) in the BRCAwt and BRCAmut cohorts, respectively.

CONCLUSION

Data from this large real-life dataset suggested that maintenance with niraparib in the real-life setting of platinum sensitive OC recurrence is effective and well tolerated.

A review of poly(ADP-ribose)polymerase-1 (PARP1) role and its inhibitors bearing pyrazole or indazole core for cancer therapy

Cancer is a disease with a high mortality rate characterized by uncontrolled proliferation of abnormal cells. The hallmarks of cancer evidence the acquired cells characteristics that promote the growth of malignant tumours, including genomic instability and mutations, the ability to evade cellular death and the capacity of sustaining proliferative signalization. Poly(ADP-ribose) polymerase-1 (PARP1) is a protein that plays key roles in cellular regulation, namely in DNA damage repair and cell survival. The inhibition of PARP1 promotes cellular death in cells with homologous recombination deficiency, and therefore, the interest in PARP protein has been rising as a target for anticancer therapies. There are already some PARP1 inhibitors approved by Food and Drug Administration (FDA), such as Olaparib and Niraparib. The last compound presents in its structure an indazole core. In fact, pyrazoles and indazoles have been raising interest due to their various medicinal properties, namely, anticancer activity. Derivatives of these compounds have been studied as inhibitors of PARP1 and presented promising results. Therefore, this review aims to address the importance of PARP1 in cell regulation and its role in cancer. Moreover, it intends to report a comprehensive literature review of PARP1 inhibitors, containing the pyrazole and indazole scaffolds, published in the last fifteen years, focusing on structure-activity relationship aspects, thus providing important insights for the design of novel and more effective PARP1 inhibitors.

A Facile Ugi/Ullmann Cascade Reaction to Access Fused Indazolo-Quinoxaline Derivatives with Potent Anticancer Activity

A facile methodology for the construction of a complex heterocycle indazolo-fused quinoxalinone has been developed via an Ugi four-component reaction (U-4CR) followed by an intramolecular Ullmann reaction. The expeditious process features an operationally simple approach, time efficiency, and a broad substrate scope. Biological activity was evaluated and demonstrated that compound 6e inhibits human colon cancer cell HCT116 proliferation with an IC50 of 2.1 μM, suggesting potential applications for developing a drug lead in medicinal chemistry.

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.

Synthesis and clinical application of small-molecule drugs approved to treat prostatic cancer

Prostate cancer is a prevalent form of cancer that primarily affects men, with a high incidence and mortality rate. It is the second most common cancer among males, following lung cancer. Typically occurring in individuals aged 50 and above, this malignant tumor originates from abnormal cells in the prostate tissue. If left untreated, it can spread to nearby tissues, lymph nodes, and even bones. Current treatment methods include surgery, radiotherapy, and chemotherapy. However, these treatments have certain limitations and side effects. Therefore, researching and developing new small-molecule drugs to treat prostate cancer is of great significance. In recent years, many small-molecule drugs have been proven to have therapeutic effects on prostate cancer. The purpose of this review is to give a comprehensive look at the clinical uses and synthetic methods of various significant small-molecule drugs that have been approved to treat prostate cancer, to facilitate the development of more powerful and innovative drugs for the effective control of prostate cancer.

Real-world data on niraparib maintenance treatment in patients with non-gBRCA mutated platinum-sensitive recurrent ovarian cancer

OBJECTIVES

The aim of this study was to provide real-world efficacy and safety data on niraparib maintenance treatment in patients with non-germline (gBRCA)1/2 mutated platinum-sensitive recurrent ovarian cancer.

METHODS

This retrospective multi-center cohort study included 94 platinum-sensitive recurrent ovarian cancer patients without known gBRCA1/2 mutation treated in an individual patient access program in Norway. The primary outcome was time from start of niraparib treatment to first subsequent treatment. Secondary endpoints included progression-free survival, safety, and tolerability.

RESULTS

After median follow-up of 13.4 months (95% confidence interval (CI) 10.0 to 16.8), 68.1% had progressed and 22.3% had died. Of the entire cohort, 61.7% had commenced a new line of treatment, and 24.5% were still receiving niraparib. The median duration of niraparib treatment was 5.0 months (range 0.4 to 27.3), and the median time to first subsequent treatment was 10.7 months (95% CI 8.4 to 13.0). Patients with elevated CA125 prior to start of niraparib had shorter time to first subsequent treatment (7.3 months, 95% CI 4.2 to 10.3) than patients with normalized CA125 (12.2 months, 95% CI 10.9 to 13.7 (p=0.002). Patients who started on individual dose based on weight and platelet counts had fewer dose reductions (p<0.001) and interruptions (p=0.02).

CONCLUSION

In a real-world setting, niraparib maintenance treatment in patients with non-gBRCA1/2 mutated recurrent platinum-sensitive ovarian cancer showed effectiveness comparable with published phase III studies and acceptable safety. Individualized dosing is essential to minimize adverse events. CA125 levels at start of niraparib treatment may help to estimate the individual prognosis.

Anti-tumour and radiosensitising effects of PARP inhibitor on cervical cancer xenografts

This study evaluated the radiosensitising effect of niraparib; a poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor on HeLa cervical cancer cells in nude mice and explored its possible mechanism. Twenty-four 3-5-week-old female BALB/c nude mice, inoculated with HeLa cells into the right hind leg, were randomly assigned into eight groups with three mice per group and treated. The tumour volume was significantly reduced under niraparib + radiotherapy combination as compared to monotherapy and untreated mice. The tumour growth was significantly delayed by 23.33-39 days when treated with combination therapy (p<.05). Further, univariate analysis revealed prolonged time for tumour growth when radiotherapy was followed by niraparib (I.G.) rather than niraparib (I.P.) (p=.003). Combination therapy reduced levels of PARP-1 precursor, PARP-1 splicer, PAR and RAD51 protein with high expression of γ-H2AX/CC3 and low expression of Ki-67. Niraparib in combination with radiotherapy can enhance the formation of DNA double strand breaks in HeLa cells and up regulate the expression of γ-H2AX/CC3.IMPACT STATEMENTWhat is already known on this subject? Asia has the highest incidence of cervical cancer (58.2%). Poly(adenosine diphosphate-ribose) polymerases (PARPs) are family of enzymes involved in single-strand break (SSB) and double-strand break (DSB) repair pathways. Niraparib is an effective inhibitor of both PARP-1 and PARP-2 and has the ability to cross the blood-brain barrier.What the results of this study add? Our study demonstrated that the combination of niraparib and radiotherapy can significantly enhance the cytotoxicity induced by radiotherapy. The inhibition effect of radiotherapy combined with niraparib on the tumour growth of mice was prominent, thereby establishing the radio-sensitisation activity of niraparib.What are the implications of these findings for clinical practice and/or further research? Niraparib can improve the cytotoxic effect of radiotherapy by increasing the formation of DSBs and up regulating the expression of apoptotic protein in HeLa cells.

Photopromoted Free Radical Silylation of 2-Aryl-2H-indazoles with Silanes

Photoinduced silylation of silanes with 2-aryl-2H-indazoles was developed under mild conditions, which could efficiently result in diverse 3-silylated 2H-indazoles with good substrate scopes. A series of scaled-up to gram level and radical capture operations were performed in this system. Meanwhile, a bioactive molecule was tolerated well under typical conditions.

Small molecule tractable PARP inhibitors: Scaffold construction approaches, mechanistic insights and structure activity relationship

Diverse drug design strategies viz. molecular hybridization, substituent installation, scaffold hopping, isosteric replacement, high-throughput screening, induction and separation of chirality, structure modifications of phytoconstituents and use of structural templates have been exhaustively leveraged in the last decade to load the chemical toolbox of PARP inhibitors. Resultantly, numerous promising scaffolds have been pinpointed that in turn have led to the resuscitation of the credence to PARP inhibitors as cancer therapeutics. This review briefly presents the physiological functions of PARPs, the pharmacokinetics, and pharmacodynamics, and the interaction profiles of FDA-approved PARP inhibitors. Comprehensively covered is the section on the drug design strategies employed by drug discovery enthusiasts for furnishing PARP inhibitors. The impact of structural variations in the template of designed scaffolds on enzymatic and cellular activity (structure-activity relationship studies) has been discussed. The insights gained through the biological evaluation such as profiling of physicochemical properties andin vitroADME properties, PK assessments, and high-dose pharmacology are covered.

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.

Efficacy and Safety of Niraparib as First-Line Maintenance Treatment for Patients with Advanced Ovarian Cancer: Real-World Data from a Multicenter Study in China

BACKGROUND

Poly (ADP-ribose) polymerase (PARP) inhibitors are a new maintenance therapy option for patients with ovarian cancer (OC).

OBJECTIVE

To evaluate the efficacy and influencing factors of the novel PARP inhibitor niraparib for maintenance treatment of Chinese patients with advanced OC.

PATIENTS AND METHODS

In this retrospective multicenter real-world study patients with advanced OC from 15 hospitals throughout China were enrolled. The primary endpoint was progression-free survival (PFS) and the secondary endpoints included the time to treatment discontinuation and safety. Least Absolute Shrinkage and Selection Operator (LASSO) regression was used to identify possible risk factors for PFS, after which a prediction model was established to evaluate the likelihood of achieving an 18-month PFS. The relationship between the dose of niraparib and PFS was also evaluated.

RESULTS

The PFS rates of 199 patients at 6, 12, 18, 24, and 30 months were 87.4%, 75.9%, 63.6%, 56.1%, and 51.8%, respectively. LASSO regression model revealed that only age < 65 years (P = 0.011), BRCA mutations (P < 0.001), and R0 status after cytoreductive surgery (P = 0.01) were significant factors associated with prolonged PFS times. Based on the LASSO logistic regression analysis, a clinical prediction formula was developed: - 2.412 + 1.396Age≥65yr + 2.374BRCAwt + 1.387R1 + 0.793Interval≥12w + 0.178BMI>24kg/m2 which yielded a cut-off value of 0.091, an area under the curve (AUC) of 0.839 (0.763-0.916), a sensitivity of 94.3%, and an accuracy of 78.5%. A nomogram was then built to visualize the results. The major treatment-emergent adverse events of ≥ grade 3 included a platelet count decrease (19.1%), white blood cell count decrease (15.1%), neutrophil count decrease (13.1%), and anemia (18.6%). The 18-month PFS rates in patients treated with 200 mg niraparib were somewhat higher than in patients treated with 100 mg after 3-months of therapy.

CONCLUSIONS

For Chinese OC patients, niraparib, particularly at a 200 mg individual starting dose, was an effective therapy with easily manageable safety.

A Review of PARP-1 Inhibitors: Assessing Emerging Prospects and Tailoring Therapeutic Strategies

Eukaryotic organisms contain an enzyme family called poly (ADP-ribose) polymerases (PARPs), which is responsible for the poly (ADP-ribosylation) of DNA-binding proteins. PARPs are members of the cell signaling enzyme class. PARP-1, the most common isoform of the PARP family, is responsible for more than 90% of the tasks carried out by the PARP family as a whole. A superfamily consisting of 18 PARPs has been found. In order to synthesize polymers of ADP-ribose (PAR) and nicotinamide, the DNA damage nick monitor PARP-1 requires NAD+ as a substrate. The capability of PARP-1 activation to boost the transcription of proinflammatory genes, its ability to deplete cellular energy pools, which leads to cell malfunction and necrosis, and its involvement as a component in the process of DNA repair are the three consequences of PARP-1 activation that are of particular significance in the process of developing new drugs. As a result, the pharmacological reduction of PARP-1 may result in an increase in the cytotoxicity toward cancer cells.

Discovery of dual PARP and CDK6 inhibitors for triple-negative breast cancer with wild-type BRCA

Inhibition of PARP is synthetic lethal with defects in BRCA, which provide effective targeted therapy strategy for BRCA mutation type of TNBC patients. However, approximately 80% of TNBC patients do not have BRCA mutations. Recent studies have shown that CDK4/6 inhibitors can increase the sensitivity of wild-type BRCA cells to PARP inhibitors. We designed a series of dual PARP and CDK6 inhibitors, and the most promising compound, P4i, showed good inhibitory activity against PARP1 and CDK6 and good inhibitory effects on MDA-MB-231 (IC50 = 1.96 μM), MDA-MB-468 (IC50 = 2.81 μM) and BT-549 (IC50 = 2.37 μM) cells with wild-type BRCA. Compared with Olaparib, the inhibition capacity of the three BRCA wild-type (MDA-MB-231, MDA-MB-468 and BT-549) cells was about 10-20 times higher, and even better than the combination of Olaparib and Palbociclib. As a novel PARP multifunctional molecule, it is a potential compound for the treatment of BRCA wild-type TNBC.

The therapeutic potential of targeting regulated non-apoptotic cell death

Cell death is critical for the development and homeostasis of almost all multicellular organisms. Moreover, its dysregulation leads to diverse disease states. Historically, apoptosis was thought to be the major regulated cell death pathway, whereas necrosis was considered to be an unregulated form of cell death. However, research in recent decades has uncovered several forms of regulated necrosis that are implicated in degenerative diseases, inflammatory conditions and cancer. The growing insight into these regulated, non-apoptotic cell death pathways has opened new avenues for therapeutic targeting. Here, we describe the regulatory pathways of necroptosis, pyroptosis, parthanatos, ferroptosis, cuproptosis, lysozincrosis and disulfidptosis. We discuss small-molecule inhibitors of the pathways and prospects for future drug discovery. Together, the complex mechanisms governing these pathways offer strategies to develop therapeutics that control non-apoptotic cell death.

Mapping the Genetic Interaction Network of PARP inhibitor Response

Genetic interactions have long informed our understanding of the coordinated proteins and pathways that respond to DNA damage in mammalian cells, but systematic interrogation of the genetic network underlying that system has yet to be achieved. Towards this goal, we measured 147,153 pairwise interactions among genes implicated in PARP inhibitor (PARPi) response. Evaluating genetic interactions at this scale, with and without exposure to PARPi, revealed hierarchical organization of the pathways and complexes that maintain genome stability during normal growth and defined changes that occur upon accumulation of DNA lesions due to cytotoxic doses of PARPi. We uncovered unexpected relationships among DNA repair genes, including context-specific buffering interactions between the minimally characterized AUNIP and BRCA1-A complex genes. Our work thus establishes a foundation for mapping differential genetic interactions in mammalian cells and provides a comprehensive resource for future studies of DNA repair and PARP inhibitors.

Oxaliplatin prior to PARP inhibitor in BRCA-mutated ovarian cancer

Background

The use of PARP inhibitor (PARPi) has shown a considerable benefit in progression-free survival (PFS) in relapsed, platinum-sensitive epithelial ovarian cancer (OC).

Objective

Our study aimed to investigate the impact of the last platinum-based chemotherapy treatment in response to PARPi.

Design

Retrospective cohort study.

Patients and methods

The study involved 96 consecutive, pretreated, platinum-sensitive advanced OC patients. Demographics and clinical data were retrieved from clinical records. PFS and overall survival (OS) were calculated from the start of PARPi.

Results

Germline BRCA mutation was investigated in all cases. Platinum-based chemotherapy before PARPi maintenance therapy included pegylated liposomal doxorubicin-oxaliplatin (PLD-Ox) in 46 patients (48%) and other platinum-based chemotherapy in 50 patients (52%). During a median follow-up of 22 months from the beginning of PARPi therapy, 57 patients relapsed (median PFS: 12 months) and 64 patients died (median OS: 23 months). During multivariable analysis, receiving PLD-Ox before PARPi was associated with improved PFS [hazard ratio (HR): 0.46, 95% CI: 0.26-0.82] and OS (HR: 0.48, 95% CI: 0.27-0.83). In 36 BRCA-mutated patients, PLD-Ox was associated with improved PFS (2-year PFS: 70.0% versus 25.0%, p = 0.02).

Conclusion

Receiving PLD-Ox before PARPi may improve prognosis in platinum-sensitive advanced OC patients and may provide advantages in the BRCA-mutated subgroup.

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.

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.

Comparative Efficacy and Selectivity of Pharmacological Inhibitors of DYRK and CLK Protein Kinases

Dual-specificity, tyrosine phosphorylation-regulated kinases (DYRKs) and cdc2-like kinases (CLKs) play a large variety of cellular functions and are involved in several diseases (cognitive disorders, diabetes, cancers, etc.). There is, thus, growing interest in pharmacological inhibitors as chemical probes and potential drug candidates. This study presents an unbiased evaluation of the kinase inhibitory activity of a library of 56 reported DYRK/CLK inhibitors on the basis of comparative, side-by-side, catalytic activity assays on a panel of 12 recombinant human kinases, enzyme kinetics (residence time and K_d), in-cell inhibition of Thr-212-Tau phosphorylation, and cytotoxicity. The 26 most active inhibitors were modeled in the crystal structure of DYRK1A. The results show a rather large diversity of potencies and selectivities among the reported inhibitors and emphasize the difficulties to avoid "off-targets" in this area of the kinome. The use of a panel of DYRKs/CLKs inhibitors is suggested to analyze the functions of these kinases in cellular processes.

Phase I Study of Niraparib in Combination with Radium-223 for the Treatment of Metastatic Castrate-Resistant Prostate Cancer

PURPOSE

To identify the safety of niraparib, a PARP inhibitor, in combination with Radium-223 for the treatment of metastatic castrate-resistant prostate cancer (mCRPC) in men without known BRCA mutations.

PATIENTS AND METHODS

Men with progressive mCPRC following ≥1 line of androgen receptor (AR)-targeted therapy and bone metastases but no documented BRCA-1 or BRCA-2 alterations or bulky visceral disease were included. Niraparib dose was escalated in combination with standard dosing of Radium-223 using a time-to-event continual reassessment method. The highest dose level with a DLT probability <20% was defined as MTD. Secondary endpoints included PSA change and progression-free survival. Exploratory analyses included assessing DNA mutations found in ctDNA as well as gene expression changes assessed in whole blood samples.

RESULTS

Thirty patients were treated with niraparib and radium-223: 13 patients received 100 mg, 12 received 200 mg, and 5 patients received 300 mg of niraparib. There were six DLT events: two (13%) for neutropenia, two (13%) for thrombocytopenia, whereas fatigue and nausea each occurred once (3%). Anemia (2/13%) and neutropenia (2/13%) were the most common grade 3 adverse events. For patients with prior chemotherapy exposure, the MTD was 100 mg, whereas the MTD for chemotherapy naïve patients was 200 mg. Whole blood gene expression of PAX5 and CD19 was higher in responders and ARG-1, IL2R, and FLT3 expression was higher in nonresponders.

CONCLUSIONS

Combining niraparib with Radium-223 in patients with mCRPC was safe; however, further studies incorporating biomarkers will better elucidate the role of combinations of PARP inhibitors with DNA damaging and other agents.

Ultrasound-assisted bromination of indazoles at the C3 position with dibromohydantoin

Bromoaryl compounds have attracted great attention in organic chemistry, especially for the synthesis of pharmaceutical intermediates. Herein, we demonstrated a novel and efficient bromination protocol of indazoles via C-H bond cleavage to give site-specific 3-bromide products that could be further employed as synthetic blocks to prepare drugs. The reaction used DBDMH as a bromine source, tolerated a wide range of indazoles, and finished in 30 min under mild, ultrasound-assisted conditions. Besides, preliminary mechanistic studies revealed that this approach was not a radical process.

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.

Pharmacokinetics and Pharmacodynamics of PARP Inhibitors in Oncology

Olaparib, niraparib, rucaparib, and talazoparib are poly (ADP-ribose) polymerase (PARP) inhibitors approved for the treatment of ovarian, breast, pancreatic, and/or prostate cancer. Poly (ADP-ribose) polymerase inhibitors are potent inhibitors of the PARP enzymes with comparable half-maximal inhibitory concentrations in the nanomolar range. Olaparib and rucaparib are orally dosed twice a day, extensively metabolized by cytochrome P450 enzymes, and inhibitors of several enzymes and drug transporters with a high risk for drug-drug interactions. Niraparib and talazoparib are orally dosed once a day with a lower risk for niraparib and a minimal risk for talazoparib to cause drug-drug interactions. All four PARP inhibitors show moderate-to-high interindividual variability in plasma exposure. Higher exposure is associated with an increase in toxicity, mostly hematological toxicity. For talazoparib, exposure-efficacy relationships have been described, but for olaparib, niraparib, and rucaparib this relationship remains inconclusive. Further studies are required to investigate exposure-response relationships to improve dosing of PARP inhibitors, in which therapeutic drug monitoring could play an important role. In this review, we give an overview of the pharmacokinetic properties of the four PARP inhibitors, including considerations for patients with renal dysfunction or hepatic impairment, the effect of food, and drug-drug interactions. Furthermore, we focus on the pharmacodynamics and summarize the available exposure-efficacy and exposure-toxicity relationships.

Visible light-promoted transition metal-free direct C3-carbamoylation of 2H-Indazoles

We reported a general transition metal-free transformation to access C3-carbamoylated 2H-indazoles via visible light-induced oxidative decarboxylation coupling, in the presence of oxamic acids as the coupling sources, 4CzIPN as the photocatalyst, and Cs2CO3 as the base. The great application potential of this mild condition is highlighted by the late-stage modification of drugs, N-terminal modification of peptides, and the good antitumor activity of the novel desired product.

A real-world pharmacovigilance study of FDA adverse event reporting system (FAERS) events for niraparib

Niraparib was approved for the treatment of platinum-sensitive recurrent epithelial ovarian cancer, fallopian tube and primary peritoneal cancer. The authors retrospectively investigated niraparib-related adverse events (AEs) through data mining of the US Food and Drug Administration Adverse Event Reporting System (FAERS). Four algorithms were employed to quantify the signals of niraparib associated AEs, using data from the FAERS between 2017 and 2021. MYSQL 8.0, Navicat Premium 15, Microsoft EXCEL 2019 and the GraphPad Prism 8 were used to conduct statistical analysis. There are 7,238,157 reports collected from the FAERS database, of which 11,701 reports listed niraparib as the 'primary suspected (PS)' drug. A total of 97 significant disproportionality PTs conforming to the four algorithms were simultaneously retained. Unexpected significant AEs such as neuropathy peripheral, photosensitivity reaction, gastrooesophageal reflux disease might also occur. The median onset time of niraparib-associated AEs was 18 days (interquartile range [IQR] 4-66 days), and most of the cases occurred within the first months after niraparib initiation. The study found niraparib-associated AEs and might provide important support for clinical monitoring and risk identification of niraparib.

Emerging Role of PARP Inhibitors in Metastatic Prostate Cancer

PURPOSE OF REVIEW

We highlight the clinical development of Poly (ADP-Ribose) polymerase (PARP) inhibitors in prostate cancer.

RECENT FINDINGS

Approximately 10 to 30% of metastatic prostate cancer patients carry germline or somatic mutations in DNA repair pathways. BRCA2 is the most commonly mutated gene in DNA damage repair pathways. Because of its critical function in homologous recombination repair (HRR) machinery, deleterious BRCA2 mutation enables synthetic lethality to a PARP inhibitor. Olaparib demonstrated clinical benefit in patients with deleterious mutations in HRR-related genes and most clearly in patients with BRCA2 mutations. Olaparib received the US FDA approval or mCRPC patients with a qualifying HRR gene mutation in May 2020. Rucaparib received an accelerated FDA approval for patients with BRCA1- or BRCA2-mutated mCRPC based on 43% objective response rate in a phase II study. To expand the application of a PARP inhibitor, several trials have evaluated various combination strategies with an androgen receptor signaling inhibitor, immunotherapy, radium-223, and others. While no PARP inhibitor combination regimen has been approved, promising data from a PARP inhibitor and an ASI combination have been reported. PARP inhibitor represents a standard treatment for patient with mCRPC with germline or somatic mutations in BRCA2 and other HRR pathway genes.

Small-molecule inhibitors, immune checkpoint inhibitors, and more: FDA-approved novel therapeutic drugs for solid tumors from 1991 to 2021

The United States Food and Drug Administration (US FDA) has always been a forerunner in drug evaluation and supervision. Over the past 31 years, 1050 drugs (excluding vaccines, cell-based therapies, and gene therapy products) have been approved as new molecular entities (NMEs) or biologics license applications (BLAs). A total of 228 of these 1050 drugs were identified as cancer therapeutics or cancer-related drugs, and 120 of them were classified as therapeutic drugs for solid tumors according to their initial indications. These drugs have evolved from small molecules with broad-spectrum antitumor properties in the early stage to monoclonal antibodies (mAbs) and antibody‒drug conjugates (ADCs) with a more precise targeting effect during the most recent decade. These drugs have extended indications for other malignancies, constituting a cancer treatment system for monotherapy or combined therapy. However, the available targets are still mainly limited to receptor tyrosine kinases (RTKs), restricting the development of antitumor drugs. In this review, these 120 drugs are summarized and classified according to the initial indications, characteristics, or functions. Additionally, RTK-targeted therapies and immune checkpoint-based immunotherapies are also discussed. Our analysis of existing challenges and potential opportunities in drug development may advance solid tumor treatment in the future.

PARP inhibition is a modulator of anti-tumor immune response in BRCA-deficient tumors

PARP inhibitors are synthetically lethal with BRCA1/2 mutations, and in this setting, accumulation of DNA damage leads to cell death. Because increased DNA damage and subsequent immune activation can prime an anti-tumor immune response, we studied the impact of olaparib ± immune checkpoint blockade (ICB) on anti-tumor activity and the immune microenvironment. Concurrent combination of olaparib, at clinically relevant exposures, with ICB gave durable and deeper anti-tumor activity in the Brca1m BR5 model vs. monotherapies. Olaparib and combination treatment modulated the immune microenvironment, including increases in CD8+ T cells and NK cells, and upregulation of immune pathways, including type I IFN and STING signaling. Olaparib also induced a dose-dependent upregulation of immune pathways, including JAK/STAT, STING and type I IFN, in the tumor cell compartment of a BRCA1m (HBCx-10) but not a BRCA WT (HBCx-9) breast PDX model. In vitro, olaparib induced BRCAm tumor cell–specific dendritic cell transactivation. Relevance to human disease was assessed using patient samples from the MEDIOLA (NCT02734004) trial, which showed increased type I IFN, STING, and JAK/STAT pathway expression following olaparib treatment, in line with preclinical findings. These data together provide evidence for a mechanism and schedule underpinning potential benefit of ICB combination with olaparib.

Advances and applications of chiral resolution in pharmaceutical field

The attention to chiral drugs has been raised to an unprecedented level as drug discovery and development strategies grow rapidly. However, separation of enantiomers is still a huge task, which leads to an increasing significance to equip a wider range of expertise in chiral separation science to meet the current and future challenges. In the last few decades, remarkable progress of chiral resolution has been achieved. This review summarizes and classifies chiral resolution methods in analytical scale and preparative scale systematically and comprehensively, including crystallization-based method, inclusion complexation, chromatographic separation, capillary electrophoresis, kinetic resolution, liquid-liquid extraction, membrane-based separation, and especially one bold new progress based on chiral-induced spin selectivity theory. The advances and recent applications will be presented in detail, in which the contents may bring more thinking to wide-ranging readers in various professional fields, from analytical chemistry, pharmaceutical chemistry, natural medicinal chemistry, to manufacturing of drug production.