Inhibitor Rucaparib Research Articles

Reversion mutations in BRCA1 or BRCA2 genes: Resistant mechanism(s) in patients treated with platinum-based agents or poly (ADP-ribose) polymerase(PARP) inhibitors.

3132 Background: Reversion mutations (RM) in homologous recombination pathway genes including BRCA1/2 have been identified in patients with ovarian, breast, and prostate cancers whose tumors have become refractory to platinum chemotherapy or PARP inhibition. Utilizing a multi-institutional molecular database, we report the prevalence of BRCA1/2 RM in a large cohort across various tumor types. Methods: Primary and/or metastatic tumor samples underwent DNA (underwent NextSeq, 592 genes; NovaSeq, whole-exome) and RNA (NovaSeq, whole transcriptome) sequencing (Caris Life Sciences, Phoenix, AZ). RM were identified by a board-certified molecular geneticist and called only if the patient had been treated with a PARPi or a platinum agent. Baseline clinical and outcomes data were obtained through linked insurance claims data. Results: Among 118,000 solid tumors profiled, RM were observed in 54 tumors samples. RMs were seen most commonly in ovarian cancer (OC), 1.5% (23/1500) of tumors with BRCA1/2 pathogenic mutations (mut), followed by breast cancer (BC) (2.4%, 17/700), endometrial cancer (1.0%, 4/400), pancreatic cancer (1.0%, 2/210), cholangiocarcinoma (2.5%, 2/80), prostate cancer (1.3%, 3/230), cervical cancer (1.4%, 1/70), cancer of unknown primary (1.0%, 1/100), and a neuroendocrine tumor of prostate (1 RM of 9 BRCA mut). Among all RM, we detected 17 in BRCA1 and 6 in BRCA2 in OC. In BC, we identified 7 RM in BRCA1 and 10 in BRCA2. Frameshift mut that restored the reading frame in BRCA1/2 were the most common type of RM. Molecular profiles of 14 high-grade serous ovarian cancers (HGSOC) with RM were compared to 87 control HGSOC with pathogenic BRCA1/2 mut without RM. Tumors with RM had lower ER expression (25% vs. 64%, p = 0.024) and higher KDM6A mut rate (15% vs. 0, p = 0.016). Additionally, TP53 mut rates were similar in RM and control (100% vs. 95%), seen in HGSOC. In patients with RM, 7 of the 14 (50%) TP53 mut were gain-of-function (GOF) while only 19 of 84 (23%) TP53 mut in the control group were GOF (p = 0.048). More detailed clinical data were available for 29 patients with RM (17 BRCA1 & 12 BRCA2). Among these patients, 7 had received prior platinum-based chemotherapy (carboplatin or cisplatin), 7 patients were treated with PARP inhibitors (olaparib or rucaparib), or both (n = 7). Notably, 5 patients had been treated with carboplatin (n = 2, ovarian), olaparib (n = 1, breast), or both agents (n = 2, ovarian and prostate) after the detection of RM. Conclusions: This dataset is one of the largest reporting on the prevalence of BRCA1/2 RM across various tumor types. We demonstrate that the rate of RM was low among BRCA1/2 mutated tumors; this may be because some patients may not have repeat profiling post-treatment. Repeating tumor profiling at times of treatment resistance can help inform therapy selection in the refractory disease setting.

The effect of PARP inhibition on androgen receptor localization and activity in castration resistant prostate cancer.

e17037 Background: The poly(ADP-ribose) polymerase inhibitors (PARPi) olaparib and rucaparib have been approved for the treatment of metastatic castration resistant prostate cancer (mCRPC) in the setting of homologous recombination deficiency (HRD). Additionally, PARPi have been shown to modulate androgen receptor (AR) signaling, with a recent report demonstrating mono-ADP-ribosylation of cysteine residues in AR by Parp7. Here, we further evaluated the effect of PARPi on AR activity and localization. Methods: The effect of PARPi on cell growth and survival of CRPC cell lines was evaluated in vitro and in vivo. AR ribosylation was assessed in CRPC cell lines by immunoprecipitation (IP) assays and proximity ligation assays (PLA). The subcellular localization of AR was determined by quantitative immunofluorescence microscopy in CRPC cell lines and xenograft models. Changes in AR activity with PARPi treatment were evaluated by a luciferase reporter assay and AR target gene expression in a PDX model. Finally, PARPi mediated alteration in the AR protein interactome was evaluated by liquid chromatography tandem mass spectrometry (LC-MS/MS) proteomics. Results: The PARPi olaparib and talazoparib, and to a lesser extent veliparib, inhibited CRPC cell growth. Evidence of AR ribosylation was seen by IP and PLA. PARPi treatment of multiple in vitro and in vivo prostate cancer models resulted in a shift of AR subcellular localization, from predominantly nuclear to cytoplasmic compartments. In luciferase reporter assays, AR transactivation activity was decreased after PARPi treatment in a dose dependent manner. In vivo, in prostate cancer xenograft models, decreased AR target gene expression was seen upon PARPi treatment. LC-MS/MS proteomic studies revealed that PARP inhibition resulted in significant changes in the composition of AR interaction partners, in particular of proteins related to intracellular trafficking and nuclear transport. This suggests a potential link between altered AR complex assembly and the observed changes in AR subcellular localization in the context of PARPi treatment. Conclusions: We describe a novel sequela of PARPi therapy to alter AR localization and activity in CRPC. Single agent PARP inhibition can alter prostate cancer cell growth in vitro and in vivo. With PARPi treatment, AR localization is shifted to the cytoplasm, the AR interactome is altered, and AR transcriptional activity decreased. These findings implicate a collateral mechanism of PARPi in preventing prostate cancer cell growth/survival that may augment previously described mechanisms related to HDR and synthetic lethality. It is essential to understand the role of PARPi beyond synthetic lethality in the context of HRD in order to better define the spectrum of response to PARPi across patients, and for development of biology-informed combination therapies.

Homogeneity of antibody-drug conjugates critically impacts the therapeutic efficacy in brain tumors.

SUMMARYGlioblastoma multiforme (GBM) is the most aggressive and fatal disease of all brain tumor types. Most therapies rarely provide clinically meaningful outcomes in the treatment of GBM. Although antibody-drug conjugates (ADCs) are promising anticancer drugs, no ADCs have been clinically successful for GBM, primarily because of poor blood-brain barrier (BBB) penetration. Here, we report that ADC homogeneity and payload loading rate are critical parameters contributing to this discrepancy. Although both homogeneous and heterogeneous conjugates exhibit comparable in vitro potency and pharmacokinetic profiles, the former shows enhanced payload delivery to brain tumors. Our homogeneous ADCs provide improved antitumor effects and survival benefits in orthotopic brain tumor models. We also demonstrate that overly drug-loaded species in heterogeneous conjugates are particularly poor at crossing the BBB, leading to deteriorated overall brain tumor targeting. Our findings indicate the importance of homogeneous conjugation with optimal payload loading in generating effective ADCs for intractable brain tumors.

Impact of provider education on prostate cancer genetic counseling referrals.

59 Background: Guidelines recommend germline genetic not only for men with advanced and metastatic prostate cancer but also those with NCCN-high risk disease. Many men harboring germline DNA repair defects would not have met criteria for testing under previous guidelines (Nicolosi et al, JAMA Oncol 2019). Knowledge of germline mutations is pertinent due to recent regulatory approval of PARP inhibitors olaparib and rucaparib and guides screening for first-degree relatives who are at increased risk for other cancers (Pritchard et al, NEJM 2016). Knowledge gaps for germline genetic testing have been previously described (Loeb et al, Cancer Treat Res Commun 2020). Through a series of educational sessions, we sought to increase utilization of appropriate genetic services for men with prostate cancer. Methods: Starting March 2021, virtual educational presentations were held for nurse navigators, urologists, and medical oncologists throughout our large community-based healthcare system. Surveys were distributed following each presentation to measure clinicians’ perception of their knowledge regarding prostate cancer genetics referrals on a five-step scale. Prostate cancer patient referral data was measured from September 2020 to August 2021, six months prior to and after the presentations. Results: Self-reported understanding of prostate cancer genetics referral practices following the educational presentations increased by an average of 1.7/5 steps (2.5 to 4.2/5) for physicians and 1.4/5 steps (2.9 to 4.1/5) for nurse navigators. From March to August 2021, there were 107 genetic referrals for prostate cancer (average 17.8 referrals/month) compared to 49 referrals from September 2020 to February 2021 (8.2 referrals/month). Conclusions: Prostate cancer genetics referrals increased 118% following educational presentations to urologists, medical oncologists, and nurse navigators. This correlates with an improvement in self-reported knowledge gaps. Provider education interventions may improve access to genetic services for men with prostate cancer. The increase in referrals likely does not account for all patients meeting criteria for germline testing. Work is ongoing to calculate the number of referrals as a proportion of the eligible population.[Table: see text]

A phase Ib, open-label study evaluating the safety and efficacy of ipatasertib + rucaparib in patients with metastatic castration-resistant prostate cancer (mCRPC).

95 Background: mCRPC remains an incurable disease with unmet need for improved therapies. PARP inhibition has demonstrated antitumor activity, and preclinical studies suggest synergy between PARP and AKT inhibition. This phase Ib trial (NCT03840200) sought to determine the maximum tolerated dose of PARP inhibitor rucaparib (ruca) with AKT inhibitor ipatasertib (ipat) and explore early safety and efficacy in patients (pts) with mCRPC. Methods: The study had 2 parts: a part 1 dose-escalation phase (cohort [C]1: ipat 300 mg QD + ruca 400 mg BID; C2a: ipat 300 mg QD + ruca 600 mg BID; C2b ipat 400 mg QD + ruca 400 mg BID; C3: ipat 400 mg QD + ruca 600 mg BID) in unselected pts with mCRPC or advanced breast or ovarian cancer, and a Part 2 dose-expansion phase in pts with mCRPC whose previous androgen deprivation therapy failed. The primary safety endpoints were AEs and dose-limiting toxicities, with the goal of identifying a recommended phase II dose (RP2D). The primary efficacy endpoint was prostate-specific antigen (PSA) response (PSA reduction of ≥ 50%) in pts with mCRPC. Secondary efficacy endpoints included ORR per RECIST 1.1, radiographic PFS (rPFS) per Prostate Cancer Working Group 3 and OS in pts with mCRPC. We assessed homologous recombination deficiency (HRD), PIK3CA/ AKT1/ PTEN status and other alterations by next-generation sequencing. Results: Part 1 enrolled 21 pts: 17 with mCRPC, 3 with ovarian cancer and 1 with breast cancer (C1 [n=8], C2a [n=6] and C2b [n=7], C3 [not opened]). Ipat 400 mg QD + ruca 400 mg BID was the selected RP2D. 30 pts enrolled in Part 2, so 37 pts with mCRPC (C2b + Part 2) received the RP2D (median follow-up 93 days). All grade AEs occurred in 37 pts (100%), serious AEs in 8 pts (22%) and AEs leading to treatment modification in 26 pts (70%). The most frequent AEs (all grade and grade 3, respectively) were diarrhea (35 [95%] and 2 [5%]); asthenia (24 [65%] and 4 [11%]); and nausea (24 [65%] and 2 [5%]). There was 1 grade 4 AE (anemia) and no grade 5 AEs. See the table for efficacy data. In biomarker subgroups, the PSA response rate was 50% (3/6) in pts with HRD tumors vs 25% (4/16) in pts with HR-proficient tumors, and 14% (1/7) vs 40% (6/15) in pts with PIK3CA/ AKT1/ PTEN–altered or intact tumors, respectively. Conclusions: The combination of ipat and ruca was well tolerated but did not show clinically relevant antitumor activity in pts with mCRPC, including in predefined biomarker subpopulations. Clinical trial information: NCT03840200. [Table: see text]

A randomized, double blind, biomarker selected, phase II clinical trial of maintenance PARP inhibition following chemotherapy for metastatic urothelial carcinoma (mUC): Final analysis of the ATLANTIS rucaparib arm.

436 Background: A subset of mUC exhibits a DNA repair deficiency (DRD) phenotype predicting benefit from platinum based chemotherapy (PBC). We hypothesised that switch maintenance therapy with the PARP inhibitor rucaparib, in patients who have derived clinical benefit from PBC, would improve outcomes for patients with mUC harbouring a DRD biomarker. Methods: ATLANTIS is an adaptive, multi-comparison, phase II trial platform. It tests multiple biomarker selected maintenance therapies for mUC after 4 to 8 PBC cycles without disease progression. Biomarker allocation to the rucaparib comparison was based on ≥10% genomic loss of heterozygosity (%LOH) and/or somatic alteration in defined DRD associated genes ( ATM, BARD1, BRCA1, BRCA2, BRIP1, CDK12, CHEK2, FANCA, NBN, PALB2, RAD51, RAD51B, RAD51C, RAD51D, RAD54L) and/or germline BRCA1 or BRCA2 alteration. Biomarker positive patients were randomised (1:1) to maintenance rucaparib 600 mg BID PO, or matched placebo, within 10 weeks of completing PBC, until disease progression. The primary endpoint was progression free survival (PFS). Statistical analysis (data cut 17/Nov/2021) was pre-planned to target a hazard ratio of 0.5. We selected a 20% 1-sided alpha for this signal seeking phase II trial with 85.4% power (requiring 30 PFS events in 40 patients). PFS (RECIST 1.1) was compared between trial arms, by intention to treat, within a Cox model incorporating baseline minimisation factors. Adverse events (AE) were assessed by CTCAE v4.03. Results: 74 of 279 (26.5%) screened patients were biomarker positive. 40 were randomised within the rucaparib comparison (Dec 2017-Dec 2020). Biomarker positive status was by high %LOH in 22 (55%), DRD gene alteration in 11 (27.5%) and both in 7 (17.5%). Patient characteristics (median age 70.5; 82.5% male; 87.5% bladder primary; 52.5% ECOG PS 0; 62.5% prior cisplatin; 45% visceral metastases) were balanced by treatment arm. 12 (60%) and 20 (100%) PFS events have occurred in the rucaparib and placebo arms respectively (median duration follow up 94.6 weeks in those still alive). Median PFS was 35.3 weeks (80% confidence interval (CI) 11.7-35.6) with rucaparib and 15.1 weeks (80% CI 11.9-22.6) with placebo (hazard ratio 0.53, 80% CI 0.30-0.92, 1 sided p = 0.07). In the safety population (n = 39) treatment related adverse events were mostly low grade. Rucaparib was tolerable with a median duration of 10 rucaparib or 6 placebo cycles on treatment. The most frequent treatment related AEs (all grades) of fatigue (63.2% vs 30.0%, p = 0.03), nausea (36.9% vs 5.0%, p = 0.03) and rash (21.1% vs 0%, p = 0.04) were more common with rucaparib respectively. Conclusions: Maintenance rucaparib, following PBC, extended PFS in DRD biomarker selected patients with mUC and is tolerable. Further investigation of PARP inhibition for mUC is warranted. Clinical trial information: 25859465.

Guidelines for Management of Treatment-Emergent Adverse Events During Rucaparib Treatment of Patients with Metastatic Castration-Resistant Prostate Cancer.

PurposeThe US Food and Drug Administration has recently granted accelerated approval of the poly(ADP-ribose) polymerase (PARP) inhibitor rucaparib as treatment for men with metastatic castration-resistant prostate cancer (mCRPC) associated with a deleterious germline or somatic BRCA1 or BRCA2 (BRCA) alteration. As the safety profile of this new addition to the mCRPC treatment landscape may be unfamiliar to clinicians and patients, we summarize the data from the literature and provide practical guidelines for the management of treatment-emergent adverse events (TEAEs) that may occur during rucaparib treatment.Materials and MethodsSafety data were identified from PubMed and congress publications of trials involving men with mCRPC treated with oral rucaparib monotherapy (600 mg twice daily). Management guidelines for TEAEs were developed based on trial protocols, prescribing information, oncology association guidance, and the authors’ clinical experience.ResultsIn clinical trials of men with mCRPC who received rucaparib (n = 193), TEAEs observed were consistent with that of other PARP inhibitors. The most frequent any-grade TEAEs included gastrointestinal events, asthenia/fatigue, anemia, increased alanine/aspartate aminotransferase, rash, and thrombocytopenia; the most frequent grade ≥3 TEAE was anemia. The majority of TEAEs were self-limiting and did not require treatment modification or interruption. Here, we provide recommendations on management of the most common TEAEs reported with rucaparib as well as other TEAEs of interest.ConclusionRucaparib’s recent approval for treatment of BRCA-mutant mCRPC is practice changing. Proper management of TEAEs will allow maximum treatment benefit for patients receiving rucaparib.

Identification of Differential Polypharmacology Between the PARP Inhibitor Rucaparib and Its Major Metabolite

Identification of Differential Polypharmacology Between the PARP Inhibitor Rucaparib and Its Major Metabolite

Response to Rucaparib in BRCA-Mutant Metastatic Castration-Resistant Prostate Cancer Identified by Genomic Testing in the TRITON2 Study.

The PARP inhibitor rucaparib is approved in the United States for patients with metastatic castration-resistant prostate cancer (mCRPC) and a deleterious germline and/or somatic BRCA1 or BRCA2 (BRCA) alteration. While sequencing of tumor tissue is considered the standard for identifying patients with BRCA alterations (BRCA+), plasma profiling may provide a minimally invasive option to select patients for rucaparib treatment. Here, we report clinical efficacy in patients with BRCA+ mCRPC identified through central plasma, central tissue, or local genomic testing and enrolled in TRITON2. Patients had progressed after next-generation androgen receptor-directed and taxane-based therapies for mCRPC and had BRCA alterations identified by central sequencing of plasma and/or tissue samples or local genomic testing. Concordance of plasma/tissue BRCA status and objective response rate and prostate-specific antigen (PSA) response rates were summarized. TRITON2 enrolled 115 patients with BRCA+ identified by central plasma (n = 34), central tissue (n = 37), or local (n = 44) testing. Plasma/tissue concordance was determined in 38 patients with paired samples and was 47% in 19 patients with a somatic BRCA alteration. No statistically significant differences were observed between objective and PSA response rates to rucaparib across the 3 assay groups. Patients unable to provide tissue samples and tested solely by plasma assay responded at rates no different from patients identified as BRCA+ by tissue testing. Plasma, tissue, and local testing of mCRPC patients can be used to identify men with BRCA+ mCRPC who can benefit from treatment with the PARP inhibitor rucaparib.

Abstract P081: In vitro activity and efficacy of novel dual PARP-HDAC inhibitors

Abstract Introduction: Inhibition of poly adenosine diphosphate-ribose polymerase (PARP) is an effective treatment strategy against tumors with homologous recombination (HR) DNA repair deficiencies. Combination treatments utilizing PARP inhibitors (PARPi) in concert with inhibitors of key DNA repair or PARPi-resistance pathways, may expand the utility of PARPi beyond cancers harboring germ-line HR deficiencies. Acetylation and deacetylation of histones is an important regulatory event in the DNA damage response. Combining histone deacetylation inhibitors (HDACi) and PARPi have sensitized PARPi-resistant cells to treatment; however, combination regimens often require sequential administration to manage overlapping toxicities and accommodate diverse pharmacokinetics, constituting a significant limitation of these strategies in a clinical setting. Here, we test the activity of kt-3000 series, a novel bi-functional class of small molecules with dual PARP and HDAC inhibitor activity in HR-proficient cancer cells where PARPi have historically lacked single-agent activity. Methods: PARP enzyme activity was measured using the Trevigen Universal Colorimetric PARP Assay Kit. HDAC activity was measured using nuclear extracts of treated cells and the HDAC Fluorometric Activity Assay Kit from Cayman Chemical, as per the manufacturer’s protocol. PARP activity was measured by fluorescence in C41 cells following compound treatment for 2 hours and PARP-activation with 1M H2O2 by staining cells with an anti-PARP Ab followed by a FITC-coupled secondary antibodies. Cell survival EC50 values were obtained by treating cells with a range of inhibitor concentrations, then quantifying cell confluency after 72-hours of treatment based on images taken with an Incucyte S3 system. Results: kt-3000 series compounds are potent inhibitors of PARP and HDAC with IC50 values for PARP enzyme activity in the low nM range, comparable to those of FDA-approved PARP inhibitors (olaparib, rucaparib, niraparib, and talazoparib) and IC50 values for the inhibition of HDAC activity comparable to FDA-approved HDAC inhibitors (panabinostat, belinostat, and vorinostat). Fluorescent assays of PARP activity in C41 cells also resulted in IC50 values in the nM range and cell survival EC50 values of the dual inhibitors are comparable to FDA-approved PARP inhibitors alone and in similar range with FDA-approved HDAC inhibitors alone. Conclusion: Our novel dual PARP-HDAC inhibitors show potent inhibition of PARP activity in vitro comparable to FDA-approved PARP inhibitors and also show potent inhibition of HDAC activity. The potency and activity of kt-3000 series compounds exhibit potential superiority to FDA-approved PARP inhibitors and HDAC inhibitors, in formulation as a single molecule. Development of these multi-target inhibitors will target unmet medical needs in the treatment of HR-proficient cancer types with dysregulation of histone deacetylation. Citation Format: Sarah Truong, Fariba Ghaidi, Louise Ramos, Jay Joshi, Dennis Brown, Neil Sankar, John Langlands, Jeffrey Bacha, Wang Shen, Mads Daugaard. In vitro activity and efficacy of novel dual PARP-HDAC inhibitors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P081.

Abstract P018: Integrative proteomics of PARP1 protein complexes and post-translational modifications implicates DDR and AKT-mTOR signaling in mediating response or primary resistance of ovarian carcinoma cells to PARP1 inhibitors

Abstract Background: About 40-50% of epithelial ovarian cancers (EOC) show defects in DNA repair by homologous recombination (HR), which are mostly associated with BRCA1/2 loss-of-function mutations. The PARP inhibitors (PARPis) olaparib, niraparib and rucaparib were recently approved for treatment of ovarian cancer patients with platinum sensitivity and recurrent ovarian cancer who carry inactivating BRCA1/2 mutations. These targeted drugs produce significant response rates ranging from 40-60% in patients with BRCA-linked advanced EOCs, but resistance is a continuing challenge. Whereas several studies have reported various mechanisms of acquired resistance to PARPis, the mechanisms of primary resistance are still poorly understood. Our goal is to develop predictors of PARPi response and to identify new targets for combination therapy to overcome primary resistance. We apply a novel integrated proteomics approach to develop mechanism-based biomarkers of response or primary resistance and to identify new therapeutic targets for rational combination approaches that can overcome resistance to single agent PARPi therapy. METHODS: The isogenic EOC cell line pair UWB1.289 with BRCA1 deletion (parental; UWB) and reconstituted with ectopic BRCA1 (UWB+B) was used. The effects of FDA approved PARPis on BRCA1-null and BRCA1-reconstituted UWB1.289 cells regarding short- and long-term cell viability were determined by CellTiterGlo and crystal violet assays. Chemical proteomics, global phosphoproteomics and ADP-ribosylation proteomics were used to identify the components of PARP1-based multiprotein complexes as well as protein post-translational modifications in the DNA damage signaling network in BRCA1/2-linked EOC cells. Specific PARP1-engaged protein complexes were further determined by immunoblotting. Frozen BRCA1-proficient and deficient ovarian cancer patient tumor samples collected at the time of debulking were also characterized by chemical proteomics. RESULTS: Cell viability assays confirmed the expected correlation between PARPi response and BRCA1/2 status. Chemical proteomics followed by validation with co-immunoprecipitation revealed differential composition of the PARP1/2-Ku70/Ku80 protein complexes in PARPi-sensitive UWB compared to UWB+B cells. Global phosphoproteomics and ADP-ribosylation proteomics further indicated that rucaparib induced the cell cycle and c-NHEJ pathways in UWB cells, but down-regulated the MAPK pathway in UWB+B cells. In addition, our results showed that inhibition of AKT PARylation and AKT-mTOR signaling may help to preserve cell viability in UWB+B cells after rucaparib treatment. Consistently, synergy with DNAPKi and AKTi was more pronounced in UWB+B cells. CONCLUSION: Ovarian cancers that do not respond to PARPi displayed significant changes in PARPi-engaged protein complexes as well as post-translational protein modifications. The combination of chemical, phospho- and ADP-ribosylation proteomics can generate a systems view of PARP1 complexes and diverse drug compensatory signaling in EOC. Citation Format: Ou Deng, Sweta Dash, Thales Nepomuceno, Bin Fang, Douglas Marchion, John Koomen, Alvaro N. Monteiro, Uwe Rix. Integrative proteomics of PARP1 protein complexes and post-translational modifications implicates DDR and AKT-mTOR signaling in mediating response or primary resistance of ovarian carcinoma cells to PARP1 inhibitors [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P018.

Pharmacological Poly (ADP-Ribose) Polymerase Inhibitors Decrease Mycobacterium tuberculosis Survival in Human Macrophages.

Diabetes mellites (DM) is correlated with increased susceptibility to and disease progression of tuberculosis (TB), and strongly impairs effective global TB control measures. To better control the TB-DM co-epidemic, unravelling the bidirectional interactivity between DM-associated molecular processes and immune responses to Mycobacterium tuberculosis (Mtb) is urgently required. Since poly (ADP-ribose) polymerase (PARP) activation has been associated with DM and with Mtb infection in mouse models, we have investigated whether PARP inhibition by pharmacological compounds can interfere with host protection against Mtb in human macrophage subsets, the predominant target cell of Mtb. Pharmacological inhibition of PARP decreased intracellular Mtb and MDR-Mtb levels in human macrophages, identifying PARP as a potential target for host-directed therapy against Mtb. PARP inhibition was associated with modified chemokine secretion and upregulation of cell surface activation markers by human macrophages. Targeting LDH, a secondary target of the PARP inhibitor rucaparib, resulted in decreased intracellular Mtb, suggesting a metabolic role in rucaparib-induced control of Mtb. We conclude that pharmacological inhibition of PARP is a potential novel strategy in developing innovative host-directed therapies against intracellular bacterial infections.

Quantitative Analysis of the Efficacy of PARP Inhibitors as Maintenance Therapy in Recurrent Ovarian Cancer.

Objective: This study aimed to establish a pharmacodynamic model and to screen reasonable covariates to quantitatively describe the efficacy of poly (ADP-ribose) polymerase inhibitors (PARPis) as maintenance treatment for recurrent ovarian cancer (ROC). Methods: The log normal hazard function model was established by using progression-free survival (PFS) data of 1,169 patients from published randomized trials on FDA-approved PARP inhibitors (olaparib, niraparib, and rucaparib). Monte Carlo simulation was used to compare PFS values in different scenarios, such as monotherapy (administered alone) and combination therapy (PARPis combined with chemo- or target-therapies), different biomarker statuses, and different PARP inhibitors. PFS was also estimated. Results: The study showed that the median PFS was 8.5 months with monotherapy and 16.0 months with combination therapy. The median PFS of patients with the BRCA mutation, BRCA wild-type, and HRD-positivity were 11.0, 7.5, and 9.0 months in monotherapy, respectively, and 23.0, 14.0 and 17.5 months, in combination therapy, respectively. In addition, the median PFS of olaparib, niraparib, and rucaparib monotherapy were about 9.5, 10.5, and 12.0 months, respectively, and about 19.0, 20.0, and 25 months, respectively, in combination therapy. The median PFS values in combination with cediranib, bevacizumab, and chemotherapy were approximately 17.0, 12.5 and 19.5 months, respectively. Conclusion: PARPi combination therapy is more effective as maintenance treatment for ROC than monotherapy, and the efficacy of PARPis in combination with chemotherapy is higher than that of the combination with antiangiogenic drugs. We found that the PFS of BRCA wild-type was similar to that of HRD-positive patients, and there was no significant difference in PFS between olaparib, niraparib, and rucaparib, which provides necessary quantitative information for the clinical practice of PARPis in the treatment of ROC.

PARP Inhibition in Advanced Prostate Cancer.

In May 2020, the poly(ADP-ribose) polymerase (PARP) inhibitors rucaparib and olaparib were Food and Drug Administration approved for the management of metastatic castration-resistant prostate cancers. Rucaparib was approved for tumors that harbor alterations in BRCA1 and BRCA2 following progression on chemotherapy and androgen receptor-directed therapy, whereas olaparib was approved for tumors that harbor alterations in a broader range of DNA damage repair genes following progression on androgen receptor-directed therapy. Loss-of-function mutations in genes such as BRCA1 and BRCA2 increase reliance on PARP-mediated mechanisms of DNA repair, and inhibition of this pathway results in the accumulation of lethal levels of DNA damage. This dependence is advantageous in the management of prostate cancer, as mutations in DNA damage repair genes are frequent. This review summarizes the role of PARP in cell homeostasis, methods of targeting PARP in cancer cells, and current clinical trials in the management of advanced prostate cancer with PARP inhibitors.

Characterization of patients with long-term responses to rucaparib treatment in recurrent ovarian cancer

ObjectiveTo describe molecular and clinical characteristics of patients with high-grade recurrent ovarian carcinoma (HGOC) who had long-term responses to the poly(ADP-ribose) polymerase (PARP) inhibitor rucaparib. MethodsThis post hoc analysis pooled patients from Study 10 (NCT01482715; Parts 2A and 2B; n = 54) and ARIEL2 (NCT01891344; Parts 1 and 2; n = 491). Patients with investigator-assessed complete or partial response per RECIST were classified based on duration of response (DOR): long (≥1 year), intermediate (6 months to <1 year), or short (<6 months). Next-generation sequencing was used to detect deleterious mutations and loss of heterozygosity (LOH) in tumors. ResultsOverall, 25.3% (138/545) of enrolled patients were responders. Of these, 27.5% (38/138) had long-term responses; 28.3% (39/138) were intermediate- and 34.8% (48/138) were short-term responders. Most of the long-term responders harbored a BRCA1 or BRCA2 (BRCA) mutation (71.1%, 27/38), and BRCA structural variants were most frequent among long-term responders (14.8%; 4/27). Responders with HGOC harboring a BRCA structural variant (n = 5) had significantly longer DOR than patients with other mutation types (n = 81; median not reached vs 0.62 years; HR, 0.21; 95% CI, 0.10–0.43; unadjusted p = 0.014). Among responders with BRCA wild-type HGOC, most long- and intermediate-term responders had high genome-wide LOH: 81.8% (9/11) and 76.9% (10/13), respectively, including 7 with deleterious RAD51C, RAD51D, or CDK12 mutations. ConclusionAmong patients who responded to rucaparib, a substantial proportion achieved responses lasting ≥1 year. These analyses demonstrate the relationship between DOR to PARP inhibitor treatment and molecular characteristics in HGOC, such as presence of reversion-resistant BRCA structural variants.

ATHENA (GOG-3020/ENGOT-ov45): a randomized, phase III trial to evaluate rucaparib as monotherapy (ATHENA–MONO) and rucaparib in combination with nivolumab (ATHENA–COMBO) as maintenance treatment following frontline platinum-based chemotherapy in ovarian cancer

BackgroundThe optimal treatment strategy for women with newly diagnosed ovarian cancer has yet to be determined. Poly(ADP-ribose) polymerase (PARP) inhibitors have demonstrated substantial improvement in progression-free survival as monotherapy maintenance...

WITHDRAWN: CNX-1351 improves the anti-tumor efficacy of PARP inhibitor rucaparib phosphate in cervical cancer through inducing DNA injury and blunting homologous recombination

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Copper-Mediated Radiosynthesis of [18F]Rucaparib.

The poly(ADP-ribose) polymerase (PARP) inhibitor rucaparib is used in the clinic to treat BRCA-mutated cancers. Herein, we report two strategies to access the 18F-isotopologue of rucaparib by applying a copper-mediated nucleophilic 18F-fluorodeboronation. The most successful approach features an aldehydic boronic ester precursor that is subjected to reductive amination post-18F-labeling and affords [18F]rucaparib with an activity yield of 11% ± 3% (n = 3) and a molar activity (Am) up to 30 GBq/μmol. Preliminary in vitro studies are presented.

Abstract CT124: Evaluation of rucaparib in Japanese patients (pts) with a previously treated advanced solid tumor

Abstract Background: The PARP inhibitor rucaparib is approved in the US for pts with recurrent ovarian or metastatic castration-resistant prostate cancer. This phase 1 study (NCT03499444) evaluated safety, pharmacokinetics (PK), and antitumor activity (per RECIST v1.1) of rucaparib in Japanese pts. Methods: Pts were enrolled in a 3+3 dose-escalation phase to establish the recommended dose (RD) in Japanese pts; dose-limiting toxicities (DLTs) were assessed in the first 21 days. Pts must have had an advanced solid tumor that had progressed on standard treatment. A dose-expansion phase enrolled pts at the RD to further assess safety, PK, and efficacy. Results: The visit cutoff was Oct 20, 2020; 29 pts received rucaparib, including 15 in the dose-escalation phase (400 mg BID, n=3; 500 mg BID, n=6; and 600 mg BID, n=6) and 14 in the dose-expansion phase at the RD of 600 mg BID. Median (range) time on treatment was 5.1 (1.3-16.4) months overall and 5.3 (1.4-16.4) months for 600 mg BID pts (n=20).One DLT was reported (treatment interruption &amp;gt;7 days due to grade 1/2 nausea, vomiting, diarrhea, fatigue; 500 mg BID cohort). Across all doses, the most frequent any-grade treatment-emergent adverse events (TEAEs) were alanine aminotransferase/aspartate aminotransferase increased (82.8%), anemia (82.8%), and nausea (69.0%); the most frequent grade ≥3 TEAE was anemia (51.7%). Among 600 mg BID pts, 25.0% (5/20) had a TEAE leading to treatment interruption or dose reduction, most commonly due to anemia (20.0%; 4/20).Steady-state PK was evaluated for the 400, 500, and 600 mg BID cohorts (Table).Most pts with measurable disease had a best response of stable disease (63.0%; 17/27); the confirmed objective response rate was 18.5% (5/27) overall and 21.1% (4/19) among 600 mg BID pts (Table).Conclusions: Rucaparib 600 mg BID had a manageable safety profile for Japanese pts with advanced solid tumors, with a PK profile similar to that of Western pts. These results support further exploration of rucaparib in Japanese pts. 400 mg BID(n=3)500 mg BID(n=6)600 mg BID(n=20)Overall(N=29)Baseline characteristicsAge, median (range), years67.0 (45.0-68.0)61.5 (44.0-73.0)59.5 (43.0-74.0)61.0 (43.0-74.0)Female, n (%)3 (100)6 (100)16 (80.0)25 (86.2)ECOG PS 0, n (%)a3 (100)4 (66.7)15 (75.0)22 (75.9)Tumor type, n (%)Ovarian2 (66.7)1 (16.7)9 (45.0)12 (41.4)Primary peritoneal1 (33.3)2 (33.3)2 (10.0)5 (17.2)Pancreatic004 (20.0)4 (13.8)Breast02 (33.3)1 (5.0)3 (10.3)Other01 (16.7)4 (20.0)5 (17.2)Steady-state PK dataCmax, mean (CV%), ng/mL1,690 (38.7)3,650 (61.9)b2,800 (37.0)cNCtmax, median (range), h1.48 (1.47-2.45)3.95 (2.47-9.95)b2.50 (0.93-9.83)cNCCmin, mean (CV%), ng/mL1,590 (38.7)2,380 (78.5)2,130 (44.4)NCAUClast, mean (CV%), h × ng/mL14,400 (36.6)30,200 (64.7)b23,800 (39.9)cNCCL/F, mean (CV%), L/h26.1 (45.2)22.1 (68.5)d24.3 (34.6)eNCAUC0-12, mean (CV%), h × ng/mL17,200 (35.8)33,900 (78.9)d28,100 (40.8)eNCEfficacy dataORR, n/N (%) [95% CI]1/3 (33.3) [0.8-90.6]0/5 (0) [0.0-52.2]4/19 (21.1) [6.1-45.6]5/27 (18.5) [6.3-38.1]aAll other pts had ECOG PS 1.bn=5.cn=18.dn=3.en=13.AUC0-12, area under the concentration-time curve up to 12 h; AUClast, area under the concentration-time curve up to last time point (10 h) with a quantifiable concentration; CL/F, apparent total clearance of drug after oral administration; Cmax, maximum concentration; CV, coefficient of variation; ECOG PS, Eastern Cooperative Oncology Group performance status; NC, not calculated; ORR, objective response rate; PK, pharmacokinetics; tmax, time to maximum concentration. Citation Format: Kenji Tamura, Koji Matsumoto, Kan Yonemori, Kosei Hasegawa, Jenn Habeck, Eric Jones, Jim Xiao, Aaron Enke, Keiichi Fujiwara. Evaluation of rucaparib in Japanese patients (pts) with a previously treated advanced solid tumor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT124.

Abstract 2066: Modulation of homologous recombination repair pathway gene expression by a dual EZH2 and EHMT2 histone methyltransferase inhibitor and synergy with PARP inhibitors in ovarian cancer

Abstract Defective DNA damage response (DDR) is a hallmark of high grade serous ovarian cancer (HGSOC). Genetic and epigenomic aberrations in DDR pathways including homologous recombination (BRCA1/BRCA2) and non-homologous end joining (PARP-1) make some HGSOC vulnerable to cisplatin and Poly (ADP-ribose) polymerase inhibitors (PARPi). However, mechanisms behind primary and acquired resistance to these agents remain unknown. We hypothesise aberrant epigenomic changes at DDR-associated genes contribute to PARPi resistance and can be reversed using a novel histone methyltransferase inhibitor (HKMT-1-005) which targets two histone methyltransferases (EZH2 and EHMT2) frequently upregulated in HGSOC. MTS assays were used to calculate the IC50 values for HKMT-1-005 and the PARPi Rucaparib in a panel of human HGSOC cell lines (n=8). Isobologram analysis using Combenefit software was used to determine synergy. RNA-seq and ATAC-seq was performed on cell lines derived from the same patient before (PEO1) and after acquired resistance to chemotherapy (PEO4) pre/post treatment with HKMT-1-005. Pathway analysis was used to identify pathways enriched in genes with altered expression and/or chromatin conformation after treatment with HKMT-1-005 and validated with qRT-PCR. Synergy between HKMT-1-005 and Rucaparib and changes in chromatin conformation with HKMT-1-005 treatment were further examined in CRIPSR modified ID8 murine ovarian cell lines with the genotypes: WT, P53-/-, P53-/-BRCA1-/- and P53-/-BRCA2-/-. Isobologram analysis revealed HKMT-1-005 in combination with Rucaparib was synergistic in multiple cell lines. Synergy was greater in PEO1 compared to PEO4. RNA-seq and ATAC-seq identified a significant (FDR &amp;lt;0.05) enrichment of genes associated with DDR pathways which had altered expression and/or chromatin accessibility in PEO1 compared to PEO4, including BRCA1 and BRCA2. qRT-PCR analysis confirmed treatment with HKMT-1-005 reduced expression of BRCA1 and BRCA2 in PEO1 but not PEO4. Synergy between HKMT-1-005 and Rucaparib was greater in P53-/-BRCA1-/- and P53-/-BRCA2-/- compared to WT or P53-/- ID8 mouse cell lines. ATAC-seq identified multiple DDR-associated genes had significantly (FDR &amp;lt;0.05) altered chromatin accessibility in P53-/-BRCA2-/- compared with P53-/- alone. HKMT-1-005 treatment in ID8 cell lines revealed changes in chromatin at multiple DDR-associated genes including BRCA2. HKMT-1-005 is synergistic with the PARP inhibitor Rucaparib and can modulate the expression and chromatin conformation of DDR-associated genes in multiple human and mouse ovarian cell lines. Depletion of BRCA2 may additionally regulate chromatin conformation of genes including those associated with DDR pathways and explain why greater synergy between HKMT-1-005 and Rucaparib was observed in BRCA deficient lines. Citation Format: Ian M. Garner, Zhuyan Su, Sawyer Hu, Yue Wu, Iain A. McNeish, Matthew J. Fuchter, Robert Brown. Modulation of homologous recombination repair pathway gene expression by a dual EZH2 and EHMT2 histone methyltransferase inhibitor and synergy with PARP inhibitors in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2066.