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

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

Talazoparib Exposure-Efficacy Analysis in Patients With Advanced Breast Cancer and Germline BRCA1/2 Mutations in the EMBRACA Trial.

In the phase 3 EMBRACA trial, treatment with the poly(ADP-ribose) polymerase inhibitor, talazoparib, led to significantly improved progression-free survival (PFS) compared with chemotherapy (hazard ratio, 0.54; 95% confidence interval, 0.41-0.71; P < .0001). We conducted an exposure-efficacy analysis using EMBRACA data from 285 patients who were treated with talazoparib and had available pharmacokinetic parameters to evaluate the effect of talazoparib exposure (time-varying average talazoparib concentration [Cavg,t ]) and other baseline variables on PFS. Graphical examination of the relationship between Cavg,t and PFS and a Cox proportional model were used. Exposure-response analyses showed that higher talazoparib exposure, absence of visceral disease, lower baseline lactate dehydrogenase levels, and disease-free interval >12 months were independent covariates associated with longer PFS. The association of talazoparib exposure with PFS (higher exposure, longer PFS) suggests the recommended starting dose of 1 mg once daily (the maximum tolerated dose) is appropriate.

Exposure-Safety Analyses of Talazoparib in Patients With Advanced Breast Cancer and Germline BRCA1/2 Mutations in the EMBRACA and ABRAZO Trials.

Poly(ADP-ribose) polymerase inhibitors, such as talazoparib, may affect hematopoiesis. This analysis characterized the relationship between talazoparib exposure and the most common grade ≥ 3 hematopoietic adverse events (AEs) leading to dose modification in the phase 2 (ABRAZO) and phase 3 (EMBRACA) trials. The relationship between time-varying average talazoparib concentration (Cavg,t ), along with other baseline variables, and grade ≥ 3 anemia, thrombocytopenia, and neutropenia were evaluated both by graphical examination and using univariate and multivariate Cox proportional hazard models. The results indicated that higher Cavg,t was associated with a higher risk of anemia and thrombocytopenia. A trend toward an association between higher Cavg,t and neutropenia was observed, although not statistically significant. Higher risk of all tested safety end points was associated with lower baseline hemoglobin. Higher risk of neutropenia was associated with lower baseline absolute neutrophil count and lower body weight. These findings support the proposed management of AEs through talazoparib dosing modification.

Development and validation of an integrated LC-MS/MS assay for therapeutic drug monitoring of five PARP-inhibitors.

An liquid chromatography-mass spectrometry (LC-MS/MS) assay was developed for the combined analysis of the five poly (ADP-ribose) polymerase (PARP) inhibitors niraparib, olaparib, rucaparib talazoparib and veliparib. A simple and fast sample pre-treatment method was used by protein precipitating of plasma samples with acetonitrile and dilution of the supernatant with formic acid (0.1% v/v in water). This was followed by chromatographic separation on a reversed-phase UPLC BEH C18 column and detection with a triple quadrupole mass spectrometer operating in the positive mode. A simplified validation procedure specifically designed for bioanalytical methods for clinical therapeutic drug monitoring (TDM) purposes, was applied. This included assessment of the calibration model, accuracy and precision, lower limit of quantification (LLOQ), specificity and selectivity, carry-over and stability. The validated range was 30-3000 ng/mL for niraparib, 100-10,000 ng/mL for olaparib, 50-5000 ng/mL for rucaparib, 0.5-50 ng/mL for talazoparib and 50-5000 for veliparib. All results were within the criteria of the US Food and Drug Administration (FDA) guidance and European Medicines Agency (EMA) guidelines on method validation. The assay has been successfully implemented in our laboratory.

Population Pharmacokinetics of Talazoparib in Patients With Advanced Cancer.

Poly(ADP-ribose) polymerase (PARP) inhibitors have been developed to treat cancers associated with somatic BRCA mutations and germline genetic aberrations involved in the DNA damage response. The efficacy, tolerability, and pharmacokinetic/pharmacodynamic (PK/PD) profile of talazoparib, a potent small-molecule PARP inhibitor, was established in 4 clinical studies in cancer patients (2 phase 1 studies PRP-001 and PRP-002, the phase 2 ABRAZO trial, and the phase 3 EMBRACA trial). The current study aimed to describe the population PK of talazoparib and identify covariates that affect talazoparib PK in patients with advanced cancers using pooled data from these 4 studies. Talazoparib PK was well characterized by a 2-compartment model with first-order absorption and absorption lag time. Based on covariate analysis, no dose adjustment for talazoparib is required based on a patient's age, sex, baseline body weight, Asian race, the presence of mild renal or hepatic impairment, or use of acid-reducing agents. A reduced 0.75-mg daily dose is recommended for patients taking a potent P-glycoprotein inhibitor and those with moderate renal impairment. Insufficient data were available to establish dosing recommendations for patients with severe renal and moderate or severe hepatic impairment. The PK of a single 1-mg talazoparib capsule is comparable with 4 0.25-mg capsules. Talazoparib can be taken with or without food. These data provide support for dosing recommendations and labeling information for talazoparib.

UPLC-MS/MS method for the determination of talazoparib in rat plasma and its pharmacokinetic study.

In the present study, an accurate and sensitive ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the determination of plasma talazoparib concentration in rats was developed and established. The purpose of chromatographic separation of talazoparib and the internal standard (bosutinib) was achieved on an Acquity BEH C18 (2.1 mm × 50 mm, 1.7 µm) column with a flow rate of 0.40 mL/min, using a gradient elution with acetonitrile and 0.1% formic acid in water as the mobile phase. The detection was performed on a XEVO TQ-S triple quadrupole tandem mass spectrometer coupled with electrospray ionization interface under positive-ion multiple reaction monitoring (MRM) mode with the precursor-to-product ion transitions of m/z 381.3 → 285.2 for talazoparib and m/z 530.2 → 141.2 for bosutinib (IS), respectively. The method was linear over the range of 0.5-200 ng/mL for talazoparib. The accuracies and precisions of intra- and inter-day were all within the acceptance limits, and no matrix effect was observed in this method. The validated method was further employed to a pharmacokinetic study of talazoparib after oral treatment with 0.2 mg/kg talazoparib to rats.

Pharmacokinetic Study of Rucaparib in Patients With Advanced Solid Tumors.

The phase 1-2 study CO-338-010 (Study 10; NCT01482715) is evaluating single-agent rucaparib, a poly(ADP-ribose) polymerase inhibitor, administered orally to patients with an advanced solid tumor. In the dose escalation phase (Part 1), we characterized the single-dose and steady-state pharmacokinetic profiles of rucaparib administered once daily (QD; dose range, 40-500 mg; n = 16) or twice daily (BID; dose range, 240-840 mg; n = 30). Across all dosing schedules examined, the plasma exposure of rucaparib was approximately dose proportional; half-life was approximately 17 hours, and median time to maximum concentration (tmax ) ranged from 1.5 to 6.0 hours after a single dose and 1.5 to 4.0 hours following repeated dosing. The steady-state accumulation ratio ranged from 1.60 to 2.33 following QD dosing and 1.47 to 5.44 following BID dosing. No effect of food on rucaparib pharmacokinetics was observed with a single dose of 40 mg (n = 3) or 300 mg (n = 6). In a phase 2 portion of the study (Part 3), the pharmacokinetic profile of rucaparib was further evaluated at the recommended phase 2 dose of 600 mg BID (n = 26). The mean (coefficient of variation) steady-state maximum concentration (Cmax ) and area under the concentration-time curve from time zero to 12 hours (AUC0-12h ) were 1940 ng/mL (54%) and 16 900 ng ⋅ h/mL (54%), respectively. A high-fat meal moderately increased rucaparib exposure. The fed-to-fasted geometric mean ratios (90% confidence interval [CI]) for AUC0-24h and Cmax were 138% (117%-162%) and 120% (99.1%-146%); the median (90%CI) tmax delay was 2.5 (0.5-4.4) hours.

Identifying the need to refine the potential patient risk factors for niraparib-induced thrombocytopenia.

OBJECTIVE: Niraparib is a poly (ADP-ribose) polymerase inhibitor (PARP) approved for use in maintenance therapy for ovarian cancer that is associated with the unpredictable grade 3/4 thrombocytopenia. This study was conducted to refine patient dosing recommendations for niraparib based upon clinical practice observations of grade 3/4 thrombocytopenia. METHODS AND MATERIALS: Six patient cases were reviewed to identify similarities in patient factors. An in vitro study was conducted using healthy volunteer blood spiked with Niraparib concentrations ranging from 0 ng/mL to 5000 ng/mL. Manual platelet counts were evaluated at different time intervals for each concentration and compared to untreated controls. Data was then analyzed based on percent change in platelet count versus untreated control for each concentration/time point. RESULTS: In three patients with body weight > 80 kg and platelet count >200 × 109/L, decreased creatinine clearance (CrCl) <60 mL/min was identified as potential signal. An additional three patients with weights below 77 kg and/or baseline platelet counts <150 × 109/L were re-evaluated, and it was observed that all had decreased CrCl of <60 mL/min. Albumin <3.5 g/dL was also observed in some patients with thrombocytopenia. The in vitro study, observed a direct concentration-dependent relationship between niraparib and thrombocytopenia. CONCLUSION: The data suggests that renal insufficiency and hypoalbuminemia may be associated with the development of niraparib-induced thrombocytopenia. Moreover, the preliminary in vitro studies also demonstrated a concentration-dependent relationship between niraparib and direct toxicity to platelets.

Development and Validation of a Simultaneous Quantification Method of Ruxolitinib, Vismodegib, Olaparib, and Pazopanib in Human Plasma Using Liquid Chromatography Coupled With Tandem Mass Spectrometry.

BACKGROUND: A simple, rapid, and sensitive liquid chromatography coupled with tandem mass spectrometry method has been developed and validated for the quantification of ruxolitinib, olaparib, vismodegib, and pazopanib in human plasma. METHODS: After a simple protein precipitation of plasma samples, the chromatographic separation was performed using an ultraperformance liquid chromatography system coupled with mass tandem spectrometry in a positive ionization mode. The mobile phase consisted of a gradient elution of 10-mmol/L formate ammonium buffer containing 0.1% (vol/vol) formic acid (phase A) and acetonitrile with 0.1% (vol/vol) formic acid (phase B) at a flow rate at 300 µL/min. RESULTS: Analysis time was 5.0 minutes per run, and all analytes and internal standards eluted within 1.5-1.73 minutes. The calibration curves were linear over the range from 10 to 2500 ng/mL for ruxolitinib and from 100 to 100,000 ng/mL for olaparib, vismodegib, and pazopanib with coefficients of correlation above 0.99 for all analytes. The intraday and interday coefficients of variation were below 14.26% and 14.81%, respectively, for lower concentration and below 9.94% and 6.37%, respectively, for higher concentration. CONCLUSIONS: Using liquid chromatography coupled with tandem mass spectrometry, we have developed and validated a simple and rapid assay for the simultaneous quantification of olaparib, vismodegib, pazopanib, and ruxolitinib in human plasma. This method is now part of our therapeutic drug monitoring service provision and is currently used clinically to manage patients prescribed these drugs.

Liquid chromatography-tandem mass spectrometry assay for the quantification of niraparib and its metabolite M1 in human plasma and urine.

Niraparib (MK-4827) is a novel poly(ADP-Ribose) polymerase (PARP) inhibitor currently investigated in phase III clinical trials to treat cancers. The development of a new drug includes the characterisation of absorption, metabolism and excretion (AME) of the compound. AME studies are a requirement of regulatory agencies and for this purpose bioanalytical assays are essential. This article describes the development and validation of a bioanalytical assay for niraparib and its carboxylic acid metabolite M1 in human plasma and urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Sample pre-treatment involved protein precipitation for plasma and dilution of urine samples using acetonitrile-methanol (50:50, v/v). Final extracts were injected onto a SunFire C18 column and gradient elution using 20mM ammonium acetate (mobile phase A) and formic acid:acetonitrile:methanol (0.1:50:50, v/v/v) (mobile phase B) was applied. Detection was performed on an API5500 tandem mass spectrometer operating in the positive electrospray ionisation mode applying multiple reaction monitoring (MRM). The assay was successfully validated in accordance with the Food and Drug Administration and latest European Medicines Agency guidelines on bioanalytical method validation and can therefore be applied in pharmacological clinical studies.

Non-invasive PET Imaging of PARP1 Expression in Glioblastoma Models.

PURPOSE: The current study presents [(18)F]PARPi as imaging agent for PARP1 expression. PROCEDURES: [(18)F]PARPi was generated by conjugating a 2H-phthalazin-1-one scaffold to 4-[(18)F]fluorobenzoic acid. Biochemical assays, optical in vivo competition, biodistribution analysis, positron emission tomography (PET)/X-ray computed tomography, and PET/magnetic resonance imaging studies were performed in subcutaneous and orthotopic mouse models of glioblastoma. RESULTS: [(18)F]PARPi shows suitable pharmacokinetic properties for brain tumor imaging (IC50 = 2.8 ± 1.1 nM; logPCHI = 2.15 ± 0.41; plasma-free fraction = 63.9 ± 12.6 %) and accumulates selectively in orthotopic brain tumor tissue. Tracer accumulation in subcutaneous brain tumors was 1.82 ± 0.21 %ID/g, whereas in healthy brain, the uptake was only 0.04 ± 0.01 %ID/g. CONCLUSIONS: [(18)F]PARPi is a selective PARP1 imaging agent that can be used to visualize glioblastoma in xenograft and orthotopic mouse models with high precision and good signal/noise ratios. It offers new opportunities to non-invasively image tumor growth and monitor interventions.

A phase 1 study evaluating the pharmacokinetics and preliminary efficacy of veliparib (ABT-888) in combination with carboplatin/paclitaxel in Japanese subjects with non-small cell lung cancer (NSCLC).

INTRODUCTION: Veliparib is a potent, orally bioavailable PARP inhibitor that enhances efficacy of DNA-damaging chemotherapeutic agents. The study objectives were to determine the recommended phase 2 dose (RPTD) of veliparib plus carboplatin and paclitaxel, and assess pharmacokinetics (PK), tolerability, and preliminary efficacy in Japanese patients with solid tumors. METHODS: Carboplatin (AUC 6 mg/mL min) and paclitaxel (200 mg/m(2)) were administered on day 3 of a 21-day cycle. Oral veliparib (40, 80, or 120 mg BID) was administered on days 1-7. Patients received ≤6 cycles. Adverse events (AEs) were reported using NCI-CTCAE version 4.03, PK parameters were analyzed using noncompartmental methods, and responses were measured by RECIST version 1.1. RESULTS: Twelve patients with non-small cell lung cancer (NSCLC) were treated. Common treatment-emergent AEs, consistent with toxicities associated with carboplatin and paclitaxel, included leukopenia (100 %), neutropenia (100 %), anemia (83 %), thrombocytopenia (75 %), increased alanine aminotransferase (67 %), and increased aspartate aminotransferase (67 %). Grade 3/4 AEs (in ≥2 patients) included neutropenia (100 %), leukopenia (33 %), anemia (25 %), and hyponatremia (17 %). No AEs led to veliparib, carboplatin, or paclitaxel interruption; no DLTs were observed. The RPTD was determined to be 120 mg BID. Veliparib C max and AUC were approximately dose proportional. Six partial responses were observed. CONCLUSIONS: Veliparib PK was not impacted by carboplatin and paclitaxel. The safety profile was manageable. The 120 mg BID RPTD confirmed in Japanese patients is the dose being evaluated in global studies of veliparib. Preliminary efficacy suggests veliparib may enhance carboplatin and paclitaxel activity, providing benefit to patients with NSCLC.

PARP activity in peripheral blood lymphocytes as a predictive biomarker for PARP inhibition in tumor tissues - A population pharmacokinetic/pharmacodynamic analysis of rucaparib.

PURPOSE: Rucaparib is a potent Poly (ADP-ribose) Polymerase (PARP) inhibitor currently under clinical development. The objectives of this analysis were to establish population PK and PK/PD models for rucaparib, and to evaluate the predictability of PARP activity in PBL for PARP activity in tumor tissues. EXPERIMENTAL DESIGN: Rucaparib concentrations and PARP activity in human PBLs and tumor issues were obtained from 32 patients with solid tumors in a Phase 1 First-in-Patient study. Simulations were conducted to evaluate different dosing regimens. RESULTS: A 3-compartment PK model best described the PK of rucaparib. An Emax model best described the exposure and PARP inhibition relationship. The maximum PARP inhibition (Imax) achieved in PBLs and in tumors were 90.9% and 90.0% of the baseline PARP activity, and the IC50 values were 1.05 ng/mL and 1.10 ng/mL, respectively. PAR polymer baseline value was found to be a covariate of Emin. CONCLUSION: Population PK and PK/PD models have been established to describe population PK of rucaparib and the relationship between rucaparib plasma concentration and PARP inhibition in both PBLs and tumor issues. Results from this trial indicated that PARP inhibition in PBLs can be used as a substitute for PARP inhibition in melanoma tumor tissues.