Absorption, Metabolism, and Excretion of Taselisib (GDC-0032), a Potent ß-Sparing PI3K Inhibitor in Rats, Dogs, and Humans.

Taselisib (also known as GDC-0032) is a potent and selective phosphoinositide 3-kinase (PI3K) inhibitor that displays greater selectivity for mutant PI3Kα than wild-type PI3Kα To better understand the absorption, distribution, metabolism, and excretion properties of taselisib, mass balance studies were conducted following single oral doses of [14C]taselisib in rats, dogs, and humans. Absolute bioavailability (ABA) of taselisib in humans was determined by oral administration of taselisib at the therapeutic dose followed by intravenous dosing of [14C]taselisib as a microtracer. The ABA in humans was 57.4%. Absorption of taselisib was rapid in rats and dogs and moderately slow in humans. The recovery of radioactivity in excreta was high (>96%) in the three species where feces was the major route of excretion. Taselisib was the major circulating component in the three species with no metabolite accounting for >10% of the total drug-derived material. The fraction absorbed of taselisib was 35.9% in rats and 71.4% in dogs. In rats, absorbed drug underwent moderate to extensive metabolism and biliary excretion of taselisib was minor. In dog, biliary excretion and metabolism were major clearance pathways. In humans, 84.2% of the dose was recovered as the parent drug in excreta indicating that metabolism played a minor role in the drug's clearance. Major metabolism pathways were oxidation and amide hydrolysis in the three species while methylation was another prominent metabolism pathway in dogs. The site of methylation was identified on the triazole moiety. In vitro experiments characterized that the N-methylation was dog-specific and likely mediated by a thiol methyltransferase. SIGNIFICANCE STATEMENT: This study provides a comprehensive description of the absorption, distribution, and metabolism and pharmacokinetic properties of taselisib in preclinical species and humans. This study demonstrated the importance of oral bioavailability results for understanding taselisib's clearance pathways. The study also describes the identification and characterization of a unique dog-specific N-methylation metabolite of taselisib and the enzyme mediating N-methylation in vitro.

Evaluation of drug interaction potential of zanubrutinib with cocktail probes representative of CYP3A4, CYP2C9, CYP2C19, P-gp and BCRP.

AIM: This study aims to assess the potential effects of zanubrutinib on the activity of cytochrome P450 (CYP) enzymes and drug transporter proteins using a cocktail probe approach. METHODS: Patients received single oral doses of probe drugs alone and after at least 8 days of treatment with zanubrutinib 160 mg twice daily in a single-sequence study in 18 healthy male volunteers. Simultaneous doses of 10 mg warfarin (CYP2C9) and 2 mg midazolam (CYP3A) were administered on Day 1 and Day 14, 0.25 mg digoxin (P-glycoprotein [P-gp]) and 10 mg rosuvastatin (breast cancer resistance protein [BCRP]) on Day 3 and Day 16, and 20 mg omeprazole (CYP2C19) on Day 5 and Day 18. Pharmacokinetic (PK) parameters were estimated from samples obtained up to 12 h post dose for zanubrutinib; 24 h for digoxin, omeprazole and midazolam; 48 h for rosuvastatin; and 144 h for warfarin. RESULTS: The ratios (%) of geometric least squares means (90% confidence intervals) for the area under the concentration-time curve from time zero to the last quantifiable concentration in the presence/absence of zanubrutinib were 99.80% (97.41-102.2%) for S-warfarin; 52.52% (48.49-56.88%) for midazolam; 111.3% (103.8-119.3%) for digoxin; 89.45% (78.73-101.6%) for rosuvastatin; and 63.52% (57.40-70.30%) for omeprazole. Similar effects were observed for maximum plasma concentrations. CONCLUSIONS: Zanubrutinib 320 mg total daily dose had minimal or no effect on the activity of CYP2C9, BCRP and P-gp, but decreased the systemic exposure of CYP3A and CYP2C19 substrates (mean reduction <50%).

GDC-0810 Pharmacokinetics and Transporter-Mediated Drug Interaction Evaluation with an Endogenous Biomarker in the First-in-Human, Dose Escalation Study.

GDC-0810 (Cheeti et al., 2018) is an orally bioavailable, selective estrogen receptor (ER) degrader developed to treat ER-positive breast cancer. A first-in-human (FIH) dose escalation phase I study (n = 41) was conducted to characterize the pharmacokinetics (PK) of GDC-0810 and its two major metabolites. GDC-0810 demonstrated linear PK from 100 to 600 mg given once daily. The mean terminal half-life following a single 600 mg dose was approximately 8 hours. Since GDC-0810 is a potent in vitro inhibitor of organic anion transporting polypeptide (OATP) 1B1/3, the kinetic profile of coproporphyrin I (CPI), a promising endogenous biomarker for OATP1B1/3, was analyzed retrospectively in a subset of the plasma samples collected in the same FIH study. CPI exhibited a GDC-0810 dose-dependent increase, suggesting in vivo inhibition of OATP1B transporters. To quantitatively predict the magnitude of OATP1B-mediated drug-drug interactions (DDIs) with pravastatin (a known OATP1B substrate), the in vivo unbound inhibition constant was first estimated using a one-compartment model, and then incorporated to a physiologically based pharmacokinetic model. The model showed some underestimation of the magnitude of the DDI when compared with a clinical DDI study result, while prediction had a relatively large uncertainty due to the small effect size, limited sample size, and variability in CPI kinetics. In conclusion, this study characterized the pharmacokinetic profiles of GDC-0810 in breast cancer patients and demonstrated the utility of CPI in detecting OATP1B-mediated DDIs of a new molecular entity as early as FIH study. SIGNIFICANCE STATEMENT: Endogenous biomarkers of transporters have recently been shown to be promising tools in evaluating the risk of clinical transporter-mediated DDIs. This is the first study to report a pharmacokinetic interaction between an investigational molecule and a transporter biomarker in a first-in-human study. The observed interaction and model-based analysis and the prediction provide important insights on the novel approach to quantitatively predict transporter-mediated DDIs as early as FIH studies in the clinical development.

Correction to: Application of a Novel 'Make and Test in Parallel' Strategy to Investigate the Effect of Formulation on the Pharmacokinetics of GDC-0810 in Healthy Subjects.

The Publisher regrets the typesetting mistake of retaining incorrect text in the Figure 1 caption. The correct text for the caption is "Molecular Structure of GDC-0810 NMG Salt". The original article has been corrected.

Application of a Novel 'Make and Test in Parallel' Strategy to Investigate the Effect of Formulation on the Pharmacokinetics of GDC-0810 in Healthy Subjects.

PURPOSE: GDC-0810, administered orally, was used in Phase I and II clinical studies to treat estrogen receptor positive breast cancers. It contains N-methyl-D-glucamine (NMG) salt of GDC-0810 with 10% sodium lauryl sulfate (SLS) as a surfactant and 15% sodium bicarbonate (NaHCO3) as an alkalizing agent to aid dissolution. To improve the processability of the formulation and reduce potential mucosal irritation in future Phase III clinical studies, the salt form and the amount of excipient required further optimization. To achieve this, we employed a novel "Make and Test in Parallel" strategy that facilitated selecting formulation in a rapid timeframe. METHODS: RapidFACT®, a streamlined, data-driven drug product optimization platform was used to bridge Phase I/II and Phase III formulations of GDC-0810. Five prototype formulations, varying in either the form of active pharmaceutical ingredient and/or the levels of the excipients SLS and NaHCO3 were assessed. Uniquely, the specific compositions of formulations manufactured and dosed were selected in real-time from emerging clinical data. RESULTS: The study successfully identified a Phase III formulation with a reduced SLS content, which when administered following a low-fat meal, gave comparable pharmacokinetic exposure to the Phase I/II formulation administered under the same conditions. CONCLUSIONS: Our novel 'Make and Test in Parallel' approach enabled optimization of GDC-0810 formulation in a time- and cost-efficient fashion.

Assessment of OATP transporter-mediated drug-drug interaction using physiologically-based pharmacokinetic (PBPK) modeling - a case example.

GDC-0810 was under development as an oral anti-cancer drug for the treatment of estrogen receptor-positive breast cancer as a single agent or in combination. In vitro data indicated that GDC-0810 is a potent inhibitor of OATP1B1/1B3. To assess clinical risk, a PBPK model was developed to predict the transporter drug-drug interaction (tDDI) between GDC-0810 and pravastatin in human. The PBPK model was constructed in Simcyp® by integrating in vitro and in vivo data for GDC-0810. The prediction of human pharmacokinetics (PK) was verified using GDC-0810 phase I clinical PK data. The Simcyp transporter DDI model was verified using known OATP1B1/1B3 inhibitors (rifampicin, cyclosporine and gemfibrozil) and substrate (pravastatin), prior to using the model to predict GDC-0810 tDDI. The effect of GDC-0810 on pravastatin PK was then predicted based on the proposed clinical scenarios. Sensitivity analysis was conducted on the parameters with uncertainty. The developed PBPK model described the PK profile of GDC-0810 reasonably well. In the tDDI verification, the model reasonably predicted pravastatin tDDI caused by rifampicin and gemfibrozil OATP1B1/3 inhibition but under-predicted tDDI caused by cyclosporine. The effect of GDC-0810 on pravastatin PK was predicted to be low to moderate (pravastatin Cmax ratios 1.01-2.05 and AUC ratio 1.04-2.23). The observed tDDI (Cmax ratio 1.20 and AUC ratio 1.41) was within the range of the predicted values. This work demonstrates an approach using a PBPK model to prospectively assess tDDI caused by a new chemical entity as an OATP1B1/3 uptake transporter inhibitor to assess clinical risk and to support development strategy.

Evaluation of HDL-modulating interventions for cardiovascular risk reduction using a systems pharmacology approach.

The recent failures of cholesteryl ester transport protein inhibitor drugs to decrease CVD risk, despite raising HDL cholesterol (HDL-C) levels, suggest that pharmacologic increases in HDL-C may not always reflect elevations in reverse cholesterol transport (RCT), the process by which HDL is believed to exert its beneficial effects. HDL-modulating therapies can affect HDL properties beyond total HDL-C, including particle numbers, size, and composition, and may contribute differently to RCT and CVD risk. The lack of validated easily measurable pharmacodynamic markers to link drug effects to RCT, and ultimately to CVD risk, complicates target and compound selection and evaluation. In this work, we use a systems pharmacology model to contextualize the roles of different HDL targets in cholesterol metabolism and provide quantitative links between HDL-related measurements and the associated changes in RCT rate to support target and compound evaluation in drug development. By quantifying the amount of cholesterol removed from the periphery over the short-term, our simulations show the potential for infused HDL to treat acute CVD. For the primary prevention of CVD, our analysis suggests that the induction of ApoA-I synthesis may be a more viable approach, due to the long-term increase in RCT rate.

A supported liquid extraction LC-MS/MS method for determination of concentrations of GDC-0425, a small molecule Checkpoint kinase 1 inhibitor, in human plasma.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of GDC-0425 concentrations in human plasma has been developed and validated. Supported liquid extraction was used to extract plasma samples (50 µL) and the resulting samples were analyzed using reverse-phase chromatography and mass spectrometry coupled with a turbo-ionspray interface. The mass analysis of GDC-0425 was performed using multiple reaction monitoring transitions in positive ionization mode. The method was validated over the calibration curve range of 1.00-1000 ng/mL using linear regression and 1/x2 weighting. Within-run relative standard deviation ranged from 0.8 to 5.1%, while between-run RSD varied from 1.9 to 4.7% for QCs. The accuracy ranged from 90.0 to 101.0% of nominal for within-run and from 94.0 to 100.0% of nominal for between-run. Overall extraction recovery was 87.4% for GDC-0425 and 87.9% for GDC-0425-d9 . Stability of GDC-0425 was established in human plasma for 374 days at -20 and -70 °C and established in reconstituted sample extracts for 88 h when stored at 2-8 °C. Stable-labeled internal standard was used to minimize matrix effects. This assay was used to characterize the pharmacokinetics of GDC-0425 in cancer patients.

Clinical dose rationale of tislelizumab in patients with solid or hematological advanced tumors.

Tislelizumab, an anti-programmed cell death protein 1 monoclonal antibody, has demonstrated improved survival benefits over standard of care for multiple cancer indications. We present the clinical rationale and data supporting tislelizumab dose recommendation in patients with advanced tumors. The phase I, first-in-human, dose-finding BGB-A317-001 study (data cutoff [DCO]: August 2017) examined the following tislelizumab dosing regimens: 0.5-10 mg/kg every 2 weeks (q2w), 2-5 mg/kg q2w or q3w, and 200 mg q3w. Similar objective response rates (ORRs) were reported in the 2 and 5 mg/kg q2w or q3w cohorts. Safety outcomes (grade ≥3 adverse events [AEs], AEs leading to dose modification/discontinuation, immune-mediated AEs, and infusion-related reactions) were generally comparable across the dosing range examined. These results, alongside the convenience of a fixed q3w dose, formed the basis of choosing 200 mg q3w as the recommended dosing regimen for further clinical use. Pooled exposure-response (E-R) analyses by logistic regression using data from study BGB-A317-001 (DCO: August 2020) and three additional phase I/II studies (DCOs: 2018-2020) showed no statistically significant correlation between tislelizumab pharmacokinetic exposure and ORR across multiple solid tumor types or classical Hodgkin's lymphoma, nor was exposure associated with any of the safety end points evaluated over the dose range tested. Hence, tislelizumab showed a relatively flat E-R relationship. Overall, the totality of data, including efficacy, safety, and E-R analyses, together with the relative convenience of a fixed q3w dose, provided clinical rationale for the recommended dosing regimen of tislelizumab 200 mg q3w for multiple cancer indications.

A Phase 1, Open-Label, Fixed-Sequence, Drug-Drug Interaction Study of Zanubrutinib with Rifabutin in Healthy Volunteers.

Zanubrutinib is a second-generation Bruton tyrosine kinase inhibitor that is primarily metabolized by CYP3A enzymes. Previous drug-drug interaction (DDI) studies have demonstrated that co-administration of zanubrutinib with rifampin, a strong CYP3A inducer, reduces zanubrutinib plasma concentrations, potentially impacting activity. The impact of the co-administration of zanubrutinib with less potent CYP3A inducers is unclear. This phase 1, open-label, fixed-sequence DDI study evaluated the pharmacokinetics, safety, and tolerability of zanubrutinib when co-administered with steady-state rifabutin, a known CYP3A inducer less potent than rifampin, in 13 healthy male volunteers (NCT04470908). Co-administration of zanubrutinib with rifabutin resulted in a less than 2-fold reduction of zanubrutinib exposures. Overall, zanubrutinib was well tolerated. The results of this study provide useful information for the evaluation of the DDI between rifabutin and zanubrutinib. In conjunction with safety and efficacy data from other clinical studies, these results will be taken into consideration to determine the appropriate dose recommendation of zanubrutinib when co-administered with CYP3A inducers.

Model-based population pharmacokinetic analysis of tislelizumab in patients with advanced tumors.

Tislelizumab, a humanized immunoglobulin G4 monoclonal antibody, is a programmed cell death protein 1 (PD-1) inhibitor designed to minimize Fc gamma receptor binding on macrophages to limit antibody-dependent phagocytosis, a potential mechanism of resistance to anti-PD-1 therapy. The pharmacokinetic (PK) profile of tislelizumab was analyzed with population PK modeling using 14,473 observed serum concentration data points from 2596 cancer patients who received intravenous (i.v.) tislelizumab at 0.5-10 mg/kg every 2 weeks or every 3 weeks (q3w), or a 200 mg i.v. flat dose q3w in 12 clinical studies. Tislelizumab exhibited linear PK across the dose range tested. Baseline body weight, albumin, tumor size, tumor type, and presence of antidrug antibodies were identified as significant covariates on central clearance, whereas baseline body weight, sex, and age significantly affected central volume of distribution. Sensitivity analysis showed that these covariates did not have clinically relevant effects on tislelizumab PK. Other covariates evaluated, including race (Asian vs. White), lactate dehydrogenase, estimated glomerular filtration rate, renal function categories, hepatic function measures and categories, Eastern Cooperative Oncology Group performance status, therapy (monotherapy vs. combination therapy), and line of therapy did not show a statistically significant impact on tislelizumab PK. These results support the use of tislelizumab 200 mg i.v. q3w without dose adjustment in a variety of patient subpopulations.

A phase 1, open-label, randomized drug-drug interaction study of zanubrutinib with moderate or strong CYP3A inhibitors in patients with B-cell malignancies.

BTK inhibitor exposure increases significantly when coadministered with CYP3A inhibitors, which may lead to dose-related toxicities. This study explored the pharmacokinetics, efficacy, and safety of zanubrutinib when coadministered with moderate or strong CYP3A inhibitors in 26 patients with relapsed or refractory B-cell malignancies. Coadministration of zanubrutinib (80 mg BID) with moderate CYP3A inhibitors fluconazole and diltiazem or zanubrutinib (80 mg QD) with strong CYP3A inhibitor voriconazole resulted in comparable exposures to zanubrutinib (320 mg QD) with AUC0-24h geometric least squares mean ratios approaching 1 (0.94, 0.81, and 0.83, for fluconazole, diltiazem, and voriconazole, respectively). The most common treatment-emergent adverse events were contusion (26.9%), back pain (19.2%), constipation and neutropenia (15.4% each), and rash, diarrhea, and fall (11.5% each). This study supports current United States Prescribing Information dose recommendations for the coadministration of reduced-dose zanubrutinib with moderate or strong CYP3A inhibitors and confirms the favorable efficacy and safety profile of zanubrutinib.

Targeting TIGIT for Immunotherapy of Cancer: Update on Clinical Development.

Immune checkpoint blockers have dramatically improved the chances of survival in patients with metastatic cancer, but only a subset of the patients respond to treatment. Search for novel targets that can improve the responder rates and overcome the limitations of adverse events commonly seen with combination therapies, like PD-1 plus CTLA-4 blockade and PD-1/PD-L1 plus chemotherapy, led to the development of monoclonal antibodies blocking T-cell immunoglobulin and ITIM domain (TIGIT), a inhibitory checkpoint receptor expressed on activated T cells and NK cells. The strategy showed potential in pre-clinical and early clinical studies, and 5 molecules are now in advanced stages of evaluation (phase II and above). This review aims to provide an overview of clinical development of anti-TIGIT antibodies and describes the factors considered and thought process during early clinical development. Critical aspects that can decide the fate of clinical programs, such as origin of the antibody, Ig isotype, FCγR binding, and the dose as well as dosing schedule, are discussed along with the summary of available efficacy and safety data from clinical studies and the challenges in the development of anti-TIGIT antibodies, such as identifying patients who can benefit from therapy and getting payer coverage.

Comprehensive PBPK model to predict drug interaction potential of Zanubrutinib as a victim or perpetrator.

A physiologically based pharmacokinetic (PBPK) model was developed to evaluate and predict (1) the effect of concomitant cytochrome P450 3A (CYP3A) inhibitors or inducers on the exposures of zanubrutinib, (2) the effect of zanubrutinib on the exposures of CYP3A4, CYP2C8, and CYP2B6 substrates, and (3) the impact of gastric pH changes on the pharmacokinetics of zanubrutinib. The model was developed based on physicochemical and in vitro parameters, as well as clinical data, including pharmacokinetic data in patients with B-cell malignancies and in healthy volunteers from two clinical drug-drug interaction (DDI) studies of zanubrutinib as a victim of CYP modulators (itraconazole, rifampicin) or a perpetrator (midazolam). This PBPK model was successfully validated to describe the observed plasma concentrations and clinical DDIs of zanubrutinib. Model predictions were generally within 1.5-fold of the observed clinical data. The PBPK model was used to predict untested clinical scenarios; these simulations indicated that strong, moderate, and mild CYP3A inhibitors may increase zanubrutinib exposures by approximately four-fold, two- to three-fold, and <1.5-fold, respectively. Strong and moderate CYP3A inducers may decrease zanubrutinib exposures by two- to three-fold or greater. The PBPK simulations showed that clinically relevant concentrations of zanubrutinib, as a DDI perpetrator, would have no or limited impact on the enzyme activity of CYP2B6 and CYP2C8. Simulations indicated that zanubrutinib exposures are not impacted by acid-reducing agents. Development of a PBPK model for zanubrutinib as a DDI victim and perpetrator in parallel can increase confidence in PBPK models supporting zanubrutinib label dose recommendations.

In vitro investigations into the roles of CYP450 enzymes and drug transporters in the drug interactions of zanubrutinib, a covalent Bruton's tyrosine kinase inhibitor.

Zanubrutinib is a highly selective, potent, orally available, targeted covalent inhibitor (TCI) of Bruton's tyrosine kinase (BTK). This work investigated the in vitro drug metabolism and transport of zanubrutinib, and its potential for clinical drug-drug interactions (DDIs). Phenotyping studies indicated cytochrome P450 (CYP) 3A are the major CYP isoform responsible for zanubrutinib metabolism, which was confirmed by a clinical DDI study with itraconazole and rifampin. Zanubrutinib showed mild reversible inhibition with half maximal inhibitory concentration (IC50 ) of 4.03, 5.69, and 7.80 µM for CYP2C8, CYP2C9, and CYP2C19, respectively. Data in human hepatocytes disclosed induction potential for CYP3A4, CYP2B6, and CYP2C enzymes. Transport assays demonstrated that zanubrutinib is not a substrate of human breast cancer resistance protein (BCRP), organic anion transporting polypeptide (OATP)1B1/1B3, organic cation transporter (OCT)2, or organic anion transporter (OAT)1/3 but is a potential substrate of the efflux transporter P-glycoprotein (P-gp). Additionally, zanubrutinib is neither an inhibitor of P-gp at concentrations up to 10.0 µM nor an inhibitor of BCRP, OATP1B1, OATP1B3, OAT1, and OAT3 at concentrations up to 5.0 µM. The in vitro results with CYPs and transporters were correlated with the available clinical DDIs using basic models and mechanistic static models. Zanubrutinib is not likely to be involved in transporter-mediated DDIs. CYP3A inhibitors and inducers may impact systemic exposure of zanubrutinib. Dose adjustments may be warranted depending on the potency of CYP3A modulators.

Human Mass Balance and Metabolite Profiling of [14 C]-Pamiparib, a Poly (ADP-Ribose) Polymerase Inhibitor, in Patients With Advanced Cancer.

Pamiparib, a selective poly (ADP-ribose) polymerase 1/2 inhibitor, demonstrated tolerability and antitumor activity in patients with solid tumors at 60 mg orally twice daily. This phase 1 open-label study (NCT03991494; BGB-290-106) investigated the absorption, metabolism, and excretion (AME) of 60 mg [14 C]-pamiparib in 4 patients with solid tumors. The mass balance in excreta, blood, and plasma radioactivity and plasma pamiparib concentration were determined along with metabolite profiles in plasma, urine, and feces. Unchanged pamiparib accounted for the most plasma radioactivity (67.2% ± 10.2%). Pamiparib was rapidly absorbed with a median time to maximum plasma concentration (Cmax ) of 2.00 hours (range, 1.00-3.05 hours). After reaching Cmax , pamiparib declined in a biphasic manner, with a geometric mean terminal half-life (t1/2 ) of 28.7 hours. Mean cumulative [14 C]-pamiparib excretion was 84.7% ± 3.5%. Pamiparib was mainly cleared through metabolism, primarily via N-oxidation and oxidation of the pyrrolidine ring. A dehydrogenated oxidative product (M3) was the most abundant metabolite in biosamples. A mean of 2.11% and 1.11% of [14 C]-pamiparib was excreted as unchanged pamiparib in feces and urine, respectively, indicating near-complete absorption and low renal clearance of parent drug. Cytochrome P450 (CYP) phenotyping demonstrated CYP2C8 and CYP3A involvement in pamiparib metabolism. These findings provide an understanding of pamiparib AME mechanisms and potential drug-drug interaction liability.

The pharmacokinetics of pamiparib in the presence of a strong CYP3A inhibitor (itraconazole) and strong CYP3A inducer (rifampin) in patients with solid tumors: an open-label, parallel-group phase 1 study.

PURPOSE: Pamiparib is an investigational, selective, oral poly(ADP-ribose) polymerase 1/2 (PARP1/2) inhibitor that has demonstrated PARP-DNA complex trapping and CNS penetration in preclinical models, as well as preliminary anti-tumor activity in early-phase clinical studies. We investigated whether the single-dose pharmacokinetic (PK) profile of pamiparib is altered by coadministration of a strong CYP3A inducer (rifampin) or a strong CYP3A inhibitor (itraconazole) in patients with solid tumors. METHODS: In this open-label, phase 1 study, adults with advanced solid tumors received either oral pamiparib 60 mg (days 1 and 10) and once-daily oral rifampin 600 mg (days 3-11) or oral pamiparib 20 mg (days 1 and 7) and once-daily oral itraconazole 200 mg (days 3-8). Primary endpoints included pamiparib maximum observed concentration (Cmax), and area under the plasma concentration-time curve from zero to last quantifiable concentration (AUC0-tlast) and infinity (AUC0-inf). Secondary endpoints included safety and tolerability. RESULTS: Rifampin coadministration did not affect pamiparib Cmax (geometric least-squares [GLS] mean ratio 0.94; 90% confidence interval 0.83-1.06), but reduced its AUC0-tlast (0.62 [0.54-0.70]) and AUC0-inf (0.57 [0.48-0.69]). Itraconazole coadministration did not affect pamiparib Cmax (1.05 [0.95-1.15]), AUC0-tlast (0.99 [0.91-1.09]), or AUC0-inf (0.99 [0.90-1.09]). There were no serious treatment-related adverse events. CONCLUSIONS: Pamiparib plasma exposure was reduced 38-43% with rifampin coadministration but was unaffected by itraconazole coadministration. Pamiparib dose modifications are not considered necessary when coadministered with CYP3A inhibitors. Clinical safety and efficacy data will be used with these results to recommend dose modifications when pamiparib is coadministered with CYP3A inducers.

Rationale for once-daily or twice-daily dosing of zanubrutinib in patients with mantle cell lymphoma.

This report summarizes a totality-of-evidence approach supporting recommendation of a 320-mg total daily dose, either as 160-mg twice daily (BID) or 320-mg once daily (QD) for zanubrutinib in patients with mantle cell lymphoma. Data were derived from a phase 2 study in patients receiving 160-mg BID and a phase 1/2 study with similar response rates observed with 160-mg BID or 320-mg QD. Given the limited number of patients in the QD dose group, population pharmacokinetics and exposure-response analyses were employed to bridge the two regimens. The analyses showed that similar plasma exposure and BTK inhibition were achieved, and differences in trough concentration and maximum plasma concentration between the two regimens are unlikely to have a meaningful impact on efficacy and safety endpoints. The totality of data, including pharmacokinetic, pharmacodynamic, safety, efficacy, and exposure-response analyses, provided support for the recommended 320-mg total daily dose for the approved indication.

Population Pharmacokinetic Analysis of the BTK Inhibitor Zanubrutinib in Healthy Volunteers and Patients With B-Cell Malignancies.

Zanubrutinib is a potent, second-generation Bruton's tyrosine kinase inhibitor that is currently being investigated in patients with B-cell malignancies and recently received accelerated approval in the United States for treatment of relapsed/refractory mantle cell lymphoma. The objective of this analysis was to develop a population pharmacokinetic (PK) model to characterize the PKs of zanubrutinib and identify the potential impact of intrinsic and extrinsic covariates on zanubrutinib PK. Data across nine clinical studies of patients with B-cell malignancies and data of healthy volunteers (HVs) were included in this analysis, at total daily doses ranging from 20 to 320 mg. In total, 4,925 zanubrutinib plasma samples from 632 subjects were analyzed using nonlinear mixed-effects modeling. Zanubrutinib PKs were adequately described by a two-compartment model with sequential zero-order then first-order absorption, and first-order elimination. A time-dependent residual error model was implemented in order to better capture the observed maximum concentration variability in subjects. Baseline alanine aminotransferase and health status (HVs or patients with B-cell malignancies) were identified as statistically significant covariates on the PKs of zanubrutinib. These factors are unlikely to be clinically meaningful based on a sensitivity analysis. No statistically significant differences in the PKs of zanubrutinib were observed based on age, sex, race (Asian, white, and other), body weight, mild or moderate renal impairment (creatinine clearance ≥ 30 mL/minute as estimated by Cockcroft-Gault), baseline aspartate aminotransferase, bilirubin, tumor type, or use of acid-reducing agents (including proton pump inhibitors). These results support that no dose adjustment is considered necessary based on the aforementioned factors.

Effect of rifampin and itraconazole on the pharmacokinetics of zanubrutinib (a Bruton's tyrosine kinase inhibitor) in Asian and non-Asian healthy subjects.

PURPOSE: Zanubrutinib (BGB-3111) is a potent Bruton's tyrosine kinase inhibitor with promising clinical activity in B-cell malignancies. Zanubrutinib was shown to be mainly metabolized through cytochrome P450 3A (CYP3A) in vitro. We evaluated the effect of steady-state rifampin (a strong CYP3A inducer) and steady-state itraconazole (a strong CYP3A inhibitor) on the pharmacokinetics (PK), safety, and tolerability of zanubrutinib in healthy Asian and non-Asian subjects. METHODS: In this open-label, two-part clinical study, 20 participants received a single oral dose of zanubrutinib (320 mg) and oral rifampin (600 mg) in Part A, and 18 participants received a single oral dose of zanubrutinib (20 mg) and oral itraconazole (200 mg) in Part B. Serial blood samples were collected after administration of zanubrutinib alone and zanubrutinib in combination with rifampin or itraconazole for the measurement of PK parameters. RESULTS: Coadministration with rifampin decreased AUC0-∞ of zanubrutinib by 13.5-fold and Cmax by 12.6-fold. Coadministration with itraconazole increased the AUC0-∞ of zanubrutinib by 3.8-fold and Cmax by 2.6-fold. The PK of zanubrutinib was consistent between Asian and non-Asian subjects, and  zanubrutinib was well tolerated in this study. CONCLUSIONS: These results confirm that zanubrutinib is primarily metabolized by CYP3A in humans. The PK of zanubrutinib was comparable between Asian and non-Asian subjects and, therefore, no dose modifications are necessary for zanubrutinib in these ethnic populations.