Mathangi Gopalakrishnan

Levonorgestrel release rates over 5 years with the Liletta® 52-mg intrauterine system

OBJECTIVE To understand the potential duration of action for Liletta®, we conducted this study to estimate levonorgestrel (LNG) release rates over approximately 5½years of product use. METHODS Clinical sites in the U.S. Phase 3 study of Liletta collected the LNG intrauterine systems (IUSs) from women who discontinued the study. We randomly selected samples within 90-day intervals after discontinuation of IUS use through 900days (approximately 2.5years) and 180-day intervals for the remaining duration through 5.4years (1980days) to evaluate residual LNG content. We also performed an initial LNG content analysis using 10 randomly selected samples from a single lot. We calculated the average ex vivo release rate using the residual LNG content over the duration of the analysis. RESULTS We analyzed 64 samples within 90-day intervals (range 6-10 samples per interval) through 900days and 36 samples within 180-day intervals (6 samples per interval) for the remaining duration. The initial content analysis averaged 52.0±1.8mg. We calculated an average initial release rate of 19.5mcg/day that decreased to 17.0, 14.8, 12.9, 11.3 and 9.8mcg/day after 1, 2, 3, 4 and 5years, respectively. The 5-year average release rate is 14.7mcg/day. CONCLUSION The estimated initial LNG release rate and gradual decay of the estimated release rate are consistent with the target design and function of the product. The calculated LNG content and release rate curves support the continued evaluation of Liletta as a contraceptive for 5 or more years of use. IMPLICATIONS STATEMENT Liletta LNG content and release rates are comparable to published data for another LNG 52-mg IUS. The release rate at 5years is more than double the published release rate at 3years with an LNG 13.5-mg IUS, suggesting continued efficacy of Liletta beyond 5years.

Parent‐Metabolite Pharmacokinetic Modeling and Pharmacodynamics of Veliparib (ABT‐888), a PARP Inhibitor, in Patients With BRCA 1/2–Mutated Cancer or PARP‐Sensitive Tumor Types

Veliparib (ABT‐888) is a novel oral poly‐ADP‐ribose polymerase (PARP) inhibitor that is being developed for the treatment of hematologic malignancies and solid tumors. Although the pharmacokinetics of veliparib have been studied in combination with cytotoxic agents, limited information exists regarding the pharmacokinetics (PK) of chronically dosed single‐agent veliparib in patients with either BRCA 1/2–mutated cancer or PARP‐sensitive tumors. The objectives of the current analysis were to characterize the population pharmacokinetics of veliparib and its primary, active metabolite, M8, and to evaluate the relationship between veliparib and M8 concentrations and poly‐ADP‐ribose (PAR) level observed in peripheral blood mononuclear cells (PBMCs). Seventy‐one subjects contributed with veliparib plasma concentrations, M8 plasma concentrations, and PAR levels in PBMCs. Veliparib and M8 concentrations were modeled simultaneously using a population PK approach. A 2‐compartment model with delayed first‐order absorption and the elimination parameterized as renal (CLR/F) and nonrenal clearance (CLNR/F) adequately described veliparib pharmacokinetics. The pharmacokinetics of the M8 metabolite was described with a 2‐compartment model. Creatinine clearance(CLCR) and lean body mass (LBM) were identified as significant predictors of veliparib CLR/F and central volume of distribution, respectively. For a typical subject (LBM, 48 kg; CLCR, 95 mL/min), total clearance (CLR/F + CLNR/F), and central and peripheral volume of distribution for veliparib were estimated as 17.3 L/h, 98.7 L, and 48.3 L, respectively. At least 50% inhibition of PAR levels in PBMCs was observed at dose levels ranging from 50 to 500 mg.

Population Pharmacokinetics of an Intranasally Administered Combination of Oxymetazoline and Tetracaine in Healthy Volunteers

The primary objective of the current investigation was to establish the pharmacokinetic characteristics of oxymetazoline and tetracaines primary metabolite, para‐butylaminobenzoic acid (PBBA), after the intranasal administration of oxymetazoline/tetracaine. Thirty‐six subjects contributing a total of 1791 plasma concentration results from 2 open‐label trials were utilized. Model development was achieved using data from the second trial (N = 24) in which 0.3 mg oxymetazoline/18 mg tetracaine was administered. External model validation utilized data from the first trial (N = 12), which included doses of 0.3 mg oxymetazoline/18 mg tetracaine and 0.6 mg oxymetazoline/36 mg tetracaine. Oxymetazoline and PBBA dispositions were described by a 2‐compartment model with first‐order absorption. An allometric model for body weight was included on volumes and clearances to describe unexplained between‐subject variability. The final oxymetazoline parameter estimates were ka 4.41 h−1; peripheral volume 418 L; clearance 66.4 L/h; central volume 6.97 L; and intercompartmental clearance 419 L/h for a 70‐kg subject. The final PBBA parameter estimates were ka 8.51 h−1; peripheral volume 32.0 L; clearance 16.7 L/h; central volume 29.8 L; and intercompartmental clearance 2.43 L/h for a 70‐kg subject. Between‐subject variability ranged from 14% to 39% for oxymetazoline and from 10% to 94% for PBBA.

Abstract CT101: A model-based exposure-response (E-R) assessment of a nivolumab (NIVO) 4-weekly (Q4W) dosing schedule across multiple tumor types

Introduction: The anti-PD-1 checkpoint inhibitor NIVO provides favorable safety and efficacy when administered at 3 mg/kg Q2W across multiple tumor types. Alternative dosing schedules would provide flexibility and offer benefits to patients and prescribers. A well-established understanding of NIVO clinical pharmacology, robust clinical data across multiple tumor types and well characterized, relatively flat E-R relationships for efficacy and safety support the use of model-based approaches to qualify other potential NIVO doses and schedules. Methods: The feasibility of extending the dosing interval of NIVO from Q2W to Q4W was investigated using a combination of quantitative clinical pharmacology analyses and safety assessments. The predicted benefit-risk profile of NIVO 480 mg Q4W relative to 3 mg/kg Q2W was assessed by the following analyses: (1) comparison of NIVO exposures produced by 3 mg/kg Q2W and 480 mg Q4W across tumor types; (2) evaluation of NIVO exposure margins for safety relative to the well-tolerated dose of 10 mg/kg Q2W; (3) comparison of predicted risk of experiencing adverse events (Gr3+ AEs, immune-mediated AEs) with 480 mg Q4W relative to 3 mg/kg Q2W across indications of melanoma, NSCLC, RCC, UC, HN and (4) comparison of predicted objective tumor response (OR) and overall survival with NIVO 480 mg Q4W relative to 3 mg/kg Q2W in patients with melanoma, NSCLC, and RCC. Results: Steady-state peak, time-averaged, and trough NIVO concentrations predicted with 480 mg Q4W were approximately 44% higher, 4% higher, and 18% lower, respectively, compared with 3 mg/kg Q2W. The aggregate of safety data accumulated for NIVO up to a dose level of 10 mg/kg Q2W in multiple tumor types provides a wide safety margin for the maximum concentration values expected with 480 mg Q4W. The steady-state exposures produced by 480 mg Q4W were lower than the corresponding exposures with 10 mg/kg Q2W, which has been shown to have acceptable safety and tolerability. The predicted probabilities of achieving an OR with NIVO 480 mg Q4W were similar to those with 3 mg/kg Q2W ( Conclusion: With a well-established understanding of NIVO clinical pharmacology, robust clinical data across multiple tumor types and well-characterized E-R relationships for efficacy and safety, the differences in exposures produced by a NIVO schedule of 480 mg Q4W relative to 3 mg/kg Q2W dosing schedule are not expected to result in clinically meaningful differences in the safety and efficacy of NIVO. The proposed 480 mg Q4W schedule has been incorporated into NIVO clinical trials (NCT02713867, NCT02714218) across multiple tumor types. Citation Format: Xiaochen Zhao, Vijay Ivaturi, Mathangi Gopalakrishnan, Jun Shen, Yan Feng, Paul Statkevich, Eric Richards, Michelle Rashford, Vicki Goodman, Joga Gobburu, Akintunde Bello, Amit Roy, Shruti Agrawal. A model-based exposure-response (E-R) assessment of a nivolumab (NIVO) 4-weekly (Q4W) dosing schedule across multiple tumor types [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT101. doi:10.1158/1538-7445.AM2017-CT101

Lacosamide Pharmacokinetics in a Critically Ill Patient Receiving Continuous Venovenous Hemofiltration

Lacosamide is a new‐generation antiepileptic drug (AED) that is eliminated by both hepatic and renal mechanisms. Lacosamide elimination by continuous renal replacement therapy (CRRT) has never been studied. The objective of this case report was to describe lacosamide pharmacokinetics in the setting of CRRT. We describe a single patient admitted to the study center with status epilepticus and multiorgan failure. The patient required both continuous venovenous hemofiltration (CVVH) and several AEDs. He was receiving intravenous lacosamide 200 mg twice/day at steady state prior to sampling. Plasma lacosamide concentrations were derived using a validated high‐performance liquid chromatography method. Parameters were calculated using Phoenix WinNonlin 7.1 software. The peak concentration at steady state was 7.7 mg/L, the trough concentration was 5.9 mg/L (goal 5–12 mg/L). The volume of distribution was 0.7 L/kg, the elimination half‐life was 21 hours, and the sieving coefficient was 0.8 (± 0.06). Lacosamide was cleared by CVVH as demonstrated by the sieving coefficient, but plasma concentrations remained within goal range throughout the dosing interval. These results may suggest that lacosamide 200 mg twice/day is a useful dosing strategy for critically ill patients who require CVVH.

Development and validation of a HPLC-UV assay for quantification of levetiracetam concentrations in critically ill patients undergoing continuous renal replacement therapy

Limited clinical data exists on the effects of continuous renal replacement therapy (CRRT) on drug pharmacokinetics. A high-performance liquid chromatography with ultraviolet detection method was developed and validated to determine levetiracetam concentrations in human plasma and CRRT effluent samples. Five hundred microliters of human plasma and 250 μL effluent samples were used to quantify levetiracetam. Plasma samples were purified by protein precipitation, evaporated under nitrogen gas at room temperature and reconstituted in 50 mm potassium dihydrogen phosphate buffer (pH of 4.5). Reverse-phase chromatographic separation was achieved within 20 min using a mobile phase eluting gradient of 50 mm potassium dihydrogen phosphate and acetonitrile. UV detection was set at 195 nm. The calibration curve was found to be linear over the range of 2-80μg/mL. Inter- and intra-day precisions were < 8% for both plasma and effluent samples. The accuracy was determined to be within -12-10% of nominal concentrations. The method was selective and sensitive with a lower limit of quantification of 2 μg/mL. Overall recovery of levetiracetam from plasma was ~100%. The validated assay was successfully applied in a pharmacokinetic study to determine potential dose adjustments in patients undergoing CRRT and receiving levetiracetam.

Bayesian Forecasting Tool to Predict the Need for Antidote in Acute Acetaminophen Overdose

Acetaminophen (APAP) overdose is the leading cause of acute liver injury in the United States. Patients with elevated plasma acetaminophen concentrations (PACs) require hepatoprotective treatment with N‐acetylcysteine (NAC). These patients have been primarily risk‐stratified using the Rumack–Matthew nomogram. Previous studies of acute APAP overdoses found that the nomogram failed to accurately predict the need for the antidote. The objectives of this study were to develop a population pharmacokinetic (PK) model for APAP following acute overdose and evaluate the utility of population PK model–based Bayesian forecasting in NAC administration decisions.

Exposure–Response of Veliparib to Inform Phase II Trial Design in Refractory or Relapsed Patients with Hematological Malignancies

Purpose: A phase I trial of veliparib in combination with topotecan plus carboplatin (T+C) demonstrated a 33% objective response rate in patients with hematological malignancies. The objective is to perform exposure–response analysis to inform the phase II trial design. Experimental Design: Pharmacokinetic, efficacy, and safety data from 95 patients, who were administered 10 to 100 mg b.i.d. doses of veliparib for either 8, 14, or 21 days with T+C, were utilized for exposure–efficacy (objective response and overall survival) and exposure–safety (≥grade 3 mucositis) analysis. Multivariate cox proportional hazards and logistic regression analyses were conducted. The covariates evaluated were disease status, duration of treatment, and number of prior therapies. Results: The odds of having objective response were 1.08-fold with 1,000 ng/hr/mL increase in AUC, 1.8-fold with >8 days treatment, 2.8-fold in patients with myeloproliferative neoplasms (MPN), and 0.5-fold with ≥2 prior therapies. Based on analysis of overall survival, hazard of death decreased by 1.5% for 1,000 ng/hr/mL increase in AUC, 39% with >8 days treatment, 44% in patients with MPN, while increased by 19% with ≥2 prior therapies. The odds of having ≥grade 3 mucositis increased by 29% with 1,000 ng.h/mL increase in AUC. Conclusions: Despite shallow exposure–efficacy relationship, doses lower than 80 mg do not exceed veliparib single agent preclinical IC50. Shallow exposure–mucositis relationship also supports the 80-mg dose. Based on benefit/risk assessment, veliparib at a dose of 80 mg b.i.d. for at least 14 days in combination with T+C is recommended to be studied in MPN patients. Clin Cancer Res; 23(21); 6421–9. ©2017 AACR.