Nitin Mehrotra

Impact of Pharmacometric Analyses on New Drug Approval and Labelling Decisions

Pharmacometric analyses have become an increasingly important component of New Drug Application (NDA) and Biological License Application (BLA) submissions to the US FDA to support drug approval, labelling and trial design decisions. Pharmacometrics is defined as a science that quantifies drug, disease and trial information to aid drug development, therapeutic decisions and/or regulatory decisions. In this report, we present the results of a survey evaluating the impact of pharmacometric analyses on regulatory decisions for 198 submissions during the period from 2000 to 2008. Pharmacometric review of NDAs included independent, quantitative analyses by FDA pharmacometricians, even when such analysis was not conducted by the sponsor, as well as evaluation of the sponsor’s report. During 2000–2008, the number of reviews with pharmacometric analyses increased dramatically and the number of reviews with an impact on approval and labelling also increased in a similar fashion. We also present the impact of pharmacometric analyses on selection of paediatric dosing regimens, approval of regimens that had not been directly studied in clinical trials and provision of evidence of effectiveness to support a single pivotal trial. Case studies are presented to better illustrate the role of pharmacometric analyses in regulatory decision making.

U.S. Food and Drug Administration Approval: Obinutuzumab in Combination with Chlorambucil for the Treatment of Previously Untreated Chronic Lymphocytic Leukemia

On November 1, 2013, the U.S. Food and Drug Administration (FDA) approved obinutuzumab (GAZYVA; Genentech, Inc.), a CD20-directed cytolytic antibody, for use in combination with chlorambucil for the treatment of patients with previously untreated chronic lymphocytic leukemia (CLL). In stage 1 of the trial supporting approval, patients with previously untreated CD20-positive CLL were randomly allocated (2:2:1) to obinutuzumab + chlorambucil (GClb, n = 238), rituximab + chlorambucil (RClb, n = 233), or chlorambucil alone (Clb, n = 118). The primary endpoint was progression-free survival (PFS), and secondary endpoints included overall response rate (ORR). Only the comparison of GClb to Clb was relevant to this approval and is described herein. A clinically meaningful and statistically significant improvement in PFS with medians of 23.0 and 11.1 months was observed in the GClb and Clb arms, respectively (HR, 0.16; 95% CI, 0.11–0.24; P < 0.0001, log-rank test). The ORRs were 75.9% and 32.1% in the GClb and Clb arms, respectively, and the complete response rates were 27.8% and 0.9% in the GClb and Clb arms, respectively. The most common adverse reactions (≥10%) reported in the GClb arm were infusion reactions, neutropenia, thrombocytopenia, anemia, pyrexia, cough, and musculoskeletal disorders. Obinutuzumab was the first Breakthrough Therapy–designated drug to receive FDA approval. Clin Cancer Res; 20(15); 3902–7. ©2014 AACR.

Enzalutamide for Treatment of Patients with Metastatic Castration-Resistant Prostate Cancer Who Have Previously Received Docetaxel: U.S. Food and Drug Administration Drug Approval Summary

This article summarizes the regulatory evaluation that led to the full approval of enzalutamide (XTANDI, Medivation Inc.) by the U.S. Food and Drug Administration (FDA) on August 31, 2012, for the treatment of patients with metastatic castration-resistant prostate cancer who have previously received docetaxel. This approval was based on the results of a randomized, placebo-controlled trial which randomly allocated 1,199 patients with mCRPC who had received prior docetaxel to receive either enzalutamide, 160 mg orally once daily (n = 800), or placebo (n = 399). All patients were required to continue androgen deprivation therapy. The primary endpoint was overall survival. At the prespecified interim analysis, a statistically significant improvement in overall survival was demonstrated for the enzalutamide arm compared with the placebo arm [HR = 0.63; 95% confidence interval: 0.53–0.75; P < 0.0001]. The median overall survival durations were 18.4 months and 13.6 months in the enzalutamide and placebo arms, respectively. The most common adverse reactions (≥10%) included asthenia or fatigue, back pain, diarrhea, arthralgia, hot flush, peripheral edema, musculoskeletal pain, headache, and upper respiratory infection. Seizures occurred in 0.9% of patients on enzalutamide compared with no patients on the placebo arm. Overall, the FDAs review and analyses of the submitted data confirmed that enzalutamide had a favorable benefit–risk profile in the study patient population, thus supporting its use for the approved indication. The recommended dose is 160 mg of enzalutamide administered orally once daily. Enzalutamide represents the third product that the FDA has approved in the same disease setting within a period of 2 years. Clin Cancer Res; 19(22); 6067–73. ©2013 AACR.

Enrolling adolescents in disease/target-appropriate adult oncology clinical trials of investigational agents

The enrollment of adolescents with cancer in clinical trials is much lower than that of younger pediatric patients. For adolescents with “adult-type” cancers, lack of access to relevant trials is cited as one of the reasons for this discrepancy. Adolescents are generally not eligible for enrollment in adult oncology trials, and initial pediatric trials for many drugs are conducted years later, often after the drug is approved. As a result, accrual of adolescents to these trials may be slow due to off-label use, prospectively collected safety and efficacy data are lacking at the time of initial approval, and, most importantly, these adolescents have delayed access to effective therapies. To facilitate earlier access to investigational and approved drugs for adolescent patients with cancer, and because drug exposure is most often similar in adolescents and adults, we recommend the inclusion of adolescents (ages 12–17) in disease- and target-appropriate adult oncology trials. This approach requires careful monitoring for any differential safety signals, appropriate pharmacokinetic evaluations, and ensuring that ethical requirements are met. Inclusion of adolescents in adult oncology trials will require the cooperation of investigators, cooperative groups, industry, institutional review boards, and regulatory agencies to overcome real and perceived barriers. Clin Cancer Res; 23(1); 9–12. ©2016 AACR.

Canagliflozin use in patients with renal impairment—Utility of quantitative clinical pharmacology analyses in dose optimization

Canagliflozin (INVOKANA™) is approved as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus (T2DM). Canagliflozin inhibits renal sodium‐glucose co‐transporter 2 (SGLT2), thereby, reducing reabsorption of filtered glucose and increasing urinary glucose excretion. Given the mechanism of action of SGLT2 inhibitors, we assessed the interplay between renal function, efficacy (HbA1c reduction), and safety (renal adverse reactions). The focus of this article is to highlight the FDAs quantitative clinical pharmacology analyses that were conducted to support the regulatory decision on dosing in patients with renal impairment (RI). The metrics for assessment of efficacy for T2DM drugs is standard; however, there is no standard method for evaluation of renal effects for diabetes drugs. Therefore, several analyses were conducted to assess the impact of canagliflozin on renal function (as measured by eGFR) based on available data. These analyses provided support for approval of canagliflozin in T2DM patients with baseline eGFR ≥ 45 mL/min/1.73 m2, highlighting a data‐driven approach to dose optimization. The availability of a relatively rich safety dataset (ie, frequent and early measurements of laboratory markers) in the canagliflozin clinical development program enabled adequate assessment of benefit‐risk balance in various patient subgroups based on renal function.

Reporting guidelines for population pharmacokinetic analyses

The purpose of this work was to develop a consolidated set of guiding principles for reporting of population pharmacokinetic (PK) analyses based on input from a survey of practitioners as well as discussions between industry, consulting and regulatory scientists. The survey found that identification of population covariate effects on drug exposure and support for dose selection (where population PK frequently serves as preparatory analysis to exposure–response modeling) are the main areas of influence for population PK analysis. The proposed guidelines consider two main purposes of population PK reports (1) to present key analysis findings and their impact on drug development decisions, and (2) as documentation of the analysis methods for the dual purpose of enabling review of the analysis and facilitating future use of the models. This work also identified two main audiences for the reports: (1) a technically competent group responsible for in-depth review of the data, methodology, and results, and (2) a scientifically literate, but not technically adept group, whose main interest is in the implications of the analysis for the broader drug development program. We recommend a generalized question-based approach with six questions that need to be addressed throughout the report. We recommend eight sections (Synopsis, Introduction, Data, Methods, Results, Discussion, Conclusions, Appendix) with suggestions for the target audience and level of detail for each section. A section providing general expectations regarding population PK reporting from a regulatory perspective is also included. We consider this an important step towards industrialization of the field of pharmacometrics such that non-technical audience also understands the role of pharmacometrics analyses in decision making. Population PK reports were chosen as representative reports to derive these recommendations; however, the guiding principles presented here are applicable for all pharmacometric reports including PKPD and simulation reports.

Considerations for assessing the potential effects of antidiabetes drugs on cardiac ventricular repolarization: A report from the Cardiac Safety Research Consortium

Thorough QT studies conducted according to the International Council on Harmonisation E14 guideline are required for new nonantiarrhythmic drugs to assess the potential to prolong ventricular repolarization. Special considerations may be needed for conducting such studies with antidiabetes drugs as changes in blood glucose and other physiologic parameters affected by antidiabetes drugs may prolong the QT interval and thus confound QT/corrected QT assessments. This review discusses potential mechanisms for QT/corrected QT interval prolongation with antidiabetes drugs and offers practical considerations for assessing antidiabetes drugs in thorough QT studies. This article represents collaborative discussions among key stakeholders from academia, industry, and regulatory agencies participating in the Cardiac Safety Research Consortium. It does not represent regulatory policy.

Quantitative Understanding of QTc Prolongation and Gender as Risk Factors for Torsade de Pointes

Several risk factors for development of a potentially fatal ventricular arrhythmia, torsade de pointes, have been observed, including female gender. However, in most investigations, only few torsade events were included and/or rarely were postdose heart rate corrected QT (QTc) measurements included, as a surrogate of drug exposure. We developed a multivariate logistic regression model using data from 22,214 patients (33% women) with 84 torsade events (56% women) to evaluate the relationship between risk factors for torsade using data from four anti‐arrhythmic drug development programs. Before model development, we evaluated different QT/QTc postdose metrics (average, maximum, etc.) to determine which QT metric should be included into the model. The developed multivariate model showed that, after accounting for known risk factors for torsade and postdose QTc, that female gender remained a significant risk factor for torsade.

Esomeprazole FDA Approval in Children With GERD: Exposure-Matching and Exposure-Response.

Objectives: Food and Drug Administration approval of proton-pump inhibitors for infantile gastroesophageal reflux disease has been limited by intrapatient variability in the clinical assessment of gastroesophageal reflux disease. For children 1 to 17 years old, extrapolating efficacy from adults for IV esomeprazole was accepted. The oral formulation was previously approved in children. Exposure-response and exposure matching analyses were sought to identify approvable pediatric doses. Methods: Intragastric pH biomarker comparisons between children and adults were conducted. Pediatric doses were selected to match exposures in adults and were based on population pharmacokinetic (PK) modeling and simulations with pediatric esomeprazole data. Observed IV or oral esomeprazole PK data were available from 50 and 117 children, between birth and 17 years, respectively, and from 65 adults, between 20 and 48 years. A population PK model developed using these data was used to simulate steady-state esomeprazole exposures for children at different doses to match the observed exposures in adults. Results: Exposure-response relationships of intragastric pH measures were similar between children and adults. The PK simulations identified a dosing regimen for children that results in comparable steady-state area under the curve to that observed after 20 mg in adults. For IV esomeprazole, increasing the infusion duration to 10 to 30 minutes in children achieves matching Cmax values with adults. Conclusions: The exposure-matching analysis permitted approval of an esomeprazole regimen not studied directly in clinical trials. Exposure-response for intragastric pH-permitted approval for the treatment of gastroesophageal reflux disease in children in whom it was not possible to evaluate the adult primary endpoint, mucosal healing assessed by endoscopy.

Utility of Exposure‐Response Analysis in Regulatory Decision on the Selection of Starting Dose of Pasireotide for Cushing Disease

In 2012 the FDAapproved pasireotide (a cyclohexapeptide analogue of endogenous somatostatin) for the treatment of adult patients with Cushing disease for whom pituitary surgery is not an option or has not been curative.1 The recommended initial dosage is either 600 μg twice a day (BID) or 900 μg BID by subcutaneous injection (the calculated effective halflife was approximately 12 hours).2 Cushing disease is a rare disease that is caused by an adrenocorticotropic hormone (ACTH)-secreting pituitary adenoma and most commonly affects adult females. The elevated levels of ACTH secreted by pituitary tumors stimulate the adrenal glands to produce excess cortisol, thereby causing the subsequent development of the clinical signs and symptoms of hypercortisolism. It is estimated that currently there are about 40,000 patients with Cushing disease: United States ( 16,848), Japan ( 6,604), France, Germany, Italy, Spain, and the United Kingdom ( 16,120 in the EU).3 Adult patients (n = 162) with Cushing disease were randomized (1:1) to 2 treatment arms (2 doses: 600 μg BID and 900 μg BID) in the phase 3 pivotal study.4 There was no placebo arm included in the registration trial. The primary analysis was to compare each group’s response rate, defined as the proportion of patients with normalizedmean urinary free cortisol (mUFC) (ie, mUFC ULN [upper limit of normal, 145 nmol/day]) at the end of 6 months with a prespecified threshold of 15%. The magnitude of this threshold was primarily selected on the basis of clinical practice experience that a response rate >15% would represent a clinically meaningful improvement in Cushing disease.5 The 900-μg BID dose met the primary efficacy criterion with a response rate of 26% and a lower bound of the 2-sided 95% confidence interval (CI) of 17%, above the prespecified 15% threshold. The 600-μg BID dose did not meet the primary efficacy criterion with a response rate of 15% and a lower bound of the 2-sided 95%CI of 7%, below the prespecified 15% threshold. This would usually be particularly convincing evidence to recommend the approval of 900 μg BID only, despite the fact that the study was not designed to detect a statistical difference in efficacy between the 2 doses. However, despite randomization, the 2 dose groups were not balanced with respect to the baseline prognostic factor (ie, mUFC): the mean values of mUFC at baseline for the 600and 900-μg BID groups were 8.0 and 5.4 × ULN, respectively.4 More importantly, this phase 3 study documented a substantial elevation in glycated hemoglobin (HbA1c) levels (approximately 1.5% mean absolute increase on treatment from baseline) that occurred early and continued throughout the duration of the study.5 This finding is of particular concern because hyperglycemia is a known complication of hypercortisolism, and one of the goals of treating Cushing disease is to improve