Challenges and opportunities in establishing scientific and regulatory standards for assuring therapeutic equivalence of modified release products: workshop summary report

Assessment of Manufacturing Related Deficiencies for Modified Release Tablet in Abbreviated New Drug Applications

Generic drugs play an important role in public health. However, the first review cycle approval rate for Abbreviated New Drug Applications (ANDAs) is generally low. To identify if the drug product (DP) manufacturing related deficiencies are the potential root causes of low first review cycle approval of the modified release (MR) tablet ANDAs, we collected and analyzed the review recommendations from each review discipline and the DP manufacturing (process and facility) related deficiencies for original MR tablet ANDAs submitted between FY17 and FY19. We identified 193 original MR tablet ANDAs. The analysis showed that 12% of the applications were approved in first review cycle, while 88% received complete responses (CR). Of the 169 CR applications, 91% were found inadequate for multiple review disciplines. A total of 1345 DP manufacturing process-related deficiencies were issued to 184 ANDAs during the first review cycle. We have identified common deficiencies across ANDAs based on DP manufacturing process categories. The top deficiencies cited reasons include facilities are out of compliance/not ready to commercialize/not ready for inspection; critical process parameter (CPP) ranges are not proposed/proposed CPP ranges are too wide and/or not supported by studied range and no in-process controls (IPCs) are proposed/proposed IPCs acceptance criteria (limits) are too wide and/or not supported by observed data etc. Avoiding the common DP manufacturing deficiencies may reduce the need for issuing DP manufacturing related deficiencies in information requests (IRs), discipline review letters (DRLs), and CRs for MR tablet ANDAs.

Approval of modified-release products by FDA without clinical efficacy/safety studies: A retrospective survey from 2008 to 2017

In principle, approval of a modified-release (MR) drug product is based on evidence from pharmacokinetic (PK) and/or pharmacodynamic studies and clinical efficacy/safety studies. The purpose of this survey is (i) to explore the number of new drug applications (NDAs) of MR drug products, approved by the FDA, employ the PK study as a bridge to already-approved immediate-release drug products without conducting their own clinical efficacy/safety studies; and (ii) to understand the type of PK studies are required for such NDAs. To this end, we surveyed the approved records of MR drug products from 2008 to 2017 from the Drug@FDA website, and filtered pertinent information from FDA's assessment reports. A total of five out of 79 products were found. A single dose PK study was conducted to investigate the underlying drug release mechanisms in four of these products. For these products, the applicants also performed multiple dose PK equivalence studies, but the PK parameters used to support the equivalence were different among studies. Information regarding the exposure-response relationship was available for all selected products, which is fundamental for such cases. Although the difference in PK curve shapes is recognized as being critical for the clinical effectiveness, this evaluation was not performed in all selected cases, as indicated in FDA's assessment reports.

Biopharmaceutical Evaluation and CMC Aspects of Oral Modified Release Formulations

This article discusses the range of outcomes from biopharmaceutical studies of specific modified release (MR) product examples in preclinical models and humans. It touches upon five major biopharmaceutical areas for MR drug products: (1) evidence for regional permeability throughout the GI tract, (2) susceptibility to food-effect, (3) susceptibility to pH-effect, (4) impact of chronopharmacology in designing MR products, and (5) implications to narrow therapeutic index products. Robust bioperformance requires that product quality is met through a thorough understanding of the appropriate critical quality attributes that ensure reliable and robust manufacture of a MR dosage form. The quality-by-design (QbD) aspects of MR dosage form design and development are discussed with the emphasis on the regulatory view of the data required to support dosage form development.

Model-Informed Development and Registration of a Once-Daily Regimen of Extended-Release Tofacitinib

Extended‐release (XR) formulations enable less frequent dosing vs. conventional (e.g., immediate release (IR)) formulations. Regulatory registration of such formulations typically requires pharmacokinetic (PK) and clinical efficacy data. Here we illustrate a model‐informed, exposure–response (E‐R) approach to translate controlled trial data from one formulation to another without a phase III trial, using a tofacitinib case study. Tofacitinib is an oral Janus kinase (JAK) inhibitor for the treatment of rheumatoid arthritis (RA). E‐R analyses were conducted using validated clinical endpoints from phase II dose–response and nonclinical dose fractionation studies of the IR formulation. Consistent with the delay in clinical response dynamics relative to PK, average concentration was established as the relevant PK parameter for tofacitinib efficacy and supported pharmacodynamic similarity. These evaluations, alongside demonstrated equivalence in total systemic exposure between IR and XR formulations, provided the basis for the regulatory approval of tofacitinib XR once daily by the US Food and Drug Administration.

Interchangeability, Safety and Efficacy of Modified-Release Drug Formulations in the USA: The Case of Opioid and Other Nervous System Drugs

BACKGROUND AND OBJECTIVES

Modified-release drugs may provide clinical advantages compared to immediate-release forms and improve convenience to the patient and health outcomes. Concerns have been raised regarding interchangeability, efficacy, and safety of modified-release formulations. This study analyses all US Food and Drug Administration (FDA)-approved modified-release formulations and market trends, and illustrates how bioequivalence and safety of generic modified-release products compare to their respective brand name drugs and other generic drugs with different formulation design characteristics. This study also examines major concerns related to modified-release formulations: safety of opioids and bioequivalence of generic bupropion and methylphenidate.

METHODS

Study data were derived from the FDA electronic versions of the FDA's Orange Book (OB) and the FDA safety communications web page. Medicare Part D utilization and expenditures data were extracted from the Centers for Medicare and Medicaid.

RESULTS

In May 2015, 276 (11.9 %) of the 2325 active ingredients and fixed-dose combinations listed in the FDA's Orange Book had at least one modified-release form approved by the FDA. The number of approvals increased over time; 52.5 % of modified releases were approved in the period 2000-May 2015. The FDA required a risk evaluation and mitigation strategy (REMS) to ensure that the benefits of extended-release opioids outweighed its risks of overdose and abuse. The REMS involved 16 new drug applications and 25 abbreviated new drug applications.

CONCLUSIONS

The FDA addressed interchangeability problems with generic modified-release alternatives of bupropion and methylphenidate including lack of bioequivalence, reduced efficacy, and increased incidence of adverse events. Systematic post-marketing surveillance studies are needed to assess differences in safety, interchangeability, and efficacy of drugs with modified- and immediate-release formulations.

Use of partial AUC (PAUC) to evaluate bioequivalence--a case study with complex absorption: methylphenidate

PURPOSE

Methylphenidate modified-release products produce early and late peak concentrations critical for treatment of morning and afternoon symptoms of attention deficit hyperactivity disorder (ADHD). Standard bioequivalence (BE) criteria cannot be applied to these products. The performance of partial area under the drug concentration-time curve (PAUC), Cmax and AUCINF to assess BE were independently evaluated for two products.

METHODS

A two-stage analysis was performed on plasma data for two methylphenidate modified-release products (Product 1 and 2). Simulations using the fitted parameters determined how changes in fast absorption rate constant (K0Fast) and fraction available (F1) affected curve shape and BE determination using Cmax, AUCINF and PAUC.

RESULTS

The sensitivity of the mean PAUC(test)/PAUC(reference) ratios to changes in K0Fast(test) are product dependent. Product 1 mean PAUC(test)/PAUC(reference) ratios for PAUC0-4h are more responsive to both decreases and increases in K0Fast(test) than Product 2. Product 2 showed a greater response in the mean PAUC(test)/PAUC(reference) ratio for PAUC0-4h when the K0Fast(test) is decreased and less response as the value is increased.

CONCLUSIONS

PAUC estimated curve shape is sensitive to changes in absorption and are product specific, and may require a new PAUC metric for each drug. A non-product specific metric to assess curve shape is warranted.

Harmonization of regulatory approaches for evaluating therapeutic equivalence and interchangeability of multisource drug products: workshop summary report

Regulatory approaches for evaluating therapeutic equivalence of multisource (or generic) drug products vary among different countries and/or regions. Harmonization of these approaches may decrease the number of in vivo bioequivalence studies and avoid unnecessary drug exposure to humans. Global harmonization for regulatory requirements may be promoted by a better understanding of factors underlying product performance and expectations from different regulatory authorities. This workshop provided an opportunity for pharmaceutical scientists from academia, industry and regulatory agencies to have open discussions on current regulatory issues and industry practices, facilitating harmonization of regulatory approaches for establishing therapeutic equivalence and interchangeability of multisource drug products.