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In vitro dissolution testing is widely used to mimic and predict in vivo performance of oral drug products in the gastrointestinal (GI) tract. This literature review assesses the current in vitro dissolution methodologies being employed to simulate and predict in vivo drug dissolution under fasted and fed conditions, with emphasis on immediate release (IR) solid oral dosage forms. Notable human GI physiological conditions under fasted and fed states have been reviewed and summarized. Literature results showed that dissolution media, mechanical forces, and transit times are key dissolution test parameters for simulating specific postprandial conditions. A number of biorelevant systems, including the fed stomach model (FSM), GastroDuo device, dynamic gastric model (DGM), simulated gastrointestinal tract models (TIM), and the human gastric simulator (HGS), have been developed to mimic the postprandial state of the stomach. While these models have assisted in expanding physiological relevance of in vitro dissolution tests, in general, these models lack the ability to fully replicate physiological conditions/processes. Furthermore, the translatability of in vitro data to an in vivo system remains challenging. Additionally, physiologically based pharmacokinetic (PBPK) modeling has been employed to evaluate the effect of food on drug bioavailability and bioequivalence. Here, we assess the current status of in vitro dissolution methodologies and absorption PBPK modeling approaches to identify knowledge gaps and facilitate further development of in vitro dissolution methods that factor in fasted and fed states. Prediction of in vivo drug performance under fasted and fed conditions via in vitro dissolution testing and modeling may potentially help efforts in harmonizing global regulatory recommendations regarding in vivo fasted and fed bioequivalence studies for solid oral IR products.

To guide developers of innovative and generic drug products that contain nanomaterials, the U.S. Food and Drug Administration issued the draft guidance for industry titled: "Drug Products, Including Biological Products, that Contain Nanomaterials" in December 2017. During the AAPS Guidance Forum on September 11, 2018, participants from industry, academia, and regulatory bodies discussed this draft guidance in an open setting. Two questions raised by the AAPS membership were discussed in more detail: what is the appropriate regulatory pathway for approval of drug products containing nanomaterials, and how to determine critical quality attributes (CQAs) for nanomaterials? During the meeting, clarification was provided on how the new FDA center-led guidance relates to older, specific nanomaterial class, or specific product-related guidances. The lively discussions concluded with some clear observations and recommendations: (I) Important lessons can be learned from how CQAs were determined for, e.g., biologics. (II) Publication of ongoing scientific discussions on strategies and studies determining CQAs of drug products containing nanomaterials will significantly strengthen the science base on this topic. Furthermore, (III) alignment on a global level on how to address new questions regarding nanomedicine development protocols will add to efficient development and approval of these much needed candidate nanomedicines (innovative and generic). Public meetings such as the AAPS Guidance Forum may serve as the place to have these discussions.

The Nanotechnology Risk Assessment Working Group in the Center for Drug Evaluation and Research (CDER) within the United States Food and Drug Administration (FDA) was established to assess the potential impact of nanotechnology on drug products. One of the working group’s major initiatives has been to conduct a comprehensive risk management exercise regarding the potential impact of nanomaterial pharmaceutical ingredients and excipients on drug product quality, safety, and efficacy. This exercise concluded that current review practices and regulatory guidance are capable of detecting and managing the potential risks to quality, safety, and efficacy when a drug product incorporates a nanomaterial. However, three risk management areas were identified for continued focus during the review of drug products containing nanomaterials: (1) the understanding of how to perform the characterization of nanomaterial properties and the analytical methods used for this characterization, (2) the adequacy of in vitro tests to evaluate drug product performance for drug products containing nanomaterials, and (3) the understanding of properties arising from nanomaterials that may result in different toxicity and biodistribution profiles for drug products containing nanomaterials. CDER continues to actively track the incorporation of nanomaterials in drug products and the methodologies used to characterize them, in order to continuously improve the readiness of our science- and risk-based review approaches. In parallel to the risk management exercise, CDER has also been supporting regulatory research in the area of nanotechnology, specifically focused on characterization, safety, and equivalence (between reference and new product) considerations. This article provides a comprehensive summary of regulatory and research efforts supported by CDER in the area of drug products containing nanomaterials and other activities supporting the development of this emerging technology.

In the past few decades, the development of medicine at the nanoscale has been applied to oral and parenteral dosage forms in a wide range of therapeutic areas to enhance drug delivery and reduce toxicity. An obvious response to these benefits is reflected in higher market shares of complex drug products containing nanomaterials than that of conventional formulations containing the same active ingredient. The surging market interest has encouraged the pharmaceutical industry to develop cost-effective generic versions of complex drug products based on nanotechnology when the associated patent and exclusivity on the reference products have expired. Due to their complex nature, nanotechnology-based drugs present unique challenges in determining equivalence standards between generic and innovator products. This manuscript attempts to provide the scientific rationales and regulatory considerations of key equivalence standards (e.g., in vivo studies and in vitro physicochemical characterization) for oral drugs containing nanomaterials, iron-carbohydrate complexes, liposomes, protein-bound drugs, nanotube-forming drugs, and nano emulsions. It also presents active research studies in bridging regulatory and scientific gaps for establishing equivalence of complex products containing nanomaterials. We hope that open communication among industry, academia, and regulatory agencies will accelerate the development and approval processes of generic complex products based on nanotechnology.

Doxil® is a complex parenteral doxorubicin (DOX) liposome formulation approved by the FDA. For generic doxorubicin liposomes, analyzing the release profile of DOX is important for quality control and comparability studies. However, there is no robust standard drug release assay available for doxorubicin liposomes. In this study, we describe a USP-4 apparatus assay capable of discriminating DOX liposomal formulations based on release profile. Establishment of the assay was hindered by limited DOX release from liposomes in physiological conditions at 37°C. The addition of NH4HCO3 to the release media facilitated DOX release proportionally to the salt concentration added but caused precipitation of released drug in USP-4 apparatus. Precipitation of DOX was avoided by adding hydroxypropyl-cyclodextrin (HP-CD) to the release medium. We optimized conditions for DOX release by varying a number of parameters such as: concentration of HP-CD, testing temperature, and concentration of tested samples. The optimized release medium contained: 100 mM NH4HCO3, 75 mM 2-(N-morpholino) ethanesulfonic acid (MES) and 5% w/v HP-CD, 5% w/v sucrose, 0.02% w/v NaN3 (pH 6). The drug release assay was performed at 45°C. The optimized release assay can discriminate between DOX liposomal formulations of different compositions, physicochemical properties, and prepared by different manufacturing methods. This indicates that the assay could be used to compare DOX release from generic DOX formulations to the innovator product Doxil®.

Various health communities have expressed concerns regarding whether average bioequivalence (BE) limits (80.00–125.00%) for the 90% confidence interval of the test-to-reference geometric mean ratio are sufficient to ensure therapeutic equivalence between a generic narrow therapeutic index (NTI) drug and its reference listed drug (RLD). Simulations were conducted to investigate the impact of different BE approaches for NTI drugs on study power, including (1) direct tightening of average BE limits and (2) a scaled average BE approach where BE limits are tightened based on the RLD’s within-subject variability. Addition of a variability comparison (using a one-tailed F test) increased the difficulty for generic NTIs more variable than their corresponding RLDs to demonstrate bioequivalence. Based on these results, the authors evaluate the fully replicated, 2-sequence, 2-treatment, 4-period crossover study design for NTI drugs where the test product demonstrates BE based on a scaled average bioequivalence criterion and a within-subject variability comparison criterion.