Use of Model-Informed Drug Development to Streamline Development of Long-Acting Products: Can These Successes Be Translated to Long-Acting Hormonal Contraceptives?

Long-acting contraceptives are the most effective reversible contraceptive methods. Increasing patients' access to these contraceptives may translate into fewer unintended pregnancies and lead to substantial individual and public health benefits. However, development of long-acting products can be complex and challenging. This review provides (a) an overview of representative development programs for long-acting antipsychotics as cases for conceptual translation to long-acting contraceptives, (b) several case examples on how modeling and simulation have been used to streamline the development of long-acting products, and (c) examples of challenges andopportunities in developing long-acting contraceptives and information on how exposure-response relationships of commonly used progestins may enable regulators and developers to rely on prior findings of effectiveness and safety from an approved contraceptive to streamline the development of long-acting contraceptives. The US Food and Drug Administration is seeking assistance from stakeholders to provide data from studies in which pharmacokinetic and pharmacodynamic or clinical outcomes of hormonal contraceptives were evaluated and not previously submitted.

Combined Oral Contraceptives As Victims of Drug Interactions.

Combined oral contraceptives (COCs) are widely used in women of reproductive age in the United States. Metabolism plays an important role in the elimination of estrogens and progestins contained in COCs. It is unavoidable that a woman using COCs may need to take another drug to treat a disease. If the concurrently used drug induces enzymes responsible for the metabolism of progestins and/or estrogens, unintended pregnancy or irregular bleeding may occur. If the concurrent drug inhibits the metabolism of these exogenous hormones, there may be an increased safety risk such as thrombosis. Therefore, for an investigational drug intended to be used in women with reproductive potential, evaluating its effects on the pharmacokinetics of COCs is important to determine if additional labeling is necessary for managing drug-drug interactions (DDIs) between the concomitant product and the COCs. It is challenging to determine when this clinical drug interaction study is needed, whether an observed exposure change of progestin/estrogen is clinically meaningful, and if the results of a clinical drug interaction study with one COC can predict exposure changes of unstudied COCs to inform labeling. In this review, we summarize the current understanding of metabolic pathways of estrogens and progestins contained in commonly used COCs and known interactions of these COCs as victim drugs and we discuss possible mechanisms of interactions for unexpected results. We also discuss recent advances, knowledge gaps, and future perspectives on this important topic. The review will enhance the understanding of DDIs with COCs and improve the safe and effective use of COCs. SIGNIFICANCE STATEMENT: This minireview provides an overview of the metabolic pathways of ethinyl estradiol and progestins contained in commonly used combined oral contraceptives (COCs) and significant drug interactions of these COCs as victims. It also discusses recent advances, knowledge gaps, future perspectives, and potential mechanisms for unexpected results of clinical drug interaction studies of COCs. This minireview will help the reader understand considerations when evaluating the drug interaction potential with COCs for drugs that are expected to be used concurrently.

Advancing Estimation of Hepatobiliary Clearances in Physiologically Based Pharmacokinetic Models of Rosuvastatin Using Human Hepatic Concentrations.

PURPOSE: To estimate hepatobiliary clearances of rosuvastatin via simultaneously fitting to reported human positron emission tomography (PET) data in the liver and gallbladder. METHODS: A hepatobiliary model incorporating five intrinsic hepatobiliary clearances (active uptake clearance at the sinusoidal membrane, efflux clearance by passive diffusion through the sinusoidal membrane, influx clearance by passive diffusion through sinusoidal membrane, clearance of biliary excretion at the canalicular membrane, and intercompartment clearance from the intrahepatic bile duct to the gallbladder) and three compartments (liver, intrahepatic bile duct, and gallbladder) was developed to simultaneously fit rosuvastatin liver and gallbladder data from a representative subject reported by Billington et al. (1). Two liver blood supply input functions, arterial input function and dual input function (using peripheral venous as an alternative to portal vein), were assessed. Additionally, the predictive performance between the established model and four reported models trained with only systemic exposure data, was evaluated by comparing simulated liver and gallbladder profiles with observations. RESULTS: The established hepatobiliary model well captured the kinetic profiles of rosuvastatin in the liver and gallbladder during the PET scans. Application of dual input function led to a marked underestimation of liver concentrations at the initial stage after i.v. dosing which cannot be offset by altering model parameter values. The simulated hepatobiliary profiles from three of the reported models demonstrated substantial deviation from the observed data. CONCLUSIONS: The present study highlights the necessity of using hepatobiliary data to verify and improve the predictive performance of hepatic disposition of rosuvastatin.

Response-guided telaprevir therapy in prior relapsers? The role of bridging data from treatment-naïve and experienced subjects.

The purpose of this report is to illustrate the US Food and Drug Administration's rationale for approving response-guided therapy (RGT) for telaprevir (TVR) in combination with pegylated interferon-α and ribavirin (P/R) for the treatment of adults with genotype 1 chronic hepatitis C who were prior relapsers. RGT was prospectively evaluated in two registration trials of treatment-naïve subjects. In these studies, RGT allowed subjects who achieved undetectable hepatitis C virus RNA from weeks 4 and 12, known as extended rapid virologic response (eRVR), to stop all treatments at 24 weeks. A patient without eRVR received an additional 36 weeks of P/R after 12 weeks of a TVR triple regimen (total of 48 weeks). However, RGT in prior P/R relapsers was not prospectively evaluated. Empirical cross-trial data indicated high sustained virologic response rates (>90%) in prior relapsers achieving eRVR, irrespective of P/R duration (24 or 48 weeks). Further analyses demonstrated that interferon responsiveness does not change in P/R-experienced subjects with a second round of P/R. The comparability in interferon responsiveness across treatment courses allowed us to bridge data between treatment-naïve and P/R-experienced subjects to support the approval of RGT in prior relapse subjects.

Why did the FDA approve efavirenz 800 mg when co-administered with rifampin?

OBJECTIVES: Literature reports regarding the efficacy of efavirenz (EFV) 600 mg with rifampin (RIF) are not consistent. Evaluation of a drug-drug interaction (DDI) study and supportive semi-mechanistic population pharmacokinetic (PK) analyses were undertaken to help delineate this issue. DESIGN/METHODS: DDI study and supportive semi-mechanistic population PK analyses were provided by BMS. Population PK analysis was based on six studies with intensive EFV PK sampling. An ACTG study with sparse PK sampling was used for model evaluation. Simulations compared EFV exposure at various doses in combination with RIF to EFV exposures at 600 mg once daily (QD). Effects of CYP2B6 genotypes on the magnitude of EFV-RIF interaction were also explored. RESULTS: In DDI study, co-administering EFV 600 mg QD and RIF reduced mean EFV exposure by ~ 30%. Population PK model provided acceptable predictive performance of central tendency and variability for EFV C0, Cmax, and AUC. Simulations predicted that increasing EFV to 800 mg QD with RIF would result in EFV AUC and Cmax similar to EFV 600 mg QD alone. EFV AUC and Cmax were ~ 2 times higher in subjects with reduced function CYP2B6 genotypes. However, the RIF effect was consistent across all genotypes. EFV dose adjustment to 800 mg QD did not increase the risk of overexposure compared to 600 mg EFV QD within each genotype. CONCLUSION: Dose adjustment based on matching systemic exposure was recommended to mitigate the potential for sub-therapeutic EFV exposures. Our review did not reveal any safety concerns in subjects receiving EFV 800 mg QD with RIF.

Clinical Pharmacology of Glucagon.

Glucagon was discovered about a hundred years ago and its role in health and disease is under continuous investigation. Glucagon is a counter regulatory hormone secreted by alpha cells of the pancreas in response to multiple stimuli. Although some of glucagon's actions and its clinical application have been described, clinical experience with glucagon has been historically overshadowed by that of insulin. To date, the role of glucagon's actions in pharmacotherapy has been under explored. Glucagon plays a considerable role as a hormonal regulator via its known actions on the liver. The rise in obesity and diabetes mellitus prevalence is bringing focus to glucagon's known physiological roles and possible clinical applications. Six glucagon products and a glucagon analog are approved for use in the United States. Clinical pharmacology studies provide crucial support of glucagon's actions as evident from comprehensive pharmacokinetics and pharmacodynamics evaluations in humans. Here, we briefly describe the established physiological role of glucagon in humans and its known relationship with disease. We later summarize the clinical pharmacology of available glucagon products with different routes of administration.

Leveraging Clinical Pharmacology Data to Assess Biosimilarity and Interchangeability of Insulin Products.

There is over a hundred years of clinical experience with insulin for the treatment of diabetes. The US Food and Drug Administration (FDA) approved the first insulin biosimilar interchangeable product in 2021 for improving glycemic control in adults and pediatric patients with type 1 diabetes mellitus and in adults with type 2 diabetes mellitus. Several recombinant insulin products are available in the United States, including the recently approved biosimilar insulins. The approval of the biosimilar insulin products was based on comparative analytical characterizations and comparative pharmacokinetic (PK) and pharmacodynamic (PD) data. The primary objective of this review is to discuss the scientific considerations in the demonstration of biosimilarity of a proposed insulin biosimilar to a reference product and the role of clinical pharmacology studies in the determination of biosimilarity and interchangeability. Euglycemic clamp studies are considered a "gold standard" for insulin PK and PD characterization and have been widely used to determine the time-action profiles of rapid-acting, intermediate-acting, and long-acting insulin products. Clinical pharmacology aspects of study design, including selection of appropriate dose, study population, PK, and PD end points, are presented. Finally, the role of clinical pharmacology studies in the interchangeability assessment of insulin and the regulatory pathways used for insulin and the experience with follow-on insulins and the two recently approved biosimilar insulin products is discussed.

Predicting Food Effects on Oral Extended-Release Drug Products: A Retrospective Evaluation.

Theoretically, the risk of food effects for extended-release (ER) products compared to IR products may be less because: (1) postprandial physiological changes are usually transient and last for 2-3 h only; and (2) the percentage of drug release from an ER product within the first 2-3 h post dose is usually small under both fasted and fed states. The major postprandial physiological changes that can affect oral absorption of ER drugs are delayed gastric emptying and prolonged intestinal transit. Oral absorption of ER drugs under fasted state mainly occurs in large intestine (colon and rectum) while the absorption of ER drugs under fed state occurs in both small and large intestines. We hypothesized that food effects for ER products are mainly caused by intestinal region-dependent absorption and food intake is more likely to increase rather than decrease the exposure of ER products due to a longer transit time and improved absorption in small intestine. For drugs with good absorption from large intestine, food effects on the area under the curve (AUC) of ER products are usually not expected. Our survey of oral drugs approved by the US FDA between 1998-2021 identified 136 oral ER drug products. Among the 136 ER drug products, 31, 6 and 99 products exhibited increased, decreased, and unchanged AUC under fed conditions, respectively. In general, when an ER product exhibits a fasted bioavailability (BA) relative to its corresponding immediate-release (IR) product between 80-125%, regardless the solubility or permeability of drug substances, substantial food effects on the AUC of ER product are generally not expected. If the fasted relative BA data are not available, a high in vitro permeability (i.e., Caco-2 or MDCK cell permeability comparable or higher than that of metoprolol) may inform no food effect on the AUC of an ER product of high-solubility (BCS class I and III) drug.

EXOGENOUS Sex Hormones and Sex Hormone Receptor Modulators in COVID-19: Rationale and Clinical Pharmacology Considerations.

Male patients with coronavirus disease 2019 (COVID-19) fare much worse than female patients in COVID-19 severity and mortality according to data from several studies. Because of this sex disparity, researchers hypothesize that the use of exogenous sex hormone therapy and sex hormone receptor modulators might provide therapeutic potential for patients with COVID-19. Repurposing approved drugs or drug candidates at late-stage clinical development could expedite COVID-19 therapy development because their clinical formulation, routes of administration, dosing regimen, clinical pharmacology, and potential adverse events have already been established or characterized in humans. A number of exogenous sex hormones and sex hormone receptor modulators are currently or will be under clinical investigation for COVID-19 therapy. In this review, we discuss the rationale for exogenous sex hormones and sex hormone receptor modulators in COVID-19 treatment, summarize ongoing and planned clinical trials, and discuss some of the clinical pharmacology considerations on clinical study design. To inform clinical study design and facilitate the clinical development of exogenous sex hormones and sex hormone receptor modulators for COVID-19 therapy, clinical investigators should pay attention to clinical pharmacology factors, such as dosing regimen, special populations (i.e., geriatrics, pregnancy, lactation, and renal/hepatic impairment), and drug interactions.

Antimicrobial Dose Selection under the Animal Rule.

The Food and Drug Administration's (FDA's) "Animal Rule" provides a unique regulatory pathway for drugs and biologics intended to treat serious or life-threatening conditions caused by exposure to lethal or permanently disabling chemical, biological, radiological, or nuclear agents when human efficacy studies are not ethical and field trials are not feasible. Human dose selection under the Animal Rule is based on integrating the totality of clinical pharmacology evidence collected in in vitro, animal, and human studies. This review discusses the necessary pharmacokinetic and pharmacodynamic information and methods for determining the effective human dose of antimicrobials under the Animal Rule and presents case studies illustrating the utility of a totality of evidence approach for different methods.

Impact of injection sites on clinical pharmacokinetics of subcutaneously administered peptides and proteins.

For most approved subcutaneously (SC) administered drug products in the US, the recommended injection sites (i.e., abdomen, thigh, and upper arm) are usually based on experience from phase 3 trials. Relative bioavailability data directly comparing the pharmacokinetics (PK) of different SC injection sites are often not available and the underlying mechanisms that may affect SC absorption have not been systematically investigated. In this study, we surveyed clinical PK data (AUC, Cmax, and Tmax) for SC administered drug products including therapeutic proteins and peptides based on literature and FDA database. The PK data after abdominal injection was used as a reference to determine the relative bioavailability of SC injections to the arm and thigh. The survey retrieved 19 immunoglobulin G (IgGs), 18 peptides/small proteins (molecular weight < 16 kDa), and 8 non-IgG proteins that had available clinical PK data from multiple SC injection sites. Among these, 5 (26%) IgGs, 9 (50%) peptides/small proteins, and 3 (38%) non-IgG proteins, exhibited injection site-dependent PK (i.e. PK differed by injection sites). Correlation analyses revealed that the PK of peptides/small proteins undergoing rapid SC absorption (Tmax ≤ 2 h), elimination (CL/F ≥ 39 L/h) or low plasma protein binding were more sensitive to injection sites. Similarly, non-IgG proteins (molecular weight ≥ 16 kDa) with high CL/F and low Tmax are associated with high risk of injection site-dependent SC absorption. IgGs with T1/2 < 15 days or Tmax < 5 days are more likely to show injection site-dependent SC absorption. Positive charge of the drug molecule (isoelectric point ≥8) may reduce SC absorption from all three injection sites but is not associated with high risk of injection site-dependent SC absorption. In summary, the results suggested that regional differences in pre-systemic catabolism and local SC blood flow potentially contribute injection site-dependent SC absorption of peptides/small proteins while local lymphatic flow and FcRn binding likely contribute to site-dependent SC absorption of IgGs.

Does Hepatic Impairment Affect the Exposure of Monoclonal Antibodies?

Limited information is available regarding the effect of hepatic impairment (HI) on the pharmacokinetics of monoclonal antibodies (mAbs). The results of an earlier report based on therapeutic proteins, including mAbs, approved through the end of 2012 were inconclusive due to limited HI data available at that time. New HI data for mAbs or antibody-drug conjugates (ADCs; with a focus on the mAb component) available between 2013 and 2018 were evaluated. The investigation indicates there is almost no data for severe HI, limited data for moderate HI, and abundant data for mild HI. A significant exposure decrease was found for several mAbs or ADCs and a trend for decreasing area under the concentration-time curve (AUC) was observed for other mAbs. Multiple potential mechanisms may contribute to the exposure decrease. Dose may need to be adjusted for patients with HI, after taking into account the exposure-response relationships for both efficacy and safety.

Biliary Excretion-Mediated Food Effects and Prediction.

Many orally administered drugs with negative food effects (i.e., lower exposure under fed conditions) are often primarily or partially eliminated by biliary excretion. The aim of this study is to assess the potential correlation between a negative food effect and biliary excretion. Correlation analysis was conducted using a training dataset containing 27 drugs which met the following criteria: (1) immediate-release formulations, (2) shows a negative food effect, (3) > 10% biliary clearance, and (4) does not undergo extensive metabolism. A correlation between fed-state biliary clearance (CLb,fed) and fasted-state biliary clearance (CLb,fast) (y = 1.81*x, R2 = 0.68) was observed. The 1.8-fold increase in biliary clearance was then used as a correction factor to improve physiologically based pharmacokinetic (PBPK) prediction of food effects for 12 test drugs. The mean deviations of predicted fed/fasting AUC ratio and Cmax ratio from clinically observed values were reduced from 32.4 to 17.2% and from 63.3 to 54.3%, respectively. In contrast to the positive food effects on most biopharmaceutics classification system (BCS) class II drugs for which food-stimulated bile flow increases drug solubility and absorption, our results suggest that the elimination of biliary excreted drugs is increased by food-stimulated bile flow, resulting in negative food effects.

Model-Informed Drug Development Approach Supporting Approval of Adalimumab (HUMIRA) in Adolescent Patients with Hidradenitis Suppurativa: a Regulatory Perspective.

On October 16, 2018, FDA expanded the adalimumab dosing regimen to adolescent hidradenitis suppurativa (HS) patients 12 years and older, weighing at least 30 kg without new clinical data. This approval was mainly supported by the model-informed drug development approach. Population pharmacokinetic simulations suggest body weight-tiered dosing regimens in adolescent patients will achieve similar exposure to adult patients across all weight range. Adalimumab has a well-established, 16-year long-term safety profile in various diseases in adult and pediatric populations. Current data of adalimumab in the pediatric population demonstrate no exposure-response relationship for adverse events. The effectiveness in adolescent patients was extrapolated from two adequate and well-controlled phase 3 studies in adult patients, assuming similar positive exposure-efficacy relationships in adults and adolescents. This article provides the insight of the application of MIDD on the adalimumab approval in adolescent HS patients and its implication on drug development and regulatory decision especially for pediatrics or rare diseases.

Assessing a drug for an eradicated human disease: US Food and Drug Administration review of tecovirimat for the treatment of smallpox.

The development and ultimate approval of tecovirimat for the antiviral treatment of smallpox, a disease that has been eradicated from the world for nearly 40 years, required a unique regulatory approach based on the US Food and Drug Administration's Animal Rule. We summarise the regulatory pathway and describe the challenges involved.

Effects of Sorbitol on the Pharmacokinetics of Lamivudine Solution and the FDA's Decision to Increase the Dose of Lamivudine Solution for Pediatric Patients.

The article by Adkison et al. described sorbitol effects on lamivudine exposures. The results indicate a plausible mechanism for lower lamivudine exposures in pediatric patients receiving the solution formulation with concomitant medications containing sorbitol. In this commentary, we discuss lower lamivudine exposures in pediatric patients receiving the solution formulation, the impact of sorbitol on lamivudine exposures, and the US Food and Drug Administration's (FDA's) decision to increase the dose of the lamivudine solution for all pediatric patients.