Optimizing Research to Speed Up Availability of Pediatric Antiretroviral Drugs and Formulations.

Globally 1.8 million children are living with human immunodeficiency virus (HIV), yet only 51% of those eligible actually start treatment. Research and development (R&D) for pediatric antiretrovirals (ARVs) is a lengthy process and lags considerably behind drug development in adults. Providing safe, effective, and well-tolerated drugs for children remains critical to ensuring scale-up globally. We review current approaches to R&D for pediatric ARVs and suggest innovations to enable simplified, faster, and more comprehensive strategies to develop optimal formulations. Several approaches could be adopted, including focusing on a limited number of prioritized formulations and strengthening existing partnerships to ensure that pediatric investigation plans are developed early in the drug development process. Simplified and more efficient mechanisms to undertake R&D need to be put in place, and financing mechanisms must be made more sustainable. Lessons learned from HIV should be shared to support progress in developing pediatric formulations for other diseases, including tuberculosis and viral hepatitis.

Pharmacokinetics of Antiretroviral Agents in Pregnant Individuals Living With HIV: Current Status and Considerations for Study Design and Interpretation.

Determining the appropriate dosing regimens of antiretroviral (ARV) drugs for pregnant individuals living with HIV-1 infection is critical to maximize maternal health and prevent perinatal HIV transmission. Throughout pregnancy, pharmacokinetics (PK) of ARVs can be significantly altered due to physiological, anatomic, and metabolic changes. As such, conducting PK studies of ARVs during pregnancy is crucial to optimize dosing regimens. In this article, we summarize available data, key issues, challenges, and considerations in interpreting results of ARV PK studies in pregnant individuals. Discussion topics include the choice of the reference population (postpartum vs historical control), pregnancy trimester-dependent changes in ARV PK, effects of pregnancy on once- versus twice-daily dosing, factors to consider for ARVs that are administered with a PK booster such as ritonavir and cobicistat, and considerations when evaluating the effects of pregnancy on unbound ARV concentrations. Common approaches for the translation of the results into clinical recommendations and rationales and considerations when making clinical recommendations are summarized. Currently, limited PK data in pregnancy are available with long-acting ARVs. Collection of PK data to characterize the PK profile of long-acting ARVs is an important goal shared by many stakeholders.

Considerations and Challenges in the Remdesivir COVID-19 Pediatric Development Program.

The US Food and Drug Administration is committed to the development of effective antiviral regimens for pediatric patients with coronavirus disease 2019 (COVID-19), including infants and neonates. On April 25, 2022, the approved indication of remdesivir (RDV) was expanded to include pediatric patients 28 days and older and weighing at least 3 kg with positive results of direct severe acute respiratory syndrome coronavirus 2 viral testing, who are: Hospitalized, or Not hospitalized and have mild to moderate COVID-19 and are at high risk for progression to severe COVID-19, including hospitalization or death. Given the similar course of COVID-19 in adults and pediatric patients, the approval of RDV for use in pediatric patients is supported by the safety and efficacy data from adequate and well-controlled phase 3 trials in adults and adolescents; and by the safety and pharmacokinetic data from a single-arm, open-label, phase 2/3 pediatric clinical trial of 53 pediatric patients at least 28 days of age and weighing at least 3 kg with confirmed severe acute respiratory syndrome coronavirus 2 infection and mild, moderate, or severe COVID-19. At the time of the April 25, 2022, approval action, the US Food and Drug Administration also revoked the emergency use authorization for RDV that previously covered this pediatric population. This article summarizes key issues and regulatory considerations involved in the RDV COVID-19 pediatric development program, including the evolution of the emergency use authorization issued for RDV as results from registrational studies became available, and discusses lessons learned.

Characterization of Plasma Protein Alterations in Pregnant and Postpartum Individuals Living With HIV to Support Physiologically-Based Pharmacokinetic Model Development.

Background: Alterations in plasma protein concentrations in pregnant and postpartum individuals can influence antiretroviral (ARV) pharmacokinetics. Physiologically-based pharmacokinetic (PBPK) models can serve to inform drug dosing decisions in understudied populations. However, development of such models requires quantitative physiological information (e.g., changes in plasma protein concentration) from the population of interest. Objective: To quantitatively describe the time-course of albumin and α1-acid glycoprotein (AAG) concentrations in pregnant and postpartum women living with HIV. Methods: Serum and plasma protein concentrations procured from the International Maternal Pediatric Adolescent AIDS Clinical Trial Protocol 1026s (P1026s) were analyzed using a generalized additive modeling approach. Separate non-parametric smoothing splines were fit to albumin and AAG concentrations as functions of gestational age or postpartum duration. Results: The analysis included 871 and 757 serum albumin concentrations collected from 380 pregnant (~20 to 42 wks gestation) and 354 postpartum (0 to 46 wks postpartum) women, respectively. Thirty-six and 32 plasma AAG concentrations from 31 pregnant (~24 to 38 wks gestation) and 30 postpartum women (~2-13 wks postpartum), respectively, were available for analysis. Estimated mean albumin concentrations remained stable from 20 wks gestation to term (33.4 to 34.3 g/L); whereas, concentrations rapidly increased postpartum until stabilizing at ~42.3 g/L 15 wk after delivery. Estimated AAG concentrations slightly decreased from 24 wks gestation to term (53.6 and 44.9 mg/dL) while postpartum levels were elevated at two wks after delivery (126.1 mg/dL) and subsequently declined thereafter. Computational functions were developed to quantitatively communicate study results in a form that can be readily utilized for PBPK model development. Conclusion: By characterizing the trajectory of plasma protein concentrations in pregnant and postpartum women living with HIV, our analysis can increase confidence in PBPK model predictions for HIV antiretrovirals and better inform drug dosing decisions in this understudied population.

Optimizing Pharmacology Studies in Pregnant and Lactating Women Using Lessons From HIV: A Consensus Statement.

Information on the extent of drug exposure to mothers and infants during pregnancy and lactation normally becomes available years after regulatory approval of a drug. Clinicians face knowledge gaps on drug selection and dosing in pregnancy and infant exposure during breastfeeding. Physiological changes during pregnancy often result in lower drug exposures of antiretrovirals, and in some cases a risk of reduced virologic efficacy. The International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) network and the World Health Organization (WHO)-convened Pediatric Antiretrovirals Working Group collaboratively organized a workshop of key stakeholders in June 2019 to define key standards to generate pharmacology data for antiretrovirals to be used among pregnant and lactating women; review the antiretroviral product pipeline; describe key gaps for use in low-income and middle-income countries; and identify opportunities to undertake optimal studies allowing for rapid implementation in the clinical field. We discussed ethical and regulatory principles, systemic approaches to obtaining data for pregnancy pharmacokinetic/pharmacodynamic (PK/PD) studies, control groups, optimal sampling times during pregnancy, and pharmacokinetic parameters to be considered as primary end points in pregnancy PK/PD studies. For lactation studies, the type of milk to collect, ascertainment of maternal adherence, and optimal PK methods to estimate exposure were discussed. Participants strongly recommended completion of preclinical reproductive toxicology studies prior to phase III, to allow study protocols to include pregnant women or to allow women who become pregnant after enrolment to continue in the trial. The meeting concluded by developing an algorithm for design and interpretation of results and noted that recruitment of pregnant and lactating women into clinical trials is critical.

Enhanced and Timely Investigation of ARVs for Use in Pregnant Women.

BACKGROUND: Concerns have been voiced that the exclusion of pregnant women from clinical trials results in a lack of safety and pharmacokinetic data for antiretroviral drugs (ARVs) in pregnancy, creating clear risks to pregnant women living with HIV (PWLHIV), and their infants. SETTING: The World Health Organization convened a Paediatric Antiretroviral Drug Optimization group meeting, December 10-12, 2018, in Geneva, Switzerland. METHODS: The group, comprised of clinicians, scientists, HIV program managers, regulators, and community representatives, were tasked to consider how ARVs are studied in PWLHIV, define alternative approaches to studying ARVs in PWLHIV, identify ways to shorten the timeline to determine safe use of new agents during pregnancy, and define strategies to collaborate with regulators and industry to change longstanding practices. RESULTS: Most new ARVs are not studied in pregnant populations until after drug licensure, primarily opportunistically among women who become pregnant while taking the ARV of interest. Acceleration of the timeline will require earlier completion of preclinical studies and a new paradigm, namely-under certain conditions-allow women who become pregnant while participating in phase III ARV studies the option of remaining on study and enroll pregnant women into phase III trials of new agents to obtain preliminary safety and dosing and efficacy data. CONCLUSION: A revision of the current approach to the study of antiretrovirals in pregnant women is urgently needed to improve timely access and safe use of new agents during pregnancy.

Considerations and challenges in developing novel long-acting antiretrovirals modalities for treatment and prevention of HIV-1 infection: a regulatory perspective.

PURPOSE OF REVIEW: Outline some regulatory considerations and scientific challenges related to the development of long-acting antiretrovirals (ARVs) for the treatment and prevention of HIV-1 infection. RECENT FINDINGS: Poor adherence to oral ARV regimens continues to pose challenges for effective treatment and prevention of HIV-1 infection. The development of long-acting ARV modalities for treatment and prevention of HIV-1 infection is emerging as a promising alternative to the current treatment and prevention paradigm and has gained considerable interest. SUMMARY: The development of long-acting ARVs can present some unique drug development challenges. Advance planning and prioritization of studies early in development can facilitate the development of long-acting ARVs for the prevention and treatment of HIV-1 infection for all populations, including pediatric patients and pregnant women.

Regulatory challenges in developing long-acting antiretrovirals for treatment and prevention of HIV infection.

PURPOSE OF REVIEW: To outline some of the regulatory challenges inherent to the development of long-acting antiretrovirals (ARVs) for the treatment or prevention of HIV infection. RECENT FINDINGS: Despite advances in drug development that have reduced ARV dosing to once daily, suboptimal drug adherence remains an obstacle to successful HIV treatment. Further, large randomized trials of once daily oral ARVs for preexposure prophylaxis (PrEP) have shown that drug adherence correlates strongly with prophylactic effect and study outcomes. Thus, the prospect of developing long-acting ARVs, which may mitigate drug adherence issues, has attracted considerable attention lately. SUMMARY: Because of their pharmacokinetic properties, the development of long-acting ARVs can present novel regulatory challenges. Chief among them is determining the appropriate dosing regimen, the need for an oral lead-in, and whether existing data with an approved oral agent, if available, can be leveraged for a treatment or prevention indication. For PrEP, because validated biomarkers are lacking, additional nonclinical studies and evaluation of tissue concentrations in multiple compartments may be necessary to identify optimal dosages. Study design and choice of controls for registrational trials of new long-acting PrEP agents might also prove challenging following the availability of an oral PrEP drug.