A regulatory perspective on the role of drug interactions in antiretroviral drug development

Office of New Drugs, Division of Antiviral Products, US Food and Drug Administration, Silver Spring, Maryland 20993, USA.
Current opinion in HIV and AIDS (Impact Factor: 4.68). 06/2008; 3(3):325-9. DOI: 10.1097/COH.0b013e3282f5f509
Source: PubMed


To provide a regulatory perspective on the role of drug interaction information in the development of antiretroviral drugs. Additionally, this review highlights novel studies that provided important information for the safe and effective use of antiretroviral medications. The management of drug interactions in HIV therapy becomes more complex with the introduction of each new drug because many antiretroviral drugs are involved in multiple metabolic and transporter-based interactions. Therefore, a comprehensive preclinical evaluation to characterize a new drug's metabolic pathway(s) followed by in-vivo studies is critical for the safe use of combination antiretroviral therapy.
This review highlights published studies to illustrate several clinical and regulatory issues for in-vivo drug interaction studies such as general design issues, study-population selection, study-design options, use of historical controls and interpretation of results.
Early identification of potential drug interactions can help identify and prioritize clinically important interaction studies essential to the overall development process. Understanding the clinical implications and management of drug interactions can lead to more effective long-term therapy, reduce toxicity, and delay the development of resistance.

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    ABSTRACT: Combination antiretroviral therapy has improved the morbidity and mortality of HIV-infected patients worldwide. As patients live longer, management of HIV infection extends to treatment of a wide spectrum of co-morbid conditions. Pharmacokinetic interactions are common among antiretroviral drugs when they are used in combination and along with treatments for other conditions. This review discusses the clinical significance of drug interactions among antiretroviral drugs and other medications, resources to use in assessing drug interaction potential, and some key principles to follow when managing patients prescribed potentially interacting drugs. Targeted pharmacokinetic drug interaction studies and extrapolations on the basis of potential mechanism of interactions provide an initial basis for recommendations regarding use of certain drug combinations. Some unexpected interactions have emerged in the literature through case reports in which untoward effects were observed. Management of patients on multiple drug therapy can be a challenge. The key to safe and effective therapy relies on the clinician's vigilance in their ongoing assessment of interaction potential among drugs prescribed to each patient, the significance for such interactions, the need for modification to therapy, and close follow up to assess safety and toxicity.
    No preview · Article · Jun 2008 · Current opinion in HIV and AIDS
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    ABSTRACT: Knowledge on the safety of new medicines is limited at the time of market entry. Nearly half of all drugs used to treat HIV registered in the EU required ≥1 Direct Healthcare Professional Communication (DHPC) in the past 10 years for safety issues identified post-approval. The aim was to evaluate the extent to which regulators and industry have addressed the risk of safety issues for HIV drugs based on prior experience with other drugs in the same class and whether doing so impacts development time of these drugs. HIV drugs receiving ≥1 DHPC in the Netherlands between January 1999 and December 2008 were identified. Each drug with a DHPC ('index' drug) was paired with subsequently approved HIV drug(s) in the same class (Anatomical Therapeutic Chemical [ATC] 4th level) ['follow-on' drugs]. Characteristics of safety issues were extracted from the DHPCs of the 'index' drugs. European Public Assessment Reports (EPARs) were reviewed regarding whether the safety issues had been considered during development and approval. Consideration of previously identified safety issues in 'follow-on' drug applications was assessed regarding attention paid to adverse drug reaction (ADR) symptoms in pre-marketing studies, Summary of Product Characteristics (SmPC) and postmarketing commitments, and whether size of the safety population was in accordance with Regulatory guidelines. 'Index' drugs were also paired with drugs in the same class already on the market ('older' drugs). For 'older' drugs, we identified whether the safety issue led to appropriate changes in the current SmPC (January 2011) compared with the SmPC at the time of marketing authorization. Clinical development time was assessed using time from first patent application to market authorization as proxy, and comparison was made between 'index' and 'follow-on' drugs. For 9 (43%) of the 21 centrally authorized HIV drugs, 11 serious safety issues that required a DHPC were identified. Two drugs were excluded from our analysis (DHPCs related to contamination/medication error). Six 'index' drugs were paired, each with one to six 'follow-on' drugs. Three concerned drug-drug interactions (DDIs); the other three were intracranial haemorrhage, neuromuscular weakness and severe skin/hepatic reactions. All but one 'follow-on' drug had information in the EPAR on that specific ADR (i.e. attention was paid to the ADR). The DDIs were addressed in pre-marketing studies and/or the SmPC. Two of the other ADRs were addressed by postmarketing surveillance commitments; intracranial haemorrhage was not addressed. Three safety issues for two 'index' drugs could not be paired with a 'follow-on' drug as no drug in the same class was approved after the corresponding DHPCs were issued. Five of the nine safety issues were added to at least one of the current SmPCs for the 'older' drugs already on the market at the time of DHPC issue. Two safety issues were already in the SmPC of the 'older' drugs at time of market approval and two were not introduced into the SmPC of 'older' drugs. Population size to assess short-term safety complied with the guidelines for four 'index', seven 'follow-on' and three 'older' drugs; population size to assess long-term safety complied for one, three and two drugs, respectively. For five drugs, EPARs did not provide adequate information on population size. No statistically significant difference in development time between 'index' and 'follow-on' drugs was found. Generally, safety issues were taken into account in the approval process of other drugs in the class. The approaches were different and determined by the nature of the ADR. Taking safety issues into account in the approval process did not seem to impact on the time taken to perform the pre-approval clinical programme.
    No preview · Article · Nov 2011 · Drug Safety