A Phase I/II, Multicenter, Open-Label, Noncomparative Study of the International Maternal, Pediatric, Adolescent AIDS Clinical Trials (IMPAACT) Group to Evaluate the Safety, Tolerability, Pharmacokinetics, and Antiviral Activity of Raltegravir (Isentress, MK-0518) in HIV-1 Infected Children and Adolescents

Integrase is one of three enzymes necessary for HIV replication. Integrase allows for the integration of HIV DNA (deoxyribonucleic acid) into the human genome. Raltegravir is a strong and selective inhibitor of HIV integrase. In adults, raltegravir has shown significant antiretroviral activity in clinical trials and is well tolerated. The purpose of this study was to determine the appropriate dose for raltegravir across the pediatric age range from 4 weeks (30 days) to 18 years of age, by acquiring short and long term safety data, intensive and population PK data, and efficacy experience with raltegravir in treatment-experienced, HIV-infected children and adolescents.

The study consisted of two sequential Stages: I and II. The dose finding period of Stage I was intended to examine the pharmacokinetics and short term tolerability and safety of raltegravir in a limited number of participants to permit dose selection for further study in Stage II. The dose finding algorithm required a preliminary assessment of data from the first 4 patients of each cohort (termed a "mini-cohort"). Failure to meet PK targets required dose adjustments, contingent upon the mini-cohort's dose having met safety criteria, followed by reassessment of safety and PK data from the new mini-cohort dose. When a mini-cohort dose had passed both safety and PK criteria, further accrual to and an assessment of results from the full cohort could occur. Again, failure to meet PK targets required dose adjustments contingent upon the full cohort's dose having met safety criteria with subsequent PK and safety evaluation of data from a new cohort taking the new dose.

Chronic dosing, which includes Stage I extension (the period after Stage I dose finding) and Stage II (additional participants enrolled), was intended to provide longer term safety and antiviral activity data in a larger sample of participants. Participants accrued into Stage I and treated only at the dose ultimately selected for their cohorts were combined with those accrued into Stage II, where all patients received only the final selected doses for their respective cohorts. This group is denoted as the Final Dose Population, and results from this group are considered primary, since they reflect only the age-specific doses proposed for commercial use. The group with all participants exposed to raltegravir (at any dose) is denoted as the All Treated Population.

Stage I lasted for a minimum of 48 weeks, Stage II was for 48 weeks, and a long-term follow-up period lasted for 5 years from initial exposure (i.e., 48 weeks of treatment plus 4 years of follow-up). Participants were stratified by age and assigned to one of six cohorts. Participants in Cohort I were between the ages of 12 and 18 years and received poloxamer film coated raltegravir tablets. Participants in Cohort IIA were between the ages of 6 and 11 years, weighed at least 25 kg, and received poloxamer film coated raltegravir tablets. Participants in Cohort IIB were between the ages of 6 and 11 years and received chewable raltegravir tablets. Participants in Cohort III were between the ages of 2 and 5 years and received chewable raltegravir tablets. Participants in Cohort IV were between the ages of 6 months (defined as 180 days) and 23 months and received oral granules for suspension. Participants in Cohort V were between the ages of 4 weeks (defined as 30 days) and 5 months and received oral granules for suspension.

Enrollment for Stage I of this study began with Cohort I and progressed to the other cohorts once preliminary dosage had been determined and safety data were reviewed. When this information had been determined for Cohort I, Cohorts IIA and IIB began enrollment. Once safety and dose data for these cohorts were reviewed, enrollment into Cohort III began. Once safety and dose data for Cohort III were reviewed, enrollment into Cohort IV began and once safety and dose data for Cohort IV were reviewed, enrollment into Cohort V began.