Attachment Inhibitor Comparison in Heavily Treatment Experienced Patients

Plasma samples were collected for analysis of HIV-1 RNA. Mean change in log10 HIV-1 RNA from Day 1 was estimated using analysis of covariance (ANCOVA) with log10 HIV-1 RNA change from Day 1 at Day 8 as dependent variable, treatment (fostemsavir or placebo) as an independent variable, and Day 1 log10 HIV-1 RNA as a continuous covariate. Change from Day 1 was calculated as value at Day 8 minus value at Day 1. The analysis was performed on Intent-to-Treat Exposed (ITT-E) Population which comprised of all randomized participants who received at least one dose of study treatment. Missing HIV-1 RNA values at Day 8 were imputed using (a) Day 1 Observation Carried Forward (D1OCF) for participants without a value during blinded treatment (i.e, imputing a zero change from Day 1) or (b) Last Observation Carried Forward (LOCF) for participants with an early value during blinded treatment before the Day 8 analysis visit window.

The percentage of participants in the Randomized Cohort with HIV-1 RNA decreases from Day 1 that exceed 0.5 log10 c/mL and 1.0 log10 c/mL at Day 8 was determined by comparing HIV-1 RNA Day 1 measurement of each participant to their Day 8 measurement. This was an ITT analysis that classified participants without HIV-1 RNA at Day 1 or Day 8 as failures. The percentage of responders along with 95% confidence interval based on Wilson score is presented.

The durability of response (that is, the number of participants achieving HIV-1 RNA <40 c/mL) at Weeks 24, 48 and 96 of open-label fostemsavir plus OBT in the Randomized Cohort was assessed using the Food and Drug Administration (FDA) snapshot algorithm in which participants without HIV-1 RNA at Weeks 24, 48 and 96 or those who changed OBT due to lack of efficacy through Weeks 24, 48 and 96 were counted as failures. The percentage of participants in the Randomized Cohort who achieved virologic success (HIV-1 RNA <40 c/mL) at Weeks 24, 48 and 96 is presented along with 95% Wilson confidence interval. All the participants received fostemsavir during the open-label period irrespective of the original arms to which they were randomized; hence, the combined totals for Randomized Cohort is presented as pre-specified in protocol and reporting and analysis plan.

An SAE is any untoward medical occurrence that at any dose: results in death; is life-threatening; requires inpatient hospitalization or causes prolongation of existing hospitalization; results in persistent or significant disability/incapacity; is a congenital anomaly/birth defect; an important medical event that may jeopardize the participant or require intervention. Number of participants with on-treatment SAEs and AEs leading to withdrawal of study treatment is presented. SAEs and AELDs were collected in Safety Population which comprised of all participants who received at least one dose of study treatment. All the participants received fostemsavir during the open-label period irrespective of the original arms to which they were randomized; hence, the combined totals for Randomized Cohort is presented as pre-specified in protocol and reporting and analysis plan.

Laboratory toxicities were graded for severity according to the Division of Acquired Immunodeficiency Syndrome (DAIDS) grading system: Grade 1 (mild); Grade 2 (moderate); Grade 3 (severe); Grade 4 (potentially life-threatening). Baseline is defined as the latest pre-dose assessment. The number of participants with clinical chemistry toxicity grade increase to Grade 3-4 at anytime post-Baseline relative to Baseline is presented. All the participants received fostemsavir during the open-label period irrespective of the original arms to which they were randomized; hence, the combined totals for Randomized Cohort is presented as pre-specified in protocol and reporting and analysis plan.

Laboratory toxicities were graded for severity according to the DAIDS grading system: Grade 1 (mild); Grade 2 (moderate); Grade 3 (severe); Grade 4 (potentially life-threatening). Baseline is defined as the latest pre-dose assessment. The number of participants with hematology toxicity grade increase to Grade 3-4 at anytime post-Baseline relative to Baseline is presented. All the participants received fostemsavir during the open-label period irrespective of the original arms to which they were randomized; hence, the combined totals for Randomized Cohort is presented as pre-specified in protocol and reporting and analysis plan.

Disease progression during open label fostemsavir plus OBT was assessed based on the occurrence of new AIDS defining events (CDC Class C events) or death. The number of participants with on-treatment CDC Class C AIDS events is presented. All the participants received fostemsavir during the open-label period irrespective of the original arms to which they were randomized; hence, the combined totals for Randomized Cohort is presented as pre-specified in protocol and reporting and analysis plan.

CD4+ T- cell counts were assessed by flow cytometry. Mean change in CD4+ T- cell count from Day 1 at Day 8 was analyzed using one-way ANCOVA with change of CD4+ cell counts from Day 1 at Day 8 as the dependent variable, treatment (fostemsavir or placebo) as an in-dependent variable, and Day 1 CD4+ cell count as a continuous covariate. Change from Day 1 was calculated as value at Day 8 minus value at Day 1. Missing CD4+ cell count values at Day 8 were imputed using (a) D1OCF for participants without a value during blinded treatment (i.e., imputing a zero change from Day 1), or (b) LOCF for participants with an early value during blinded treatment before the Day 8 analysis visit window.

CD4+ T- cell counts were assessed by flow cytometry. Mean change in CD4+ T- cell count percentage from Day 1 at Day 8 was analyzed using one-way ANCOVA with change of CD4+ cell count percentage from Day 1 at Day 8 as the dependent variable, treatment (fostemsavir or placebo) as an independent variable, and Day 1 CD4+ cell count percentage as a continuous covariate. Change from Day 1 was calculated as value at Day 8 minus value at Day 1. Missing CD4+ cell count values at Day 8 were imputed using (a) D1OCF for participants without a value during blinded treatment (ie, imputing a zero change from Day 1), or (b) LOCF for participants with an early value during blinded treatment before the Day 8 analysis visit window.

Blood samples were collected for the analysis of HIV-1 RNA. Baseline is defined as the last non-missing value on or before the date of first dose of study treatment. Change from Baseline was calculated as the value at post-dose visit minus the value at Baseline. All the participants received fostemsavir during the open-label period irrespective of the original arms to which they were randomized; hence, the combined totals for Randomized Cohort is presented as pre-specified in protocol and reporting and analysis plan.

CD4+ T- cell counts were assessed by flow cytometry. Baseline is defined as the last non-missing value on or before the date of first dose of study treatment. Change from Baseline was calculated as the value at post-dose visit minus the value at Baseline.

Percentage CD4+ T- cell counts were assessed by flow cytometry. Baseline is defined as the last non-missing value on or before the date of first dose of study treatment. Change from Baseline was calculated as the value at post-dose visit minus the value at Baseline.

Plasma samples were collected for emergent drug resistance testing. The number of participants with emergent viral genotypic substitutions of interest in the GP160 domain was identified by the next-generation sequencing (NGS) assay. Protocol defined virologic failure (PDVF) through Week 96 Population comprised of all participants with available phenotypic and genotypic resistance data meeting at the time protocol defined virologic failure (PDVF) was met. The criteria for PDVF was a) Confirmed, or last available prior to discontinuation, HIV-1 RNA >=400 c/mL at any time after prior confirmed suppression to <400 c/mL prior to Week 24 or Confirmed, or last available prior to discontinuation, > 1 log10 c/mL increase in HIV-1 RNA at any time above nadir level where nadir is >=40 c/mL prior to Week 24. b) Confirmed, or last available prior to discontinuation, HIV-1 RNA >=400 c/mL at or after Week 24.

The phenotypic resistance to a drug is defined in terms of a fold change (FC) in IC50s, i.e., the ratio of the 50% inhibitory concentration (IC50) of the clinical isolate to the IC50 of a reference strain (wild type control). FCR was calculated as FC at PDVF divided by Baseline FC. The number of participants with the indicated change (ratio) in the two values at the time of PDVF is presented. FCR<1 indicates that FC is smaller on-treatment than at Baseline. FCR >3 indicates that on-treatment FC is 3 times greater than it was at Baseline.