Comparable HIV suppression by pegylated-IFN-α2a or pegylated-IFN-α2b during a 4-week analytical treatment interruption

Abstract

We report on the post-hoc analysis of three clinical studies (NCT01935089, NCT00594880, and NCT00051818) with chronically HIV-infected, immune-reconstituted individuals with similar entry criteria, and demographics interrupting antiretroviral therapy (ART) without or with 5 weeks of weekly pegylated (Peg)-IFN-α2b or Peg-IFN-α2a immunotherapy added onto ART. Results show similar rates of viral suppression between both immunotherapies when continued during a 4-week ART interruption, despite Peg-IFN-α2a maintaining significantly higher trough blood levels.

Type-I interferons (IFNs) are potential candidates for immunotherapy approaches, due to their antiviral effects ^[1–3], and have been used with or without viral reactivation approaches [e.g. histone deacetylase (HDAC) inhibitors] to more efficiently lower the levels of latently infected cells ^[4]. Pegylated (Peg)-IFN-α2a or Peg-IFN-α2b have both been tested as immunotherapy against HIV in chronically antiretroviral therapy (ART)-suppressed individuals ^{[5, 6]}. Both molecules bind the same receptor, and have equivalent clinical response outcomes when used in anti-HCV therapy trials ^[7]. While Peg-IFN-α2b is reported as better tolerated and is expected to achieve greater tissue volume distribution than Peg-IFN-α2a ^[7–9], no study has yet compared these two strategies with regards to control of viral load after ART interruption. We have independently reported on the anti-HIV effect and safety of Peg-IFN-α2a or Peg-IFN-α2b when administered in ART-suppressed individuals using similar study designs that consist of 5 weeks of immunotherapy combined with ART followed by an analytical treatment interruption (ATI) on just immunotherapy ^{[5, 6]}. Here, we performed a post-hoc analysis between three clinical studies in order to compare the rate of viral suppression during a 4-week ATI period among individuals receiving 90 or 180 μg/wk Peg-IFN-α2a (NCT00594880 ^[5]) or 1 μg/kg/week Peg-IFN-α2b (NCT01935089 ^[6]) monotherapy or individuals undergoing an ATI without any immunotherapy (NCT00051818 ^[10]). Fig. 1a shows comparable time points from all three clinical trials that were used in this post-hoc analysis. All three clinical trials were conducted at the same clinical sites with participants having similar entry criteria, and demographics as described ^{[5, 6, 10]}. Briefly, and based on study entry criteria, participants in Peg-IFN-α2a immunotherapy study ^[5] had ART-mediated CD4⁺ T cell count for >6 months at ≥400 cells/mm³ (nadir ≥200 cells/mm³) and undetectable HIV RNA <50 copies/ml (including at entry). Participants in Peg-IFN-α2b immunotherapy study ^[6] had ART-mediated CD4⁺ T cell count ≥450 cells/mm³ at screening, and plasma HIV-1 RNA <50 copies/ml for ≥1 year and at screening. Finally, participants in ATI without immunotherapy study ^[10] had ART-mediated CD4⁺ T cell count at >400 cells/mm³ (nadir ≥100 cells/mm³) and HIV RNA <500 copies/ml for >6 months and <50 copies/ml at entry. Statistics were performed with JMP Pro11 (SAS Institute, Cary, NC). Chi-Square tests were used to test whether there was a difference in the frequency of participants with plasma HIV-1 RNA <50 copies/ml at the end of a 4-week ATI among the clinical trials with Peg-IFN-α2b monotherapy ^[6], Peg-IFN-α2a monotherapy ^[5], or ATI without immunotherapy ^[10]. All studies were registered under an investigational new drug application (IND) from the United States (US) Food and Drug Administration (FDA) and conducted in accordance with the human subject research guidelines of the US Department of Health and Human Services, under the supervision of the authors’ institutional review boards (IRBs). Written informed consent was obtained from all study participants.

Fig. 1. Effect of Peg-IFN-α2b and Peg-IFN-α2a on HIV-1 RNA and plasma IFN-α levels.

(a) Time points from clinical trials NCT00594880, NCT01935089 and NCT00051818 used in the current retrospective analysis; (b) Frequency of individuals based on HIV RNA copies/ml after a 4-week analytical treatment interruption (ATI) in participants of the NCT00051818, NCT00594880, and NCT01935089 clinical trials; (c) Plasma levels of IFN-α during 5 weeks of in vivo treatment with Peg-IFN-α2a+ART or Peg-IFN-α2b+ART for participants of the NCT00594880, and NCT01935089 clinical trials. In panel (a) treatment is represented by blue boxes [antiretroviral therapy (ART)], green boxes [combined administration of ART and pegylated interferon alfa-2a (Peg-IFN-α2a) or Peg-IFN-α2b], orange boxes (ATI, Peg-IFN-α2a or Peg-IFN-α2b monotherapy) or pink boxes (ATI, no IFN-α immunotherapy); Blue arrows indicate time points used for data and cryopreserved plasma sample analysis that are shown in panels (b) and (c). In panel (b) blue and orange boxes illustrate frequency of individuals with HIV RNA ≥50 copies/ml and <50 copies/ml respectively after a 4-week ATI. In panel (c) available data for study participants are shown at baseline (Baseline: ART) and after 5 weeks of combined administration of ART and Peg-IFN-α2a or Peg-IFN-α2b together with the median and interquartile range, and significant P values. Statistics were performed with JMP Pro11 (SAS Institute, Cary, NC). In panel (b) Chi-Square tests were used to test the whether there was a difference in the frequency of participants with plasma HIV-1 RNA <50 copies/ml at the end of a 4-week ATI among the NCT01935089 (Peg-IFN-α2b as immunotherapy), the NCT00594880 (Peg-IFN-α2a as immunotherapy), and the NCT00051818 (ATI without immunotherapy) clinical trials. In panel (c) differences between baseline and 5 weeks of combined administration of ART and Peg-IFN-α2a or Peg-IFN-α2b were tested, using Wilcoxon Signed-Rank or paired t-tests depending on data distribution.

The rate of individuals with plasma HIV-1 RNA <50 copies/ml at the end of a 4-week ATI with monotherapy was not statistically different (p=0.2235) between the two studies using Peg-IFN-α2a [66.67% (14/21)] or Peg-IFN-α2b [47.06% (8/17)] immunotherapy (Fig. 1b). However, individuals who did not receive any immunotherapy ^[10] had a statistically lower rate of individuals with HIV-1 RNA <50 copies/ml at the end of a 4-week ATI [12.5% (2/16)] when compared to Peg-IFN-α2a ^[5] [66.67% (14/21), p=0.001] or Peg-IFN-α2b ^[6] [47.06% (8/17), p=0.0309] monotherapy.

We also compared the plasma levels of IFN-ɑ in cryopreserved plasma samples collected at entry and after 5 weeks of in vivo treatment with Peg-IFN-α2a+ART ^[5] or Peg-IFN-α2b+ART ^[6] from 19 and 20 individuals participating in each clinical trial, respectively. Trough plasma levels of IFN-α (collected before next weekly dose) were measured using ELISA per manufacturer’s specifications (PBL assay science, Piscataway, NJ). All measurements were based on the average of duplicate undiluted plasma samples, with lowest IFN-α limits of detection of 12.5 pg/ml. Differences between time points were tested using Wilcoxon Signed-Rank or paired t-tests depending on data distribution assessed by the Anderson-Darling normality test. Due to the pilot nature of the study, unadjusted P-values <0.05 were considered as significant. As shown in Fig. 1c, expected increases from baseline were detected in steady-state trough IFN-α levels after 5 weeks (4 doses) of in vivo Peg-IFN-α administration in both IFN monotherapy clinical trials (Peg-IFN-α2a: p<0.0001; Peg-IFN-α2b: p=0.0121). However, plasma levels of IFN-α were 89% lower in participants receiving Peg-IFN-α2b [16.61 pg/ml (6.69–22.15 pg/ml)] when compared to participants receiving Peg-IFN-α2a [150.28 pg/ml (29.15–345.91 pg/ml)] indicating greater retention of Peg-IFN-α2a in peripheral circulation than Peg-IFN-α2b. This finding is in agreement with previous studies ^[11], and could be attributed to differences in the size and structure of the Peg chain between the two IFNs (i.e. Peg-IFN-α2a: branched chain 40 kDa; Peg-IFN-α2b: linear chain 12 kDa), thereby resulting in a shorter half-life ^[7]. Our observations documenting that both immunotherapy strategies maintain different plasma levels will need to be confirmed in studies inclusive of larger sample size.

In conclusion, our analysis shows a comparable rate of control of plasma viral load after ART interruption between Peg-IFN-α2a and Peg-IFN-α2b despite lower steady state IFN-α blood levels with Peg-IFN-α2b. While this post-hoc analysis provides the first comparative analysis to date between Peg-IFN-α2a and Peg-IFN-α2b with regards to outcomes of plasma viral control following an ART interruption, randomized studies with a larger sample size and direct same-study comparisons are required to confirm these observations.