A Phase 1 Randomized, Open Label, Rectal Safety, Acceptability, Pharmacokinetic, and Pharmacodynamic Study of Three Formulations of Tenofovir 1% Gel (the CHARM-01 Study)

OBJECTIVES

The CHARM-01 study characterized the safety, acceptability, pharmacokinetics (PK), and pharmacodynamics (PD) of three tenofovir (TFV) gels for rectal application. The vaginal formulation (VF) gel was previously used in the CAPRISA 004 and VOICE vaginal microbicide Phase 2B trials and the RMP-02/MTN-006 Phase 1 rectal safety study. The reduced glycerin VF (RGVF) gel was used in the MTN-007 Phase 1 rectal microbicide trial and is currently being evaluated in the MTN-017 Phase 2 rectal microbicide trial. A third rectal specific formulation (RF) gel was also evaluated in the CHARM-01 study.

METHODS

Participants received 4 mL of the three TFV gels in a blinded, crossover design: seven daily doses of RGVF, seven daily doses of RF, and six daily doses of placebo followed by one dose of VF, in a randomized sequence. Safety, acceptability, compartmental PK, and explant PD were monitored throughout the trial.

RESULTS

All three gels were found to be safe and acceptable. RF and RGVF PK were not significantly different. Median mucosal mononuclear cell (MMC) TFV-DP trended toward higher values for RF compared to RGVF (1136 and 320 fmol/106 cells respectively). Use of each gel in vivo was associated with significant inhibition of ex vivo colorectal tissue HIV infection. There was also a significant negative correlation between the tissue levels of TFV, tissue TFV-DP, MMC TFV-DP, rectal fluid TFV, and explant HIV-1 infection.

CONCLUSIONS

All three formulations were found to be safe and acceptable. However, the safety profile of the VF gel was only based on exposure to one dose whereas participants received seven doses of the RGVF and RF gels. There was a trend towards higher tissue MMC levels of TFV-DP associated with use of the RF gel. Use of all gels was associated with significant inhibition of ex vivo tissue HIV infection.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01575405.

Nonreproducibility of "snap-frozen" rectal biopsies for later use in ex vivo explant infectibility studies

Sexual transmission accounts for the majority of new HIV infections worldwide with sexually exposed cervicovaginal and colorectal mucosae being primary sites of infection. Two recent Phase 1 rectal microbicide trials included, as an ancillary endpoint, suppression of ex vivo HIV infection of in vivo microbicide-exposed rectal mucosal tissue biopsies. Both trials demonstrated significant suppression of biopsy infectibility in drug-exposed versus placebo-exposed tissue. This potential early biomarker of efficacy has raised the feasibility of utilizing "snap-frozen" tissue samples, acquired at multiple trial sites to be shipped for central processing, providing a mechanism to correlate tissue drug concentrations with a functional index of HIV prevention. While previous reports have indicated acceptable comparability of fresh versus freeze-thawed cervicovaginal tissue samples, no similar evaluations with colorectal tissue biopsies have been done. In this study, rectal biopsies from healthy, HIV-seronegative participants were assessed for structural integrity (histology), viability (MTT assays), and tissue infectibility to compare results from fresh versus combinations of freeze/thaw protocols. Results indicated that while all protocols showed equivalent viability with fresh samples (MTT), histology documented poor preservation of tissue integrity following freezing. Infectibility results from freeze-thawed colorectal tissue were markedly lower (usually<25% of fresh samples) and varied greatly and unpredictably. Centralized colorectal tissue infectibility assays using biopsies from remote trial sites cannot currently be supported under these protocols.

RMP-02/MTN-006: A phase 1 rectal safety, acceptability, pharmacokinetic, and pharmacodynamic study of tenofovir 1% gel compared with oral tenofovir disoproxil fumarate

This study was designed to assess the safety, acceptability, pharmacokinetic (PK), and pharmacodynamic (PD) responses to rectal administration of tenofovir (TFV) 1% vaginally formulated gel and oral tenofovir disoproxil fumarate (TDF). This study was designed as a phase 1, randomized, two-site (United States), double-blind, placebo-controlled study of sexually abstinent men and women. Eighteen participants received a single 300-mg exposure of oral TDF and were then randomized 2:1 to receive a single and then seven daily exposures of rectal TFV or hydroxyethyl cellulose (HEC) placebo gel. Safety endpoints included clinical adverse events (AEs) and mucosal safety parameters. Blood and colonic biopsies were collected for PK analyses and ex vivo HIV-1 challenge. No serious AEs were reported. However, AEs were significantly increased with 7-day TFV gel use, most prominently with gastrointestinal AEs (p=0.002). Only 25% of participants liked the TFV gel. Likelihood of use "if somewhat protective" was ∼75% in both groups. Indices of mucosal damage showed minimal changes. Tissue TFV diphosphate (TFV-DP) C(max) 30 min after single rectal exposure was 6-10 times greater than single oral exposure; tissue TFV-DP was 5.7 times greater following 7-day versus single rectal exposure. In vivo exposure correlated with significant ex vivo tissue infectibility suppression [single-rectal: p=0.12, analysis of covariance (ANCOVA) p=0.006; 7-day rectal: p=0.02, ANCOVA p=0.005]. Tissue PK-PD was significantly correlated (p=0.002). We conclude that rectal dosing with TFV 1% gel resulted in greater TFV-DP tissue detection than oral dosing with reduced ex vivo biopsy infectibility, enabling PK-PD correlations. On the basis of increased gastrointestinal AEs, rectally applied, vaginally formulated TFV was not entirely safe or acceptable, suggesting the need for alternative rectal-specific formulations.

First phase 1 double-blind, placebo-controlled, randomized rectal microbicide trial using UC781 gel with a novel index of ex vivo efficacy

OBJECTIVES

Successful control of the HIV/AIDS pandemic requires reduction of HIV-1 transmission at sexually-exposed mucosae. No prevention studies of the higher-risk rectal compartment exist. We report the first-in-field Phase 1 trial of a rectally-applied, vaginally-formulated microbicide gel with the RT-inhibitor UC781 measuring clinical and mucosal safety, acceptability and plasma drug levels. A first-in-Phase 1 assessment of preliminary pharmacodynamics was included by measuring changes in ex vivo HIV-1 suppression in rectal biopsy tissue after exposure to product in vivo.

METHODS

HIV-1 seronegative, sexually-abstinent men and women (N = 36) were randomized in a double-blind, placebo-controlled trial comparing UC781 gel at two concentrations (0.1%, 0.25%) with placebo gel (1∶1∶1). Baseline, single-dose exposure and a separate, 7-day at-home dosing were assessed. Safety and acceptability were primary endpoints. Changes in colorectal mucosal markers and UC781 plasma drug levels were secondary endpoints; ex vivo biopsy infectibility was an ancillary endpoint.

RESULTS

All 36 subjects enrolled completed the 7-14 week trial (100% retention) including 3 flexible sigmoidoscopies, each with 28 biopsies (14 at 10 cm; 14 at 30 cm). There were 81 Grade 1 adverse events (AEs) and 8 Grade 2; no Grade 3, 4 or procedure-related AEs were reported. Acceptability was high, including likelihood of future use. No changes in mucosal immunoinflammatory markers were identified. Plasma levels of UC781 were not detected. Ex vivo infection of biopsies using two titers of HIV-1(BaL) showed marked suppression of p24 in tissues exposed in vivo to 0.25% UC781; strong trends of suppression were seen with the lower 0.1% UC781 concentration.

CONCLUSIONS

Single and 7-day topical rectal exposure to both concentrations of UC781 were safe with no significant AEs, high acceptability, no detected plasma drug levels and no significant mucosal changes. Ex vivo biopsy infections demonstrated marked suppression of HIV infectibility, identifying a potential early biomarker of efficacy. (Registered at ClinicalTrials.gov; #NCT00408538).

Acceptability of UC781 gel as a rectal microbicide among HIV-uninfected women and men

We studied the overall acceptability of UC781 gel formulation when applied rectally. Ten women and twenty-six men, all HIV-uninfected, were enrolled in a Phase 1, randomized, blinded, placebo-controlled safety and acceptability study of the vaginal microbicide gel UC781 applied rectally. Participants were randomized to three groups: 0.1% UC781 gel, 0.25% UC781 gel, or a placebo gel. Acceptability was assessed using structured questionnaires and qualitative in-depth interviews. After using UC781 gel rectally for seven consecutive days, participants’ reports suggest that a UC781 gel formulation is highly acceptable and comparable to a placebo gel. The gels received favorable ratings overall and on attributes such as color, smell and consistency. All of the participants reported high intentions to use a gel like the one they used in this study. Acceptability research is essential in early phases of microbicide development to identify potential problems, understand user preferences, and introduce changes if needed.