Efficacy of a Carrageenan gel Against Transmission of Cervical HPV (CATCH): interim analysis of a randomized, double-blind, placebo-controlled, phase 2B trial

Abstract

Objectives: To evaluate the efficacy of a carrageenan-based lubricant gel in reducing the risk of genital human papillomavirus (HPV) infections in women.

Methods: We conducted a planned interim analysis of a randomized, double-blind, placebo-controlled, phase 2B trial. Women aged 18 years and older were randomly assigned (1:1) to a carrageenan-based gel or a placebo gel to be self-applied every other day for the first month and before and after each intercourse during follow-up. Assessments were performed at 0.5, 1, 3, 6, 9 and 12 months. The primary outcome was incidence of a new infection by an HPV type that was not present at baseline. Intention-to-treat analyses were performed.

Results: Between January 2013 and June 2017, a total of 280 participants were randomly assigned to the carrageenan (n = 141) or the placebo (n = 139) arm. All participants were included in safety analyses, but three (1%) were excluded from efficacy analyses (HPV results unavailable for two participants in the carrageenan and one participant in the placebo arm). The median follow-up time was 9.2 months (interquartile range, 1.9-13.2 months). A total of 59 (42%) of 139 participants in the carrageenan arm and 78 (57%) of 138 participants in the placebo arm became infected by at least one new HPV type (hazard ratio = 0.64, 95% confidence interval = 0.45-0.89, p 0.009). A total of 62 (44%) of 141 participants in the carrageenan arm versus 43 (31%) of 139 participants in the placebo arm reported an adverse event (p 0.02), none of which was deemed related to the gels.

Conclusions: Our trial's interim analysis suggests that using a carrageenan-based lubricant gel can reduce the risk of genital HPV infections in women.

Keywords: Carrageenan; Gel; HPV; Human papillomavirus; Microbicide; Randomized controlled trial.

Fig. 1.

Trial profile design and participant allocation.

Fig. 2.

Cumulative incidence of new HPV infections by arm. Cumulative incidence of (a) first new HPV infection and (b) all new HPV infections. Numbers at risk for (b) correspond to number of HPV types that participants could have potentially acquired at each time point, i.e. 36 HPV types tested multiplied by number of participants at time point minus HPV types positive at baseline for these participants. HPV, human papillomavirus.

Fig. 3.

Subgroup analyses. Cumulative compliance to gel use is calculated from enrolment to time of failure or censoring. ‘Not applicable’ corresponds to participants who reported no intercourse between enrolment and time of failure or censoring.