BACKGROUND: Anogenital warts (AGW) can cause physical discomfort and decreased quality of life. Recent case reports suggest that ingenol mebutate gel might be an effective treatment of AGW.

OBJECTIVE: To explore primarily the safety, and secondarily the efficacy of ingenol mebutate gel 0.05% in patients with AGW.

METHODS: This was an exploratory, open-label, 1-arm trial of ingenol mebutate gel 0.05% administered up to three times to patients with AGW. Safety was assessed by occurrence and severity of local skin reactions (LSRs) and treatment-related adverse events (AEs). Efficacy was assessed by complete clearance and reduction in AGW count 14 days after last treatment, and recurrence 12 weeks after clearance.

RESULTS: Of 41 patients enrolled, 40 received treatment and 26 completed the trial. Patients had a median AGW count of 11.0 and AGW duration of 3.0 years at baseline. All patients experienced transient LSRs following treatment with a maximum composite LSR score of 7.5 (on a scale from 0 to 18). A total of 93% of patients reported treatment-related AEs, most frequently pain (85%) and procedural complications (35%) due to smearing of the gel. 78% of patients took mild analgesics for the pain, typically for 1-2 days following treatment. The majority of AEs were of moderate-to-severe intensity. Seventeen of 39 patients (43.6%) had complete clearance 14 days after last treatment, and AGW count was reduced by 90.9%. There was a tendency towards lower clearance rate in patients with longer duration of AGW. Eight of 14 patients (57.1%) had AGW recurrence 12 weeks after clearance.

CONCLUSION: Ingenol mebutate gel was associated with a high number of AEs and withdrawals due to painful local and adjacent skin reactions. Furthermore, it showed promising efficacy in reducing AGW despite a difficult-to-treat population. Optimization of the formulation is warranted to improve the safety profile of the treatment.