Tecovirimat for Mpox (STOMP Trial)
Abstract
BACKGROUND Tecovirimat is approved for smallpox treatment under the FDA Animal Rule based on efficacy in non-human primate models of mpox, but its clinical efficacy against human Clade II mpox is unproven. METHODS In a phase 3, multinational, randomized, double-blind, placebo-controlled trial (ACTG5418/STOMP), we evaluated the efficacy of oral tecovirimat in adults with laboratory-confirmed Clade II mpox. Participants were randomized 2:1 to receive tecovirimat or placebo for 14 days. The primary endpoint was time from randomization to clinical resolution. Secondary endpoints included pain reduction, time to complete lesion healing, viral DNA clearance, and safety. RESULTS Of 412 randomized participants, 344 had laboratory-confirmed mpox and 336 had active skin or mucosal lesions and were included in the primary analysis. By day 29, clinical resolution occurred in 79% of participants in the tecovirimat group and 81% in the placebo group (subdistribution hazard ratio [sHR], 0.98; 95% CI, 0.74 to 1.31; P=0.89). There were no differences in pain reduction among those with severe pain on 11-point numeric rating scale (difference, 0.1; 95% CI, −0.8 to 1.0), complete lesion healing (sHR, 0.97; 95% CI, 0.75 to 1.26), or viral DNA clearance. Adverse events were similar between arms. CONCLUSIONS This trial found no evidence that tecovirimat improved time to clinical resolution, pain, or viral clearance in adults with Clade II mpox.
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 412 participants or records.
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