159 – Host and Disease Factors Were Not Associated With Mpox Resolution in Participants Receiving Tpoxx

Background

ACTG A5418/STOMP is a phase 3 randomized placebo-controlled double-blind trial evaluating the efficacy of tecovirimat in people with mpox.  It includes an open-label arm for people <18 years, pregnant or breastfeeding, with severe immune suppression, or protocol-defined severe disease. We analyzed host and disease factors associated with clinical mpox resolution and mpox DNA clearance from skin lesions in individuals receiving open-label tecovirimat for 14 days.   

Methods

Time to clinical resolution was the time from treatment initiation until all skin lesions were scabbed, desquamated, or healed and all visible mucosal lesions were healed through 28 days. An index skin lesion chosen at enrollment was swabbed weekly; mpox DNA levels were measured by PCR. Associations between baseline characteristics and time to clinical resolution were explored using Kaplan-Meier plots and Cox proportional hazards models. 

Results

Of 233 enrolled in the open-label arm, 107 had lab-confirmed clade II mpox (skin, oral or rectal swabs) who enrolled early enough to have completed 28-day follow-up and had baseline skin lesion mpox DNA available were included. Ninety-six (90%) were cisgender male, 3 (3%) were transgender female, median age was 34 years, 45 (42%) are living with HIV, including 11 with CD4 <200 cells/mm³ or HIV-1 RNA >1000 copies/ml, and 12 (11%) had previously received ≥1 dose of the smallpox/mpox vaccine. At enrollment, median skin lesion count was 26 (IQR: 13, 49), 78 (73%) had >5 days of symptoms at time of enrollment, and 11 (10%) had undetectable skin lesion mpox DNA. By Days 8 and 15, 47% (of 76) and 82% (of 77) had undetectable skin lesion mpox DNA. The cumulative probability of clinical resolution by 28 days was 86% (95% CI: 79, 92); median days to clinical resolution was 14 (Q1, Q3: 8, 22). While there were trends between faster clinical resolution, lower levels of mpox DNA, and younger age, no associations were found in multivariable modeling (Table 1).  Similarly, there were no factors significantly associated with clearance of mpox DNA at day 8.  Clearance of mpox DNA at Day 8 was not associated with faster clinical resolution.   

Conclusions

This interim exploratory analysis of participants receiving open-label tecovirimat did not identify predictors of clinical mpox resolution. Compared to PALM007 participants with Clade 1 mpox, we found lower lesion counts and slower clinical resolution. Further investigation is needed. 

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