Tecovirimat Shows No Efficacy in Mpox Treatment for Mild to Moderate Cases

NEW YORK, December 10, 2024 (GLOBE NEWSWIRE) — The National Institutes of Health’s (NIH) National Institute of Allergy and Infectious Diseases (NIAID) announced interim results from the Study of Tecovirimat for Human Mpox Virus (STOMP) clinical trial (NCT05534984). The study found that SIGA’s tecovirimat, a targeted antiviral treatment for mpox, did not demonstrate improved time to skin and mucosal lesion resolution compared to a placebo in patients with mild to moderate clade II mpox.

Based on these findings, alongside additional analyses, the study’s Data Safety and Monitoring Board (DSMB) recommended halting enrollment in the randomized arms. NIAID accepted this recommendation and subsequently made a similar decision for the open-label arm of the study, which included patients with severe or at-risk of severe mpox.

While data analysis for primary endpoint subgroups and detailed secondary and exploratory endpoints is still ongoing, Diem Nguyen, Chief Executive Officer of SIGA Technologies, stated, “Antivirals are most effective when administered early in the course of an infection and tend to demonstrate the greatest benefit in patients with more severe disease. The STOMP results are not unexpected as the study design was similar to the PALM007 study but focused on patients with mild to moderate clade II mpox compared to patients with clade I mpox. It is important to note that approximately 75% of mpox patients in the randomized arms of the STOMP trial received tecovirimat more than five days after symptom onset, and higher risk patients were included in an open-label arm.”

Dennis Hruby, Chief Scientific Officer at SIGA Technologies, added, “Tecovirimat’s mechanism of action halts viral transmission. Once the virus is present, the body’s natural immune system plays a key role in clearing it. Typically, this process takes two to four weeks in immune-competent patients. Research suggests that early treatment with tecovirimat, including post-exposure prophylaxis and treatment in severe cases, may offer the greatest potential for patient benefit.”

Importantly, the STOMP trial confirmed tecovirimat’s strong safety profile, with adverse effects comparable to a placebo. This finding aligns with prior studies, reinforcing tecovirimat’s safety record over the past 15 years.

Dr. Nguyen concluded, “We thank our partners, the National Institute of Allergy and Infectious Diseases (NIAID) and the National Institutes of Health (NIH), the patients who participated in this trial, and the investigators who supported it. Their dedication to public health has been instrumental in advancing our understanding of mpox and tecovirimat.”

SIGA Technologies is currently participating in three additional randomized clinical trials – UNITY (Switzerland, Brazil, Argentina), Platinum-CAN (Canada), and EPOXI (EU). Given the similarities between the design of these trials and the STOMP and PALM007 results, the company anticipates similar findings.

About the STOMP Clinical Trial in Mpox

The STOMP study is a randomized, placebo-controlled, double-blind study evaluating the safety and efficacy of tecovirimat for treating individuals with laboratory-confirmed or presumptive mpox. Starting in September 2022, the study enrolled participants with mpox symptoms lasting less than 14 days from Argentina, Brazil, Japan, Mexico, Peru, Thailand, and the United States, including Puerto Rico.

Participants were randomly assigned (2:1) to receive tecovirimat or a placebo for 14 days. Dosing frequency and capsule quantity were based on patient weight. Individuals with severe disease, specific skin conditions, or significantly suppressed immune systems received open-label tecovirimat instead of randomization. The study monitored participants’ safety across both randomized and open-label arms. In the randomized arms, STOMP examined the time to full mpox lesion resolution, viral clearance, and participants’ self-reported pain levels. Participants were followed for 28 days with a study site visit at day 29 and a second visit at day 57 to assess potential mpox recurrence.

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