Siga slides, GeoVax jumps after mpox study shows limited effectiveness

Shares of Siga Technologies (SIGA) are under pressure on Thursday morning after the company announced preliminary results from the PALM 007 clinical trial. The analysis shows that Siga’s antiviral drug tecovirimat helped the very sickest mpox patients in a trial in the Democratic Republic of Congo recover more quickly than those given a placebo. However, the company said that the majority of patients in the trial did not recover more quickly than those given a placebo, which was the main goal of the study. The news sent the shares of competitor GeoVax Labs (GOVX) trading higher.

STUDY MISSES PRIMARY ENDPOINT: The National Institutes of Health’s, NIH, National Institute of Allergy and Infectious Diseases, NIAID, announced topline results from a preliminary analysis of the PALM 007 clinical trial. NIAID reported that the study did not meet its primary endpoint of a statistically significant improvement in time to lesion resolution within 28 days post-randomization for patients in the Democratic Republic of the Congo with monkeypox, who were administered Siga Technologies’ tecovirimat, a highly targeted antiviral treatment, versus placebo.

All patients in this study were hospitalized for the entire duration of treatment. This study was not a registration study conducted under an U.S. FDA Investigational New Drug Application.

A meaningful improvement was observed in patients receiving tecovirimat whose symptoms began seven days or fewer before randomization and in those with severe or greater disease, defined by the World Health Organization, or WHO, as having 100 or more skin lesions. While more analysis is required, the company believes these data support further trials to assess the potential benefit of tecovirimat in those who present to medical care soon after symptoms and in those with severe disease.

OF NOTE: Shares of Geovax Labs are moving higher after Siga Technologies announced topline results from a preliminary analysis of the PALM 007 study for the treatment of monkeypox virus. In December 2023, GeoVax amended a previously executed license agreement with the National Institute of Allergy and Infectious Diseases to expand the company’s commercial license to include mpox and smallpox as additional indications.

INTERNATIONAL EMERGENCY: This week, the World Health Organization declared mpox an international emergency. Shares of both Siga Technologies and GeoVax Labs rallied following the WHO’s announcement on Wednesday.

PRICE ACTION: In morning trading, shares of Siga Technologies have dropped almost 37% to $7.56, while GeoVax’s stock has gained about 5% to $3.41.