Topline results from PALM 007 study of tecovirimat in treatment of Mpox released.- Siga Technologies

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 (DRC) with monkeypox (mpox), who were administered SIGA’s 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 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 (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.

“These data showing maximum benefit in patients treated early and with severe disease are entirely consistent with the mechanism of action of tecovirimat and with the studies in animals that led to FDA approval of this medicine for smallpox, a virus closely related to monkeypox virus, but which produces much more severe illness. We believe these data warrant further investigation and support our view that post exposure prophylaxis will be vital for treatment of severe cases of mpox and all cases of smallpox,” stated Dennis Hruby, Chief Scientific Officer.

Additionally, in this study, tecovirimat exhibited a safety profile comparable to placebo. These results are consistent with several prior studies in healthy volunteers and further support the strong safety profile that has been observed with tecovirimat over the past 15 years.

“We are highly encouraged by the PALM 007 study results which showed that tecovirimat is safe and offers potential benefit to important groups of patients with mpox disease, particularly those with severe disease and those who sought treatment early. As with other acute viral infections, patients benefit the most when antiviral treatment is administered as soon as possible after infection. Missing the primary endpoint is not entirely unexpected given that the study population was hospitalized during the duration of treatment receiving a high level of supportive care, and since many presented for treatment more than a week after their illness started,” stated Diem Nguyen, Chief Executive Officer.

“SIGA and the National Institute of Allergy and Infectious Diseases (NIAID), the trial sponsor, are in the process of thoroughly analyzing the data to gain a comprehensive understanding of the results and potential implications. We look forward to future research on the impact of early treatment on improving outcomes in mpox patients in real world settings. Our team is committed to leveraging these findings to investigate effective treatment regimens for mpox and other infectious diseases.”

As background, the PALM 007 study was part of a globally coordinated initiative to address the 2022 mpox outbreak occurring in the DRC and around the world. It was, therefore, designed with important humanitarian considerations, such as allowing patients at varying stages of disease, age, health, among other factors, to participate in the trial. To ensure study data could be collected accurately and that patients had access to food, all patients in the study were hospitalized for the duration of treatment, and therefore received a level of care unavailable to most mpox patients in real world situations. In PALM 007, patients in the placebo arm had much more favorable outcomes than those in the observational studies from the DRC that were used to plan this trial, which could have reduced the measured benefit of tecovirimat compared to placebo. The exact impact of this controlled environment on the trial results is not yet known.

Additional studies are being conducted by trial sponsors around the world and are expected to help the Company gain a deeper understanding of the potential for tecovirimat to benefit patients with mpox. Four randomized clinical trials are currently enrolling patients, including STOMP (U.S. and other countries), UNITY (Switzerland, Brazil, Argentina), Platinum-CAN (Canada), and EPOXI (EU). Because the PALM 007 study differs in significant respects from these other studies, data from these studies will help SIGA to understand whether the PALM 007 results were influenced by factors such as trial design, patient population, medical protocols, disease clade, or other variables. For example, compared to PALM 007, the STOMP, UNITY, Platinum-CAN, and EPOXI trials to date have enrolled no children and a much higher percentage of immunocompromised patients, such as those living with HIV.