Shares of Siga (Siga.US) fell nearly 40% in premarket trading after a key study of its monkeypox treatment drug tecovirimat failed to meet expectations.

Shares of SIGA Technologies(SIGA.US) fell nearly 40% in pre-market trading on Thursday after the company's oral treatment for monkeypox, tecovirimat, failed to meet expectations in a key clinical trial in the Democratic Republic of Congo. The study, funded by the National Institute of Allergy and Infectious Diseases (NIAID), showed that tecovirimat failed to meet its primary endpoint of a statistically significant improvement in disease resolution at 28 days.

The placebo-controlled trial, named PALM007, was designed to evaluate the safety and efficacy of tecovirimat in combination with standard treatment for monkeypox. The results showed that while tecovirimat was safe as the placebo, it did not show an advantage in improving disease resolution.

It is worth noting that the PALM007 study was not designed to meet the requirements of a registration trial needed for an FDA new drug clinical trial application. Researchers noted that ongoing other trials would help further assess factors that influenced the study results, including trial design and patient populations.

It was also reported that the World Health Organization (WHO) declared on Wednesday that the monkeypox outbreak in the Democratic Republic of Congo and its neighboring countries constituted a global health emergency, highlighting the urgent need for effective treatments.