SIGA Technologies, Inc Submits NDA for First-Ever Oral Smallpox Treatment

In April 2017, we covered news that SIGA Technologies, Inc, had just completed enrollment and dosing in the final cohort of a phase 1 trial of an intravenous formulation for the drug TPOXX (tecovirimat), an antiviral drug for the treatment of orthopoxvirus infections, such as smallpox. Now, the company has been able to see the drug through another major milestone, submitting a New Drug Application (NDA) to the US Food and Drug Administration (FDA) for an oral formulation.

Although deemed eradicated throughout the world in 1980 thanks to a protective vaccine, research on smallpox continues to this day given the potential for the highly contagious virus to be used in biological warfare. Because the United States stopped routinely administering the smallpox vaccine in 1972, those individuals born after that time would be particularly vulnerable to an outbreak. Currently, there is no cure or treatment for smallpox; however, should SIGA’s drug be approved, that will change.

TPOXX, SIGA’s novel small-molecule drug, has been funded by the US government’s Biomedical Advanced Research and Development Authority (BARDA). According to a press release from SIGA, “TPOXX (tecovirimat) was developed under the FDA “Animal Rule,” in which efficacy endpoints are determined in animal studies, and human clinical studies are conducted to determine safety and confirm dosing. There have been no drug-related serious adverse events during the development of oral TPOXX.”

Chief Scientific Officer of SIGA Technologies, Dennis Hruby, PhD, elaborated on this further in an email to Contagion^®, stating, “Given that smallpox was eradicated in 1979, efficacy testing of TPOXX was not possible in humans. At an FDA Advisory Committee on smallpox antiviral development, 3 animal models were proposed: monkeypox in nonhuman primates, rabbitpox in rabbits, and ectromelia (mousepox) in mice. SIGA worked closely with BARDA to develop efficacy models and final efficacy testing in nonhuman primates and rabbits. This data will form the efficacy package to support the use of TPOXX as a therapeutic in the event of an outbreak of smallpox.”

Pursuant to a contract with BARDA, SIGA has successfully delivered 2 million courses of TPOXX to the Strategic National Stockpile. The anticipated shelf-life for the drug is 7 years.

Based on regulatory review requirements, considering SIGA’s NDA submission, the Company expects to receive notification from the FDA that the filing was accepted for review, confirmation of priority review status, and notification of its final action date in February 2018. Since TPOXX is designed to treat a serious medical condition for which there is no approved therapy, SIGA has requested an expedited review of its application.