The Food and Drug Administration (FDA) has approved the intravenous (IV) formulation of Tpoxx® (tecovirimat) for the treatment of human smallpox disease caused by variola virus in adults and pediatric patients.

Previously, Tpoxx was only supplied as oral capsules. The IV formulation is designed to provide an alternative option for patients who are unable to swallow the oral capsules.

Tpoxx works by targeting and inhibiting the activity of the orthopoxvirus VP37 protein and blocking its interaction with cellular Rab9 GTPase and TIP47, which prevents the formation of egress-competent enveloped virions necessary for cell-to-cell and long-range dissemination of virus. The FDA approved Tpoxx based on results from adequate and well-controlled animal efficacy studies of nonhuman primates and rabbits infected with nonvariola orthopoxviruses.

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“We are grateful to the FDA for their work leading to approval of IV Tpoxx, which will provide access to a broader patient population,” said Dr Dennis Hruby, CSO of SIGA. “We are also appreciative to our colleagues at BARDA who have been working with us for many years to include oral and IV Tpoxx in US preparedness efforts and look forward to continuing to work with them on our liquid pediatric formulation.”

While not approved in the US, Tpoxx is indicated to treat monkeypox in Europe. According to SIGA, the IV formulation of Tpoxx was cited in the Biden administration’s recent budget request to treat a patient in the US with monkeypox.


  1. SIGA receives approval from the FDA for intravenous (IV) formulation of Tpoxx® (tecovirimat). News release. SIGA Technologies, Inc. Accessed May 19, 2022.
  2. New contract awarded by US Department of Defense for the procurement of up to approximately $7.5 million of oral Tpoxx®. News release. SIGA Technologies, Inc. May 12, 2022. Accessed May 19, 2022.

This article originally appeared on MPR