Our lead product, TPOXX (tecovirimat), is a highly targeted antiviral treatment against orthopoxviruses, including smallpox.
OUR INNOVATION
Our Path to Approval and Use
Mpox is a serious disease caused by the monkeypox virus that continues to spread throughout the world, presenting a threat to global health. While available vaccines can be effective at preventing mpox, protection is neither complete nor durable, leaving patients vulnerable to disease progression and transmission.
In the U.S., TPOXX is an antiviral drug not currently approved by the FDA for the treatment of mpox, but it is used to treat patients with mpox through an expanded access investigational new drug protocol held by the U.S. Centers for Disease Control and Prevention (CDC).
Access to TPOXX for mpox
How TPOXX Works
Developing a drug for which there are no human cases requires innovative clinical and regulatory strategies. With smallpox eradicated in 1980, it is unethical to conduct efficacy testing in human trials. Consequently, TPOXX was evaluated using a novel development path based on the FDA’s “Animal Rule,” in which safety studies were conducted in healthy human volunteers and efficacy and toxicology studies were conducted in animal models. The FDA also granted TPOXX Fast Track and Orphan Drug Designation.
TPOXX was among the first novel small molecule therapies delivered to the Strategic National Stockpile (SNS) under Project BioShield, a U.S. government program designed to accelerate the research, development, purchase, and availability of effective medical countermeasures against chemical, biological, radiological, and nuclear (CBRN) agents. TPOXX’s advanced development has been funded in partnership with the Biomedical Advanced Research and Development Authority (BARDA) of the U.S. Department of Health and Human Services.
Naturally-occurring smallpox has been successfully eradicated through global vaccine campaigns. Despite this important public health achievement, there is an enduring concern that smallpox could be used as a bioweapon. DNA synthesis technology and the possibility of unaccounted for smallpox stocks pose significant risks. While there are two acknowledged stocks of smallpox virus held by the U.S. and Russia, some believe that additional stores of the virus could be in the hands of governments or organizations that might use them to cause harm. The DNA sequence of the smallpox genome is in the public domain and could be synthesized in a laboratory from scratch or created by genetically modifying a similar virus (e.g., camelpox).
A smallpox bioterror attack could be especially damaging because the majority of today’s population is not immune to the virus, as routine vaccination ended in the 1970s. Vaccination alone would likely not be effective in the event of a smallpox bioterror attack. The vaccine must be administered within 5 days following infection to be therapeutically effective, but symptoms do not appear until 14 days post infection. When combined with social media-escalated disinformation and vaccine hesitancy, these limitations underscore the need for an effective smallpox antiviral therapy. As the first antiviral agent specifically indicated for the treatment of smallpox, TPOXX would play a critical role in responding to a smallpox bioterror attack.
TPOXX specifically inhibits the activity of a protein called VP37, found on the surface of all orthopoxviruses. This prevents the virus from leaving infected cells, slowing the spread of the infection and limiting it to a point where the immune system can clear the virus.
Oral TPOXX is considered safe and well-tolerated in patients. The safety profile can be attributed to the targeted nature of the drug, which limits adverse reactions. Despite the lack of controlled clinical trial data that demonstrate efficacy in humans, TPOXX was proven to be effective in animal models of smallpox, mpox, and other orthopoxviruses.
Smallpox is one of the world’s deadliest threats and an outbreak cannot be addressed with vaccines alone. Both medicines and vaccines are essential to combat orthopoxviruses.
Oral TPOXX (tecovirimat capules) was the first drug approved by the U.S. Food and Drug Administration (FDA) specifically indicated for treating smallpox disease in adults and pediatric patients weighing at least 13 kg. Following U.S. approval in 2018, in 2021 Health Canada also authorized the use of oral TPOXX to treat smallpox disease in adults and pediatric patients weighing at least 13 kg. Tecovirimat capsules, under the brand name Tecovirimat SIGA, was approved in 2022 by the European Medicines Agency (EMA), the Norwegian Medicines Agency, and the Medicines and Healthcare products Regulatory Agency (MHRA-UK) for the treatment of smallpox, mpox, cowpox, and vaccinia complications following vaccination against smallpox in adults and children weighing at least 13 kg. Under the brand name TEPOXX, tecovirimat capsules was approved in 2024 by the Pharmaceuticals and Medical Devices Agency (PMDA) for the treatment of smallpox, mpox, cowpox, as well as complications following smallpox vaccination in adults and pediatric patients weighing at least 13 kg.
U.S. - See FDA Prescribing Information
Canada - See Health Canada Prescribing Information
Europe - See EMA Prescribing Information
U.K. - See MHRA Prescribing Information
TPOXX Injection, the intravenous (IV) formulation of TPOXX, has been approved by the FDA for the treatment of smallpox in patients weighing at least 3 kg. This important option will allow patients who are too sick to swallow oral capsules to receive treatment. Healthcare providers can click here for important prescribing information on proper preparation and administration of TPOXX Injection.