U.S. flag An official website of the United States government
  1. Home
  2. Emergency Preparedness and Response
  3. Counterterrorism and Emerging Threats
  4. Medical Countermeasures Initiative (MCMi)
  5. MCM Issues
  6. FDA Monkeypox Response
  1. MCM Issues
Image
Image of Monkeypox virus
Caption
Colorized scanning electron micrograph of monkeypox virus (orange) on the surface of infected VERO E6 cells (green). (Credit: NIAID)

Español

FDA’s Role | What’s New | Fast Facts | Vaccines | Therapeutics |  Monkeypox and medical devices |  Fraud and Misinformation | Contact the FDA |  Additional Resources

FDA’s Role  

The U.S. Food and Drug Administration plays a critical role in protecting the U.S. from chemical, biological, radiological, nuclear (CBRN) attacks, and emerging infectious disease threats.

The FDA's roles in monkeypox preparedness and response during this public health emergency include:

Return to Top


What’s New

Return to Top


Fast Facts

Return to Top


Vaccines

The FDA approved JYNNEOS Vaccine in 2019, for the prevention of smallpox and monkeypox disease in adults 18 years of age and older determined to be at high risk for smallpox or monkeypox infection.

  • This is the only currently FDA-approved vaccine for the prevention of monkeypox disease. 
  • The vaccine does not contain the viruses that cause smallpox or monkeypox. 
  • Given the emerging public health need, the FDA and government partners worked to accelerate submission of information needed to make additional U.S. doses of JYNNEOS available much more quickly than scheduled.  
  • The vaccine is part of the Strategic National Stockpile, overseen by the Department of Health and Human Services’ Assistant Secretary for Preparedness and Response, which helps ensure that the vaccine is accessible in the U.S. if needed.
  • Get the Fast Facts on the Intradermal JYNNEOS Monkeypox VaccineSimplified ChineseKoreanTagalogVietnameseSpanish

For more information: FDA Fast Facts: Jynneos, Korean, Simplified Chinese, Spanish, Tagalog, Vietnamese

Return to Top


Therapeutics  

Currently, there are no FDA-approved treatments for monkeypox; however, TPOXX (tecovirimat), an antiviral medication, is being made available through a randomized controlled clinical trial sponsored by the National Institutes of Allergy and Infectious Diseases (NIAID) and also through the CDC under an FDA authority called Expanded Access, or “compassionate use.”

TPOXX (tecovirimat) history:

As background, in 2018, the FDA approved TPOXX for treatment of smallpox in adults and children. Because smallpox is eradicated globally, the FDA approved TPOXX under “Animal Rule” regulations, as it was neither ethical nor feasible to test the efficacy of the drug in humans. TPOXX was approved for treatment of smallpox based on efficacy data obtained from animal studies, specifically non-human primates infected with monkeypox virus and rabbits infected with rabbitpox virus. Such studies were relevant since the viruses that cause smallpox, monkeypox, and rabbitpox are in the same family of viruses called “orthopoxviruses.” Safety data was obtained in healthy human volunteers without a smallpox or monkeypox infection.

Unlike smallpox, monkeypox was endemic in other parts of the world (e.g., the Democratic Republic of the Congo) at the time of TPOXX’s initial approval. Consequently, it remained both ethical and feasible to conduct clinical trials in humans to study TPOXX for the treatment of monkeypox disease. Therefore, TPOXX for the treatment of monkeypox disease was not appropriate for approval under the pathway described in the FDA’s Animal Rule regulations. 

TPOXX as a treatment for monkeypox infections:

The safety and efficacy of TPOXX to treat monkeypox in humans has not been established. Conducting randomized, controlled trials to assess TPOXX’s safety and efficacy in humans with monkeypox infections is essential. We don’t currently know if TPOXX will be beneficial in treating patients with monkeypox, since drugs that are effective in animal studies are not always effective in humans. 

On September 8, 2022, NIAID opened a randomized, controlled clinical trial to assess the safety and efficacy of TPOXX for the treatment of monkeypox infection. Health care providers should encourage their patients with monkeypox infection to be evaluated for enrollment in this trial. For patients for whom enrollment in this trial is not feasible (e.g., a clinical trial site is not geographically accessible), use of tecovirimat under CDC’s expanded access protocol should be consistent with applicable guidelines for tecovirimat use.

Risk of Viral Resistance to TPOXX:

Viruses can change over time. Sometimes these changes make antiviral drugs less effective at combating the virus they are targeting, meaning those drugs won’t work as well or might not work at all. 

TPOXX works by inhibiting a viral protein, called VP37, that all orthopoxviruses (e.g., smallpox virus, monkeypox virus, vaccinia virus) share. However, as noted in the drug label, TPOXX has a low barrier to viral resistance. This means small changes to the VP37 protein could have a large impact on the antiviral activity of TPOXX. 

CDC scientists are actively monitoring for changes in the monkeypox virus that could make the virus less susceptible to TPOXX.  Because of the potential for the virus to become resistant to TPOXX, it is important the drug be used in a judicious manner. 

Patients should enroll in NIAID’s randomized, controlled clinical trial when feasible to facilitate assessment of the safety, efficacy, and resistance profile of TPOXX. For patients for whom enrollment in a randomized clinical trial is not feasible (e.g., a clinical trial site is not geographically accessible), use of TPOXX under CDC’s expanded access protocol should be consistent with applicable guidelines for TPOXX use.

Information for the Scientific Community:

On September 12, 2022, the FDA released additional information in publicly posted reviews supporting approval of the new drug application for tecovirimat to describe specific changes in the VP37 proteins of orthopoxviruses (e.g., vaccinia virus and monkeypox virus) that are associated with tecovirimat drug resistance. 

As described in the FDA reviews, multiple independent studies characterized tecovirimat resistance development in orthopoxviruses in cell culture studies, in animal studies, and in an anecdotal human case of progressive vaccinia. These studies identified several genetic pathways for orthopoxviruses to become resistant to tecovirimat, which involves the emergence of amino acid substitutions in the viral VP37 drug target (see Table below). Many of the resistance pathways require only a single amino acid change in VP37 to cause a substantial reduction in tecovirimat antiviral activity. 

Table: Orthopoxvirus VP37 Amino Acid Substitutions Associated with Tecovirimat Resistance

Resistance Analysis Study Amino Acid Substitutions
VP37 amino acid substitutions associated with high-level phenotypic resistance to tecovirimat in cell culture (defined as ≥10-fold increase in EC50 value) in vaccinia virus, cowpox virus or camelpox virus
 

Single amino acid substitutions: H238Q, N267D/S, G277C, D283G/Y, A290V, D294V, A295E, L302P/Q

Combinations of amino acid substitutions: F25V+I372N, L178S+Y258C, N179H+D283G, H194N +303insSVK, N267D+I309T, N267S+I317V, G277C+I372N, D280G+D294G, A290V+L315M, K68N+Y258C+T308S, W2C+D225A+Y258C+D280G 
 

VP37 amino acid substitutions detected in monkeypox virus infected, tecovirimat-treated nonhuman primates that succumbed to disease H238Q, N267del/I/D/S/K, R268G, D280Y, A290V, A295E, L297ins, I372N/ILKIKNRK (mutation of stop codon and extension of reading frame)
 
VP37 amino acid substitutions detected in a tecovirimat-treated individual with progressive vaccinia virus infection
 
A290V, L315M
1Due to the conserved nature of VP37, tecovirimat resistance-associated substitutions in one orthopoxvirus are expected to apply to other orthopoxviruses.

Collectively, these studies indicate tecovirimat has a low barrier to resistance, and this must be considered in the context of the current monkeypox public health emergency because there is a risk that tecovirimat resistant virus could emerge and possibly spread. 

The FDA is releasing this information to aid the scientific community’s genomic sequencing efforts to support national surveillance of the current monkeypox virus outbreak in the U.S. The FDA believes releasing this additional information will further facilitate the ability to monitor for the development and spread of tecovirimat-resistant virus and therefore is important in promoting public health. 

For more information: FDA Fast Facts: TPoxx, Korean, Simplified Chinese, Spanish, Tagalog, Vietnamese 
Also see: Smallpox therapeutic information from the FDA.

For FDA Center for Drug Evaluation and Research (CDER) therapeutic product development questions, please contact: [email protected]

Return to Top


Monkeypox and medical devices

For information on medical devices, including monkeypox tests, please see: Monkeypox and Medical Devices.

Return to Top


Fraud and Misinformation 

Unfortunately, during emergency situations, fraudulent products claiming to prevent, treat or cure conditions associated with the emergency almost always appear for sale. The FDA monitors for fraudulent products and false product claims related to emerging infectious disease threats and takes appropriate action to protect consumers.

You can report a fraudulent monkeypox product to the FDA. The page includes options for phone and online reporting in English or en Español.

Moreover, the FDA has taken significant steps to combat misinformation about FDA-regulated products being communicated online, in the news, and by high-profile public officials, celebrities, and other outlets. We continue to look for opportunities to combat misinformation head-on in ways easy for consumers to understand and communicate the potential for real harm. Find trusted health information from the FDA and our government partners. See the resources below.

Return to Top


Additional Resources

Return to Top


Contact the FDA 

Consumers and general information: contact FDA
You may also call 1-888-INFO-FDA / (1-888-463-6332)

For CDER therapeutic product development questions, please contact: [email protected]

FDA’s Role | What’s New | Fast Facts | Vaccines | Therapeutics |  Diagnostics |  Fraud and Misinformation | Contact the FDA |  Additional Resources

 

  • 1. 1Due to the conserved nature of VP37, tecovirimat resistance-associated substitutions in one orthopoxvirus are expected to apply to other orthopoxviruses.

Subscribe

Sign up to receive email alerts on emergency preparedness and response topics from FDA, including medical countermeasures and emerging infectious diseases.

Back to Top