Tpoxx Is Our Best Bet for Treating Mpox. So Why Is It So Hard to Get?

Tpoxx pills

Verywell / Photo Illustration by Ellen Lindner

Key Takeaways

  • Tpoxx (tecovirimat) is the only antiviral drug available to manage the symptoms of an mpox infection.
  • The drug was designed to treat smallpox and is available under a special license for use in mpox patients.
  • The drug appears to be safe and effective. But there are no clinical trials of how the drug performs in mpox patients, so scientists don’t know just helpful it is.

To slow infection and ease discomfort for mpox (formerly known as monkeypox) patients, healthcare providers only have one antiviral drug at their disposal—tecovirimat, also known as Tpoxx. But only a fraction of the more than 13,000 confirmed mpox patients in the United States have been treated with the drug.

Tpoxx was first approved to treat smallpox. But various animal studies and safety tests in healthy volunteers indicate that the drug can also be effective at managing illness from mpox.

There aren’t yet any clinical trials quantifying how well Tpoxx performs in mpox patients, leaving providers in the dark about how effective the drug is and when best to prescribe it.

Even though the drug is free, accessing Tpoxx requires providers to fill out a slew of paperwork and schedule multiple follow-up appointments with patients—a process that takes time and resources.

Still, Tpoxx is considered the best option for managing mpox symptoms and slowing infections.

How Tpoxx Works

Tpoxx was designed to target the smallpox virus, which is in the same family as the mpox virus. It works by disabling a certain protein that the virus needs to escape a cell it has infected. Without this protein, the virus can’t breach other healthy cells and spread throughout the body.

How Is Tpoxx Administered?

Tecovirimat comes as both a pill and an intravenous (IV) injection. The pill is the most common way to take the drug, as mpox patients often isolate at home, rather than in a hospital where an IV would be available, said Elizabeth Gilliams, MD, MS, MSc, an infectious disease expert at Johns Hopkins University School of Medicine.

The pills are taken over two weeks two to three times a day, depending on the patient’s weight. To properly absorb the drug, the patient must take the pills along with a full and fatty meal.

In this outbreak, there are very few deaths due to mpox. Still, someone can wind up in the hospital if they have another infection or a particularly bad case. The IV route can be useful for people who have difficulty swallowing, especially due to lesions in the mouth and throat.

According to the existing clinical data on Tpoxx, the injection route is associated with a higher likelihood of developing side effects than the pill. The most common side effects in those who took it orally were headache and nausea.

Who Is Eligible?

Providers might prescribe Tpoxx to mpox patients who fall into one of three categories: people who are experiencing severe outcomes of the infection, those who are at risk of severe illness, and those who have lesions in sensitive areas that could be damaged if those lesions scar.

How Effective Is Tpoxx at Treating Mpox?

Among her patients who have taken Tpoxx, Gilliams said she notices that their lesions and sores tend to heal quickly.

“None of the patients I’ve worked with had side effects that stopped them from taking it and it has overall been a really positive experience for them,” Gilliams told Verywell. “I’m hopeful and optimistic about how it’s working. And really within the first couple of days, people are feeling better.”

At the time of the Tpoxx approval, researchers only tested it in animals who had mpox. The drug decreased the likelihood that monkeys died of mpox. To establish its safety in humans, the researchers also gave the drug to a group of healthy human volunteers to see whether there were any serious side effects.

Elizabeth Gilliams, MD, MS, MSc

The main barriers that exist are provider awareness, having the drug on hand, and the fact that the procedure for distributing it is quite different from just writing a prescription and sending it to a regular pharmacy.

— Elizabeth Gilliams, MD, MS, MSc

According to the informed consent form that patients are required to sign when they seek the treatment, the CDC stated: “We do not know for certain if you will benefit from tecovirimat.”

Gilliams said all her patients who take Tpoxx have seen a noticeable improvement, and none had safety concerns that caused them to stop using the drug.

“Where the data gap exists is really in efficacy,” she said. “It has a good track record on its performance and a lot of that data supports its use right now, but we don’t have the full information yet.”

Specifically, scientists don’t know how much the drug actually reduces the duration of the disease, nor when to offer the treatment for optimal results. Gathering more data could help inform public recommendations and individual care.

“If it can reduce the duration of illness, maybe that can help people leave isolation earlier. Maybe that can help reduce transmission from environmental surfaces or to their household contacts,” Gilliams said.

Gilliams said she often prescribes other pain medications and topical creams along with Tpoxx to help reduce pain and inflammation. That makes it difficult to know how effective the therapy is on its own.

Besides, in most cases, mpox patients will fully recover without any treatment. The only way to know how much Tpoxx speeds up the recovery process is to compare mpox patients who take the drug with a placebo group.

Marshall Glesby, MD, PhD is an infectious disease specialist at New York Presbyterian Hospital and Weill Cornell Medical School, where he leads the tecovirimat expanded access program.

“Anecdotally, many people seem to respond to the drug and have improved… But we don’t have the comparison group of the people who did not get the drugs,” Glesby told Verywell. “We eagerly look forward to having those data in the coming months.”

The National Institutes of Health is working with the AIDS Clinical Trials Group—the largest HIV research group—to develop a trial on the effectiveness of Tpoxx in treating mpox. This data may help federal regulators decide whether to authorize the drug for this use.

It’s Still Hard to Get Tpoxx

Tpoxx is considered an “investigational new drug.” This status means that providers can apply to give certain medications that aren’t yet FDA-approved.

The initial application required 125 pages of paperwork on the patient's illness before, during, and after taking the drug.

The CDC has since simplified the process by reducing the number of required forms and making certain documentation and follow-up evaluations optional. Now, providers can begin prescribing the drug before all the paperwork is complete.

Though the process has become more streamlined, it still requires providers to have certain infrastructure or support. For instance, not every provider has access to software for telehealth visits or digital signatures, nor a separate space for sick individuals to fill out the forms in person without infecting others.

“The main barriers that exist are provider awareness, having the drug on hand, and the fact that the procedure for distributing it is quite different from just writing a prescription and sending it to a regular pharmacy,” Gilliams said. “It’s not really an issue with the actual amount of drug that is possibly out there. I think it’s really a matter of implementation and comfort with the procedures.”

The drug is available at no cost. But patients may be required to present a positive test result to their local health department, and those tests may not be covered by insurance if run through a commercial laboratory.

“Determining how to access tecovirimat is a potential challenge probably in most parts of the country,” Glesby said. “One place to start could be local health department because they should know who is able to prescribe the medication.”

Academic medical centers often have the infrastructure to help patients access tecovirimat. Glesby said people who live near these centers may see if they can be seen by a provider there.

In this outbreak, the virus appears to spread largely through sexual contact, primarily among men who have sex with men. At sexual health and other clinics that service this community, providers may have some leads on how to best access Tpoxx.

The FDA said adults and children of all ages can access Tpoxx through the expanded access protocol, and it has been given to children as young as 28 months old. But there haven’t been any clinical studies in children yet.

The Best and Only Treatment Option

For now, Tpoxx is the only available option to treat mpox.

The CDC said people who have been exposed to the virus can receive either the Jynneos or ACAM2000 vaccines to decrease their odds of the infection taking hold. Getting vaccinated within four days of the exposure gives the best chance of preventing the disease, though it may be effective up to 14 days after exposure. Still, the vaccines won’t work to treat the disease once it has taken hold in the body.

It may help to start taking Tpoxx early in the infection, but the CDC doesn’t give a recommended window for starting treatment.

“For most viral infections, early treatment is generally better than later treatment,” Glesby said. “But has this been proven in the case of tecovirimat and monkeypox? No.”

People who have questions about whether they qualify for Tpoxx and whether it’s right for them should get in touch with their primary health care provider.

But don’t expect your provider to be on board with doling out the treatment right away, Gilliams said. Many providers have never treated mpox patients before and may have limited knowledge about how to best treat a case.

“Advocacy for yourself is important here, because this is a new thing and providers may not be super familiar with what to do,” Gilliams said. “Do not rest until you feel comfortable with sort of the responses you’ve received.”

What This Means For You

If you are infected with mpox, contact a health provider about how to access tecovirimat. Be sure to check if will interact with other medications you are taking.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Monkeypox: 2022 U.S. map & case count.

  2. National Library of Medicine: DailyMed. Tpoxx—tecovirimat monohydrate injection, solution, concentrate [drug label].

  3. Centers for Disease Control and Prevention. Guidance for tecovirimat use under expanded access investigational new drug protocol during 2022 U.S. monkeypox cases.

  4. Laudisoit A, Tepage F, Colebunders R. Oral tecovirimat for the treatment of smallpox. N Engl J Med. 2018;379(21):2084-2085. doi:10.1056/NEJMc1811044

  5. Sherwat A, Brooks JT, Birnkrant D, Kim P. Tecovirimat and the treatment of monkeypox — past, present, and future considerations. N Engl J Med. Published online August 3, 2022. doi:10.1056/NEJMp2210125

  6. Centers for Disease Control and Prevention. Information for healthcare providers on obtaining and using TPOXX (tecovirimat) for treatment of monkeypox.

  7. Centers for Disease Control and Prevention. Monkeypox and smallpox vaccine guidance.

By Claire Bugos
Claire Bugos is a health and science reporter and writer and a 2020 National Association of Science Writers travel fellow.