CHICAGO, Aug 4 ― As US monkeypox cases rise, US health agencies in a medical journal article published yesterday defended their decision to require human trial data to show that SIGA Technologies' experimental drug TPOXX is safe and effective to treat the virus.

US agencies have been under pressure to ease access to the drug, which is being distributed by the US Centers for Disease Control and Prevention (CDC) under a special "compassionate use” access that requires doctors to request it from the agency or their health department and enroll each patient in a study.

As of July 22, 223 people have been treated with the drug, compared with more than 6,000 known cases in the United States.

The FDA approved TPOXX in 2018 for smallpox in adults and children based on studies of animals infected with monkeypox and rabbitpox, as well as safety data in healthy people. It can only be sold to the US Strategic National Stockpile.

Authors of the article in the New England Journal of Medicine from the Food and Drug Administration, the CDC and the National Institutes of Health (NIH) said the latter is planning a US-based randomised clinical trial.

Data from that study will be used to determine whether the drug gains US approval for monkeypox.

The drug, also known as tecovirimat, is approved for both smallpox and monkeypox in the UK and Europe. The European Union approved it under an "exceptional circumstances” pathway that allows for marketing approval when data cannot be obtained even after authorisation.

Although TPOXX was only tested in healthy people, the European Medicines Agency said it expects side effects to be similar in infected people, and deemed the drug's benefits to be greater than its risks.

Dr Jay Varma, director of the Cornell Center for Pandemic Prevention and Response who has advocated for broader access to the drug, said the FDA's standards ensure US drugs are safe and set a high bar for the world, but in some circumstances, "those strict standards are harming us.”

There were 1.7 million doses of the treatment in the US Strategic National Stockpile at the start of the current outbreak in May.

On July 21, the CDC and the FDA began allowing doctors to prescribe the drug before the trial paperwork is completed, but still requires approval of a hospital's institutional review board for each dose.

"It's definitely better. It's still very burdensome,” said Dr Karen Krueger, an infectious disease expert at Northwestern Medicine in Chicago, who said there is additional paperwork after the patient visit and for several follow-up visits.

"It's doable but certainly a lot more challenging than how we normally prescribe drugs.”

Neither the FDA nor the CDC immediately responded to a request for comment.

Northwestern has treated at least 20 monkeypox patients with TPOXX and will be one of the sites for the NIH trial.

To win approval, SIGA Chief Scientific Officer Dennis Hruby estimates it will likely take a 500-patient, placebo-controlled clinical trial in the United States.

If cases remain high, the trial could be fully enrolled within a few months. "It's not a terribly long trial,” he said.

SIGA Chief Executive Phillip Gomez said the company is working to launch trials in the UK, Canada, the United States and Europe.

If the United States declares monkeypox a national emergency, Gomez said the drug could be granted an emergency use authorisation.

However, because the FDA has been "very clear” they want full, placebo-controlled trials, that could still take time, he said. ― Reuters