Effectiveness of Antiviral Drugs Against Monkeypox Uncertain: Study

WEDNESDAY, May 25, 2022 (HealthDay News) -- Up until recently monkeypox infection outside of Africa was rare, but a look back at seven cases occurring in Britain over the past few years gives hints at what drugs work to fight the disease -- and which don’t.

The need to better understand treatments for monkeypox became more urgent this month when more than a hundred new cases were recorded across Europe and North America.

"As public health officials are trying to understand what is causing the May 2022 monkeypox outbreaks in Europe and North America -- which have affected several patients who reported neither travel nor an identified link to a previously known case -- our study offers some of the first insights into the use of antivirals for the treatment of monkeypox in humans," said study lead author Dr. Hugh Adler. He's with the Liverpool University Hospitals NHS Foundation Trust.

The new analysis, published May 24 in The Lancet Infectious Diseases, looked at outcomes for seven people treated in Britain for monkeypox between 2018 and 2021. Three patients were thought to have become infected while in Africa, while three more occurred as part of a "case cluster" in Britain.

According to a Lancet news release, one more case "occurred in a health care worker 18 days after initial exposure to the virus and was the first example of monkeypox transmission in a hospital setting outside of Africa."

Two antiviral medications used against smallpox, brincidofovir and tecovirimat, were used "off-label" -- meaning they are not specifically approved to treat monkeypox -- as treatment in the monkeypox cases.

Speaking at a U.S. Centers for Disease Control and Prevention press conference on Monday, Dr. Brett Petersen, a medical officer with the agency's Poxvirus and Rabies Branch said both of these antivirals could be tried against cases that are newly emerging in the United States.

Tecovirimat has already gotten expanded access approval by the U.S. Food and Drug Administration to treat monkeypox, he noted. The CDC is working to get similar emergency access approval for the newer smallpox medication, brincidofovir.

The British researchers noted there are currently no licensed treatments in the United Kingdom for monkeypox, and it's uncertain how long the disease is contagious. Patients are typically placed in isolation in the hospital while treatment occurs.

According to Adler's team, only one of the two antivirals appeared to have any benefit in curbing monkeypox.

Used a week after the onset of the typical monkeypox rash, brincidofovir "was not observed to have any convincing clinical benefit in treating monkeypox and alterations in liver blood tests were observed," according to the release.

In any case -- and as often happens -- all four patients who got brincidofovir did make a full recovery from their illness, the researchers noted.

On the other hand, one patient treated in 2021 with the other antiviral, tecovirimat, "experienced a shorter duration of symptoms and upper respiratory tract viral shedding than the other cases in this cluster," according to the release.

However, the British team stressed that the number of patients studied remains so small that no definite conclusions can be drawn at this point in time as to what drugs might work best to shorten or ease the disease.

They noted all of the patients experienced "mild" cases of monkeypox, and none developed severe complications such as pneumonia or sepsis (blood infection). One patient did develop an abscess that required drainage, and another suffered a relapse about six weeks after hospital discharge.

New information on how long a patient might remain infectious with monkeypox did emerge from the study.

"During previous outbreaks of monkeypox, patients were considered infectious until all lesions crusted over. In these seven UK cases, viral shedding was observed for at least three weeks following infection. However, data on infectivity remains limited, and is an important area for future study," study co-author Dr. Catherine Houlihan said in the release. She's with the UK Health Security Agency and University College London.

According to the study authors, typical symptoms of monkeypox include fever, rash, and swollen lymph nodes. Complications can sometimes occur, such as inflammation of the lungs, inflammation of the brain, vision-threatening inflammation of the cornea, and secondary bacterial infections.

The current outbreak affecting the United States, Canada, Britain and some other European countries is troubling because patients typically did not contract the illness while in Africa.

However, "although this latest outbreak has affected more patients than we had previously encountered in the UK, historically monkeypox has not transmitted very efficiently between people, and overall the risk to public health is low," Adler said in the journal release.

Speaking at the Monday CDC briefing, one agency expert echoed those sentiments.

"The strain in the identified cases, both in the United States and globally, is West African strain, which is the milder of the two strains of monkeypox virus," said Capt. Jennifer McQuiston, deputy director of the agency's Division of High Consequence Pathogens and Pathology.

"Most people who are infected with monkeypox recover within two to four weeks without specific treatment," she said.

More information

The U.S. Centers for Disease Control and Prevention has more about monkeypox.

SOURCES: The Lancet Infectious Diseases, news release, May 25, 2022; U.S. Centers for Disease Control and Prevention media briefing, May 23, 2022