Merck Drops COVID-19 Vaccines After Disappointing Trials

Merck & Co. is pulling the plug on its two COVID-19 vaccine candidates and focusing on developing treatments, the drugmaker announced Monday after getting lackluster results in early clinical trials. 

Phase one trials showed that both of its candidates were "well tolerated," but that the immune response they provoked was less than natural infection or what was reported by competing vaccine makers, Merck said. 

"We are grateful to our collaborators who worked with us on these vaccine candidates and to the volunteers in the trials," Merck Research Laboratories President Dean Y. Li said in a statement. "We are resolute in our commitment to contribute to the global effort to relieve the burden of this pandemic on patients, health care systems and communities."

Merck is one of the biggest vaccine makers in the world, touting on its website that it makes vaccines for 11 of the 17 diseases the Centers for Disease Control and Prevention has on its recommended immunization schedules, and that it distributed about 190 million vaccine doses worldwide in 2019. A scientist for the company also notably developed the first vaccines for mumps, rubella and hepatitis B, among other vaccine milestones. 

But Merck had less luck with COVID-19, where its candidates had drawn attention because they used viruses that could replicate once in the body, meaning only one dose would be needed and the effects would be long lasting, according to STAT News. While Merck's statement Monday did not include data, the company said it will be publishing its results in a peer-reviewed journal. 

The two vaccines approved in the U.S. each require two doses. The U.S. Food and Drug Administration first approved Pfizer and BioNTech's vaccine on Dec. 10, which the companies report is 95% effectiveThe agency then approved Moderna's vaccine, which is reportedly 94% effective, just over a week later. The U.K. has also approved a vaccine made by AstraZeneca and the University of Oxford.

One of Merck's vaccines had been developed by Themis Bioscience, which Merck bought in June. The second was a partnership with the International AIDS Vaccine Initiative.

A third vaccine by Australia's University of Queensland was also abandoned in December.

Merck is also working on two drugs to treat COVID-19. One, called MK-7110, is an "investigational recombinant fusion protein that modulates the inflammatory response" to the SARS-Cov-2 virus, the company said. A phase three trial for this treatment shows more than a 50% reduction in the risk of death or respiratory failure for patients hospitalized with COVID-19, it added.

The full results from the phase three trial should be ready by the end of this quarter, and the company said it already has a supply agreement with the U.S. government.

The second, Molnupiravir or MK-4482, is an oral antiviral being developed with Ridgeback Bio. Right now it's in phase two and three trials, Merck said. It's being tested in both hospital and out-patient settings, and Merck said results should be out in May.

--Editing by Alyssa Miller.

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