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Merck to discontinue development of COVID-19 vaccine candidates

Following Phase I results, Merck will discontinue its development of V590 and V591, two COVID-19 vaccine candidates.

COVID-19 vaccines

Merck has announced that the company is discontinuing development of its COVID-19 vaccine candidates, V590 and V591. The company now plans to focus its COVID-19 research strategy and production capabilities on advancing two therapeutic candidates, MK-4482 (molnupiravir) and MK-7110.

This decision follows Merck’s review of findings from Phase I clinical studies for the vaccines. In these studies, both V590 and V591 were generally well tolerated, but the immune responses were inferior to those seen following natural infection and those reported for other COVID-19 vaccines. Merck says it is continuing to advance clinical programmes and to scale-up manufacturing for MK-7110 and MK-4482.

MK-7110 (formerly CD24Fc) is a potentially first-in-class investigational recombinant fusion protein that modulates the inflammatory response to SARS-CoV-2, principally by targeting a novel immune pathway checkpoint. Interim results from a Phase III study showed a greater than 50 percent reduction in the risk of death or respiratory failure in patients hospitalised with moderate to severe COVID-19. Full results from this study are expected in the first quarter of 2021. 

MK-4482 is an oral novel investigational antiviral agent being developed in collaboration with Ridgeback Bio. The drug is currently being evaluated in Phase II/III clinical trials in both the hospital and out-patient settings. The primary completion date for these studies is May 2021. The company anticipates initial efficacy data in the first quarter of 2021.

“We are grateful to our collaborators who worked with us on these vaccine candidates and to the volunteers in the trials,” said Dr Dean Li, President of Merck Research Laboratories. “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.”

Due to the discontinuation, the company will record a charge in the fourth quarter of 2020. The charge will be included in Merck’s generally accepted accounting principles (GAAP) results, but will not impact non-GAAP results.

Merck and its collaborators plan to submit the results of the Phase I studies for V590 and V591 for publication in a peer-reviewed journal. In addition to advancing the development and production of MK-7110 and MK-4482, Merck says it will continue to conduct COVID-19 research. 

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