Merck (NYSE: MRK), known as MSD outside the United States and Canada, today announced that the company is discontinuing development of its SARS-CoV-2/COVID-19 vaccine candidates, V590 and V591, and plans to focus its SARS-CoV-2/COVID-19 research strategy and production capabilities on advancing two therapeutic candidates, MK-4482 and MK-7110. This decision follows Merck’s review of findings from Phase 1 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 SARS-CoV-2/COVID-19 vaccines. Merck continues to advance clinical programs and to scale-up manufacturing for two investigational medicines, MK-7110 and MK-4482 (molnupiravir); molnupiravir is being developed in collaboration with Ridgeback Bio. “We are grateful to our collaborators who worked with us on these vaccine candidates and to the volunteers in the trials,” said Dr.