Merck, known as MSD outside the United States and Canada, has announced that the company is discontinuing development of its two COVID-19 vaccine candidates, V590 and V591, following a review of findings from Phase 1 clinical studies for the vaccines.

In these studies, both candidates 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 now plans to focus its research strategy and production capabilities on advancing two therapeutic candidates, MK-4482 and MK-7110. 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 and is an oral antiviral being studied in both hospital and outpatient settings. Merck will also continue to evaluate the potential of the measles-virus vector and vesicular stomatitis virus vector-based platforms and pursue broader pandemic-response capabilities.

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.

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