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# Merck Scraps 2 ‘Inferior’ Covid Vaccine Candidates
- URL: https://www.fdaweb.com/merck-scraps-2-inferior-covid-vaccine-candidates/
- Published: 2021-01-25T12:00:00.000Z
- Updated: 2026-09-14T16:43:58.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5148515

Merck says it is discontinuing developing two Covid-19 vaccine candidates, V590 and V591 based on Phase 1 data showing that the immune responses were inferior to those seen following natural infection and those reported for other Covid-19 vaccines. The Pfizer and Moderna mRNA vaccines that are currently on the market were both shown to be over 90% effective.

The company now says that under its Covid-19 research strategy, it will focus resources on advancing two therapeutic candidates, MK-4482 and MK-7110\. MK-4482 (molnupiravir) is described by Merck as an oral novel investigational antiviral agent being developed in collaboration with Ridgeback Bio, and is currently being evaluated in Phase 2/3 clinical trials in both the hospital and out-patient settings. The company expects initial efficacy data later this quarter. MK-7110 (formerly CD24Fc) is a potentially first-in-class investigational recombinant fusion protein that modulates the inflammatory response to Covid-19 by targeting a novel immune pathway checkpoint. “Interim results from a Phase 3 study showed a greater than 50% reduction in the risk of death or respiratory failure in patients hospitalized with moderate to severe Covid-19,” Merck says. Study results for the therapeutic are also expected this quarter.