In a phase 1 trial, the discontinued candidates, V590 and V591, were well tolerated but demonstrated “inferior” immune responses compared with natural infection or those found in other COVID-19 vaccine candidates, the company said.
V590 used the same recombinant vesicular stomatitis virus technology that is the basis for Merck’s FDA-approved Ebola virus vaccine, and V591 used a measles virus vector platform.
“The fewer vaccines [that] make it to market, the lower the global production capacity will be," Florian Krammer, PhD, a professor of vaccinology at the Icahn School of Medicine at Mount Sinai in New York, told Healio. “I liked both approaches Merck took, and it is unfortunate that development is not going to continue.”
Florian Krammer
Merck said the results of the phase 1 trials will be submitted for publication in a peer-reviewed journal.
The company said it will continue to advance clinical programs for its MK-7110 and MK-4482 investigational COVID-19 medicines. MK-7110 is a fusion protein that modulates inflammatory response for SARS-CoV-2, and MK-4482, which is being developed in collaboration with Ridgeback Biotherapeutics, is an antiviral agent that is currently undergoing phase 2 and 3 trials.
“We are grateful to our collaborators who worked with us on these vaccine candidates and to the volunteers in the trials,” Dean Y. Li,MD, PhD, president of Merck Research Laboratories, said in a press release. “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.”