Washington, Jan 26 (IANS): US pharmaceutical giant Merck & Co announced that it is discontinuing development of its Covid-19 vaccine candidates -- V590 and V591 -- after they failed to generate immune responses as compared to a natural infection or existing vaccines in the early trial.

The company now plans to focus its Covid-19 research strategy and production capabilities on advancing two therapeutic candidates -- MK-4482 and MK-7110.

"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," Dean Y. Li, president, Merck Research Laboratories, said in a statement late on Monday.

Merck continues to advance clinical programmes and to scale-up manufacturing for two investigational medicines, MK-7110 and MK-4482 (molnupiravir); molnupiravir is being developed in collaboration with Ridgeback Bio.

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, the company said.

Interim results from a Phase 3 study showed a greater than 50 per cent reduction in the risk of death or respiratory failure in patients hospitalized with moderate to severe Covid-19.

Full results from this study are expected in the first quarter of 2021.

In December, Merck announced a supply agreement with the US government to advance the manufacturing and initial distribution of MK-7110.

Molnupiravir (MK-4482) is an oral novel investigational antiviral agent and is currently being evaluated in Phase 2/3 clinical trials in both the hospital and out-patient settings. The primary completion date for the Phase 2/3 studies is May 2021.

Due to the discontinuation of two potential Covid-19 vaccines, 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 1 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 will continue to conduct Covid-19 research.