Merck ends COVID vaccine program, cites inferior immune responses

Drugmaker Merck & Co said on Monday it would stop development of its two COVID-19 vaccines and focus pandemic research on treatments, with initial data on an experimental oral antiviral expected by the end of March.

Merck was late to join the race to develop a vaccine to protect against the coronavirus, which has so far killed more than 2 million people and continues to surge in many parts of the world including the United States.

The company will record a pre-tax discontinuation charge in the fourth quarter for vaccine candidate V591, which it acquired with the purchase of Austrian vaccine maker Themis Bioscience, and V590, developed with nonprofit research organization IAVI, Merck said in a statement.

In early trials, both vaccines generated immune responses that were inferior to those seen in people who had recovered from COVID-19 as well as those reported for other COVID-19 vaccines, the company said.

The announcement is a setback to the fight against the pandemic and comes a month after Sanofi and GlaxoSmithKline delayed launch of their shot to late 2021, underscoring the challenges of developing vaccines at record speed.

Tens of millions of doses of vaccines from rivals Pfizer Inc and German partner BioNTech as well as from Moderna Inc have so far been administered globally.

Johnson & Johnson, AstraZeneca Plc and others are also racing to develop safe and effective vaccines to protect against the virus.

Merck said it would focus COVID-19 research and manufacturing efforts on two investigational medicines: MK-7110 and MK-4482, which it now calls molnupiravir.

Molnupiravir, which is being developed in collaboration with Ridgeback Bio, is an oral antiviral being studied in both hospital and outpatient settings.

Merck said a Phase 2/3 trial of the drug was set to finish in May, but initial efficacy results were due in the first quarter and would be made public if clinically meaningful.

Merck said results from a Phase 3 study of MK-7110, an immune modulator being studied as a treatment for patients hospitalized with severe COVID-19, were expected in the first quarter.

Shares of Merck fell 1% to $80.12 in trading before the bell.