Merck cans one COVID-19 drug, scraps a clinical trial of another

Merck has disclosed more setbacks to its COVID-19 strategy. Having already pulled out of vaccines, Merck has now stopped developing one medicine in hospitalized patients and given up completely on another drug in COVID-19.

The total discontinuation relates to MK-7110, the biological immunomodulator that Merck picked up in its $425 million buyout of OncoImmune late last year. Merck splashed the cash after seeing phase 3 data that offered encouragement that MK-7110 fortifies an innate immune checkpoint against excessive inflammation. Months later, the FDA said Merck would need more data for approval. 

After weighing up what it will take to meet the FDA’s request, Merck has stopped development of the drug in COVID-19. Merck said new clinical trials and “research related to manufacturing at scale” would be needed to win approval, pushing market access back to the first half of next year.

“Given this timeline and these technical, clinical and regulatory uncertainties, the availability of a number of medicines for patients hospitalized with COVID-19, and the need to concentrate Merck’s resources on accelerating the development and manufacture of the most viable therapeutics and vaccines, Merck has determined to discontinue development of MK-7110 for COVID-19,” Merck said in a statement.

Merck also shared a mixed update on its other COVID-19 drug candidate, molnupiravir. The oral antiviral, which Merck is developing with Ridgeback Biotherapeutics, is advancing into phase 3 in COVID-19 outpatients but has reached the end of the line in the hospitalized population. 

Ridgeback and Merck scrapped plans to move into phase 3 in hospitalized patients after mid-stage data showed “molnupiravir is unlikely to demonstrate a clinical benefit” in the population. The action is in keeping with findings that other drugs that target the virus, notably anti-SARS-CoV-2 antibodies, are less effective in hospitalized patients, who may have inflammatory complications of infection that are unaffected by molecules that tackle the pathogen itself. 

The changes leave the molnupiravir outpatient trial as Merck’s big hope in COVID-19. Merck said the phase 2 portion of the outpatient study linked molnupiravir to a lower rate of hospitalization and death than placebo, but “the number of events reported are not sufficient to provide a meaningful measure of clinical effect.”  

Both phase 2 trials generated evidence that molnupiravir inhibits replication of the coronavirus. The effect was most pronounced in patients enrolled within five days of symptom onset—pointing to one reason the antiviral may be more effective in outpatients—and the highest, 800-mg dose drove the biggest antiviral effect.

Merck expects to have data from the phase 3 outpatient trial in September or October, putting it on track to seek emergency use authorization in the second half of the year. If approved, molnupiravir could fill the gap in the COVID-19 toolkit for a simple way of reducing the risk of negative outcomes in people recently infected with the coronavirus. A clinical trial of molnupiravir for post-exposure prophylaxis is planned for the second half of the year.