Merck just pulled the plug on its COVID-19 vaccines - Here's why

Merck is abandoning its COVID-19 vaccine development, dropping two work-in-progress drugs after they failed to live up to expectations in early testing. The pharmaceutical company says it will now focus its attentions on COVID-19 therapeutic candidates, which could help reduce the death rate of those infected with serious cases of coronavirus.

SARS-CoV-2/COVID-19 vaccine candidates V590 and V591 had been in Phase 1 clinical studies, and it's the results from those which have prompted today's decisions. According to Merck, "both V590 and V591 were generally well tolerated, but the immune responses were inferior to those seen following natural infection and those reported for other SARS-CoV-2/COVID-19 vaccines."

Those other vaccines, such as Pfizer and BioNTech's BNT162b2 and Moderna's mRNA-1273, have already begun widespread deployment in the US and abroad. Administered in two doses, split 3-4 weeks apart, the vaccines typically showed upward of 95-percent efficacy in trials by the companies. Elsewhere, efforts are underway in the UK and other countries on other vaccine candidates.

The reality, however, is that demand for vaccinations outstrips production of the drugs themselves, and that's unlikely to change significantly in the coming months. Cases of COVID-19 in the US continue to rise dramatically, meanwhile, with over 171,000 new cases recorded yesterday alone. Almost 25 million cases of coronavirus have been recorded in the US since the start of the pandemic, and COVID-19 has been blamed for over 416,000 deaths in America.

Even as production ramps up, issues with distribution have arisen. Earlier this month, for example, differing approaches across the US states were highlighted as a pinch-point for vaccination efforts. Some states, such as New York, have warned healthcare providers that they face fines of up to $100,000 if they're found to be falling behind in administering their allotted supplies of the drugs.

Effective therapeutic treatment, therefore, is just as vital as vaccines are, if the death rate is to be managed. Merck's two candidates for that – MK-7110 and MK-4482 – are currently in the process of scaling up manufacturing.

MK-7110 – previously known as CD24Fc – has been shown to have a greater than 50-percent reduction in death or respiratory failure of those hospitalized with moderate to severe COVID-19. A study is underway with full results expected sometime in Q1 2021, but Merck has already inked an agreement with the US government on manufacturing and initial distribution. Upon FDA approval or emergency use authorization (EUA), the US will pay Merck up to around $356 million for 60,000-100,000 doses of the drug.

Molnupiravir, or MK-4482, meanwhile, is being developed by Merck and Ridgeback Bio, and is currently in Phase 2/3 clinical trials. An oral novel investigational antiviral agent, it was originally developed for cases of influenza; Merck says it expects initial efficacy data sometime this quarter.