In a tiny study of largely low-risk patients, Atea Pharmaceuticals Inc's investigational COVID-19 antiviral tablet, which is being developed with Roche, failed to help patients with mild and moderate COVID-19, sending the U.S. drugmaker's shares falling more than 70% on Tuesday.

As a result, the business said that it will not deliver results from larger late-stage research this quarter as anticipated, instead it will consider altering the experiment and deferring the data read-out until the second half of 2022.

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The news puts Atea and Roche considerably behind Merck & Co of the United States in the race to develop a COVID-19 treatment tablet.

Merck requested emergency use authorization for its medicine in the United States last week after a trial of mild-to-moderately unwell individuals with at least one risk factor for the disease revealed that it decreased the rate of hospitalization and death by half.

Pfizer is expected to provide antiviral results as early as this quarter.

In premarket trading, Atea's stock plunged 70.9 % to $11.78 while Roche's stock fell 3%. Before the bell, Merck shares were up 3% to $79.60, while Pfizer shares were up roughly 1%.

In the mid-stage research, Atea reported the medication did not reveal a clear reduction in SARS-CoV-2 virus load in the general group of patients with mild or moderate COVID-19 when compared to placebo.

The viral load, on the other hand, decreased in high-risk patients with underlying medical problems.

COVID-19 vaccinated participants were included in the general study group, and nearly two-thirds of the patients in the trial had minor symptoms with no underlying health issues, according to Atea. Vaccinated patients were not included in the Merck study.

Atea said it was changing the main target and patient population of an ongoing late-stage study assessing the medication in non-hospitalized individuals with mild to moderate COVID-19.