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Atea, Roche change plans for oral COVID-19 drug after trial setback

Atea’s fast ascent last year was due to its plan to use a pill originally developed for hepatitis C infections as a treatment for COVID-19. The strategy resonated with investors and drugmakers. In quick succession, the Boston biotech raised nearly $900 million through a private fundraising, a partnership with Roche and an initial public offering.

Anticipation for Atea’s treatment, known as AT-527, grew earlier this month when Merck and partner Ridgeback Biotherapeutics’ molnupiravir succeeded in a Phase 3 trial. The study proved an oral antiviral could keep infected COVID-19 patients out of the hospital, a hopeful sign that other, similar treatments in development might work, too.

But the results Atea disclosed Tuesday likely mean its drug won’t be an option for at least another year, by which time the acute phase of the pandemic might be past in some countries. That leaves Merck and potentially Pfizer, which has a rival treatment in late-stage testing, in better position, and Atea with an uncertain future. Shares of both Merck and Pfizer each ticked up about 2%, while more than half of Atea’s market value was erased.

Still, Atea believes its pill has a role to play. On a conference call with analysts, chief development officer Janet Hammond said AT-527 could be used when COVID-19 “becomes endemic,” or remains in certain areas but not rapidly spreading worldwide as it is today. That plan depends on whether Atea’s hypothesis — that its drug will prove beneficial if tested only in so-called high-risk patients — is borne out in further testing.

In the study Atea reported on Tuesday, known as MOONSONG, the company enrolled 220 non-hospitalized people with mild or moderate disease and gave them either two doses of AT-527 or a placebo for five days. The study’s goal was to show the drug reduced levels of the virus in patients’ bodies at day seven.

Researchers detected no difference between patients given the pill or placebo. But Atea executives pointed to better results in a group of enrollees with underlying health conditions who were singled out for a separate analysis before the trial began. In those study participants, the researchers detected a “trend” toward viral load reduction that wasn’t different enough to be statistically significant from placebo.

Explaining the study’s failure, Hammond pointed to Atea’s decision to enroll participants with mild to moderate disease regardless of vaccination or underlying health status. Merck, by comparison, enrolled only unvaccinated COVID-19 patients with at least one risk factor for developing severe disease in its Phase 3 trial of molnupiravir.

Umer Raffat, an analyst with Evercore ISI, wrote in a note to clients that AT-527’s viral load reduction in the high-risk patients looks “comparable” to molnupiravir, suggesting the treatment could have a similar benefit in reducing hospitalizations and deaths if tested in that group.

Yet obtaining those results will take time. Atea is now reconsidering the design of its pivotal trial, MORNINGSKY. It plans to enroll only high-risk patients and may change the study’s main goal. That trial isn’t expected to produce results until the second half of 2022, the company said.