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With repurposed antiviral, Atea draws $215M as it preps Phase II COVID-19 trial

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Led by veteran biotech entrepreneur Jean-Pierre Sommadossi, Atea believes an antiviral it had been developing to treat HCV has promise to treat COVID-19 in a population that extends beyond hospitalized patients. The company said Wednesday an investor syndicate has provided $215 million in a series D round that will fund a clinical study of the pill, with dosing of coronavirus patients to begin this month.

Bain Capital Life Sciences led the round, with participation from fellow new investors RA Capital Management, Perceptive Advisors, Rock Springs Capital, Adage Capital Management, Redmile Group, Omega Funds, and funds and accounts managed by T. Rowe Price. Existing investors including Morningside Ventures, Cormorant Asset Management, Ally Bridge Group, Sectoral Asset Management also took part.

After it became clear the COVID-19 outbreak would become a pandemic, Atea Pharmaceuticals Inc. began exploring development of direct-acting antiviral AT-527 against SARS-CoV-2, the virus that causes COVID-19. The purine nucleotide prodrug, which targets RNA polymerase to inhibit viral replication, was in Phase II testing for HCV.

Bain’s Andrew Hack told BioCentury the firm had been in talks with Atea over the last year, but was particularly attracted to the biotech when it decided to adapt AT-527’s development to address the outbreak.

“We think it’s going to enable the company to have the first orally available pill for the disease,” he said.

Sommadossi, Atea’s chairman and CEO, told BioCentury the company had begun talking to investors at the J.P. Morgan Healthcare Conference in January about raising a mezzanine round with crossover investors.

The company realized in February that COVID-19 was going to become a pandemic. “We shifted all our immediate resources,” Sommadossi said.

Thanks to a combination of clinical safety data and in vitro activity data, Atea was able to move quickly to a Phase II COVID-19 trial, Sommadossi said. AT-527 has been tested in 40 HCV patients.

“The fact that this has already been in a substantial number of patients allows for AT-527 to potentially leapfrog some of the other molecules that are being developed for COVID-19,” Hack said.

Sommadossi said the company already has enough doses to treat 8,000 patients and an established manufacturing process. Atea’s current capacity could be scaled up to produce doses for about 80,000-90,000 patients, but the company would partner with either a large pharma or CMO to produce doses past that level.

The Phase II trial is to enroll up to 180 adults hospitalized with moderate COVID-19 and one or more risk factor. Sommadossi expects the first patient to be dosed this month, with data due in August.

According to BioCentury’s COVID-19 Resource Center, there are at least 10 antivirals in development that target viral polymerases, including remdesivir from Gilead Sciences Inc. (NASDAQ:GILD), which received Emergency Use Authorization from FDA this month. Remdesivir was also approved in Japan as Veklury (see “Spotlight on Strategies to Block Viral Entry or Replication”).

Remdesivir’s efficacy and authorization has been helpful to validate the target, Sommadossi said, but because it is administered intravenously, its use will be limited to hospitalized patients.

Hack echoed the sentiment. “AT-527 potentially has a significant advantage over remdesivir, because the reality is that it’s an IV medicine that also has some toxicity, so that’s only going to be appropriate for the most severe hospitalized patients,” he said. “An oral medicine like this, we think, can be developed not only for less sick hospitalized patients, but also for outpatient use.”

Atea is already designing a trial of AT-527 in an outpatient setting, Sommadossi said. After safety has been shown, the company plans to start a large study this fall in high-risk individuals, such as healthcare workers, who have tested positive. The study is to include symptomatic and asymptomatic patients.

“The goal is not to just decrease disease progression, but to have an early treatment and prevent hospitalization -- to curb any damage until there’s a vaccine,” Sommadossi said.

Sommadossi helped found two prior antiviral companies: Idenix Pharmaceuticals Inc., which Merck & Co. Inc. (NYSE:MRK) acquired for $3.9 billion in 2014; and Pharmasset Inc., which Gilead took out for $11.2 billion in 2012, gaining HCV blockbuster therapy Sovaldi sofosbuvir.

For Atea, which was formed in 2014, the goal was to develop antivirals for RNA viruses, specifically purine nucleotide analogs. Although the class had been known for over a decade to be a potent antiviral, severe toxicities had plagued the area, Sommadossi said.

The company’s platform utilizes specific chemical modifications in the structure of the purine, especially at the base level, to enhance efficacy and safety.

AT-527, for example, is a double prodrug modified to maximize absorption and rapid distribution to key sites of viral replication.

Atea’s expertise in the area was another key draw for Bain.

“In the virology space, we’ve come to understand that nucleotide analogs are probably the most potent and least susceptible to resistance of the direct acting antivirals. We’re very attracted to nucleotide as a category,” Hack said. “There are few groups that have the kind of nucleoside chemistry and development expertise that’s necessary to make safe and effective orally available nucleoside analogs, and Atea certainly has one of the leading teams in that arena.”

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