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2025 Power 100: Mike Cloonan

President & CEO of Sionna Therapeutics

Mike Cloonan

Title

President & CEO

Company

Sionna Therapeutics, in Waltham

Employees

47

Colleges

College of the Holy Cross, University of Virginia

Cloonan is on the frontline of the fight against cystic fibrosis.

As the leader of Sionna Therapeutics, the Holy Cross graduate is leading efforts to develop novel medicines aiming to deliver relief to those suffering from the life-threatening genetic disease, creating high-value biotech jobs in the process.

Originally based in ABI-LAB complex in Natick, the company has had great success in raising funds to support its efforts, with an IPO which resulted in $219.2 million in gross proceeds earlier in 2025. That was just one of multiple nine-figure raises Sionna Therapeutics has pulled off, as the firm has raised more than $500 million in the past three years and is now listed on the Nasdaq.

The successful capital raises have been matched with meaningful progress toward bringing relief to patients, with clinical trials showing its treatments were well tolerated and achieved target clinical exposures.

That success in the laboratory allowed for the company to reach a licensing agreement with biotech giant AbbVie in July 2024.

Sionna Therapeutics graduated from ABI-LAB’s lab space in 2022, moving into a new headquarters in Waltham in 2023.

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Eric Casey is the managing editor at Worcester Business Journal, who primarily covers the manufacturing and real estate industries. 

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