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Korro Bio stock plummets after mixed AATD trial results

Published 12/11/2025, 22:56
© Reuters.
KRRO
-4.21%

Investing.com -- Korro Bio Inc. (NASDAQ:KRRO) stock plummeted 80% after the company reported mixed results from its KRRO-110 clinical trial in Alpha-1 Antitrypsin Deficiency (AATD) patients.

The clinical-stage biopharmaceutical company announced that while KRRO-110 successfully produced functional M-AAT protein in AATD patients, the treatment failed to reach projected levels of functional protein following a single administration. The company’s REWRITE Phase 1/2a clinical trial showed the greatest increase of M-AAT protein from baseline was approximately 2 µM, falling short of the protective threshold of 11 µM needed for therapeutic benefit.

In response to these disappointing results, Korro Bio is pivoting its strategy to focus on GalNAc delivery for AATD patients, with a development candidate nomination expected in the first half of 2026. The company also announced KRRO-121 as its next development candidate, designed to create a de novo protein variant for patients with hyperammonemia.

"While a single administration of KRRO-110 achieved functional protein production, it did not achieve the protein levels we projected based on preclinical data," said Ram Aiyar, Ph.D., CEO and President of Korro Bio. He noted that initial analysis indicated differences in pharmacokinetics between healthy volunteers and AATD patients.

The company is implementing a strategic restructuring that will reduce its workforce by approximately 34% while extending its cash runway into the second half of 2027. Korro reported $102.5 million in cash, cash equivalents and marketable securities as of September 30, 2025, compared to $163.1 million at the end of 2024.

For the third quarter, Korro reported a net loss of $18.1 million, improved from a $21.0 million loss in the same period last year. The company also announced the resignation of Chief Medical Officer Dr. Kemi Olugemo, effective November 12, 2025.

This article was generated with the support of AI and reviewed by an editor. For more information see our T&C.

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