Korro Bio delivered a double whammy of bad news, reporting lackluster data on its lead candidate and a pause to its partnership with Novo Nordisk. The biotech, which suffered a 79% stock drop in the wake of the updates, is laying off 34% of its employees to extend its cash runway deeper into 2027.
Massachusetts-based Korro was focused on KRRO-110, an RNA editing oligonucleotide encapsulated in a lipid nanoparticle (LNP). The biotech designed the drug candidate to treat alpha-1 antitrypsin deficiency (AATD) by repairing a mutation and restoring normal levels of AAT protein. Wave Life Sciences has a rival GalNAc-conjugated RNA editing oligonucleotide in development.
Korro is pivoting its AATD program to GalNAc after levels of functional AAT fell short of expectations in a phase 1/2a trial of KRRO-110. An initial analysis indicated that the pharmacokinetics of the delivery components were different in healthy volunteers and AATD patients.
In response, Korro has dropped plans to complete additional single-ascending dose cohorts. The biotech is still assessing the next steps, if any, for KRRO-110 in the multiple-ascending dose part of the trial. The assessment is taking place in parallel to the ramping up of a GalNAc-based AATD program, which Korro is aiming to get into the clinic in 2027.
The pivot to GalNAc eliminates one way for Korro to differentiate its program from Wave, which shared data on its AATD asset in September. Korro CEO Ram Aiyar, Ph.D., told attendees at the J.P. Morgan Healthcare Conference in January that the company chose LNPs as its delivery vehicle because the challenge with the AATD program “was to get super high levels of editing.”
Preclinical data suggested the bet on LNPs may pay off. BMO Capital Markets analysts wrote in a note to investors in September that “Korro’s LNP delivery may be advantageous over [Wave’s] GalNAc delivery, given the LNP's anticipated biodistribution into lungs.” The analysts published the note in response to preclinical data showing 40% RNA editing in patient monocytes with LNPs versus 0% with GalNAc.
The unraveling of the LNP bet leaves Korro’s near-term hopes on KRRO-121, a GalNAc-conjugated construct designed to create a de novo protein variant to activate a biological pathway for patients with hyperammonemia. Korro is aiming to start testing KRRO-121 in humans in the second half of 2026.
The biotech shared details of the pipeline changes alongside news of a 12-month pause to its Novo Nordisk pact. Novo committed up to $530 million to form the deal and paid $10 million in relation to the first program 13 months ago. The partners have paused work to reassess the rationale for the current target under the first research program. Korro has agreed to promptly wind down its R&D activities.
Executives at Korro are now revising revenue expectations for the next 12 months. The biotech responded to the setbacks by outlining plans to lay off 34% of the workforce. Having laid off one-fifth of its workforce in May, Korro had 87 full-time employees at the end of September.
The latest round of layoffs is intended to extend Korro’s runway into the second half of 2027. Moving the end of the runway later into 2027 positions the biotech to generate clinical data on KRRO-121, advance at least one additional program and execute partnership talks to broaden pipeline development before it runs out of money.
Korro shares fell 79% to $6.55 in premarket trading. Shares in Wave rose 6% to $7.35.