Korro Bio Adds Drug Candidate for Genetic Liver and Lung Disease
The RNA-editing drug developer ended June with $137.9 million in cash and securities, which it expects to fund operations into the second half of 2028.
Korro Bio, Inc. (KRRO), a biopharmaceutical company developing RNA-editing medicines, nominated KRRO-111 for alpha-1 antitrypsin deficiency during the second quarter, delivering a pipeline milestone outlined in its previous two updates. The nomination extended a sequence that began with the selection of hyperammonemia candidate KRRO-121 in the fourth quarter of 2025 and continued with preparations to select the AATD candidate in 2026.
The addition gave Korro another named development candidate using GalNAc-conjugated oligonucleotides, which are delivered by injection under the skin. KRRO-111 was engineered to reach liver cells and enlist their naturally occurring ADAR enzyme to repair a mutation in the RNA instructions for alpha-1 antitrypsin. The intended result is restoration of normal protein production in a genetic disorder affecting the liver and lungs.
The supporting evidence remained preclinical. In mouse studies, KRRO-111 corrected more than 90% of the targeted transcripts, translating into approximately 90% repaired functional protein in plasma. The company said the findings supported the potential for repeat dosing to achieve effects functionally equivalent to a DNA-modifying therapy without changing the genome.
Korro's lead program also advanced toward its next regulatory step. KRRO-121 received European Medicines Agency orphan drug designation for urea cycle disorders. Korro said it remains on track to commence a first-in-human trial in the second half of 2026; its first-quarter update had described an expected regulatory filing in that period. Korro listed obtaining regulatory approval to initiate clinical trials among its remaining milestones for the year.
KRRO-121 addressed a different problem from KRRO-111. It was designed to generate a stabilized version of glutamine synthetase, an enzyme involved in an alternative route for clearing ammonia, rather than repair an individual urea-cycle mutation. The company said that approach could address urea cycle disorders across different mutational backgrounds, as well as hepatic encephalopathy, a complication of liver disease associated with impaired ammonia clearance.
The pipeline additions accompanied a lower research bill. Research and development expenses for the three months ended June 30 fell to $13.6 million from $20.1 million a year earlier. The decline primarily reflected lower external expenses for KRRO-110, personnel costs, and other research and pre-development candidate expenses. Higher external spending on KRRO-121 and KRRO-111 partly offset those reductions.
Korro's quarterly net loss narrowed to $18.9 million from $25.8 million a year earlier. General and administrative expenses totaled $6.5 million, and total operating expenses were $20.1 million. The financial results accompanied work on both nominated candidates and continued refinement of the oligonucleotide chemistry used in the company's OPERA RNA-editing platform.
The smaller loss came despite the absence of collaboration revenue. Collaboration revenue was zero for the quarter, against $1.5 million a year earlier. The decrease reflected an agreed 12-month pause in Korro's Novo Nordisk collaboration. The pause remained the explanation for the missing collaboration income while the company advanced its own development programs.
Financing provided the financial backdrop to those programs. Korro had reported an $85 million private placement in its preceding updates. It now expects its June-end cash, cash equivalents, and marketable securities to cover operating expenses and capital expenditure requirements into the second half of 2028. The company said those resources are sufficient to reach clinical data milestones for KRRO-121 and KRRO-111.
Beyond the planned clinical start for KRRO-121, Korro expects to nominate a development candidate for a third GalNAc-conjugated program in the second half of 2026, putting another candidate-selection milestone on its remaining calendar.
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