Korro Starts First-In-Human Dosing of KRRO-121

The Tip Desk · November 5, 2026 · 3 min read

The company said cash of $124.8 million as of September 30, 2026 will fund operations into the second half of 2028.

Korro Bio, Inc. (KRRO), a clinical-stage biopharmaceutical company developing oligonucleotide RNA-editing medicines, dosed the first cohort of healthy volunteers in ANCHOR, the global Phase 1/2 trial of KRRO-121, and said it expects to dose participants with urea cycle disorders in the first half of 2027.

The start of first-in-human dosing marked the quarter’s defining step. In the second-quarter update, the company had said KRRO-121 remained on track to commence first-in-human trials in the second half of 2026. Part 1 of ANCHOR is a Phase 1 placebo-controlled single ascending dose study, followed by multiple ascending dose cohorts, in up to 50 healthy volunteers. Participants in the first SAD cohort received either a single 2 mg/kg dose of KRRO-121 or placebo. Part 2 is planned as a Phase 2 multiple-dose study in up to 15 participants with UCDs, subject to regulatory clearance. Interim data from ANCHOR are anticipated in the second half of 2027. Korro also received rare pediatric disease designation from the U.S. Food and Drug Administration for KRRO-121 in UCDs.

KRRO-121 is a GalNAc-conjugated RNA-editing oligonucleotide intended to generate a stabilized, de novo glutamine synthetase protein to augment ammonia clearance in hyperammonemia associated with UCDs and hepatic encephalopathy. Chief Executive Officer and President Ram Aiyar said initiating dosing in ANCHOR brings KRRO-121 a meaningful step closer to patients with urea cycle disorders.

The second GalNAc program, KRRO-111 for alpha-1 antitrypsin deficiency, moved from development-candidate nomination in the second quarter to a planned regulatory submission in the first half of 2027. Korro reported best-in-class preclinical data, including more than 95% editing of SERPINA1 transcripts in repeat-dose studies in the NSG-Piz mouse model, with functional M-AAT making up about 93% of total circulating AAT and total AAT reaching 172 micromolar, approximately six-fold above vehicle at Day 57. In the C57BL/6-PiZ model, repeat dosing produced a near-complete elimination of about 95% of pathogenic liver Z-AAT.

Cash, cash equivalents and marketable securities were $124.8 million as of September 30, 2026, compared with $85.2 million as of December 31, 2025. The company said that cash position will fund operating expenses and capital expenditure into the second half of 2028. Cash declined from $137.9 million as of June 30, 2026.

Collaboration revenue was zero for the three months ended September 30, 2026, versus $1.1 million a year earlier, which Korro attributed to the agreed 12-month pause of the Novo Nordisk collaboration in November 2025. Research and development expenses were $12.1 million, versus $13.8 million a year earlier. The company said the decrease was driven primarily by lower KRRO-110 external expenses, personnel and facilities costs, partially offset by higher KRRO-121 and KRRO-111 external expenses and other research and pre-development candidate expenses. General and administrative expenses were $6.4 million, versus $6.5 million a year earlier, primarily from lower information technology and facilities expenses, partially offset by higher personnel expenses mainly from increased stock-based compensation.

Net loss was $17.5 million for the three months ended September 30, 2026, versus $18.1 million a year earlier. Net loss per share was $0.98, versus $1.92, on weighted-average shares of 17.87 million, versus 9.39 million.

Korro said it is focused on execution with two GalNAc-delivered RNA-editing programs advancing toward clinical data. Over the next 12 months, the company listed beginning UCD dosing in Part 2 of ANCHOR in the first half of 2027, subject to regulatory clearance, reporting interim ANCHOR data in the second half of 2027, and submitting a regulatory application for KRRO-111 in the first half of 2027. Preclinical work continued on OPERA-derived REOs targeting AMPKγ1 for longevity and TDP-43 for neurodegenerative diseases including ALS.