Coultreon Biopharma Secures $125M Series A for SIK3 Inhibitor

Coultreon Biopharma, a Belgium-based biotechnology company formerly known as Onco3R Therapeutics, completed a $125 million oversubscribed Series A financing round on April 28, 2026. The funds will drive the clinical development of COL-5671, a highly selective oral once-daily SIK3 inhibitor currently in Phase 1 studies. Coultreon plans to initiate Phase 2 trials in psoriasis and ulcerative colitis, targeting clinical proof-of-concept data in 2027. The asset originated from Galapagos, which transferred full ownership to Coultreon in April 2025 following a seed investment.

Sofinnova Investments led the round, with Forbion and Novo Holdings serving as co-leads. Additional participants included Galapagos, Regeneron Ventures, Balyasny Asset Management, Luma Group, Samsara BioCapital, Longwood Fund, and Finchley Healthcare Ventures. This financing equips Coultreon to explore SIK3 inhibition as a novel mechanism for autoimmune diseases, building on preclinical evidence in conditions like Crohn's disease and rheumatoid arthritis. The company, led by CEO Pierre Raboisson who previously headed discovery at Galapagos, has shifted focus to immunology and metabolic diseases after rebranding.

The round underscores investor confidence in Coultreon's platform, which targets salt-inducible kinases to address inflammation more precisely than existing therapies. With Phase 1 data supporting progression, the funding positions the startup to generate mid-stage results that could validate SIK3 as a breakthrough target in immunology, amid a competitive landscape for oral autoimmune treatments.