Coultreon Biopharma Raises $125 Million in Series A Financing to Advance Immunology Pipeline

Financing led by Sofinnova Investments and co-led by Forbion and Novo Holdings

Proceeds to advance lead immunology program COL-5671, a potential first-in-class, oral once-daily therapy, across a range of auto-immune indications

Leuven, Belgium. April 28, 2026 - Coultreon Biopharma (formerly Onco3R Therapeutics), a biotechnology company developing best-in-class therapies in immunology, today announced the closing of an oversubscribed $125 million Series A financing round. Sofinnova Investments led the financing round, with Forbion and Novo Holdings as co-leads, joined by Galapagos, Regeneron Ventures, Balyasny Asset Management, Luma Group, Samsara BioCapital, Longwood Fund and Finchley Healthcare Ventures.

Autoimmune diseases remain a significant area of unmet medical need, with many patients cycling through therapies that fail to deliver durable control of inflammation or disease progression. Coultreon’s approach is rooted in more than 15 years of research into salt-inducible kinases (SIKs), a family of proteins that regulate key inflammatory pathways. The company has identified SIK3 as a central driver of pathogenic immune signaling, offering a differentiated and potentially more targeted approach to treating autoimmune disease.

The financing will support the further clinical development of Coultreon’s lead immunology program, COL-5671 (formerly O3R-5671), a highly selective, oral once-daily SIK3 inhibitor currently in Phase 1 studies. The company plans to advance COL-5671 into psoriasis and ulcerative colitis Phase 2 clinical trials, with potential to demonstrate clinical proof-of-concept in 2027.

“This financing marks a major inflection point for our company,” said Pierre Raboisson, CEO at Coultreon Biopharma. “With the support of this top-tier syndicate, we are well positioned to advance our SIK program, while unlocking the broader potential of our pipeline. I am extremely proud of what the team has achieved, and I look forward to advancing our novel first-in-class therapies to patients.”

“We are impressed by Coultreon’s scientific depth, disciplined development strategy, and the strength of its team,” said Maha Katabi, General Partner at Sofinnova Investments. “We have strong conviction in the company’s lead SIK3 program to be valuable across a range of auto-immune diseases where patients would benefit from an alternative oral treatment option.”

COL-5671 is an oral SIK3 inhibitor designed to address core inflammatory pathways across multiple autoimmune diseases. By targeting SIK3, the therapy reduces transcription of key pro-inflammatory cytokines, including TNFα and IL-23, while increasing expression of the immunoregulatory cytokine IL-10. This differentiated mechanism has the potential to deliver broader and more durable disease control compared to existing therapies. COL-5671 was initially developed by Galapagos NV, and ownership was fully transferred to Coultreon in April 2025, when Galapagos provided an initial seed investment.

In preclinical and early clinical studies, COL-5671 has demonstrated favorable pharmacokinetics with once-daily dosing, potent and sustained suppression of inflammatory cytokines, and a safety profile supported by extensive toxicology studies. These data support its development across multiple immune-mediated diseases, including ulcerative colitis, Crohn’s disease, psoriasis, psoriatic arthritis and rheumatoid arthritis.

About Coultreon Biopharma
Coultreon Biopharma is developing best-in-class therapies targeting clinically-validated pathways across immunology and metabolic diseases. The company leverages deep expertise in disease biology, drug discovery, and translational science to select the optimal therapeutic modality to address underlying disease biology with best-in-class therapies. Coultreon’s pipeline is anchored by its leadership in salt-inducible kinase (SIK) biology, with a focus on selectively modulating key inflammatory pathways to deliver broader and more durable disease control. Its lead program, COL-5671, is a highly selective SIK3 inhibitor in clinical development for autoimmune diseases, with potential applicability across multiple immune-mediated conditions. For more information, visit www.coultreon.com or follow us on LinkedIn.

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• Coultreon Biopharma PR Series A_April 28 2026