Coultreon Biopharma Raises $125M to Challenge Autoimmune Giants

LEUVEN, BELGIUM – April 28, 2026 – In a powerful display of investor confidence, Coultreon Biopharma has closed an oversubscribed $125 million Series A financing round, arming the Belgian biotech with the capital to advance a novel oral therapy for autoimmune diseases. The funding, one of the largest of its kind for a European early-stage company this year, is a significant bet on Coultreon's potential to disrupt a market dominated by blockbuster injectable drugs.

The proceeds will propel the company’s lead candidate, COL-5671, into mid-stage clinical trials for psoriasis and ulcerative colitis. This move positions the therapy as a potential first-in-class treatment that aims to offer patients the efficacy of powerful biologics in the convenience of a once-daily pill.

A New Identity and a Formidable War Chest

The financing round marks a transformative moment for the company, which recently rebranded from Onco3R Therapeutics to Coultreon Biopharma, signaling a sharpened focus on immunology and metabolic diseases. The round was led by Sofinnova Investments and co-led by Forbion and Novo Holdings, with a syndicate of premier life science investors including Regeneron Ventures, Galapagos, and Balyasny Asset Management also participating.

“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.”

Raboisson, a former head of discovery at Galapagos, has steered the company since its inception in 2025. His leadership provides a direct link to the scientific origins of Coultreon's core technology, which was spun out of his former employer. The substantial funding not only validates the team's strategy but also provides a crucial financial runway to navigate the expensive and lengthy process of drug development, with plans to establish clinical proof-of-concept for COL-5671 by 2027.

The Science: Targeting Inflammation at its Source

Coultreon is betting on a novel biological target to overcome the limitations of current autoimmune treatments. The company's approach is built on more than 15 years of research into salt-inducible kinases (SIKs), a family of enzymes that act as master regulators of inflammation. Specifically, Coultreon has identified SIK3 as a central driver of the pathogenic immune signaling that underlies numerous autoimmune conditions.

Its lead drug, COL-5671, is a highly selective, oral SIK3 inhibitor. By targeting this specific kinase, the therapy is designed to orchestrate a dual-action anti-inflammatory response. It reduces the production of key pro-inflammatory cytokines like TNFα and IL-23—the same targets of multi-billion dollar injectable drugs like Humira and Skyrizi—while simultaneously boosting the production of IL-10, a powerful natural cytokine that helps regulate and suppress the immune system.

This differentiated mechanism holds the potential to deliver broader and more durable disease control. For millions of patients who cycle through existing therapies that either lose effectiveness or come with significant side effects and the burden of injections, a safe and effective oral alternative could be life-changing.

A Legacy of Innovation from Galapagos

The story of COL-5671 began within the labs of European biotech giant Galapagos NV as part of its "Toledo" program, an ambitious project exploring SIK inhibitors. An earlier-generation compound, GLPG3970, showed promising clinical signals in patients with psoriasis and ulcerative colitis, providing crucial validation for the SIK-inhibition concept.

However, Galapagos ultimately chose not to advance its initial SIK candidates, instead spinning out the refined and highly selective COL-5671 (then known as O3R-5671) into the newly formed Coultreon in April 2025. As part of the deal, Galapagos provided an initial €20 million seed loan, which has now converted to equity, and joined the Series A round as an investor. This continued financial involvement underscores Galapagos's belief in the underlying science, even as it has shifted its own strategic priorities.

Coultreon's asset is designed to be a more precise tool. By selectively targeting only SIK3, COL-5671 aims to avoid potential toxicities associated with inhibiting other SIK family members, a key improvement over earlier compounds and a critical factor in its favorable safety profile observed in early studies.

Top Investors Bet on a Market Ripe for Disruption

The sheer size of the Series A round and the caliber of its participants speak volumes about the perceived value of Coultreon's platform. The global markets for psoriasis and ulcerative colitis are collectively worth tens of billions of dollars annually and are projected to continue growing. While crowded with treatments from pharmaceutical heavyweights, investors see a clear opening for a differentiated oral therapy.

“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.”

The participation of firms like Sofinnova, known for backing foundational science, and Forbion, with its track record of building billion-dollar companies, highlights the blend of scientific novelty and commercial potential. Furthermore, the inclusion of Regeneron Ventures, the new corporate venture arm of the biopharma giant Regeneron, adds another layer of strategic validation.

With its coffers full, Coultreon now faces the critical task of execution. The company will advance COL-5671 into Phase 2 trials for both psoriasis and ulcerative colitis, with the potential to expand into other immune-mediated conditions like Crohn's disease and rheumatoid arthritis. The data from these upcoming trials will be the true test of whether this new approach to taming inflammation can deliver on its immense promise for patients.