Onco3R Therapeutics, a clinical-stage immunology and oncology biotech company based in Leuven, Belgium, has successfully completed dosing of the first cohort in the Phase 1 trial of its novel SIK3 inhibitor, O3R-5671. Dosing is now underway in the second cohort, which is investigating a higher dose.

In this first cohort, six subjects received a dose of 5mg O3R-5671. Preliminary pharmacokinetic and safety data support investigating a higher dose in the second cohort, the company said.

O3R-5671 is a highly selective SIK3 inhibitor, specifically designed to avoid the toxicities associated with SIK1 and SIK2 inhibition. Preclinical studies have shown that O3R-5671 inhibits the release of inflammatory cytokines TNFα and IL-23 while promoting the release of the immunomodulatory cytokine IL-10. Data from animal models of autoimmune disease suggest that O3R-5671 could potentially treat  a variety of autoimmune diseases including ulcerative colitis, Crohn’s Disease, psoriasis, psoriatic arthritis and rheumatoid arthritis.

“Many patients with autoimmune diseases relapse or cannot tolerate existing therapies. With O3R-5671, we aim to develop an effective and well-tolerated oral treatment,” said Pierre Raboisson, CEO and Founder of Onco3R Therapeutics.

“Dosing completion of the first cohort in our first-in-human trial marks an important step forward in this research. In this group, we observed no clinically significant safety findings, and the pharmacokinetics were consistent with our expectations. We are proud of this milestone and remain on track to complete the trial, with final results anticipated in the first half of 2026,” he added.