AbolerIS Pharma Announces First Patient Dosed in Part II of Phase 1 Study of ABO21009, a Novel Anti-CD45RC Antibody, for Rheumatoid Arthritis

– ABO21009’s unique mechanism of action depletes pathogenic Effector T and B cells while inducing expansion of Regulatory T cells for lasting efficacy, and preserving overall immunity –

GOSSELIES, Belgium and NANTES, France, Jan. 8, 2026 /PRNewswire/ — AbolerIS Pharma (“AbolerIS”), a clinical-stage biopharmaceutical company committed to improving the lives of people suffering from autoimmune and inflammatory diseases, announced today that the first patient has been dosed with ABO21009, a humanized anti-CD45RC monoclonal antibody, in an ongoing Phase 1 study for the treatment of Rheumatoid Arthritis (RA).  Despite significant advances in management of RA and other autoimmune diseases, many patients don’t achieve durable remission and/or suffer from treatment-related side effects. ABO21009 was designed to address this unmet medical need by providing a curative-intent therapy inducing an immune reset and restoring immune tolerance.

This milestone marks the Company’s transition from healthy volunteer evaluation to patient dosing, underscoring the continued advancement of ABO21009 toward establishing clinical proof-of-concept in autoimmune disease.

“Dosing the first patient in our Phase 1 study represents a major step forward for AbolerIS and our mission to redefine the treatment of autoimmune disease, including in RA where patients are in need of new options,” said Dr. Ann Meulemans, CEO of AbolerIS Pharma. “ABO21009 is the first antibody of its class and represents an entirely new way to reset the immune system and restore immune tolerance. ABO21009 targets the underlying drivers of disease that are currently preventing a transition from remission to cure,” according to Dr. Ronald Van Brempt, CMO of AbolerIS Pharma.

The ongoing Phase 1 study is a first-in-human, adaptive design, randomized, single-blind, placebo-controlled dose escalation study with single ascending dosing in healthy volunteers (part I), single ascending dosing in patients with RA (part II) and multiple ascending dosing in patients with RA (part III) to evaluate safety, tolerability, pharmacokinetics and pharmacodynamics of ABO21009.  In part I, 24 patients were enrolled and received one of four single doses of ABO21009 and will be followed up for up to 10 weeks; the Phase 1 study has been initiated in the Netherlands and is currently enrolling and dosing patients with RA under part II.  More information about the ABO21009 clinical trial can be found at AbolerIS EU Clinical Trials.

About ABO21009 

ABO21009 is the Company’s lead monoclonal antibody program stemming from its novel immunomodulatory approach to treating autoimmune and inflammatory diseases. ABO21009 is effective through a multi-pronged mechanism of action, selectively depleting CD45RC-positive cells that are actively sustaining the autoimmune response in Rheumatoid Arthritis. These CD45RC-positive cells are present in the T-, B-, and NK-cell compartments of the adaptive immune system. By selectively depleting these cells, the cells driving the autoimmune disease are taken out of the immune cell population.

ABO21009 also spares regulatory T cells, which can unleash their full potential and suppress ongoing and future autoimmune activity in the adaptive immune system. Treatment with ABO21009 may enable a long-lasting and durable remission in RA, which will improve the patient experience and lessen the burden of side effects from currently available therapeutic options. In May 2025, AbolerIS began patient dosing under an authorized Clinical Trial Application (CTA) for a first-in-human Phase 1 study of ABO21009 in RA.  Pending clinical proof-of-concept in RA, the Company intends to broaden its development into other autoimmune diseases.

About AbolerIS Pharma

AbolerIS Pharma is a clinical-stage biopharmaceutical company committed to improving the lives of patients suffering from autoimmune and inflammatory diseases. The Company is advancing potentially best-in-class and first-in-class immunomodulatory antibodies that target CD45RC, a key regulator of the immune system. AbolerIS’ lead program, ABO21009, is designed to demonstrate broad efficacy in multiple autoimmune and inflammatory disorders with large unmet medical needs including rheumatoid arthritis (RA), inflammatory bowel disease (IBD), and organ transplantation.

At AbolerIS, we envision a future where patients can enjoy long-term remission and improved quality of life through therapies that are effective and safe. The Company is based in Gosselies, Belgium and Nantes, France, and is backed by a syndicate of experienced investors, which includes Newton Biocapital, Criteria Bio Ventures, Invested Tech, Sound Bioventures, WE, Sambrinvest, SFPIM and Sham Innovation Santé.

For more information, please visit www.aboleris-pharma.com or follow us on LinkedIn to learn more about our transformative approach to immunotherapies.

Company Contact: 
Dr. Ann Meulemans, CEO Aboleris
+32479900357
[email protected]

Media & Investor Contact
Amy Conrad
Juniper Point
[email protected]

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SOURCE AbolerIS Pharma