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

-Company is advancing a new class of immunomodulators for autoimmune and inflammatory disorders with high unmet medical need-

- ABO21009's unique mechanism of action depletes pathogenic T and B cells, induces expansion of Tregs for lasting efficacy, and preserves overall immunity-

GOSSELIES, Belgium and NANTES, France, May 7, 2025 /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 cohort of participants has been dosed with ABO21009, a humanized anti-CD45RC monoclonal antibody, in a first-in-human Phase 1 study for the treatment of Rheumatoid Arthritis (RA).  ABO21009 was designed to address the unmet medical need for patients with RA who have not responded well to currently available therapeutic options, including anti-TNF therapeutics.

"AbolerIS is at the forefront of innovation in autoimmune and inflammatory diseases with our approach in targeting CD45RC and we are thrilled to transition to a clinical-stage company," said Dr. Ann Meulemans, Ph.D., CEO of AbolerIS. "ABO21009 is the first antibody of its class to enter clinical trials in Europe and we believe it has great potential as a disease-modifying treatment for RA due to its multi-pronged mechanism of action.  This year we are focused on the determination of safety, target engagement and dose range finding in patients suffering from RA. Pending clinical proof-of-concept in RA with ABO21009, we'll advance ABO21009 in the clinic for additional indications like Sjögren`s Disease, Graft-versus-Host Disease, Inflammatory Bowel Disease, and Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy as we continue to grow our company."

The 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 are planned to be enrolled who will receive 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 participants.

Studies have shown that the C domain of specific CD45 protein isoforms is a target of significant global interest given its unique role in modulating the immune system. The CD45 protein is a transmembrane protein found on the surface of all nucleated hematopoietic cells, and is involved in the regulation of signaling pathways that control various immune cell functions.

"Despite the recent progress in the management of RA, it remains one of the most difficult to treat autoimmune disorders, as many patients do not respond to the currently available therapies or they experience unwanted side effects," added Prof. Dirk Elewaut, MD and Chairman of the SAB AbolerIS. "I am very excited to bring the first anti-CD45RC agent to my patients, with the hope of providing long-term remission and improved quality of life."

More information about the ABO21009 clinical trial can be found at AbolerIS EU Clinical Trials.

"Rheumatoid arthritis is a chronic, progressive autoimmune disease that significantly impacts patients' quality of life and physical health, and we believe that ABO21009 has the potential to disrupt the field and bring innovation to patients," commented Ronald van Brempt, MD, Chief Medical Officer of AbolerIS.  "Further, I am very proud of our team who have executed well to open the Phase 1 study so quickly in Europe, and we look forward to expanding the study into additional indications." 

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 Criteria Bio Ventures, Sound Bioventures, Newton Biocapital, 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
Ann.meulemans@aboleris-pharma.com

Media & Investor Contact
Amy Conrad
Juniper Point
Amy@juniper-point.com

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