- Randomized multi-center study designed to assess the efficacy, safety, and tolerability of CIT-013 in patients with moderately active rheumatoid arthritis
Oss, Netherlands – 2 September 2025 – Citryll, a biotech company pioneering a transformative approach to treating immune-mediated inflammatory diseases by targeting Neutrophil Extracellular Traps (NETs), today announces that the first patient has been successfully dosed in its Phase IIa clinical trial “Citydream”. The trial will evaluate CIT-013, a first-in-class monoclonal antibody, in patients with moderately active rheumatoid arthritis (RA). To support the advancement of the clinical investigations and broader strategy, Citryll has established an RA Clinical Advisory Board, comprising leading experts in the field to provide strategic and scientific guidance throughout the clinical development of CIT-013 in RA and other autoimmune diseases.
RA is a chronic autoimmune disease characterized by inflammation of the joints. Its hallmark symptoms include joint pain, stiffness and swelling, resulting in reduced mobility and loss of joint integrity, severely impacting the quality of life. Despite significant advances in treatment options, there remains a high medical unmet need, with a high proportion of patients unable to maintain adequate disease control through current therapies.
“The dosing of the first patient in our Phase IIa trial marks a significant milestone in Citryll’s mission to transform the treatment landscape for patients suffering from immune-mediated inflammatory conditions such as rheumatoid arthritis,” said Maarten Kraan, Chief Medical Officer of Citryll. “With a compelling preclinical and clinical data set together with strong backing from a top-tier investor syndicate we are proud to advance our lead programme into Phase 2 trials. Citydream represents an important step in validating the potential of CIT-013 in rheumatoid arthritis and we remain deeply committed to bringing this promising therapy to patients.”
“The initiation of the Phase IIa trial of CIT-013 is a critical step in advancing what we believe to be a first-in-class therapeutic approach,” said Rogier Thurlings, MD, PhD, Lead Investigator of Citydream. “By targeting NETs, CIT-013 represents a novel and potentially disease-modifying approach to RA as well as other immune mediated conditions. This mechanism offers a fundamentally different mode of action from current therapies, which often fail to achieve sustained disease control in patients.”
Citydream is a Phase IIa, randomized, double-blind, placebo-controlled, multi-center study conducted across multiple sites in Europe. The study is designed to assess the efficacy, safety, and tolerability of CIT-013 in patients with moderately active RA. The trial will enroll 88 patients who will undergo a 6-week treatment period, followed by an open-label extension phase to further assess safety and efficacy.
Citydream follows the successful completion of Citryll’s first-in-human Phase 1 study, which included successful repeat dosing of rheumatoid arthritis (RA) patients as well as an €85 million Series B fundraise. An additional Phase IIa trial is also planned in hidradenitis suppurativa (HS) starting later this year.
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About CIT-013
CIT-013 is Citryll’s first-in-class monoclonal antibody targeting Neutrophil Extracellular Traps (NETs), a key driver of inflammation in RA and other immune-mediated diseases, which has yet to be addressed therapeutically. It has a unique dual mechanism of action, which enhances the clearance of existing NETs and inhibits the formation of new NETs. CIT-013 is highly selective for its epitope, minimising off-target effects and representing a potentially transformative therapeutic strategy, going beyond individual pathway management and symptom treatment.
About Citryll
Citryll is pioneering a transformative approach to treating inflammatory diseases by targeting Neutrophil Extracellular Traps (NETs), a fundamental component of the inflammatory process that has yet to be addressed therapeutically.
Citryll is developing the first NET-targeting therapy and potentially creating a new class of therapeutics with broad applications across immune-mediated inflammatory diseases.
Our lead asset, CIT-013, is a first-in-class monoclonal antibody with a unique dual mechanism of action: it enhances the clearance of existing NETs and inhibits the formation of new NETs.
By addressing this key driver of inflammation, CIT-013 has the potential to offer a differentiated and comprehensive treatment option for conditions such as rheumatoid arthritis and hidradenitis suppurativa, where current therapies often fall short of providing adequate disease control.
Contacts
Citryll
Sjoerd van Gorp, COO
Email: info@citryll.com
Citryll Media Contacts
ICR Healthcare
Amber Fennell, Stephanie Cuthbert, Lucy Featherstone
Email: citryll@icrinc.com