Subcutaneous CLN-978 for treatment‑refractory rheumatoid arthritis

A Phase I, Open-Label Study of CLN-978 in Patients With Treatment-Refractory Rheumatoid Arthritis (RA)

This Phase I trial tests a subcutaneously given drug called CLN-978 that redirects T cells to CD19 to try to help people with treatment‑refractory, B‑cell–driven rheumatoid arthritis.

Quick facts

• Phase: Phase 1
• Study type: Interventional
• Enrollment: 37 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: Cullinan Therapeutics Inc. (Industry-sponsored)
• Drugs / interventions: blinatumomab, obinutuzumab, rituximab, ocrelizumab, ofatumumab, CAR-T, chimeric antigen receptor, Cyclophosphamide, prednisone
• Locations: 2 sites (Erlangen and 1 other locations)
• Trial ID: NCT06994143 on ClinicalTrials.gov

What this trial studies

This is an open‑label Phase I trial of CLN-978, a CD19‑directed T cell engager given subcutaneously to adults with active, treatment‑refractory rheumatoid arthritis. Participants must have evidence of B‑cell‑driven disease (seropositivity for RF/AMPA or synovial B‑cell infiltration), a DAS28‑ESR ≥3.2, and prior inadequate response to at least two targeted therapies. The trial enrolls patients who meet specific laboratory thresholds for lymphocytes, peripheral CD19+ B cells, neutrophils, hemoglobin, and platelets to support safety monitoring. The primary focus in this early‑phase trial is safety and tolerability with initial dosing and clinical observation in a small, selected population.

Who should consider this trial

Good fit: Adults with RA meeting 2010 ACR/EULAR criteria who have active disease (DAS28‑ESR ≥3.2), evidence of B‑cell–driven disease (RF/AMPA positivity or synovial B‑cell infiltration), prior inadequate response to at least two targeted therapies, and meeting required lab thresholds (ALC ≥0.5 x10^9/L, CD19+ ≥25 cells/µL, ANC ≥1.0 x10^9/L, Hgb ≥8 g/dL, platelets ≥75 x10^9/L) are the intended participants.

Not a fit: Patients whose disease is not B‑cell driven, who have very low peripheral B cells (<25 cells/µL), who respond well to standard treatments, or who do not meet the laboratory safety criteria are unlikely to benefit from this trial.

Why it matters

Potential benefit: If successful, CLN-978 could reduce B‑cell–mediated joint inflammation and improve symptoms in people with refractory RA.

How similar studies have performed: B‑cell‑depleting therapies such as anti‑CD20 agents (e.g., rituximab) have proven benefit in RA, but CD19‑directed T cell engagers like CLN‑978 are a novel approach with limited prior clinical data in autoimmune disease.

Eligibility criteria

Inclusion Criteria:

* Documented diagnosis of RA which fulfills the 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) Classification Criteria ≥12 weeks prior to screening.
* Evidence of B-cell-driven disease at Screening or previous medical documentation, defined as either (i) seropositivity for RF and/or any AMPA and/or (ii) a synovial biopsy showing B-cell infiltration
* Active RA disease, as demonstrated by a DAS28 - ESR ≥3.2 and at least one swollen joint at screening.
* Inadequate response to at least 2 targeted treatments with different mechanisms. These can include tsDMARD and/or bDMARD, after failing conventional synthetic DMARD (unless contraindicated).
* Local laboratory assessments must meet the following criteria:

  * Absolute lymphocyte count (ALC) ≥0.5 x 10\^9/L
  * Peripheral CD19+ B cell count ≥25 cells/μL
  * Absolute neutrophil count (ANC) ≥1.0 x 10\^9/L
  * Hemoglobin (Hgb) ≥8 g/dL
  * Platelet count ≥75 x 10\^9/L
  * Estimated glomerular filtration rate (eGFR) (based on the Chronic Kidney Disease Epidemiology Collaboration \[CKD-EPI\] formula) ≥30 mL/min/1.73m\^2
  * Total bilirubin ≤1.5 × ULN, except patients with confirmed Gilbert's Syndrome
  * Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 × ULN
* Concurrent corticosteroids is permitted if the dose is ≤10 mg/day prednisone equivalent in the 2 weeks prior to initiation of study treatment. Hydroxychloroquine ≤400 mg/d or chloroquine ≤ 250 mg/d is allowed.

Exclusion Criteria:

* Active inflammatory disease other than RA within 12 months prior to screening or during screening that may interfere with the study assessments. Thyroiditis or secondary Sjogren's syndrome is allowed.
* Clinical evidence of any other significant unstable or uncontrolled acute or chronic disease not due to RA which, in the opinion of the Investigator could put the patient at undue risk or confound study results.
* Prior treatment with the following:

  * Cellular therapy (e.g., chimeric antigen receptor T-cell (CAR-T) or gene therapy product directed at any target.
  * Receipt of an investigational therapy within 30 days or 5 drug-elimination half-lives (whichever is longer) prior to Day 1 and during the study.
  * Received any anti-CD19 or anti-CD20 therapy such as blinatumomab, obinutuzumab, rituximab, ocrelizumab, or ofatumumab within 3 months prior to Day 1.
  * Non-biologic DMARD within 14 days prior to Day 1.
  * Cyclophosphamide or a biologic immunomodulating therapy within 2 months of Day 1.
* Live or live-attenuated vaccines within the 4 weeks prior to the Screening visit or during the Screening Period
* Active or latent tuberculosis (TB) evidenced by a positive or indeterminant Interferon Gamma Release Assay (IGRA), unless the patient has documented previous completion of TB treatment and no current clinical indication of TB.

Where this trial is running

Erlangen and 1 other locations

• Cullinan Investigative Site — Erlangen, Germany (Recruiting)
• Cullinan Investigative Site — Rome, Italy (Recruiting)

Study contacts

• Study coordinator: Amy Gubits, MPH

Conditions Rheumatoid Arthritis (RA; RA; Treatment-refractory RA