Cullinan Therapeutics' CLN-978 shows remissions in SLE and RA at EULAR
Cullinan Therapeutics has presented initial Phase 1 clinical data for CLN-978, its CD19xCD3 bispecific T cell engager, at the EULAR 2026 European Congress of Rheumatology in a poster session on 6 June. The dataset, drawn from 29 patients enrolled across the OUTRACE SLE and OUTRACE RA studies, reported clinical benefit including remissions in both indications following a single target dose.
In the systemic lupus erythematosus cohort, 71% of evaluable patients — 10 of 14 with at least four weeks of follow-up — achieved a four-point or greater reduction in the hSLEDAI disease activity score, with five meeting the DORIS definition of remission. Peripheral B cell counts fell by more than 80% from baseline in 82% of patients, with dose-dependent recovery observed. In the rheumatoid arthritis cohort, disease activity improved in five of seven evaluable patients, and B cell depletion below the limit of quantification was achieved in four of six patients receiving target doses of 20 µg or above. Notably, B cell depletion was detected not only in peripheral blood but also in lymph node and synovial tissue biopsies, which the company and its investigators described as supporting the mechanism of action.
Safety profile and administration
CLN-978 was reported to be well tolerated at single target doses up to 30 µg. Most cytokine release syndrome events were Grade 1 and occurred after the initial 10 µg step-up dose. One Grade 3 CRS event was observed at the 45 µg target dose, prompting discontinuation of enrolment to that cohort; the company said it may implement additional step-up dosing schedules in subsequent multi-dose regimens. No cases of immune effector cell-associated neurotoxicity syndrome (ICANS) were reported, which will be welcomed by clinicians given the ICANS burden seen with some CAR-T programmes in this space.
Jeffrey Jones, Cullinan's chief medical officer, said the "emerging safety profile and subcutaneous administration support the potential to deliver substantial clinical benefit to patients in the outpatient, community-based care setting," positioning CLN-978 as potentially more accessible than cell therapies requiring hospital admission.
Competitive landscape
The results arrive at a moment of intense interest in B cell depletion strategies for autoimmune disease. CD19-targeting CAR-T therapies, pioneered for autoimmune indications by academic groups in Germany and now advanced by several commercial developers, have demonstrated striking remissions in SLE and RA, but require specialist infusion centres, lymphodepletion conditioning, and carry significant safety monitoring burdens. A subcutaneously delivered, off-the-shelf bispecific engager targeting the same pathway could offer a substantially broader addressable population if the efficacy signal holds at scale.
Several other biopharmaceutical companies are developing CD19-directed or BCMA-directed T cell engagers for autoimmune applications, making the competitive window for CLN-978 dependent on the pace and depth of its Phase 1 to Phase 2 transition. Cullinan also holds velinotamig, a BCMAxCD3 engager, with initial clinical data expected at the company's Immunology Day on 10 June alongside new multi-dose RA cohort data for CLN-978. The MHRA and EMA have shown growing receptivity to accelerated pathways for therapies addressing high unmet need in refractory autoimmune disease, which may shape the regulatory strategy for CLN-978 as the dataset matures.
Investors will be focused on whether multi-dose regimens can deepen and sustain responses seen after single dosing, and on durability data as follow-up extends beyond the current cutoff of 15 May 2026.