Cullinan Therapeutics Inc. (NASDAQ: CGEM) presented initial clinical data from Phase 1 studies of CLN-978, a CD19xCD3 T cell engager, at the European Alliance of Associations for Rheumatology Congress. The data was based on 29 patients evaluated across various dose levels in the OUTRACE SLE and RA trials as of May 15, 2026.

In the systemic lupus erythematosus trial, 10 of 14 patients with at least four weeks of follow-up showed a reduction of four points or more in hSLEDAI scores, with five achieving DORIS remission following a single target dose. All laboratory markers of disease activity improved in patients with clinically significant abnormalities at baseline.

For rheumatoid arthritis patients, disease activity improved in five of seven patients, including one DAS28-ESR remission in a patient treated with a single 30 microgram target dose. The treatment reduced RA autoantibody levels without affecting protective vaccine titers.

The drug demonstrated dose-dependent B cell depletion in both peripheral blood and tissue. Following a single target dose, peripheral B cell counts were reduced by more than 80% from baseline in 14 of 17 patients in the SLE trial. In the RA trial, peripheral blood B cell depletion below the limit of quantification was achieved in four of six patients treated at target doses of 20 micrograms or higher.

CLN-978 was well tolerated across the 10, 20, and 30 microgram target dose cohorts. Most cytokine release syndrome events were Grade 1 and occurred following the first 10 microgram dose. One case of Grade 3 cytokine release syndrome was observed at the 45 microgram dose level, leading to discontinuation of enrollment to that cohort. No immune effector cell-associated neurotoxicity syndrome was observed.

The company will host an Immunology Day on June 10 to present additional data from the first RA multi-dose regimen cohort and initial clinical data for velinotamig, a BCMAxCD3 T cell engager.