Cullinan Therapeutics' CLN-978 Shows Promising Results in Lupus and Rheumatoid Arthritis

By Tamara Parker • Monday, June 08 13:01 • Permanent Link

Cullinan Therapeutics said early clinical data for CLN-978 showed remissions and broad B-cell depletion in patients with systemic lupus erythematosus and rheumatoid arthritis after a single target dose, with the clearest responses seen at higher doses.

The company said the data set includes 29 patients evaluated as of May 15, 2026: 18 with SLE and 11 with RA.

In SLE, 14 patients had at least four weeks of follow-up. Of those, 10 patients, or 71%, posted at least a 4-point drop in HsLEDAI, and 5 achieved DORIS remission. In the same group, all lab markers of disease activity cited in the release — anti-dsDNA, UPCR, C3 and C4 — improved in patients who had abnormal values at baseline.

CLN-978 also drove strong B-cell depletion in SLE. Peripheral B-cell counts fell by more than 80% from baseline in 14 of 17 patients, or 82%. Peripheral B-cell depletion below the limit of quantification was reached in 7 of 14 patients, or 50%, among those treated at target doses of at least 20 micrograms.

In RA, 6 of 7 patients, or 86%, had high baseline disease activity. Disease activity improved in 5 of 7 patients, or 71%, and 1 patient treated with a single 30 microgram target dose reached DAS28-ESR remission. The drug also reduced RA autoantibody levels without affecting protective vaccine titers.

B-cell depletion in RA was also dose-linked. Peripheral blood B-cell depletion below the limit of quantification was achieved in 4 of 6 patients, or 67%, at target doses of at least 20 micrograms. The company said dose-dependent B-cell depletion was also seen in lymph node and synovial tissue.

Across the 10, 20 and 30 microgram target-dose cohorts, CLN-978 was described as well tolerated. Most cytokine release syndrome events were grade 1 and followed the first 10 microgram dose. One grade 3 cytokine release syndrome event occurred after the 45 microgram target dose, and enrollment to that cohort was discontinued. No ICANS was observed.

The company also said it is advancing a multi-dose regimen. In SLE, 3 patients received three 20 microgram administrations, and in RA, the first multi-dose regimen cohort is ongoing. Today the company's shares have moved -3.0% to a price of $13.105. Check out the company's full 8-K submission here.

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