Cullinan Therapeutics, Inc. 8-K

What Happened
Cullinan Therapeutics, Inc. (CGEM) filed an 8‑K (dated June 8, 2026) to disclose a June 6, 2026 press release announcing initial clinical data from its Phase 1 OUTRACE trials of CLN‑978 presented at the EULAR congress. As of a May 15, 2026 data cutoff, 29 patients had been evaluated across OUTRACE SLE (n=18) and OUTRACE RA (n=11) across multiple dose cohorts (target doses included 10 µg, 20 µg, 30 µg, and a discontinued 45 µg cohort).

Key Details

• Total patients evaluated: 29 (SLE 18; RA 11); data are interim and based on varying follow-up.
• OUTRACE SLE (single target dose, ≥4 weeks follow-up in 14 patients): 10/14 (71%) had ≥4‑point reduction in hSLEDAI; 5 achieved DORIS remission. Anti‑dsDNA, UPCR, C3 and C4 improved in patients with baseline abnormalities.
• Pharmacodynamics: Peripheral B cell counts fell >80% from baseline in 14/17 SLE patients (82%); BLOQ peripheral B cells in 7/14 (50%) at target doses ≥20 µg.
• OUTRACE RA: 5/7 patients (71%) showed improved disease activity; one patient achieved DAS28‑ESR remission at a single 30 µg dose. BLOQ peripheral B cells in 4/6 RA patients (67%) at ≥20 µg; dose‑dependent depletion seen in lymph node and synovial tissue.
• Safety: CLN‑978 was generally tolerated at 10, 20 and 30 µg; cytokine release syndrome (CRS) occurred in 11/29 patients (38%), mostly Grade 1. One Grade 3 CRS occurred after 45 µg and enrollment to that cohort was halted. No ICANS observed.

Why It Matters
These are early, interim Phase 1 results showing pharmacodynamic activity (notably robust B‑cell depletion) and signs of clinical activity in small, heavily pretreated RA and SLE populations. Safety signals are broadly manageable at lower doses but the Grade 3 CRS at 45 µg prompted stopping that cohort, underscoring dose‑dependent risk. For investors, the filing confirms the company is publicly presenting progress on CLN‑978 at a major rheumatology meeting (EULAR) and provides concrete early efficacy and biomarker data; however, the data are preliminary, from small cohorts, and subject to change as the trials continue.