Safety and preliminary efficacy of a novel loop-optimized, BCMA/CD19 bispecific CAR-T therapy for refractory or relapsed autoimmune diseases patients

Abstract Background:Anti-CD19 CAR-T cell therapy has achieved breakthrough efficacy in B cell-driven autoimmune diseases such as systemic lupus erythematosus (SLE). However, these diseases are often associated with excessive antibody production by B cells and plasma cells. Dual-target CD19/BCMA CAR-T may synchronously eliminate CD19+ and BCMA+ cells to achieve deep remission in autoimmune diseases (AIDs) and preliminary clinical data in refractory or relapsed (r/r) SLE had been reported on 2025EHA meeting. However, more clinical datas are needed for other AIDs like systemic sclerosis (SSc) and primary Sjögren's syndrome (pSS). Objective:This study aimed to develop a bispecific CAR structure using proprietary nanobodies, systematically evaluate its functional advantages over FDA-approved monospecific CAR-T therapies, and conduct a pilot study on r/r SLE, SSc, and pSS to clarify its safety and efficacy. Methods:We engineered a bispecific CAR structure using our proprietary nanobodies, and systematically evaluated its functional advantages over FDA-approved monospecific CAR-T therapies. Furthermore, we conducted a pilot study in r/r AIDs for evaluating safety and preliminary efficacy. R/r SLE met the 2019 American College of Rheumatology(ACR)/European Union of Rheumatology Associations(EULAR) classification criteria, and confirmed by renal tissue biopsy to have active. Proliferative lupus nephritis were confirmed by the 2019 ACR criteria and the 2018 International Society of Nephrology/Society of Nephropathology criteria. R/r SSc and pSS met the SSc classification criteria proposed by the 2013 ACR /European League Against Rheumatism. SLE response criteria is assessed via SLEDAI, LLDAS, SRI-4; SSC via EUSTAR-AI; PSS via ESSDAI. Results:The CD19-targeting moiety uses FMC63-derived scFv. Specific nanobodies against new BCMA epitopes were identified via alpaca immunization and phage display. We pioneered a novel structural design: the BCMA nanobody was inserted into a loop region within the middle of the FMC63 scFv. Preliminary in vitro experiments demonstrated that this loop-embedded dual CAR (Loop-dCAR) exhibits comparable CAR expression efficiency and expansion kinetics during culture to single CARs targeting either CD19 or BCMA alone. During serial rechallenge killing assays. Loop-dCAR cells co-cultured with NALM-6 cells (BCMA+, CD19-) and RPMI 8226 cells (CD19+, BCMA-) at an Effector-to-Target (E:T) ratio of 2:1, with fresh tumor cells added every 3 days, successfully eliminated tumor cells over 3 consecutive rounds. Their persistent killing capacity against CD19+ or BCMA+ targets was comparable to that of single CD19 or BCMA CAR-T cells. 12 patients were infused CAR-T products and finished 3-month follow-up: median age 30.5 (12-45) years, including 6 r/r SLE, 3 pSS, 3 SSc,with median treatment duration 22.5 (5-168) months. 4 SLE patients had organ involvement (3 lupus nephritis, 1 interstitial pneumonia). 2 pSS patients had complications (pulmonary hypertension, fibrosis). All had >2 prior treatments. All steroids ans immunosuppressants were stopped at least 2 weeks before apheresis and not reused post-infusion. The dose of CAR-T products was 1*10^6/kg. Within 30 days post-infusion, 4 patients (33.3%) had grade 1 CRS. No neurotoxicity and severe adverse events were observed.By 1 Aug 2025, SLE overall response rate was 83.3% ，including 4 complete remission(CR), 1 partial remission(PR). 1 and 3 month remission rates were 66.7%/83.3% (DORIS), 83.3%/83.3% (LLDAS), 66.7%/66.7% (SRI-4), respectivily. SLEDAI/PGA scores decreased 2-19/0.5-2.5 points. Among SSc patients, 100% patients acheived PR at 1 month, and 2 CR (EUSTAR-AI: 13→4, 2.5→0) and 1 PR (30→24) at 3 months.Modified Rodnan scores down 1-9 points. Among pSS patients, 1 CR, 2 PR achieved at 3 months (ESSDAI: 3→0, 9→5, 6→3). All 3 pulmonary hypertension patients had reduced pulmonary arterial pressure, and with euvalations by WHO class: 100% low-risk at 1 and 3 months; By 6-min walk: 100% medium-risk at 1 month, 100% low-risk at 3 months;By WSPH: 33.3%/66.7% low-risk at 1/3 months. All had B-cell depletion and C3/C4 recovery at 1 month.11/12 had peripheral B-cell recovery by day 58; CAR-T peak expansion at day 8 (43,913 copies/20ul, range 6,434–117,163). Conclusion: NovelLoop dual CD19/BCMA CAR-T demonstrated favorable efficacy and safety in relapsed/refractory autoimmune diseases and new clinical trial is ongoing (NCT06947460).