Safety and efficacy of non-viral aPD1-MSLN JL-lightning–CAR-T in advanced malignant mesothelioma in a phase I trial.

2534 Background: CAR-T cells face challenges in solid tumors, including weak in vivo proliferation, immunosuppressive tumor microenvironments (TME), and limited tumor infiltration. We firstly developed an innovative non-viral JL-Lightning-CAR-T fast process to enhance CAR-T stemness, in vivo expansion, and persistence. The autologous non-viral aPD1-MSLN JL-Lightning-CAR-T cells were manufactured in just 30 hours, targeting mesothelin (MSLN) and secreting anti-PD-1 antibodies to counteract the immunosuppressive TME and improve the efficacy of solid tumor treatment. Here, we report the safety and preliminary efficacy of this novel CAR-T therapy in advanced malignant pleural mesothelioma (MPM) in a first-in-human phase I pilot study (ClinicalTrials.gov: NCT06249256). Methods: A single-arm, open-label, dose-escalation study was designed and enrolled MPM patients who had failed standard therapies and had confirmed MSLN and PD-L1 expression on tumors by IHC. Patients received a single dose of non-viral aPD1-MSLN JL-Lightning-CAR-T cells following lymphodepletion (Flu 30 mg/m²/day, Cy 300 mg/m²/day) for 2-3 days. The dose escalation was designed as DL1 (0.5-0.6×10⁶/kg) and DL2 (0.8-1.0×10⁶/kg). Adverse events were evaluated using CTCAE v5.0, and clinical responses were assessed by mRECIST 1.1 or RECIST 1.1. CAR expression was analyzed by qPCR, and anti-PD-1 antibodies were detected by MSD. Results: Patients: Seven advanced MPM patients were enrolled and received single dose CAR-T cell infusion. Efficacy: In DL1 (0.5-0.6×10⁶/kg), one patient achieved partial response (PR) with a disease control rate (DCR) of 75% (3/4). In DL2 (0.8-1.0×10⁶/kg), all of three patients achieved objective response (ORR 100%, 3/3), with one patient achieving complete response (CR) at 3 months and maintaining it for over 9 months. Pharmacokinetics: Anticipated CAR-T cell expansion and anti-PD-1 antibodies increase detected in circulation. CAR-T Cmax reached up to 47,307 copies/µg, detectable for over 3 months. Anti-PD-1 antibody Cmax reached up to 376,938 pg/ml, detectable for over 6 months. Tmax for MSLN-CAR-T and anti-PD1 nanobody occurred between Day 7 and Day 14 post infusion. IFN-γ and IL-6 levels also increased during this period. Safety: In DL1, CRS was observed in 1 of 4 patients (Grade 1), with no ICANS or DLT. In DL2, CRS was observed in 2 of 3 patients (Grade 3-4), with no ICANS. Grade 3 immune-mediated pneumonia occurred in 2 of 3 patients in DL2, managed by clinical intervention strategies. All patients experienced Grade 3-4 hematologic toxicity, reversible with supportive care. Conclusions: Non-viral aPD1-MSLN JL-Lightning-CAR-T cells demonstrated robust proliferative capacity, manageable safety profile, and significant anti-tumor potential, offering a promising therapeutic approach for advanced MPM patients. Clinical trial information: NCT06249256 .