Final Results of a Phase 1 Study of AntiCD19 CAR-T Cells with TNFRSF19 Transmembrane Domain

Background: AntiCD19 CAR-T cells are effective against chemorefractory B cell lymphoma. Patients (pts) with rapidly progressive disease and urgent need for therapy have very poor prognosis and may not be able to receive CAR-T cells in time. Decreasing the apheresis to infusion time can make CAR-T cells rapidly available. We conducted a dual-center phase I trial using on-site manufacture of CAR-T cells for treatment of relapsed and refractory (r/r) B cell lymphoma. Methods: Adult pts with r/r CD19+ B cell lymphomas who failed ≥ 2 lines of therapy were enrolled. Autologous T cells were transduced with a lentiviral vector (Lentigen Technology, Inc, LTG1563) encoding an antiCD19 binding motif, CD8 linker, TNFRS19 transmembrane region, and 4-lBB/CD3z intracellular signaling domains. GMP-compliant manufacture was done using CliniMACS Prodigy in a 12-day culture, subsequently shortened to 8 days. Dose escalation was done using 3+3 design. Lymphodepletion included cyclophosphamide (60mg/kg x 1) and fludarabine (25mg/m2/d x 3). Cytokine release syndrome (CRS) and immune effector cell associated neurotoxicity syndrome (ICANS) were graded using the Lee and CARTOX criteria, respectively. CAR-T persistence was measured with qPCR and flow cytometry. Plasma cytokine concentrations were measured using electrochemiluminescence (MesoScale Diagnostics, Inc). Results: Thirty-one pts were enrolled and treated. Baseline patient and disease characteristics are listed in table 1. Twenty-nine (94%) pts were refractory to the prior line of therapy and 21 (68%) had symptomatic disease at the time of lymphocyte collection. CAR-T cell product manufacture was successful in all pts. Median transduction rate was 45% [range 15-66], median culture expansion was 36-fold [range 3-79]. CAR-T cell doses were 0.5 x 10 6/kg (n = 4), 1 x 10 6/kg (n = 16), and 2 x 10 6/kg (n = 11). Median time from apheresis to lymphodepletion was 7 days (range 2 - 15) and median time from apheresis to CAR-T cell infusion time was 13 days (range 9 - 20). Twenty-eight pts were infused fresh product. Seventeen pts (55%) experienced CRS. Grade 1-2 CRS was observed in 15 pts (48%), grade ≥ 3 was observed in 3 pts (10%). One patient had grade 4 CRS that was later complicated by hemophagocytic syndrome and died on day 21; a second patient had grade 5 CRS in the context of bulky disease and died on day 8. Ten pts (32%) had ICANS and 4 pts had grade 3-4 ICANS. Treatment for CRS / ICANS included tocilizumab (n = 12), siltu