Safety and Preliminary Efficacy in Patients with Relapsed/Refractory Mantle Cell Lymphoma Receiving Lisocabtagene Maraleucel in Transcend NHL 001

Background: Mantle cell lymphoma (MCL) is an aggressive subtype of B-cell non-Hodgkin lymphoma (NHL). Most patients with MCL relapse after first-line immunochemotherapy, with poor responses to salvage therapy. Chimeric antigen receptor (CAR) T cell therapy has shown clinical efficacy in patients with relapsed/refractory (R/R) NHL. We report the results of the dose-finding and dose-expansion parts of the ongoing phase 1 TRANSCEND NHL 001 study (NCT02631044) in patients with R/R MCL (MCL cohort) who received lisocabtagene maraleucel (liso-cel), an investigational, CD19-directed, defined composition, 4-1BB CAR T cell product administered at equal target doses of CD8⁺ and CD4⁺ CAR⁺ T cells.

Methods: Eligible patients had confirmed MCL (cyclin D1 expression, t[11;14]) with R/R disease after ≥1 prior line of therapy. After lymphodepleting chemotherapy, patients received liso-cel infusion at 1 of 2 dose levels (DLs): DL1 (50 × 10⁶ CAR⁺ T cells) or DL2 (100 × 10⁶ CAR⁺ T cells). Bridging therapy was allowed between leukapheresis and initiation of lymphodepleting chemotherapy. Primary endpoints were safety and objective response rate (ORR). Secondary endpoints included complete response (CR) rate, duration of response, progression-free survival, overall survival, and pharmacokinetics (PK).

Results: At data cutoff, 41 patients had undergone leukapheresis and 32 had received liso-cel (DL1, n = 6; DL2, n = 26). Among the 32 patients who received liso-cel, the median (range) age was 67 (36‒80) years and 27 patients (84%) were male. Twelve patients (37.5%) had blastoid morphology, 23 (72%) had documented Ki67 ≥30%, 7 (22%) had a TP53 mutation, and 11 (34%) had a complex karyotype. Patients had a median (range) sum of the product of perpendicular diameters before lymphodepleting chemotherapy of 28.7 (0–209.6) cm² and median lactate dehydrogenase of 251.5 (117–811) U/L. Patients had received a median (range) of 3 (1–7) prior systemic therapies, and most (72%) were refractory to their last prior therapy. Of 28 patients (87.5%) who had received a prior Bruton tyrosine kinase inhibitor, 11 (34%) were refractory to the therapy. Seventeen patients (53%) received bridging therapy.

Eighteen patients (56%) had serious treatment-emergent adverse events (TEAEs), and 27 (84%) had grade ≥3 TEAEs, primarily neutropenia (41%), anemia (34%), and thrombocytopenia (31%). Grade ≥3 thrombocytopenia was more frequent at DL2 (n = 9/26 [35%]) than at DL1 (n = 1/6 [17%]). Prolonged grade ≥3 cytopenias (present at study Day 29) occurred in 11 patients (34%). Sixteen patients (50%; DL1, n = 2/6 [33%]; DL2, n = 14/26 [54%]) had cytokine release syndrome (CRS), including 1 grade 4 event at DL2. There were no grade 3 or 5 CRS events. Median (range) time to CRS onset and resolution was 6 (2‒10) days and 4 (2‒9) days, respectively. Nine patients (28%) had neurological events (NEs), all at DL2, including 3 grade 3 NEs. No grade 4 or 5 NEs were reported. Median (range) time to NE onset and resolution was 8 (2‒25) days and 3 (1‒51) days, respectively. Ten patients (31%) received tocilizumab and/or corticosteroids for treatment of CRS and/or NEs. Grade 5 TEAEs occurred in 2 patients (at DL2): one patient with high tumor burden had tumor lysis syndrome and 1 patient had cryptococcal meningoencephalitis. DL2 was selected for dose expansion.

Of 32 patients, 27 responded to liso-cel (ORR, 84%: DL1, n = 4/6 [67%]; DL2, n = 23/26 [88%]), and 19 (59%) achieved a CR (DL1, n = 2/6 [33%]; DL2, n = 17/26 [65%]). Among the 12 patients with blastoid morphology, 9 patients had a response (ORR, 75%), including 7 (58%) who achieved a CR. Overall, the median (range) time to first CR was 1 (1–6) month. At data cutoff, 20 (74%) of 27 responders were censored with an ongoing response or had completed the study. Median (range) follow-up duration was 10.9 (1.2–24.8) months for DL1 and 3.1 (0.4–23.0) months for DL2. Preliminary PK analysis indicated that median maximum expansion was higher among patients at DL2 than at DL1.

Conclusions: In this phase 1 study of patients with R/R MCL, treatment with liso-cel was associated with a low incidence of grade ≥3 CRS and NEs, late onset of CRS/NEs, and promising clinical activity. Dose confirmation is ongoing at DL2 in the MCL cohort.