A durable 4-1BB-based CD19 CAR-T cell for treatment of relapsed or refractory non-Hodgkin lymphoma

Previous studies reported that 4-1BB-based CD19 chimeric antigen receptor (CAR)-T cells were more beneficial for the clinical outcomes than CD28-based CAR-T cells, especially the lower incidence rate of severe adverse events. However, the median progression-free survival (mPFS) of 4-1BB-based product Kymriah was shorter than that of CD28-based Yescarta (2.9 monthsvs. 5.9 months), suggesting that Kymriah was limited in the long-term efficacy. Thus, a safe and durable 4-1BB-based CD19 CAR-T needs to be developed.

We designed a CD19-targeted CAR-T (named as IM19) which consisted of an FMC63 scFv, 4-1BB and CD3ζ intracellular domain and was manufactured into a memory T-enriched formulation. A phase I/II clinical trial was launched to evaluate the clinical outcomes of IM19 in relapsed or refractory (r/r) B cell non-Hodgkin lymphoma (B-NHL). Dose-escalation investigation (at a dose of 5×10⁵/kg, 1×10⁶/kg and 3×10⁶/kg) was performed in 22 r/r B-NHL patients. All patients received a single infusion of IM19 after 3-day conditional regimen.

At month 3, the overall response rate (ORR) was 59.1%, the complete response rate (CRR) was 50.0%. The mPFS was 6 months and the 1-year overall survival rate was 77.8%. Cytokine release syndrome (CRS) occurred in 13 patients (59.1%), with 54.5% of grade 1-2 CRS. Only one patient (4.5%) experienced grade 3 CRS and grade 3 neurotoxicity.

These results demonstrated the safety and durable efficacy of a 4-1BB-based CD19 CAR-T, IM19, which is promising for further development and clinical investigation.