Relapses After CAR-T Therapy

Long-Term Safety and Efficacy of CD19 Humanized Selective CAR-T Therapy in B-ALL Patients Who Have Previously Received Murine-Based CD19 CAR-T Therapy

Murine-based CD19 CAR-T (CD19m CAR-T) therapy can lead to a relatively high CR rate when administered to B-ALL patients for the first time. However, the DOR is sub-optimal and a subset of patients even show primary resistance to CD19m CAR-T. To address these issues, we employed a humanized selective CD19CAR-T (CD19hs CAR-T) and evaluated the long-term safety and efficacy of treating 8 R/R B-ALL patients who had relapsed or failed to achieve CR following CD19m CAR-T infusion (Clinical trials’ number: ChiCTR1800014761 and ChiCTR1800017439). Of the 8 patients, 7 achieved CR on Day 30 after the 1^st infusion of CD19hs CAR-T. The median CRS grade was 1 without significant neurotoxicity seen in any of the 8 patients. The median DOR was 11 months, significantly longer than the DOR following CD19mCAR-T infusions. Anti-CAR antibodies were induced in patients who had received prior CD19m CAR-T infusions but not in those following a single or repeated CD19hsCAR-T treatment, which probably had contributed to the sub-optimal DOR and/or failure of effective response in these patients. CD19hs CAR-T, in contrast, induced low immunogenicity compared with CD19m CAR-T, suggesting that a repeat dosing strategy might be feasible and efficacious for patients who have relapsed and/or show primary resistance to CD19m CAR-T therapy. In this clinical study, CD19hs CAR-T showed a significant clinical efficacy with mild side effect among patients with R/R B-ALL who had previously received CD19m CAR-T.

Case Report: Humanized Selective CD19CAR-T Treatment Induces MRD-Negative Remission in a Pediatric B-ALL Patient With Primary Resistance to Murine-Based CD19CAR-T Therapy

Background

CD19 chimeric antigen receptor T cell (CD19CAR-T) has shown great potential to treat acute B cell lymphoblastic leukemia (B-ALL) and B cell lymphoma, and most of anti-CD19 scFv are derived from murine antibody sequences. However, about 10–20% of B-ALL patients exhibit primary resistance to murine-based CD19CAR-T (CD19mCAR-T). Herein, we report that a humanized selective CD19CAR-T (CD19hsCAR-T) may offer a solution to this problem.

Case Description

A 10-year old boy was diagnosed with high-risk B-ALL in Mar., 2013, and relapsed in Oct., 2018, after he underwent haplo-identical hematopoietic stem cell transplantation (HSCT) in 2017. The patient then received haplo-identical CD19mCAR-T infusions twice following induction chemotherapy with Vincristine, Dexamethasone and Asparaginase (VDL), but no response was observed. We further treated this patient with CD19hsCAR-T following chemotherapy with Vindesine, Idarubicin, Dexamethasone, and Pegylated Asparaginase (VDLD) plus bortezomib. The patient achieved minimal residual disease-negative (MRDneg) complete remission with incomplete hematopoietic recovery (CRi), and remained in CRi for more than 8 months with manageable side effect. The patient, unfortunately, died of unidentified pulmonary infection on Jan. 25 2020.

Conclusion

CD19hsCAR-T may have the potential to induce remission in patients who are primarily refractory to CD19mCAR-T.