The success of chimeric antigen receptor T (CAR T)-cell therapy for patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL) has garnered much attention, but the field is still in its infancy – with toxicity and relapse rates remaining unacceptably high.
in the use of the therapy in this setting, according to review authors Vanessa A. Fabrizio, MD, a fellow at Duke University, Durham, N.C., and Kevin J. Curran, MD, a pediatric oncologist at Memorial Sloan Kettering Cancer Center and Weill Cornell Medical College, New York.
Based on their review of early pivotal clinical trials, relapse data, toxicities, and mechanisms to optimize CAR T-cell therapy, Dr. Fabrizio and Dr. Curran outlined several “practice points” and proposed a research agenda aimed at optimizing the use of CAR T-cell therapy for B-ALL (Best Pract Res Clin Haematol. 2021 Aug 27. doi: 10.1016/j.beha.2021.101305).
Practice points
CAR T-cell therapy has transformed the treatment of both pediatric and adult patients with relapsed/refractory (R/R) B-ALL, the authors said, adding that “[c]linical trial results across multiple institutions with different CAR constructs report significant response rates in treated patients.”
Dr. Fabrizio and Dr. Curran specifically note that only one product (tisagenlecleucel) is currently approved for the treatment of R/R B-ALL in patients under age 26 years. Further, the successful application of this therapy is limited by high relapse rates, significant toxicity in some cases, and challenges related to collection and production issues.
They contend that areas in which optimization of CAR T-cell therapy can occur include apheresis, production, chemotherapy bridging, pretreatment disease burden management, toxicity management, disease monitoring after therapy, and use of consolidative allogeneic hematopoietic stem cell transplantation.
Research agenda
Key ways to heighten the success of CAR T-cell therapy for B-ALL are the development of off-the-shelf CAR T-cell products and the selection of optimal T cells to enhance apheresis and production, they said, adding that research is needed on the use of bridging chemotherapy to reduce tumor burden.
Bridging chemotherapy has been shown to impact outcomes while minimizing toxicity, but it remains undefined.
“Prospective trials are required to determine if the optimization of lymphodepleting chemotherapy can improve outcomes, and if consolidative therapy with transplantation should be considered in select patients,” they wrote. “Continued efforts to improve this technology for patients is ongoing while remaining questions are being investigated.”
The authors acknowledge that CAR T-cell therapy has transformed the treatment landscape for both pediatric and adult patients with R/R B-ALL, but this extensive review of all published data on the subject shows that “the incidence of relapse among responders is unacceptably high, demonstrating the need to improve this therapy.”
In conclusion, they wrote: “To be effective following infusion, CAR T cells must expand, persist, exhibit enduring anti-tumor cytotoxicity, withstand and/or counteract an immunosuppressive tumor microenvironment, and overcome targeted tumor antigen escape. In designing CAR T cells for cancer immunotherapy, all of these factors must be harmonized to generate the optimal therapy,” noting that “[t]oxicity management and, ideally the prediction of toxicity in individualized patients, should continue to be a focus of ongoing efforts.”
Dr. Curran has received research support from Juno Therapeutics and Novartis, and has consulted, participated in advisory boards, or taken part in educational seminars for Juno Therapeutics, Novartis, and Mesoblast. Dr. Fabrizio reported having no conflict of interests.