Defining an Optimal Dual-Targeted CAR T-cell Therapy Approach Simultaneously Targeting BCMA and GPRC5D to Prevent BCMA Escape–Driven Relapse in Multiple Myeloma

Abstract

Chimeric antigen receptor (CAR) T-cell therapy for multiple myeloma targeting B-cell maturation antigen (TNFRSF17; BCMA) induces high overall response rates; however, relapse occurs commonly. A reservoir of multiple myeloma cells lacking sufficient BCMA surface expression (antigen escape) may be implicated in relapse. We demonstrate that simultaneous targeting of an additional antigen-here, G protein-coupled receptor class-C group-5 member-D (GPRC5D)-can prevent BCMA escape-mediated relapse in a model of multiple myeloma. To identify an optimal approach, we compare subtherapeutic doses of different forms of dual-targeted cellular therapy. These include; (i) parallel-produced and pooled mono-targeted CAR T cells, (ii) bicistronic constructs expressing distinct CARs from a single vector, and (iii) a dual-scFv "single-stalk" CAR design. When targeting BCMA-negative disease, bicistronic and pooled approaches had the highest efficacy, whereas for dual-antigen-expressing disease, the bicistronic approach was more efficacious than the pooled approach. Mechanistically, expressing two CARs on a single cell enhanced the strength of CAR T-cell/target cell interactions. SiGNifiCANCE: Myeloma frequently relapses post-CAR T-cell therapy; antigen escape-mediated relapse can be mitigated with upfront dual-targeting (BCMA/GPRC5D). A bicistronic vector encoding two CARs avoids the challenge of parallel manufacturing separate CAR T-cell products, while providing superior efficacy; this dual-targeted approach may enhance the durability of responses to cellular therapy for myeloma. See related commentary by Simon and Riddell iNtRODUctiON Treatment options for multiple myeloma have substantially improved over the last decade, resulting in improved overall survival (1, 2); however, despite this progress, patients are rarely cured. The natural history of multiple myeloma involves multiple relapses with progressively shorter durations of remission, until the patient develops refractory disease (3, 4). Addressing relapsed/refractory multiple myeloma (RRMM) necessitates the development of novel treatment approaches; one such approach under development, with early clinical data demonstrating unprecedented response

Bone Marrow Mesenchymal Stromal Cell-mediated Resistance in Multiple Myeloma Against NK Cells can be Overcome by Introduction of CD38-CAR or TRAIL-variant

“…In principle, CAR activity itself can also be improved by the inclusion of strong co-stimulatory domains or high affinity single chain variable fragment (scFv) sequences. 8 , 23 In addition, dual-targeted CARs can enhance the strength of CAR T cell-target cell interactions 24 and may hereby avoid BMMSC-mediated resistance against classical single antigen-targeted CARs. Next to the CAR technology, the cytotoxic activity of the effector cells can be improved by increasing the cytotoxic potential of immune killer cells.…”

Chimeric antigen receptor natural killer (CAR-NK) cell design and engineering for cancer therapy

“…In addition, two scFvs can be fused together in one construct, generating a tandem scFv or “single stalk” CAR. While these techniques have been employed for the generation of CAR-T cells [ 55 ], we are not aware of such attempts for generating CAR-NK cells.…”

CART-Cell Therapy: Recent Advances and New Evidence in Multiple Myeloma

“…Some of them, such as GPRC5D, is expressed on the surface of CD138+ multiple myeloma cells, independent of BCMA expression, but it is minimally expressed in other cell lines [ 72 ]. Dual-targeted T-cells are actively being investigated, and recently, some groups reported preclinical data investigating dual-targeting approaches for CAR T-cell therapy, using BCMA and GPRC5D as a model [ 73 ]. Although many patients respond to CARs, some have not long-lasting responses, and many relapses despite achieving in-depth responses.…”