GPRC5D is a target for the immunotherapy of multiple myeloma with rationally designed CAR T cells

Abstract

Early clinical results of chimeric antigen receptor (CAR) T cell therapy targeting B cell maturation antigen (BCMA) for multiple myeloma (MM) appear promising, but relapses associated with residual low-to-negative BCMA-expressing MM cells have been reported, necessitating identification of additional targets. The orphan G protein–coupled receptor, class C group 5 member D (GPRC5D), normally expressed only in the hair follicle, was previously identified as expressed by mRNA in marrow aspirates from patients with MM, but confirmation of protein expression remained elusive. Using quantitative immunofluorescence, we determined that GPRC5D protein is expressed on CD138+ MM cells from primary marrow samples with a distribution that was similar to, but independent of, BCMA. Panning a human B cell–derived phage display library identified seven GPRC5D-specific single-chain variable fragments (scFvs). Incorporation of these into multiple CAR formats yielded 42 different constructs, which were screened for antigen-specific and antigen-independent (tonic) signaling using a Nur77-based reporter system. Nur77 reporter screen results were confirmed in vivo using a marrow-tropic MM xenograft in mice. CAR T cells incorporating GPRC5D-targeted scFv clone 109 eradicated MM and enabled long-term survival, including in a BCMA antigen escape model. GPRC5D(109) is specific for GPRC5D and resulted in MM cell line and primary MM cytotoxicity, cytokine release, and in vivo activity comparable to anti-BCMA CAR T cells. Murine and cynomolgus cross-reactive CAR T cells did not cause alopecia or other signs of GPRC5D-mediated toxicity in these species. Thus, GPRC5D(109) CAR T cell therapy shows potential for the treatment of advanced MM irrespective of previous BCMA-targeted therapy.

Chimeric Antigen Receptor T-Cell Therapy for Multiple Myeloma

“…CAR T cells that are generated by fusing APRIL, a ligand for BCMA and TACI, with T cell-activating molecules are also shown to be effective in pre-clinical experiments [36]. Smith et al in Memorial Sloan Kettering Center recently reported GPRC5 as a promising target for CAR T cells against MM [37]. Not reported yet - [38] We also developed a new CAR T cell for MM.…”

A review of antibody-based therapeutics targeting G protein-coupled receptors: an update

“…In addition to bispecific antibodies and ADCs in early clinical development, there are now at least two CAR-T therapies in the research pipeline at the preclinical stage. These target EMR1, an aGPCR, for the treatment of eosinophilic leukemia [72] and GPRC5D, an orphan GPCR, for the treatment of multiple myeloma [73]. Another important area of interest in the field of antibody engineering is the use of BBB receptor-mediated transcytosis delivery (e.g., via the transferrin receptor) which could equally be applied to GPCR targeting using antibody-based modalities.…”

Chimeric antigen receptor T-cell therapy for multiple myeloma

“…Recently, 2 groups independently reported that the orphan G protein-coupled receptor, class C group 5 member D (GPRC5D), is specifically expressed in MM cells [18,19]. A group identified GPRC5D-specific scFvs and used them to generate CAR T cells [18]. One of the GPRC5D-targeted CAR T cells eradicated MM and enabled long-term survival in mouse models.…”