Human GPRC5D Stable Cell Line - CHO-K1

Although advances in treatment over the past few decades have significantly improved the survival of patients with multiple myeloma, more effective treatments remain a significant unmet medical need. Here, researchers discovered that G protein-coupled receptor family C group 5 member D (GPRC5D) is expressed on the surface of multiple myeloma malignant cells but is not significantly expressed on the surface of normal hematopoietic cells and bone marrow progenitor cells (including hematopoietic stem cells), except for plasma cells and B cells. Furthermore, researchers constructed an IgG-based anti-GPRC5D/CD3 bispecific T cell redirecting antibody (GPRC5D TRAB), which inhibited tumor growth of GPRC5D-positive myeloma cells by activating T cells both in vitro and in xenograft models. Together, these findings suggest that GPRC5D is a specific antigen for multiple myeloma and a potential target for TRAB therapy.

To verify the binding affinity of GPRC5D TRABs to GPRC5D, the researchers performed flow cytometric analysis using human GPRC5D-expressing CHO cells. All four GPRC5D TRABs bound to GPRC5D. GPA0018 TRAB and GPA0039 TRAB had stronger binding affinities than GPA0021 TRAB and GPA0032 TRAB (Figure 1A). The binding affinities (KD values) of GPA0018 TRAB and GPA0039 TRAB to GPRC5D were 4.9 and 7.4 nmol/L, respectively, while the KD values of both for CD3ϵ were between 94 and 100 nmol/L. To investigate T cell activation and simultaneous binding to GPRC5D-expressing cancer cells and CD3+ T cells, the researchers used a luciferase assay system with GloResponse NFAT-luc2 Jurkat cells as effector cells and the GPRC5D-expressing human multiple myeloma cell line NCI-H929 as cancer cells. All four GPRC5D TRABs crosslinked T cells to GPRC5D-expressing cancer cells, activating CD3 downstream signaling pathways. GPA0018 TRAB and GPA0039 TRAB exhibited significantly stronger activation than GPA0021 TRAB and GPA0032 TRAB (Figure 1B), consistent with their binding activity. These results demonstrate that the novel GPRC5D TRABs can efficiently bind to human CD3+ T cells and GPRC5D-expressing cells and activate human T cells in vitro in a manner dependent on their affinity for GPRC5D.

Figure 1. Functional analysis of GPRC5D TRABs. (Kodama T, et al., 2019)