Clinical Report: GPRC5D as a Novel Therapeutic Target in Multiple Myeloma

Overview

GPRC5D is a promising new target for multiple myeloma (MM) therapy due to its high expression on malignant plasma cells and limited presence in normal tissues. Its unique expression profile and independence from BCMA suggest potential for improved treatment strategies, including combination therapies.

Background

Multiple myeloma is a genetically complex hematologic malignancy with significant morbidity and mortality, affecting multiple organ systems and leading to a high symptom burden. Despite advances in therapies targeting BCMA, patients often relapse and develop resistance, necessitating new targets with distinct mechanisms. GPRC5D, an orphan G-protein coupled receptor with limited normal tissue expression, has emerged as a novel target for T-cell–redirecting immunotherapies. Understanding its biology and expression patterns is critical for developing effective MM treatments.

Data Highlights

Key Findings

• GPRC5D is highly expressed on malignant plasma cells in MM and smoldering MM, with minimal expression in normal hematopoietic cells.
• Its expression is independent of BCMA, allowing for potential combination therapies targeting both antigens.
• GPRC5D protein is localized mainly to plasma cells and epithelial structures such as hair follicles and tongue filiform papillae.
• Increased GPRC5D mRNA expression correlates with high-risk disease features and poorer prognosis, although this may reflect tumor burden rather than causation.
• GPRC5D’s short extracellular domain and membrane proximity may facilitate effective T-cell–redirecting immunotherapy with reduced antigen shedding.
• There is no evidence of significant GPRC5D expression in critical normal tissues such as cerebral cortex or bone marrow progenitors, suggesting a favorable safety profile.

Clinical Implications

Targeting GPRC5D offers a novel immunotherapeutic approach for MM patients, especially those who relapse after BCMA-directed therapies. Its restricted normal tissue expression may reduce off-target toxicities, and combining GPRC5D and BCMA targeting could address tumor heterogeneity and improve outcomes. Clinicians should consider GPRC5D-directed therapies as part of evolving treatment paradigms for relapsed/refractory MM.

Conclusion

GPRC5D represents a validated and promising target for multiple myeloma immunotherapy with a distinct expression profile and potential to overcome limitations of current BCMA-targeted treatments. Ongoing clinical development of GPRC5D-directed agents may expand therapeutic options and improve patient prognosis.

References

1. Smith EL et al. 2019 -- GPRC5D is a target for the immunotherapy of multiple myeloma with rationally designed CAR T cells