Study Identifies Protein Changes Driving Immunotherapy Resistance in Multiple Myeloma

Treatment resistance emerges as malignant plasma cells evolve under selective pressure, limiting durable responses. Clarifying how tumor cells evade immune attack is essential for optimizing monitoring and care. New findings demonstrate how myeloma cells adapt following immunotherapy, illuminating mechanisms linked to relapse.

At the University of Calgary, investigators at the Arnie Charbonneau Cancer Institute examined why patients often relapse after a form of immunotherapy known as a bispecific T-cell engager. The therapy helps the immune system identify and attack multiple myeloma by targeting GPRC5D, a protein located on the tumor-cell surface. The study, published in Nature Medicine, focused on tumor-cell changes that arise under therapeutic pressure.

The team assessed data collected from clinics across North America, Europe, and Asia and analyzed tumor cells from patients who relapsed after receiving GPRC5D-targeted bispecific T-cell engagers. Researchers observed that myeloma cells adapted through multiple mechanisms during and after treatment exposure. These observations were made to understand resistance as it developed over time in the clinical setting.

Results showed that tumor cells frequently underwent protein-level changes associated with escape from immune recognition. According to the investigators, protein mutation or adaptation accounted for approximately 60%–70% of relapsed cases studied. The work was led from the University of Calgary’s Arnie Charbonneau Cancer Institute, with contributing clinical data from sites across three continents.

The researchers emphasized that treatment cannot be a one-size-fits-all approach and that responses vary substantially among patients despite similar therapies. They noted the importance of tailoring strategies as resistance emerges and highlighted the potential for more targeted screening within routine practice. The stated goal is to implement faster-turnaround screening to support real-time treatment decisions.

"Immunotherapy is quite an active topic when it comes to myeloma research because it's really changing how we practice in our clinics and what we're able to offer to patients," said Holly Lee, MD, Ph.D., clinical assistant professor at the Cumming School of Medicine. "For us to really cure myeloma, we have to understand the tumor cells and develop treatments to stay ahead of them building that resistance."

"Cancer is not one disease. Each cancer and each patient behave very, very differently. We have patients who are in remission for four or five years and others who relapse within six months after receiving the same therapy. I think this paper and this study is a step towards personalized cancer therapy," added Dr. Lee.

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Arnie Charbonneau Cancer Institute