External Beam Radiation Therapy in Combination With Talquetamab for the Treatment of Multiple Myeloma Patients With Extramedullary Disease

This phase I/II trial tests the safety and effectiveness of extramedullary disease (EMD)-directed external beam radiation therapy (EBRT) in combination with talquetamab for the treatment of multiple myeloma patients with extramedullary disease. Extramedullary disease in multiple myeloma involves the infiltration of organs and soft tissues by malignant plasma cells and has proven difficult to treat. Radiation therapy uses high energy x-rays, particles, or radioactive seeds to kill cancer cells and shrink cancers. EBRT is a type of radiation therapy that delivers high-energy beams to the cancer from outside of the body. In this trial, the EBRT will be directed to a site of extramedullary disease. Talquetamab is a monoclonal antibody that may interfere with the ability of cancer cells to grow and spread. A monoclonal antibody is a type of protein that can bind to certain targets in the body, such as molecules that cause the body to make an immune response (antigens). Combining EMD-directed EBRT with talquetamab may be safe, tolerable, and/or effective in treating multiple myeloma patients with extramedullary disease.

PRIMARY OBJECTIVES: I. To evaluate the safety and tolerability of single-field, palliative, extramedullary disease (EMD)-directed external beam radiotherapy (EMD-EBRT) in combination with talquetamab as assessed by incidence of adverse events (AEs) throughout the trial and unexpected toxicities (UTs) during step-up and cycle 1. (Phase 1b) II. To evaluate the systemic anti-tumor activity/preliminary efficacy of EMD-EBRT in combination with talquetamab as assessed by EMD-modified overall response rate (ORR). (Phase 2) SECONDARY OBJECTIVE: I. To additionally evaluate efficacy through International Myeloma Working Group (IMWG) overall response rate (ORR), duration of response (DOR), progression-free survival (PFS), and overall survival (OS). EXPLORATORY OBJECTIVES: I. To assess the impact of EMD-EBRT combined with talquetamab on peripheral blood immune cell populations. II. To assess the spatial transcriptomic changes in the medullary and extramedullary tumor microenvironment in response to EMD-EBRT combined with talquetamab. OUTLINE: STEP-UP PERIOD: Patients undergo EMD-EBRT once daily (QD) for 5 treatment fractions on weekdays (Monday to Friday), and receive talquetamab subcutaneously (SC) starting after the first fraction of EMD-EBRT and continuing every 2-4 days for up to 3 step-up doses in the absence of unacceptable toxicity. SUBSEQUENT TREATMENT: Starting 2-7 days after step-up dose 3, patients receive talquetamab SC on days 1 and 15 of each cycle. Cycles repeat every 28 days for up to a maximum of 13 total cycles in the absence of disease progression or unacceptable toxicity. Patients also undergo computed tomography (CT) and/or positron emission tomography (PET)/CT and collection of blood samples throughout the trial and undergo image-guided EMD biopsy at screening and on study. Patients undergo bone marrow biopsy/aspiration at screening and optionally at end of treatment. After completion of study treatment, patients are followed up every 28 days for up to 12 months.