Plain language summary of the MajesTEC-1 study of teclistamab for the treatment of people with relapsed or refractory multiple myeloma

This is a summary of a phase 1-2 clinical trial called MajesTEC-1. This trial tested the cancer drug teclistamab in people with relapsed or refractory multiple myeloma, a cancer that forms in a certain type of white blood cells known as plasma cells. Most participants who took part in the study had at least 3 prior treatments for multiple myeloma before their cancer came back. A total of 165 participants from 9 countries were included in this study. All participants were given teclistamab once per week and monitored for side effects. Once participants started taking teclistamab, they were checked regularly to monitor if their cancer had no change, improved (responded to treatment), or worsened or spread (known as disease progression). After approximately 14.1 months of follow-up (from 2020 to 2021), 63% of participants who were given teclistamab had a decrease in myeloma burden, meaning that they responded to treatment with teclistamab. Participants who responded to teclistamab lived without their myeloma coming back for approximately 18.4 months. The most common side effects were infections, cytokine release syndrome, abnormally low white and red blood cell counts (neutropenia, lymphopenia, and anemia), and low platelet cell counts (thrombocytopenia). Approximately 65% of participants experienced serious side effects. Overall, more than half of the participants (63%) in the MajesTEC-1 study responded to treatment with teclistamab despite previous myeloma treatment failures. NCT03145181, NCT04557098 (ClinicalTrials.gov).