The novel drug melflufen with dexamethasone was effective in treating patients with relapsed and refractory multiple myeloma who were heavily pretreated with pomalidomide (a chemotherapy drug) and/or an anti-CD38 monoclonal antibody (a substance that helps the immune system eliminate cancer cells).
In this phase 2 study, researchers enrolled 157 patients (median age, 65 years; median of five prior lines of therapy) with relapsed or refractory multiple myeloma, defined as nonresponse disease with primary or salvage therapy or disease progression within 60 days of the last administered therapy. These patients received 40 mg of melflufen intravenously on the first day of a 28-day cycle, in addition to 40 mg of dexamethasone once per week. If patients were older than 75 years, their dose of dexamethasone was reduced to 20 mg once per week.
The primary end point of this study was overall response rate (ORR), which included patients who had a partial response or better. Secondary end points included progression-free survival (PFS), duration of response, safety and overall survival (OS).
Of the patients in the study, 76% had triple class-refractory disease (those treated with three major classes of drugs for multiple myeloma), 35% had extramedullary disease (myeloma cells forming tumors in organs or soft tissues) and 59% did not respond when previously treated with alkylator therapy (agents that damage the DNA of cancer cells to prevent them from producing copies of themselves).
Overall, patients had an ORR of 29%, which was 26% when researchers focused on patients with triple class-refractory disease. In all patients who were treated in this study regardless of disease type, median PFS was 4.2 months and median duration of response was 5.5 months. These patients also had a median overall survival of 11.6 months during a median follow-up of 14 months.
The majority of people (96%) had grade three or greater side effects as a result of the treatment, or side effects that were considered severe or life threatening. The most common of these side effects include thrombocytopenia (low levels of platelets in blood; 76%), neutropenia (low levels of a type of white blood cell in blood; 79%) and anemia (low levels of red blood cells in blood; 43%). The most common grade three to four event not related to blood was pneumonia (10%).
Other grade three or four events related to the treatment included thrombocytopenia and bleeding, which occurred in 3% of patients, although they were fully reversible. Gastrointestinal events occurred in 93% of patients, which were mainly grade one or two, or considered mild or moderate.
“Patients were … able to tolerate treatment, with rates of discontinuation from (side effects) lower than or comparable with other studies (which range from 6% to 33%) in this patient population and with a prolonged median duration of treatment, together with the added convenience of monthly infusions, which is an especially important consideration in the current era of COVID-19,” the study authors wrote.
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