Daratumumab monotherapy was associated with an overall response rate of 29.2% and was well tolerated in 106 heavily treated patients with multiple myeloma, based on results from the SIRIUS trial.
Of 106 patients who received daratumumab at 16 mg/kg, 3% achieved a stringent complete response, 9% had a very good partial response, and 17% had a partial response. The median progression-free survival was 3.7 months and median duration of response was 7.4 months. The 12-month overall survival was 64·8%, and, at a subsequent cutoff, median overall survival was 17.5 months.
All of the study patients had been treated with proteasome inhibitors and immunomodulatory drugs, with a median of five previous therapies. Most patients (80%) had received autologous stem cell transplantation, and 97% were refractory to the last line of therapy before study enrollment.
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“Resistance to any previous therapy had no effect on the activity of daratumumab, lending support to a novel mechanism of action, but these findings need to be confirmed in larger studies,” wrote Dr. Sagar Lonial of Emory University, Atlanta, and colleagues (Lancet 2016;387:1551-60). Response rates were similar for patients with moderate renal impairment, those over age 75, and those with extramedullary disease or high-risk baseline cytogenetic characteristics.
Daratumumab was well tolerated, and none of the patients discontinued treatment because of treatment-related adverse events. The most common adverse events of any grade were anemia (33%), thrombocytopenia (25%), and neutropenia (23%). Additional supportive care in the form of red blood cell transfusions was received by 38% of patients, platelet transfusions by 13%, and granulocyte colony-stimulating factor by 8%. Fatigue (40%) and nausea (29%) were the most common nonhematologic adverse events. Serious adverse events were observed in 30% of patients.
Daratumumab compares favorably with other regimens such as pomalidomide alone or with dexamethasone or carfilzomib monotherapy, according to the investigators.
The favorable safety profile of daratumumab makes it an attractive candidate for combination regimens, the authors noted, and daratumumab combined with other backbone agents are currently under investigation.
This study was sponsored by Janssen, maker of daratumumab (Darzalex). Dr. Lonial reported consulting or advisory roles with Janssen and several other drug companies.