Daratumumab is safe but ineffective for the treatment of patients with relapsed or refractory non-Hodgkin lymphoma (NHL) and CD38 expression of at least 50%, according to findings from a recent phase 2 trial.
Unfortunately, the study met headwinds early on, when initial screening of 112 patients with available tumor samples showed that only about half (56%) had CD38 expression of at least 50%, reported lead author, of Claude Bernard University in Lyon, France, and his colleagues. The cutoff was based on preclinical models, suggesting that daratumumab-induced cytotoxicity depends on a high level of CD38 expression.
“Only 36 [patients] were eligible for study enrollment, questioning the generalizability of the study population,” the investigators wrote in.
Of these 36 patients, 15 had diffuse large B-cell lymphoma (DLBCL), 16 had follicular lymphoma (FL), and 5 had mantle cell lymphoma (MCL). Median CD38 expression was 70%. Patients were given 16 mg/kg of IV daratumumab once a week for two cycles, then every 2 weeks for four cycles, and finally on a monthly basis. Cycles were 28 days long. The primary endpoint was overall response rate. Safety and pharmacokinetics were also evaluated.
Results were generally disappointing, with ORR occurring in two patients (12.5%) with FL and one patient (6.7%) with DLBCL. No patients with MCL responded before the study was. On a more encouraging note, 10 of 16 patients with FL maintained stable disease.
“All 16 patients in the FL cohort had progressed/relapsed on their prior treatment regimen; therefore, the maintenance of stable disease in the FL cohort may suggest some clinical benefit of daratumumab in this subset of NHL,” the investigators wrote.
Pharmacokinetics and safety data were similar to those from multiple myeloma studies of daratumumab; no new safety signals or instances of immunogenicity were encountered. The most common grade 3 or higher treatment-related adverse event was thrombocytopenia, which occurred in 11.1% of patients. Infusion-related reactions occurred in 72.2% of patients, but none were grade 4 and only three reactions were grade 3.
The investigators suggested that daratumumab may still play a role in NHL treatment, but not as a single agent.
“It is possible that daratumumab-based combination therapy would have allowed for more responses to be achieved within the current study,” the investigators wrote. “NHL is an extremely heterogeneous disease and the identification of predictive biomarkers and molecular genetics may provide new personalized therapies.”
The study was funded by Janssen Research & Development; two study authors reported employment by Janssen. Others reported financial ties to Janssen, Celgene, Roche, Gilead, Novartis, Amgen, and others.
SOURCE: Salles G et al. Clin Lymphoma Myeloma Leuk. 2019 Jan 2.