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Introduction: Daratumumab is a human IgGκ monoclonal antibody targeting CD38. Despite the demonstrated benefit of daratumumab in multiple myeloma, not all patients have access to commercially available daratumumab. Here we report a pooled analysis of patients from the UK, Spain, Italy, and Russia enrolled in an open-label, early access treatment protocol (EAP) that provided daratumumab (16 mg/kg) monotherapy to patients with heavily pre-treated relapsed or refractory multiple myeloma (RRMM).

Methods: Intravenous daratumumab 16 mg/kg was administered to patients who had received ≥ 3 prior lines of therapy, including a proteasome inhibitor (PI) and an immunomodulatory drug (IMiD), or who were double refractory to both a PI and an IMiD. Safety and patient-reported outcomes data were collected.

Results: A total of 293 patients received  ≥ 1 dose of daratumumab. The median duration of daratumumab exposure was 4.2 (range 0.03-24.1) months, with a median number of 13 (range 1-37) infusions. The overall response rate was 33.1%, and the median progression-free survival was 4.63 months. Grade 3/4 treatment-emergent adverse events occurred in 60.1% of patients, of which the most common were thrombocytopenia (18.8%), anemia (11.9%), and neutropenia (11.6%). The most common serious adverse events were pneumonia (4.4%) and pyrexia (4.1%). Infusion-related reactions occurred in 45.1% of patients. The median change from baseline in all domains of patient-reported outcome instruments (European Quality of Life Five Dimensions Questionnaire [EQ-5D-5L], European Organisation for Research and Treatment of Cancer [EORTC] Quality of Life Questionnaire [QLQ-C30], and EORTC Multiple Myeloma Module [QLQ-MY20]) was generally 0 or close to 0.

Conclusion: These EAP results are consistent with those from previous trials of daratumumab monotherapy and confirm its safety in patients from Europe and Russia with heavily pre-treated RRMM.

Trial Registration: ClinicalTrials.gov identifier, NCT02477891.