Safety and Efficacy of Daratumumab with Lenalidomide and Dexamethasone in Relapsed or Relapsed, Refractory Multiple Myeloma

Background: Daratumumab (DARA) (HuMax™-CD38), a human IgG1κ monoclonal antibody effectively mediates destruction of CD38-expressing malignant plasma cells. In the first-in-human dose-escalation study, 42% of heavily pretreated patients with relapsed, or relapsed, refractory (RR) multiple myeloma (MM) treated with DARA alone (≥4mg/kg) achieved partial response (PR) and 25% had minimal response (MR) (modified IMWG guidelines) (1). In preclinical studies, DARA + lenalidomide (LEN) enhanced killing of MM cells in vitro (2). We evaluated safety, pharmacokinetics (PK) and efficacy of DARA + LEN + low-dose dexamethasone (DEX) in patients with relapsed or RR MM.

Methods: This ongoing phase I/II open-label multicenter study consisted of 2 parts: Part1 was dose-escalation study in which patients (≥ 18 years old) with life expectancy ≥3 months and ECOG status 0, 1 or 2 received DARA+LEN+DEX (DARA [2-16 mg/kg] per week [8 weeks], twice a month [16 weeks], then, once monthly until disease progression, unmanageable toxicity or 24 months in total; LEN [25 mg PO day 1 through 21 of 28-days cycles]; DEX [40 mg] once weekly). Part 2 was cohort expansion study which explored the testing of maximum tolerated DARA dose (MTD) (16 mg/kg) determined in part 1 along with LEN (25 mg mg PO day 1 through 21 of 28-days cycles) and DEX (40 mg) once weekly.

Results: Data from 22 patients (13 patients [fully enrolled] from part 1 and 9 patients from part 2, [ongoing enrollment]) were presented at ASCO earlier this year (3). These results demonstrated that the most frequent (>30% patients) adverse events (AEs) were neutropenia and diarrhea; no dose limiting toxicities (DLTs) were reported. Infusion reactions (grade 1 and 2) were reported in 4 patients. 8 serious AEs were reported, all assessed as unrelated to DARA. MTD was not reached. DARA+LEN+DEX PK-profile was similar to DARA alone suggesting LEN and DEX do not affect the DARA PK-profile. Available preliminary efficacy data from 20 patients demonstrated marked decrease in M-protein in all patients; 15/20 patients achieved PR or better, 3/20 with CR, 6/20 with VGPR. Median time to response was 4.3 weeks (range: 2.1-11.3). Overall response rate (ORR) was 75% (15/20) combining all patients in part 1 and 2 and 92.3% (12/13) for part 1 patients, who had at least 2 months of follow-up or discontinued earlier.

Conclusions: DARA+LEN+DEX has favorable safety profile with manageable toxicities in relapsed and RR MM. Encouraging early activity is seen with marked reduction in M-protein and majority of the patients (~75%) achieved PR or better. Results of approximately 30 patients from part 2 with at least 2 months of treatment exposure and 10 patients (out of 30 patients) with shortened duration of infusion will be presented.

References

1. Lokhorst et. al., EHA 2013 abstract #8512

2. van der Veer et. al., Haematologica 2011;96(2):284-90

3. Plesner et. al. J Clin Oncol 32:5s, 2014 (suppl; abstr 8533).