Daratumumab with Dexamethasone in Patients with Relapsed/Refractory Multiple Myeloma and Severe Renal Impairment: Results on Efficacy and Safety of the Phase 2 Dare Study

Introduction: Renal impairment (RI) is common in multiple myeloma (MM), with up to 40% of the patients (pts) experiencing this complication during the course of their disease. RI increases risk of early death and affects disease management in multiple ways, as it may complicate treatment options and dosing, and render pts more susceptible to infections and prolonged hospitalizations. Therefore, there is an urgent need to restore renal function in these pts in order to improve their quality of life and prognosis. Bortezomib-based therapies are the most commonly used in pts with RI, but eventually pts may become refractory to bortezomib and other drug classes such as IMIDs. Thus, new therapeutic options are needed in order to manage pts with MM and RI who fail these drugs. Daratumumab, an IgG1κ human monoclonal antibody that targets CD38, has shown durable responses and a favorable safety profile in heavily pretreated pts with relapsed/refractory MM (RRMM) as monotherapy. Pharmacokinetic analyses suggest that there are no clinically important differences in exposure to daratumumab in pts with normal or impaired renal function, but the available data on safety and efficacy of pts with RRMM and severe RI is scarce.

Methods: DARE is a prospective, open-label, multicenter, phase 2 study, which completed the enrolment of 38 adult pts with documented RRMM and severe RI, defined as either eGFR<30 mL/min/1.73m² or requiring hemodialysis. Pts had ≥2 lines of therapy with both bortezomib- and lenalidomide-based regimens and an Eastern Cooperative Oncology Group performance status (ECOG PS) score ≤2. Exclusion criteria included previous daratumumab or other anti-CD38 therapy exposure. Pts receive 28-day treatment cycles with 16 mg/kg intravenous daratumumab (weekly for cycles 1–2, every 2 weeks for cycles 3–6, and every 4 weeks thereafter) and oral dexamethasone (40 mg weekly, each cycle). The primary endpoint is progression-free survival (PFS). Secondary endpoints are overall response rate (ORR; proportion of pts with partial response or better), renal response rate as evaluated per IMWG criteria (RRR; proportion of pts with best response of renal partial response or better), and safety. All responses are based on investigators’ assessment per International Myeloma Working Group criteria. This preliminary analysis presents results for pts who received the first dose of study treatment at least 5 months prior to the cut-off date (01/05/2020).

Results: The current analysis includes 35 pts, enrolled in 7 Sites. Median age was 72 years, and 77.1% were male. The median time from diagnosis to first daratumumab dose was 4.2 years. Pts had a median of 3 prior systemic therapies, and 37.1% had a prior autologous stem cell transplantation. At study initiation 8.6% and 91.4% of pts had international staging system (ISS) 2 and 3 disease, respectively, while 51.4% and 48.6% were revised ISS 2 and 3. The median eGFR at baseline was 13 mL/min/1.73 m².and 17 pts (48.6%) were on dialysis. The median number of cycles administered until the cut-off date was 5 and the median follow-up duration was 5.5 months. The 6-month progression-free survival rate, was 50% (figure). Overall, ORR was 45.7%, with 31.4% of all pts achieving a VGPR and 14.3% a PR. For pts on dialysis (n=17), ORR was 35.3%, equally divided between pts achieving VGPR and PR (17.6%). The median time from the first dose of study treatment until the first response (≥PR) was 0.9 months. RRR was 17.1%. By the cut-off date, 37.1% of the pts were still receiving protocol therapy, 17.1% discontinued treatment due to death, and 31.4% due to disease progression. Overall, 17 pts (48.6%) had at least 1 adverse event (AE) of grade 3 or 4, most frequent being anemia (17.1%) and hyperglycemia (8.6%). Nine (25.7%) pts had at least 1 SAE: Septic shock (fatal, 2 pts), and performance status decreased (fatal), lower respiratory tract infection (fatal), myocardial infarction (fatal), peritonitis (fatal, in a patient receiving peritoneal dialysis), cerebrovascular accident, pneumonia, acute kidney injury, and hyperkalemia (1 pt each).

Conclusions: The administration of daratumumab with dexamethasone led to rapid hematologic responses in pts with RRMM and severe RI, including those in dialysis, and at the same time it resulted in a major renal response for 17.1% of the pts. Importantly, new safety signals were not observed, and daratumumab can be safely administered in pts with severe RI or those on dialysis.