Phase II Trial of Combination of Elotuzumab, Lenalidomide, and Dexamethasone in High-Risk Smoldering Multiple Myeloma

Purpose: This study aimed to determine the benefit of early therapeutic intervention with the combination of elotuzumab, lenalidomide, and dexamethasone in patients with high-risk smoldering multiple myeloma (SMM). The overarching objective of this trial is to determine progression free survival to symptomatic myeloma (MM). Furthermore, the study examined the activity and safety of the combination therapy in patients with high-risk SMM.

Patients & Methods: Patients enrolled on study met eligibility for high-risk SMM based on the newly defined criteria proposed by Rajkumar et al, Blood 2014. Patients were administered weekly elotuzumab (10 mg/kg) on days 1, 8, 15, and 22 for the first two 28-day cycles while receiving lenalidomide on days 1-21. An initial cohort of patients were randomized to a low dose dexamethasone treatment arm (Arm B) based on the following stratification factors: age >65 years and high-risk cytogenetics based on t(4:14), t(14:16), 17p deletion or p53 mutation, and +1q amplification. For cycles 3-8, patients on both treatment arms were administered elotuzumab infusions on days 1, 8, and 15. Patients on treatment Arm A received dexamethasone (40mg) on days 1, 8 and 15. After 8 cycles or best response, patients were given the option to mobilize with either cyclophosphamide or plerixafor and collect stem cells for future transplant. Patients on both treatment arms were then allowed to continue on maintenance therapy where they were administered elotuzumab (20 mg/kg) on day 1, in combination with lenalidomide days 1-21 of a 28 day cycle. After 11 patients were enrolled on each arm, arm B closed due to similar activity and toxicity to the high-dose dexamethasone arm based on published data demonstrating that high-dose dexamethasone, given once a week, does not have a detrimental effect on the immune system in patients with smoldering myeloma.

Results: In total, 39 patients were enrolled on this study from January 2015 to date, with the participation of eight sites. The median age of patients enrolled was 62 years (range 26 to 75) with 15 males (38%) and 24 females (62%). The median number of cycles completed is 6 (range 1 to 19). Therapy related grade 3 toxicities included hypophosphatemia (23%), neutropenia (8%), infection (8%), anemia (3%), pulmonary embolism (3%), rash (3%), and diarrhea (3%). No related grade 4 or 5 toxicities have occurred thus far. Stem cell collection was successful in all patients collected to date. Unrelated toxicities include one instance of grade 4 prolonged QTc Interval. Of the 34 evaluable patients enrolled to both arms of the study, the clinical benefit rate is 97%. The overall response rate is 71%, including 9 very good partial responses (26%) and 15 partial responses (44%). The VGPR cases are currently under evaluation of possible complete responses due to the potential interference of elotuzumab with immunoelectrophoresis. Thus far, no patients have progressed to active multiple myeloma during, or after, protocol therapy.

Conclusion:The combination of elotuzumab, lenalidomide, and dexamethasone is very well tolerated among patients with high-risk SMM. The high response rates among this patient population, who would otherwise remain untreated, is a promising starting point for the paradigm shift towards early therapeutic intervention in patients with high-risk SMM.