Multicenter Phase II Trial of Bendamustine, Lenalidomide and Dexamethasone (BRd) As 2^nd-Line Therapy for Multiple Myeloma

Background

High quality response [very good partial remission (VGPR), complete remission (CR)] is associated with improved long-term outcome in multiple myeloma (MM) therapy. Lenalidomide (Len)/ dexamethasone (Dex) (Rd) is considered a standard 2^nd-line regimen. However, after 1^st-line MM therapy containing a “novel agent” like thalidomide, only a relatively small fraction (21.3%) of patients (pts) achieved VGPR or better when RD was used in relapsed/refractory MM (RRMM)¹. Bendamustine (Ben) is an alkylating agent with superior activity compared to melphalan/prednisone. The combination of Ben, Len and Dex (BRd) in pts with advanced RRMM resulted in dose-limiting hematotoxicity, which restricted its efficacy in extensively pretreated pts². However, recent phase I experience demonstrated the feasibility of BRd as 2^nd- and 3^rd-line myeloma therapy³. We therefore evaluated the efficacy and toxicity of the BRd-regimen as 2^nd line therapy for RRMM.

Patients and methods

This multicenter Phase II study was designed to enroll 50 pts with RRMM undergoing 2^nd-line MM therapy [including also pts with prior autologous stem cell transplantation (ASCT)]. Pts had to have measurable disease, ECOG performance status 0-2, adequate hematological values and a creatinine clearance > 50 ml/min.

Study treatment consisted of Ben 75 mg/m² i.v. day (d) 1 & 2 and Len 25 mg p.o. d 1-21 for a total of six 28-day induction cycles. Dex (40 and 20 mg p.o. for pts <= or > 75 years of age, respectively) was given on d 1, 8, 15, and 22. Pegfilgrastim 6 mg s.c. was administered on d 3 in case of severe neutropenia, treatment delay due to neutropenia or febrile neutropenia according to predefined application rules. Induction treatment was followed by 12 cycles (28 d) of maintenance therapy with Rd at the same dose.

The primary study endpoint was the CR/VGPR rate after induction therapy, based on standard IMWG criteria. A Simon's two stage design was used to differentiate between 20% (considered uninteresting) vs 40 % (considered promising, power of 80%, p=5%) of high quality responses. At least 13 pts with VGPR or better after induction therapy were required to meet the statistical threshold predefined for promising activity of the BRd regimen in this study.

Results

50 pts were enrolled between 04/2012 and 07/2014 (median age 68 years [46-84y], 73% men). 49% pts had ISS stage II/III, 42.5% had undergone prior SCTs, and 13% had known high risk cytogenetic aberrations. 91% of pts had received novel agents (thalidomide, bortezomib) during 1^st-line therapy.

At the time of abstract submission, data from 38 pts having completed induction treatment were available. Final analysis of the primary study endpoint including all patients will be updated and presented at the meeting.

Of the currently 38 evaluable pts, 20 (52.6%, Table 1) achieved a CR/VGPR after a median of 3.3 induction cycles. Only 1 patient experienced disease progression (PD) during induction phase.

77% of pts received pegfilgrastim. Dose reduction during induction therapy was required in 7.7% of pts. 42.5% received < 6 scheduled induction cycles (50% due to toxicities, 50% for other reasons). 49% had treatment-related SAEs. Grade 3/ 4 neutropenia and thrombocytopenia occurred in 51%/25.5% and 23.4%/8.5% of pts, respectively. Only 1 patient developed CTC grade 3 febrile neutropenia. Most common grade 3/4 non-hematologic toxicities were infections (14%), rash (9.5%), and diarrhea (9.5%). Anaphylactic reaction grade 4 related to Ben and pulmonary embolism grade 3 occurred in 1 patient each. A cerebral insult grade 4 occurred in a patient non-compliant with the anti-thrombotic prophylaxis required per protocol. One death due to respiratory failure (considered to be unlikely related to study treatment) was reported for an 83 year old male.

Conclusion

BRd is a safe and efficacious regimen for 2^nd line treatment of RRMM patients whose 1^st-line therapy included thalidomide or bortezomib. High quality responses (>= VGPR) can be achieved in a considerable proportion (52.6%) of these pts. Our study suggests that the fraction of patients achieving VGPR or better after BRd treatment may be substantially higher than attainable with Rd alone.

References

¹ Wang et al. Blood, 2008, 112: 4445-51

² Lentzsch et al. Blood, 2012, 119: 4608-13

³ Poenisch et al., Br J Haematol, 2013, 162, 202–9