Oral and Poster Abstracts
653. Myeloma: Therapy, excluding Transplantation: Poster I
Saturday, December 7, 2013, 5:30 PM-7:30 PM, Hall G (Ernest N. Morial Convention Center)
Background: Pomalidomide is a distinct IMiD® immunomodulatory agent with activity in subjects with relapsed or refractory MM (RRMM), including those with prior lenalidomide treatment. We have previously reported that the addition of clarithromycin enhances the anti-myeloma activity of pomalidomide+dexamethasone (Pom/Dex) in the treatment of RRMM (Mark et al, ASH 2012). We now report updated results with extended follow up from a phase 2 trial of large group of patients treated with ClaPd in RRMM.
Methods: One hundred nineteen patients with heavily pretreated RRMM were enrolled into a single-institution study to investigate the effectiveness and tolerability of ClaPd. Eligible subjects had at least 3 prior lines of therapy, one line of which must have included lenalidomide. ClaPd is clarithromycin 500mg twice daily; pomalidomide 4mg for days 1-21, and dexamethasone 40mg on days 1,8,15,22 of a 28-day cycle. All subjects had thromboprophylaxis with 81mg aspirin daily. Disease response evaluation was performed monthly with immunoelectrophoresis and free light chain analysis; bone marrow biopsy with skeletal imaging was used to confirm MM progression or complete response (CR). Treatment was continued as tolerated by the patient until disease progression.
Results: One hundred fourteen patients had completed at least 1 cycle of ClaPd and were eligible for disease response analysis at data cut-off. All patients were included in the safety analysis. Patients had undergone a median of 5 (range 3-15) prior lines of therapy. The proportion of patients who were refractory to lenalidomide, refractory to bortezomib, and double (lenalidomide+bortezomib) refractory were 85%, 79%, and 68% respectively. The median number of ClaPd cycles received was 7 (range 1-34). Overall response rate (ORR, ≥PR, entire cohort/double-refractory subgroup) was 61.4/56.4% [stringent complete remission (sCR): 4.4/4%, complete response (CR): 0.9/1.3%, very good partial response (VGPR): 14.9/11.5%, partial response (PR): 41.2/38.5%, minimal response (MR): 7/9%, stable disease (SD): 21.9/21.8%, progressive disease (PD): 9.6/12.8%, ³VGPR rate of 20.2/16.7%]. Clinical benefit (³ MR) was achieved in 68.4/65.4%. Median time to PR and maximum response was 1 (range 1-7) and 2 (range 1-18) cycles, respectively. After a mean follow up time of 11.9 months, 40 patients (34%) remain free from progression, with a median progression free survival of 8.1 months (95% CI: 5.1, 9.8). Median duration of response (DOR) was 9.3 months (95% CI: 7.2,16.1). Median overall survival (OS) has not been reached with 68 patients (57%) alive at last follow-up. Median PFS, DOR, OS were not significantly different in the double-refractory subgroup at 6.3 (CI 4.7, 8.7; p = 0.21), 8.6 (CI 6.5, 16.1; p = 0.87), and 16.8 months (CI 12.4, 28.7; p = 0.11) respectively. The most common (³?%? grade 3 and 4 toxicities were: neutropenia (49%), thrombocytopenia (39%), anemia (27%), pneumonia (10%), fatigue 8%, and muscular weakness 7%. Febrile neutropenia was uncommon at 2%. There were 6 cases of lower extremity venous thrombosis (5%, 1 grade 1, 4 grade 2, 1 grade 3) and no instances of pulmonary embolism. Mild peripheral neuropathy was present in 32% (19% grade 1, 13% grade 2), 0% grade 3 or 4). Grade 2 congestive heart failure, due to dexamethasone, emerged in 1 subject (0.8%). Four patients (3.3%) withdrew due to treatment related toxicity (1 with Grade 3 muscular weakness, 2 due to Grade 3 fatigue, 1 grade 4 neutropenic sepsis). There was no treatment related mortality.
Conclusions: ClaPd is a highly effective and tolerable regimen for heavily treated RRMM that has progressed after prior treatments. Response to ClaPd is rapid and sustained at > 8 months in the majority of subjects. The presence of double refractory disease did not significantly impact clinical outcomes. The ORR and PFS compare favorably and toxicity profile is similar to other published reports of Pom/Dex.