Background: The addition of clarithromycin has been reported to enhance anti-myeloma activity of lenalidomide+dexamethasone in the upfront treatment of multiple myeloma (MM). Pomalidomide is a distinct IMiD® immunomodulatory agent with a significant response rate in subjects with relapsed or refractory MM (RRMM), including those with prior lenalidomide treatment. We hypothesized that clarithromycin may similarly enhance the activity of pomalidomide + dexamethasone in patients with RRMM after prior lenalidomide therapy. We now report the initial results from a phase 2 trial of ClaPD (Clarithromycin/[Biaxin®], Pomalidomide, Dexamethasone) therapy in RRMM.
Methods: Fifty-two patients with heavily pre-treated RRMM were enrolled into a single-institution study and received ClaPD. Eligible subjects had at least 3 prior lines therapy, one line of which must have included lenalidomide. ClaPD is clarithromycin 500mg twice daily; dexamethasone 40mg on days 1,8,15,22; and pomalidomide 4mg for days 1-21 of a 28-day cycle. All subjects had thromboprophylaxis with aspirin. 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: Forty-six patients had completed at least 1 cycle of ClaPD and were eligible for analysis. The median number of cycles received was 6 (range 2-10). ClaPD responses were progressive disease (PD): 20%, stable disease (SD): 15%, minimal response (MR): 7%, partial response (PR): 33%, very good partial response (VGPR): 20%, stringent complete remission (sCR): 7%, giving an overall response rate (ORR) of 60% and a ≥VGPR rate of 27%. In responding patients, time to PR was rapid at a median of 1.5 cycles (range 1-7). After a median follow up time of 6.7 months, 28 patients (61%) remain on study free from disease progression and 39 patients (85%) are alive. Two patients withdrew from treatment due to regimen toxicity (one due to Grade 3 fatigue, another due to Grade 4 muscular weakness).
Conclusions: ClaPD is a highly effective regimen for heavily treated RRMM, particularly in patients with disease progression after prior lenalidomide therapy. When compared to other published Phase 2 data, the addition of clarithromycin in ClaPD appears to enhance the efficacy of Pomalidomide-Dexamethasone in lenalidomide-relapsed patients, (ORR 60% versus 40% - Lacy et. al JCO 2009) without induction of excess toxicity. Response to ClaPD is rapid, well tolerated, and sustained at > 6 months in the majority of subjects. These data support the use of pomalidomide therapy in RRMM that has progressed after lenalidomide.
Disclosures: Mark: Celgene Corp: Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Millenium Inc.: Speakers Bureau; Genzyme Inc.: Speakers Bureau. Off Label Use: There is no FDA indication for pomalidomide at this time. . Zafar: Celgene Corp: Speakers Bureau. Pekle: Celgene Corp: Speakers Bureau. Coleman: Celgene Corp: Membership on an entity’s Board of Directors or advisory committees, Speakers Bureau. Niesvizky: Millennium Pharmaceuticals, Inc.: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding, Speakers Bureau; Onyx: Research Funding.