Lenalidomide (CC-5013) Treatment for Anemia Associated with Myelofibrosis with Myeloid Metaplasia.

Background: We had previously piloted thalidomide treatment in MMM and showed an approximately 20% response in terms of both anemia and splenomegaly (Elliott et al. BJH2002;117:288). Encouraged by this experience, we undertook the current phase II study to explore the therapeutic activity of the more potent as well as less neurotoxic immunomodulatory drug, lenalidomide (CC-5013). Methods: The study group comprised a consecutive series of patients with MMM that fulfilled protocol entry criteria that included hemoglobin level ≤ 10 g/dL, platelet count ≥ 100 x 10 9 /L, and neutrophil count ≥ 1 x 10 9 /L. The treatment program consisted of daily oral lenalidomide (10 mg/day) for 3 consecutive 28-day cycles with a plan to continue with additional 3 cycles in case of response. Results: i. Pretreatment patient information Twenty-seven patients (median age, 66 years; range, 40–78) were accrued between March 5, 2004 and June 15, 2005. Median duration of disease prior to protocol treatment was 30 months (range, 1–245). Previous therapy was documented in all but 2 patients. Twenty patients were RBC transfusion-dependent. Baseline median (range) values for palpable spleen size, leukocyte count, platelet count, CD34 cell count, and serum lactate dehydrogenase (LDH) were 16 cm (0–31), 8.4 x 10 9 /L (1.8–84.4), 299 x 10 9 /L (124–831), 166.1 x 10 6 /L (2.8–5176.4), and 778 U/L (267–1725), respectively. Cytogenetic abnormalities were detected in 13 patients (48%). JAK2 V617F mutation analysis was performed in 21 patients and revealed homozygous, heterozygous, and wild-type alleles in 3, 8, and 10 patients, respectively. ii. Adverse events Adverse events (any/grade 3 or 4) with definite, probable, or possible attributions to the drug included fatigue (52%/12%), neutropenia (40%/24%), pruritus (36%/0%), thrombocytopenia (28%/8%), anemia (16%/8%), rash (12%/8%), and respiratory distress with hypoxia (8%/8%). To date, 7 deaths have been reported, all occuring after discontinuation of protocol therapy, and none were directly linked to the drug. iii. Response The median post-treatment follow up is now 16 months (range 1–17 months). During this period, 6 patients (22%) have experienced either a major (3 patients normalized their hemoglobin level), minor (2 patients became transfusion-independent), or marginal response in anemia. The median time to response and response duration were 2 and 7 months, respectively. Two of the 3 major responders had a baseline der(1;18)(q10;q10) or del(5)(q13q33) cytogenetic abnormality, the latter one of which displayed a major cytogenetic remission. In the patient with der(1;18)(q10;q10), the hemoglobin level increased to a level of 19.1 g/dL from being transfusion-dependent at the start of lenalidomide therapy. Interestingly, the particular patient was homozygous for the JAK2 V617F mutation. Responses were also recorded for palpable splenomegaly (26%), constitutional symptoms (67%), and serum LDH level (70%). Seven patients normalized their LDH. Conclusion: Lenalidomide therapy improved anemia in at least 20% of patients with MMM. Some of the responses were spectacular and appeared to be associated with specific cytogenetic abnormalities. The documentation of a positive drug effect on LDH, constitutional symptoms, and splenomegaly in patients not showing early response in anemia suggests the possibility of an even higher response rate with a longer treatment schedule.