Background: Myelodysplastic syndromes (MDS) are hematological disorders characterized by chronic anemia, and are often refractory to cytokine therapy. Two phase 2 studies evaluating lenalidomide in MDS (MDS-001 and MDS-003), demonstrated a high frequency of erythroid response in patients with a chromosome 5q31 deletion (

List AF et al.,
N Eng J Med
and List AF et al., in press). Herein we report on the durability of response with long term follow-up approaching 4 years.

Methods: All enrolled subjects were evaluated for frequency and duration of red blood cell transfusion independence (RBC-TI), change in hemoglobin (Hgb), pathologic and cytogenetic response, and safety.

Results: Ten 5q31- patients achieved a cytogenetic and/or major erythroid response in MDS-001. Four of these patients have maintained a major response for at least 2 years (range 2.2 to 3.7 years). In MDS-003, 99 (67%) of 148 enrolled patients achieved RBC-TI. Of the 99 responders 83 were Low/Int-1, 3 were Int-2/High and 13 were not classified. Median increase in Hgb from baseline to maximum achieved during RBC-TI was 5.4 g/dL (range 1.1, 11.4). The estimated median duration of response was 115.9 weeks, and 52 (53%) of 99 responders remain on study with ongoing RBC-TI response as of 30 June 2006. Duration of response was at least 52 weeks for 63 (64%), 78 weeks for 52 (53%), and 104 weeks for 36 (36%) of 99 responding patients. Variables (or co-variates) associated with longer duration of TI in multivariate analysis included low baseline transfusion requirement (<4 units per 8 wks, p=0.002), 5q- syndrome (p=0.01) and low IPSS (p=0.02) classifications. Among 85 evaluable patients, major cytogenetic responses were achieved in 37 (44%) and minor responses in 24 (28%). Cytogenetic responses occurred in patients with complex karyotypes as well as those with an isolated 5q31 deletion. The frequencies of major and minor cytogenetic responses were similar among patients with and without 5q- syndrome. The most common drug-related adverse events (AE) were Grade 3/4 neutropenia and thrombocytopenia, reported in 87 (59%) and 74 (50%) of 148 patients, respectively although hematologic AEs led to study discontinuation in only 13 (9%) of patients. Pneumonia was the only serious adverse event that occurred in >10% of patients (15/148; 10%). Adverse events were manageable through supportive treatment and dose reduction.

Conclusion: Lenalidomide is an effective treatment in MDS patients with an associated chromosome 5q31 deletion, with RBC-TI and major erythroid response maintained for median duration > 2 years.

Disclosures: JZ, RK, KW, MS are employees of Celgene.; AL, JB, PG, GD, AG consultancy in the past two years.; JZ, RK, KW and MS have ownership interest (stock options) in Celgene.; EF, AG, AL, PG, BP have received research funding.; AL, PG, AR, JB, AG have revceived honoraria from an entity.; JZ, as Chief Medical Office of Celgene, I have given expert testimony to a variety of legal and financial fora.; AL, PG, AR, JB, SN participated in Speakers Bureau and advisory committees.

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