Phase II Study of High Dose Lenalidomide as Initial Treatment for Older Acute Myeloid Leukemia Patients: Early Results Show a Significant Reduction of Bone Marrow Blasts after 14 Days of Therapy.

AML patients over the age of 60 years have a poor prognosis, share disease characteristics with myelodysplastic syndrome (MDS) patients, and warrant novel therapeutic approaches. Lenalidomide has immunomodulatory and anti-neoplastic properties which can induce morphologic and cytogenetic responses in MDS patients, including those with excess blasts. We hypothesized that lenalidomide may be active against AML, and have employed a high dose strategy without dose reductions for hematologic toxicities. Here, we report preliminary results from a phase II study of high dose lenalidomide for front-line treatment of AML ≥ 60 without chromosome 5q deletion or favorable cytogenetics. Treatment included 2 cycles of high dose lenalidomide (50mg/day x 14 days, 30 days of rest, 50mg/day x 21 days), followed by maintenance therapy (10 mg/day) in non-progressing patients. Fifteen patients were enrolled in the first stage between 2/27/07 and 8/3/07. Median age was 71 years (range 60–86 years); ECOG performance status was 0 (4/15, 27%), 1 (10/15, 67%), or 2 (1/15, 7%); 11/15 (73%) patients were male; and 5/15 (33%) patients had prior MDS. Cytogenetics were normal (n=9), loss of chromosome 7 (n=2), loss of chromosome 20 (n=1), trisomy 13 (n=1), or complex (n=2). Overall, the treatment regimen was well tolerated. In the first stage of the study, 12/15 patients are evaluable for day 15 bone marrow and peripheral blood blast changes following the initial high dose lenalidomide cycle (50 mg/day x 14 days). Pre-therapy WBC counts (mean ± SEM) were 13,825 ± 4,447/uL (range 1,100–45,300/uL) and day 15 WBC counts were 4,742 ± 2,136/uL (range 300–24,400/uL). Day 15 bone marrow myeloblast percentages were significantly reduced in 9/12 patients (mean ± SEM decrease of 53 ± 10%, P=0.01, range 18–100%). In addition, the bone marrow blast index (% cellularity x fraction of blasts) decreased significantly after 14 days of high dose lenalidomide (mean ± SEM reduction of 66 ± 11%, P=0.02). Moreover, 5/8 patients with circulating blasts at diagnosis showed clearance of their peripheral blasts at day 15. These findings suggest that lenalidomide is an active agent against acute myeloid leukemia. Results on AML blast changes, response by international working group criteria, and toxicities in this patient cohort with ≥4 months of follow-up will be updated and presented.