Lenalidomide (L) induces high response rates with molecular remission in patients (pts) with relapsed (rel) or refractory (ref) chronic lymphocytic leukemia (CLL)

6517 Background: Tumor microenvironment (ME) is critical in CLL pathogenesis. Targeting the ME is a novel approach in CLL therapeutics. Lenalidomide (Revlimid, L) is an immunomodulating agent (IMiD), approved for pts with transfusion-dependent low or intermediate-1 risk myelodysplastic syndrome with deletion 5q cytogenetic abnormality. Its antitumor activity is possibly mediated through (a) downregulation of cytokine(s) - TNF-α, VEGF, PDGF and IL-6 and/or (b) activation of immune effector cells (T & NK cells). We investigated its antitumor activity in rel/ref CLL pts. Here we present the final results of the first cohort of pts treated with 25mg daily dose of L. Methods: Oral L was given at 25mg/day for 21 out of a 28 day cycle. Anti-leukemic effects were recorded after each cycle using NCI-WG 1996 criteria. Treatment was continued until molecular complete response (mCR) or progressive disease (PD). Those with PD were then treated with L in combination with rituximab (reported separately). Polymerase chain reaction (PCR) for immunoglobulin heavy chain gene was used to determine molecular remission (mCR). Results: Twenty-nine pts (median age 64 years; range: 47–75) have been enrolled. Toxicity is reported on all, while response on 19 evaluable pts. Nine pts are inevaluable (2 withdrew consent and 5 received < 2 months of therapy due to toxicity). Major response was noted in 13 of 19 evaluable pts (68%) with 3 CR (2 mCR) and 10 PR. Toxicity: Most common grade 3/4 adverse effects (AE) were neutropenia (60%) and thrombocytopenia (55%). Another common AE was tumor flare (79%); characterized by tender swelling of lymph nodes and/or rash, noted in almost all pts. Conclusions: L at 25mg/day dose given on days 1–21 in a 28 day cycle yields high ORR including mCR in rel/ref CLL. Hematologic toxicity was the most common AE requiring dose reduction. Overall safety profile was predictable and manageable. A slow dose escalation schema, starting at 15mg is being investigated. [Table: see text]