Results of Phase II Study of Lenalidomide (L) {Revlimid^®} in Patients with Relapsed or Refractory Chronic Lymphocytic Leukemia (CLL).

Introduction: Lenalidomide (L) is a compound in a new group of drugs called ImiDs® which have Immunomodulatory properties and with anti-tumor activity reported in multiple myeloma and MDS. Although the exact mechanism of action of L is unknown, they are reported to affect the tumor microenvironment through modulation of critical cytokines such as TNF-a, VEGF and IL-6. These cytokines also play an important role in pathogenesis of CLL. Based on these properties we have investigated and previously reported on the anti-leukemic activity of thalidomide in CLL. We subsequently conducted a phase II study with L, to evaluate its clinical activity in pts with relapse (rel) or refractory (ref) CLL. Here we present the results of this study.

Patients and Methods: CLL pts with rel or ref disease were eligible. L was given at 25mg PO QD x 21 days followed by 7 days rest on a 28 day cycle. Absolute lymphocyte counts (ALC) were measured at Day 0, 7 and 30. Response was assessed at day 30 and monthly thereafter using the NCI-WG 1996 criteria. Pts with stable disease (SD) or better response were continued on therapy for a maximum of 12 months while those with progressive disease (PD) were to receive rituximab (R) (375mg/m2) added to L. Pts were considered evaluable for response if they completed at least 2 months of treatment. Target enrollment is 29 patients.

Results: Twenty nine pts, median age of 64 years (range: 47–75) were enrolled. All pts are available for toxicity and 17 out of 29 pts available for response evaluation. Three pts on treatment are too early for response assessment while 9 pts are off study (2 withdrew consent and 5 got < 2 months of therapy due to toxicity). Response is reported based on evaluable pts. Complete remission (CR) was noted in 2/17 (11.7%) pts while partial remission (PR) was noted in 9/17 (52.9%) pts. Additional 5/17 (29.4%) pts, currently on treatment, achieved stable disease (SD). ORR (CR+PR) in the intent to treat population is 42.3% (11/26, excluding pts currently too early for response assessment). To date only 1 pt has PD after 3 months of L and is on LR per protocol. Toxicity: Flare reaction (tender swelling of lymph nodes and/or rash) was the most common SE noted in almost all pts. Other important SE were tumor lysis syndrome (n=2); grade 3/4 hematologic toxicities (n=7) and febrile neutropenia (n=3).

Conclusion: This is the first study to report the clinical activity of L in pts with CLL. Our findings are encouraging and provide evidence of the anti-CLL activity of L. Although some of the pts did achieve a CR, longer follow-up will determine the durability of responses noted to date. Update results of this study along with toxicity profile of L in CLL will be presented at the meeting.