Combination of Ofatumumab and Lenalidomide in Patients with Relapsed Chronic Lymphocytic Leukemia (CLL): Results of a Phase II Trial

Abstract 720

Based on the demonstrated activity of ofatumumab and lenalidomide as monotherapy in patients (pts) with CLL and on the activity of rituximab in combination with lenalidomide in pts with relapsed CLL, we conducted a phase II study to investigate efficacy and tolerability of a combination regimen of ofatumumab and lenalidomide in patients with relapsed CLL who had received prior treatment with purine analogs. Thirty-six pts entered this study between January 2010 and January 2011. All pts had an indication for therapy. Other inclusion criteria required prior treatment with purine analogs, an ECOG PS score of 0–2 and adequate organ function (creatinine clearance > 30ml/min, total bilirubin < to 2 mg/dl, ALT < 2 X ULN). Pts with any neutrophil count were eligible. Pts were excluded for platelets < 30,000 mm³, positivity for HIV, active hepatitis B or C or recent history of tuberculosis. Treatment consisted of ofatumumab IV given weekly for 4 weeks (300 mg week 1; 1,000 mg weeks 2 and thereafter), monthly during months 2–6 and every other month during months 7–24, and lenalidomide 10 mg PO/day started on day 9 and continued for 24 months. Allopurinol 300 mg PO daily was given during the first two weeks of cycle 1. No pts received antibiotic or DVT prophylaxis. The use of growth factors was allowed according to ASCO guidelines. Responses were assessed (2008 IWG criteria) at months 3 and 6 and every 6 months thereafter. Thirty-four pts are evaluable (one pt withdrew consent prior to treatment with lenalidomide, and one was excluded because of concomitant MDS at study entry). Median age was 64 yrs (34–82). Twenty-two pts (65%) had Rai stage III-IV disease. Median β-2M level was 4.1 mg/dL (1.7–16). Twenty-two pts (65%) had unmutated IgHV and 23 pts (68%) expressed ZAP-70. Nine pts (26%) had del(17p), and 4 pts (12%) had del(11q). Median number of prior treatments was 2 (1–8). All pts had been previously treated with FCR and 13 pts (38%) were fludarabine-refractory. Three pts (9%) had relapse following SCT.Twenty-three pts achieved a response, for an overall response (OR) rate of 68%. Eight pts (24%) achieved a complete response (CR), including 3 MRD-negative CR, and 15 pts (44%) achieved a partial response (PR). Median duration of response is 22 months (4–30), with a median follow up of 24 months. Among the 9 pts with del17p, 5 (55%) achieved a PR. The average daily dose of lenalidomide was 10 mg in 9 pts (26%), 7.5 mg in 4 pts (12%), 5 mg in13 pts (38%) and 5 mg in 8 pts (23%). Seventy-six % of the pts are alive. No pt deaths occurred while on therapy. Eight deaths occurred after discontinuation of therapy: progression of CLL despite subsequent therapy (5 pts), complications of HSCT (1 pt), CLL/lung cancer (1 pt) and causes unrelated to CLL(1 pt). Seven pts are still on therapy and 10 pts have an ongoing response. Six pts discontinued therapy despite an ongoing response due to transition to HSCT (3 pts), toxicity (2 pts) and physician choice (1 pts), and 7 pts discontinued therapy because of loss of response [after 12 (1 pt), 16 (2 pts), 19 (2 pts), 22 (1 pt) and 29 (1 pt) months].The most common grade 3–4 treatment-related hematological adverse events consisted of neutropenia in 16 pts (47%), thrombocytopenia in 3 pts (9%) and anemia in 2 pts (6%). One pt (3%) experienced G4 pulmonary embolism while on ESAs. One pt (3%) had G3 infusion reaction to ofatumumab. Fourteen G3 infectious episodes occurred: pneumonia (4), fever/bacteremia (5), parotitis (1), cellulitis (2), HZV (1) and CNS toxoplasmosis (1). No G3-4 tumor lysis syndrome or tumor flare reaction (TFR) was observed. G1-2 TFR was observed in 8 pts (24%), In conclusion, the combination of ofatumumab and lenalidomide induced responses in 68% of pts with relapsed CLL, including pts with del17p, all of whom had received prior chemoimmunotherapy. This treatment was well tolerated and neutropenia was the most common toxicity. The severity of TFR with this combination was less than with single agent lenalidomide, possibly due to attenuation by the addition of treatment with ofatumumab. Several studies are currently investigating the combination of anti-CD20 mAb and lenalidomide used both as initial and salvage therapy of CLL.