Combination of Ofatumumab and Lenalidomide In Patients with Relapsed Chronic Lymphocytic Leukemia: Initial Results of a Phase II Trial

Abstract 2464

Frontline chemoimmunotherapies induce high response rates in patients with CLL. Once disease recurs, however, effective treatment options are limited and new therapeutic modalities and combinations are needed. Ofatumumab is a fully humanized anti-CD20 monoclonal antibody which produces an overall response rate (ORR) of 47%–58% in patients with fludarabine-refractory CLL (Wierda W. et al, 2010). Lenalidomide, an immunomodulatory agent, induces an ORR of 32–47% in patients with relapsed/refractory CLL, (Chanan-Khan A.A. et al. 2006; Ferrajoli A. et al. 2008). The rationale for combining ofatumumab and lenalidomide is based on their single agent efficacy, distinct and potentially complimentary mechanisms of action and non-overlapping toxicity profiles. Furthermore, the combination of lenalidomide and rituximab has shown significant activity in patients with relapsed disease (Ferrajoli et al. 2009). We, therefore, designed a phase II study to evaluate efficacy and tolerability of ofatumumab and lenalidomide given in combination in patients with relapsed CLL. Patients with active disease were eligible if they had received prior treatment with purine analog-based therapy, had an ECOG/WHO performance status of 0–2, adequate renal (creatinine clearance > 30ml/min) and hepatic function (total bilirubin < to 2 mg/dl and ALT < 2 × ULN). Patients with any neutrophil count were eligible, whereas patients with platelet counts < 30,000 mm³, positivity for HIV, active hepatitis B or C or recent history of tuberculosis were excluded from participation. In this trial ofatumumab is administered intravenously weekly for four consecutive weeks (300mg week 1, 1,000 mg week 2 and all subsequent doses), then monthly for months 2–6 and once every two months for months 7–24. Lenalidomide is given orally at the dose of 10 mg daily, starting on day 9 and continued daily. Allopurinol at the dose of 300mg daily is given during the first two weeks of treatment as tumor lysis prophylaxis. Treatment duration is 24 months, and responses are assessed after 3, 6, 12, 18 and 24 months of therapy. Thus far 26 of the 40 planned patients have been accrued to this study and we present an analysis of response and toxicity for the first 16 patients that have been on study for at least 3 months. The median age of the patients is 62 yrs (45–82). Eight patients (50%) had Rai stage III-IV disease. The median Beta-2M level was 4.4 mg/dL (2–6.1). The median number of prior treatments was 2 (1–8). Four patients (25%) were refractory to fludarabine and all pts had received prior rituximab. Nine patients (56%) had unmutated IGHV genes, 5 patients (31%) had chromosome 17p deletion and 3 patients (19%) had 11q deletion as detected by FISH analysis. Responses were evaluated according to the 2008 IWCLL criteria: 10 of the 16 evaluable patients achieved a response [2 CR (13%), 8 PR (50%)] for an ORR of 63%. Four patients with stable disease are continuing on treatment. One patient discontinued therapy and did not return for response assessment and another patient progressed. All patients are alive.

The most common grade 3–4 treatment related adverse events observed were: neutropenia (8 pts, 50%) and anemia (2 pts, 13%). One patient (6%) developed grade 2 superficial vein thrombosis. Lenalidomide-associated tumor flare reaction was limited to grade 1 in 2 patients (13%) while a grade 3 infusion reaction was observed in 1 patient (6%) during the first ofatumumab administration. Three grade 3 infectious episodes occurred: 2 cases of pneumonia and 1 case of parotiditis. None of the patients received routine antibiotic prophylaxis. The median daily dose of lenalidomide tolerated was 5 mg/day (2.5–10 mg).

In conclusion, our initial analysis indicates that the combination of ofatumumab and lenalidomide is therapeutically active in patients with relapsed CLL. This treatment is well tolerated. Neutropenia is the most common toxicity observed. Enrollment is ongoing, and updated results will be provided.