Fludarabine, Cyclophosphamide, Ofatumumab (FC-O2) As Front-Line Treatment for Young and Fit Patients with Chronic Lymphocytic Leukemia (CLL): Preliminary Results of the Prospective Phase 2 LLC0911 Gimema Study

Introduction. The fludarabine, cyclophosphamide, rituximab (FCR) regimen is associated with high complete response (CR) rates and a negative residual disease status in a significant proportion of cases and is considered the optimal front-line treatment for fit patients with chronic lymphocytic leukemia (CLL). In addition, long-term follow-up of patients treated with FCR at the MD Anderson Cancer Center, in the multicenter German CLL8 study and at Italian institutions indicate that a sizable fraction of patients characterized by a favorable biologic profile remains free from progression in excess of 10 years. FC combined with ofatumumab (FC-O), a human monoclonal antibody which targets an epitope of the CD20 molecule, has also been associated with a high CR rate. The aim of this study was to evaluate whether a double dose of ofatumumab (O2) combined with FC could improve the CR rate in young (≤65 yrs) and fit patients with CLL.

Methods. Sixty-one fit CLL patients from 15 Italian institutions were enrolled in this front-line study and treated with the FC-O2 regimen based on the FC schedule (F 25 mg/sqm i.v. d1–3, C 250 mg/sqm i.v. d1–3) combined with 13 doses of O (300 mg i.v. d14; 1000 mg d21 at the first cycle; 1000 mg d1 and d15 at cycles 2-6 and d28 at cycle 6). As infection prophylaxis, patients received bactrim and peg-filgrastim in order to prevent granulocytopenia. CLL diagnosis, treatment requirement and response were assessed according to the 2008 iwCLL guidelines. Minimal residual disease (MRD) was evaluated by flow cytometry in the peripheral blood (PB) and bone marrow (BM), and also by RQ-PCR in flow negative cases. CT scan evaluation was included in the response assessment. Adverse events (AEs) were graded according to the NCI-CTCAE.

Results. The median age of patients was 60 years (range 36-65), Binet stages B and C were recorded in 86% of cases, B-symptoms in 21%, increased β2M values in 74% and bulky nodes (≥5 cm) in 10%. An IGVH unmutated status was recorded in 60% of cases, deletion 13q in 37%, no aberrations in 33%, deletion 11q in 14%, trisomy 12 in 12%, 17p deletion and/or TP53 mutation were found in 10% of cases. At present, the median follow-up of patients is 7 months (range 1-20). Response to treatment has been assessed in 29 patients after a median number of 6 courses of treatment (range 2-6). The overall response rate is 90%, with a CR rate of 69% (20 patients). No evidence of MRD was observed by flow cytometry in both PB and BM in 15/20 CR patients (75%). To date, 11 patients with cytometric MRD negative CR have been evaluated by RQ-PCR and no residual disease was detected in 3. Grade 3-4 granulocytopenia was recorded in 4 patients (7%), a severe infection in 4 (7%) and 5 patients (8%) experienced a severe infusion-related reaction during ofatumumab administration. Treatment was discontinued in 8 patients as a result of toxicity (infection, 2 cases; FUO, 1; infusion-related toxicity, 1; autoimmune hemolytic anemia, 1; recurrent granulocytopenia, 1; tachyarrhythmia, 1; non-specified toxicity,1). A non-treatment-related death (traumatic aortic transaction due to a dislocated aortic endoprostheses) has been recorded in a patient after 2 months from treatment discontinuation and 1 showed a disease progression after 4 courses of FC-O2.

Conclusions. Taken together, the first analysis of this ongoing front-line study suggests that the combination of FC with an increased dose of ofatumumab is well tolerated with acceptable and no unexpected toxicity. Our preliminary results show that the FC-O2 treatment is associated with a high rate of cytometric MRD-negative CR in young and fit patients with previously untreated CLL.