A Phase II Multi-Center Trial Of Pentostatin Plus Cyclophosphamide With Ofatumumab (PCO) In Older Previously Untreated Chronic Lymphocytic Leukemia (CLL) Patients

The seminal phase 3 trial conducted by the German CLL Study Group demonstrated that the addition of the anti-CD20 monoclonal antibody [mAb] rituximab to the FC platform (FCR) improved response rates, progression free survival and also overall survival. However, FCR showed considerable hematologic toxicity, particularly among patients over age 70. Pentostatin demonstrated similar response frequency to other purine analogues in CLL. Furthermore, its relative lack of myelotoxicity has allowed to use it with improved tolerability particularly when administered in combination with myelotoxic agents such as cyclophosphamide. Ofatumumab is a fully human anti-CD20 mAb with clinical activity as a single agent in patients with fludarabine-refractory CLL. Ofatumumab appears to have greater single agent clinical activity than rituximab in patients with previously treated CLL and also has activity in rituximab-refractory patients. Given the reported efficacy of chemo immunotherapy [CIT] in CLL and the activity and toxicity profile of pentostatin combinations, we designed a trial of pentostatin, cyclophosphamide, and Ofatumumab for previously untreated older patients with CLL.

Patients with CLL who required therapy (2008 NCI-WG guidelines) aged ≥ 65 years and ECOG PS of 0-2 were enrolled to receive Pentostatin 2 mg/sqm and Cyclophosphamide 600 mg/sqm both as intravenous infusions at day 1 of each 21 day cycle and Ofatumumab administered as intravenous infusions (Cycle 1: 300 mg day 1 and 1000 mg day 2, subsequent cycles: 1000 mg at day 1). Ofatumumab premedication included acetaminophen, antihistamine and glucocorticoid. Treatment duration was of 6 cycles. The primary endpoint was overall response rate (ORR) including detection of minimal residual disease (MRD) and secondary endpoints included, progression-free survival (PFS) overall survival (OS) and safety.

49 patients from 12 centres from the italians regions of Lombardy and Piedmont were included. Baseline demographics were: Median age 72.8 years with 64% aged over 70, among them 32 were males (65%). Disease characteristics in 32 patients evaluable at this point were: 76% Binet stage B and 24% C; 45% of patients had unmutated IGVH, 7 % showed 17p deletions.

ORR was 93.7% with 41% CR(11)/CR(2) with incomplete marrow recovery [CRi]. All six intended courses of treatment were administered to 30 (94%), and 90% of these patients received full-dose treatment. The reason for discontinuing treatment before completing six courses was myelosuppression occurring in 2 patients. The primary reason for dose reduction was again myelosuppression. Grade ≥3 AEs that occurred from start of treatment until 60 days after the last dose were experienced by 62% of patients receiving PCO with the most common being neutropenia [Total number of patients with at least one Grade 3 or 4 event: 19 patients] while anemia and thrombocytopenia were detected only as grade 1 to 2 in 41% and 25% of cases respectively. Of the grade 1 to 2 toxicities, fever occurred in 2 patients (6%), hypotension occurred in 2 patients (6%), nausea and vomiting occurred in 3 patients (9%), skin rash of grade 1 occurred in 2 patients. Grade 3 infusion-related AEs were reported in 12% of patients. There were no grade 4 toxicities associated with any Ofatumumab infusion. Grade 3 infection was reported in 1 patient (3%) being a pneumonia. No deaths during treatment occurred in these 32 subjects.

Ofatumumab added to Pentostatin and Cyclophosphamide demonstrated clinically important results and is well tolerated in patients with previously untreated CLL. In this preliminary report the efficacy of this ofatumumab-based CIT compares favorably to the historical rituximab-based CIT using the same chemotherapeutic agents with a more manageable side effect profile in this older population. Further data in a higher number of enrolled patients and including MRD detection will be presented at the Meeting.

Montillo:Roche: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; GSK: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Mundipharma: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Janssen: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding. Rambaldi:Novartis: Honoraria; Sanofi: Honoraria; Italfarmaco: Honoraria.