Ofatumumab + Chlorambucil Versus Chlorambucil Alone In Patients With Untreated Chronic Lymphocytic Leukemia (CLL): Results Of The Phase III Study Complement 1 (OMB110911)

Chemoimmunotherapy with purine analogues and the anti-CD20 antibody rituximab is the standard of care as initial therapy in younger and physically fit patients with chronic lymphocytic leukemia (CLL). However, most CLL patients are elderly and/or have comorbidities, meaning that fludarabine-containing regimens are often inappropriate, carry greater toxicity, and treatment of these patients remains challenging. Most randomized studies in previously untreated CLL have been conducted in younger or fit patients and results cannot necessarily be extrapolated to older, less fit patients. While chlorambucil (CHL) remains a standard of care for this patient population, more effective but tolerable treatment choices are still needed. Ofatumumab (O) demonstrated superior preclinical activity, compared to rituximab, against cells with low CD20 density like CLL and showed clinical activity as monotherapy, with high overall response rates (ORR) in patients with refractory CLL. Therefore, the addition of O to CHL could provide superior clinical outcomes than CHL alone, while being tolerable, for patients who are elderly and/or have comorbidities and currently have limited treatment options.

Patients with CLL who required therapy (2008 NCI-WG guidelines) and were considered inappropriate for fludarabine-based therapy due to advanced age and/or co-morbidities were randomized (1:1) to receive either O+CHL or CHL. CHL was given orally (10mg/m² at days 1-7 of each 28 day cycle) and O was administered as intravenous infusions (Cycle 1: 300mg day 1 and 1000mg day 8, subsequent cycles: 1000mg at day 1). O premedication included acetaminophen, antihistamine and glucocorticoid. Treatment duration was a minimum of 3 cycles, until best response up to a maximum of 12 cycles. The primary endpoint was progression-free survival (PFS) assessed by an Independent Review Committee (IRC) and secondary endpoints included overall response rate (ORR), overall survival (OS) and safety.

447 patients from 16 countries were randomized. Baseline demographics and disease characteristics were well balanced between the 2 arms. Median age was 69 years with 82% ≥65 years and/or having ≥2 comorbidities. All modified Rai stages were represented (Low 8%, intermediate 51%, high 40%). 56% of patients had unmutated IgVH, 6% showed 17p deletions and 75% had β-2-microglobulin levels ≥3500μg/L.

PFS as assessed by an IRC was significantly prolonged in the O+CHL arm (22.4 months) compared to CHL alone (13.1 months, p<0.001). ORR was higher for O+CHL vs CHL (82% vs 69%, p=0.001), with a superior CR rate (12% vs 1%). 37% of O+CHL subjects with an IRC-assessed CR were MRD negative. With a median follow-up of 29 months, median OS was not reached for O+CHL or CHL. Median duration of treatment for both arms was 6 cycles and 82% of patients received 6 or more cycles of O+CHL.

Grade ≥3 AEs that occurred from start of treatment until 60 days after the last dose were experienced by 50% of patients receiving O-CHL and 43% of patients on CHL with the most common being neutropenia (O+CHL: 26%, CHL: 14%). Grade ≥3 infusion-related AEs were reported in 10% of patients. No fatal infusion reactions were reported. Grade ≥3 infections were reported in 15% (O+CHL) and 14% (CHL) of patients, with the most common infection being pneumonia (O+CHL: 4%, CHL: 3%). Deaths during treatment occurred in 2% of subjects in both arms.

Ofatumumab added to chlorambucil (O+CHL) demonstrated clinically important improvements with a manageable side effect profile in patients with CLL who have not received prior therapy and who are considered inappropriate for fludarabine based therapy.

Hillmen:Roche Pharmaceuticals: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Pharmacyclics: Research Funding; Celgene: Honoraria; GlaxoSmithKline: Honoraria, Research Funding. Off Label Use: The use of ofatumumab in combination with chlorambucil in previously untreated CLL. The reported trial will support the extension of the ofatumumab licence. Robak:GlaxoSmithKline: Honoraria, Research Funding. Janssens:GlaxoSmithKline: Speakers Bureau; Roche: Speakers Bureau; Mundipharma: Speakers Bureau; Amgen: Speakers Bureau. Mayer:Glaxo: Consultancy, Research Funding; Roche: Consultancy, Research Funding. Panagiotidis:Novartis: Consultancy, Honoraria; Roche: Consultancy, Honoraria; GSK: Consultancy, Honoraria. Kimby:Pharmacyclics: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Teva: 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; Roche: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Emergent: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding. Schuh:GSK: Honoraria, Research Funding. Montillo:Janssen: 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; GSK: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding. McKeown:GSK: Employment. Carey:GlaxoSmithKline: Employment. Gupta:GSK: Employment. Chang:GSK: Employment. Lisby:Genmab: Employment, hold stock options Other. Offner:Lilly: Membership on an entity’s Board of Directors or advisory committees.