Phase 2 Trial of Intracycle Sequential Ofatumumab and Lenalidomide for the Treatment of Relapsed and Refractory Chronic Lymphocytic Leukemia

Ofatumumab is a novel fully humanized anti-CD20 monoclonal antibody with antigenic target distinct from rituximab and enhanced antibody dependent cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC) with single agent activity in relapsed or refractory (R/R) chronic lymphocytic leukemia (CLL), including heavily pretreated patients. The immunomodulatory agent (IMID) lenalidomide has been shown to induce T cell and NK cell activation and in vitro enhances rituximab induced killing of B-CLL cells via NK cell-mediated and monocyte-mediated ADCC. We hypothesized that the sequential treatment of patients with ofatumumab and lenalidomide would provide optimal pharmacodynamic interaction and be active in R/R patients previously treated with rituximab containing regimens.

Eligibility criteria included confirmed diagnosis of R/R CLL meeting criteria for treatment, prior therapy containing rituximab, age≥ 18 years, ECOG performance status ≤ 2 adequate hepatic, renal and bone marrow function and willingness to comply with the required birth control measures. Patients were excluded if they had been previously exposed to any of the experimental agents, had active hepatitis B or carried HIV. Treatment consisted of ofatumumab 2000 mg (300 mg on the first cycle) intravenously on day 1 and lenalidomide 10 mg (5mg on the first cycle) on days 8–28. Treatment was administered for up to 6 cycles of 28 days duration. Patients received prophylaxis with acyclovir and trimethoprim + sulfamethoxazole. Toxicity was assessed according to CTC v.4.0 and response was evaluated following the 2008 National Cancer Institute Working Group criteria.

Seventeen patients have been enrolled and 14 have sufficient follow-up to be assessed for response. Median age of patients was 65 years (range 51–80). Median number of prior lines of therapy was 2 (range 1–4) and median baseline white blood cell count was 75,000/mm³. The proportions of cases with unmutated IgvH chain and positive ZAP-70 expression were 15/17 (88%) and 13/16 (81%), respectively. There were 4/16 (25%) cases with del17p and 4/16 (25%) with del11q detected by fluorescence in situ hybridization (FISH). Thirteen cases (76%) were refractory to, or had relapsed after treatment containing a purine analogue. The most frequent adverse event (AE) > Grade 1 was tumor flare reaction (TFR), seen in 8/14 (57%) patients and infusion reactions seen in 6/14 (43%) patients. Four patients with TFR were managed successfully with non-steroidal anti inflammatory agents while 4 required glucocorticoids allowing continuation of therapy in all patients. The most common Grade 3+4 AE was neutropenia (11/14, 79%) although it was associated with infection in only 1 episode. One subject had early discontinuation due to toxicity (elevation in AST and ALT precluding further administration of ofatumumab). The majority of patients (11/14, 79%) required dose reduction or could not have the planned dose increase of lenalidomide after cycle 1 due to hematological toxicity. Overall 6/14 (43%) had objective response and 3/14 (21%) had stable disease for an overall clinical benefit in 64% of patients. All patients with TFR> Grade 1 had at least stable disease.

Intracycle sequential ofatumumab plus lenalidomide is well tolerated in advanced, high-risk CLL except for high rate of TFR and neutropenia without infection. Sequential ofatumumab and lenalidomide may be associated with higher rate of TFR than concomitant therapy. Approximately half the patients treated with this combination will obtain disease control. Further investigation is warranted in earlier lines and/or for more prolonged therapy.

Costa:GSK: Research Funding. Off Label Use: Lenalidomide for treatment of CLL.