APhase 2 Study of Rituximab in Combinationwith Recombinant Interleukin-2 for Rituximab-Refractory Indolent Non-Hodgkin ’ s Lymphoma

The incidence of non-Hodgkin’s lymphoma (NHL), the fifth most commonmalignancy in the United States, has increased over 70% in the last 30 years. Fifty percent to 75% of patients with low-grade or follicular NHL respond to rituximab therapy. However, responses are generally of limited duration, and complete responses are rare. Preclinical work suggests that human recombinant interleukin-2 (rIL-2; aldesleukin, Proleukin) enhances rituximab efficacy. Antibody-dependent cellular cytotoxicity (ADCC) is an important mechanism of action of rituximab. rIL-2 induces expansion and activation of Fc receptor (FcR)^ bearing cells, thereby enhancing ADCC. Therefore, a large, multicenter phase 2 trial to assess the effects of rIL-2 on rituximab therapy in patients with rituxumab-refractory low-grade NHL was conducted. The combination of rituximab and rIL-2 was studied in 57 patients with rituximab-refractory low-grade NHL (i.e., patients must have received a single-agent course of rituximab and showed no tumor response, or had a response lasting <6 months). I.V. rituximab was given at 375 mg/m (weeks1-4). S.C. rIL-2 was given thrice a week at 14 MIU (weeks 2-5) and at10 MIU (weeks 6-9).  Rituximab plus rIL-2 combination therapy was safe and generally well tolerated, but responses were low. Fifty-seven patients were enrolled with 54 evaluable for response; however, only five responses (one complete and four partial) were observed. Correlative data indicate that rIL-2 expanded FcR-bearing cells and enhanced ADCC. However, other factors, such as FcgR polymorphisms in patients refractory to single-agent rituxumab and heterogeneous tumor biology, may have influenced the lack of clinical efficacy seen with this combination therapy.  rIL-2 expands FcR-bearing cellular subsets in vivo and enhances in vitroADCC of rituxumab. However, these findings do not directly translate into meaningful clinical benefit for patients with rituxumab-refractory NHL.  American Health Network Oncology/Hematology, Indianapolis, Indiana; Division of Hematology/Oncology, University of California Los Angeles Medical Center, Los Angeles, California; Division of Hematology and Oncology, Department of Internal Medicine; Department of Epidemiology; The Ohio State University Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio; Chiron Corp., Emeryville, California; Cancer Institute Medical Group, Santa Monica, California; and Weill Medical College of Cornell University, New York, New York Received 6/29/06; revised 7/28/06; accepted 8/17/06. Grant support: NIH grants P01CA95426-01A1 (M.A. Caligiuri), K08 CA9351801 (C.F. Eisenbeis), and K23 CA102155 (P. Porcu); The Lymphoma Research Foundation (C.F. Eisenbeis); andThe Chiron Corp. (all authors). The costs of publication of this article were defrayed in part by the payment of page charges.This article must therefore be hereby marked advertisement in accordance with18 U.S.C. Section1734 solely to indicate this fact.  Ferketich designed and did statistical analyses on lymphocyte subsets.  Byrd assisted in securing genotyping of Fc receptors. M.A. Caligiuri codesigned the study, edited the final version of the article, and cosupervised the project in its entirety. Requests for reprints: Michael A. Caligiuri, The Ohio State University Comprehensive Cancer Center, Division of Hematology/Oncology,The Ohio State University, 458A Starling-Loving Hall, 320 West 10th Avenue, Columbus, OH 43210. ;  E-mail: Michael.caligiuri@ osumc.edu.  American Association for Cancer Research. doi:10.1158/1078-0432.CCR-06-1571 www.aacrjournals.org ) December1, 2006 7046 Research. on April 14, 2017.  is the second most frequently observed subtype of NHL. In most instances, patients present with advanced-stage disease, and the course is one of inexorable progression. With the exception of allogeneic transplant-based therapies, these diseases remain incurable. Strategies to increase the effectiveness of rituximab are needed. Rituximab is a humanized monoclonal IgG1 antibody that selectively binds to CD20, a surface antigen present on nearly all B-cell NHL (2). Approximately 75% of patients respond to rituximab as first-line therapy (3), and half of previously treated NHL patients respond to rituximab as a single agent (4). Unfortunately, responses to rituximab therapy are often short-lived, and complete responses to single-agent rituximab therapy are rare (2). Furthermore, the overall response of recurrent NHL patients, who previously responded to rituximab, is <40% (5). Strategies to increase the effectiveness of rituximab are being developed, including combination therapy with traditional chemotherapy agents (6) as well as with immunomodulatory cytokines (7, 8). The addition of human recombinant interleukin-2 (rIL-2; aldesleukin, Proleukin) may enhance rituximab-mediated antibody-dependent cellular cytotoxicity (ADCC) because rIL-2 promotes natural killer (NK) cell expansion (9–11) and enhances intrinsic NK cell cytotoxicity (11, 12). NK cells are large granular lymphocytes that comprise 10% to 15% of peripheral blood lymphocytes (13, 14) and mediate ADCC via expression of an activating receptor for the Fc portion of IgG antibodies (13, 14). Rituximab is thought to exert its antitumor effect through ADCC (7, 8, 15–17) in addition to complementdependent cytotoxicity (18) and direct induction of apoptosis (19). Indeed, this concept was previously shown in a preclinical mouse model of human B-cell NHL in which the efficacy of rituximab and rIL-2 was synergistic compared with either treatment alone (12). Based on this concept, several early clinical investigations of the combination of rIL-2 and rituximab have been reported. In one study, 20 rituximab-naive patients with relapsed or refractory follicular lymphoma received rIL-2 in combination with rituximab. An encouraging 55% response rate (RR) was observed; however, this RR is comparable with that observed with single-agent rituximab in a similar setting (3). In another study of 30 heavily pretreated patients with various B-cell NHL histologies, most of whom had received prior rituximab, a RR of 29% was found in patients receiving rituximab and daily rIL-2, and a RR of 54% was reported in patients receiving rituximab and thrice weekly rIL-2 (7). In these studies, expansion of circulating NK cells and increased cytotoxicity was observed. Previous studies with rituximab and rIL-2 combination therapy do not address whether or not, or to what extent, the clinical efficacy of rituximab is affected by the addition of rIL-2. To address this question, we conducted a large, multiinstitutional phase 2 study of the combination of rIL-2 and rituximab in patients with rituximab-refractory low-grade follicular NHL, all of whom had previously failed rituximab therapy as evidenced by no tumor response or a response lasting <6 months. By restricting eligibility only to patients with rituximab-refractory disease, a more rigorous assessment of any incremental benefit conferred to rituximab therapy by the addition of rIL-2 could be determined. rIL-2 and rituximab were given in doses and schedules previously reported to be feasible and safe (7). Although the addition of rIL-2 augmented NK cell expansion and ADCC, the present study failed to confirm results from smaller studies suggesting that rIL-2 confers enhanced clinical efficacy of rituximab in low-grade NHL patients.  Adult (ages >17 years) patients with CD20, B-cell, lowgrade, or follicular NHL with measurable relapsed or unresponsive disease after prior rituximab therapy were eligible. Specifically, patients must have received a single-agent course of rituximab and showed no tumor response, or had a response lasting <6 months. Institutional source documents were examined to verify that the rituximab therapy must have included at least 75% of the standard 4-week regimen (4 375 mg/m). Patients had to provide full, written informed consent in accordance with Institutional Review Board guidelines. Patient inclusion criteria included a Karnofsky performance score of z70%, serum creatinine <1.5 mg/dL, bilirubin V3 mg/dL, alanine aminotransferase and aspartate aminotransferase z2.5 times the institutional upper limit of normal, absolute neutrophil count >1,000/AL, hemoglobin >9 g/dL, platelet count >75,000/AL, lymphocyte count <20,000/AL, and willing and able to receive rIL-2