Early Treatment of High Risk Chronic Lymphocytic Leukemia with Alemtuzumab, Rituximab, and PGG Beta Glucan: A Phase I Clinical Trial

Abstract 1792 High risk disease can be identified in patients with early stage chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) using biological prognostic markers. We have shown that early therapy of high risk CLL patients with alemtuzumab (ALM) and rituximab (RTX) is effective and could possibly delay first standard treatment (Cancer 2008;113:2110-8). Efficacy of unconjugated monoclonal antibody (mAb) therapy in these patients could be improved by enhancing mAb mediated cellular cytotoxicity. Preclinical studies show that yeast cell wall derived beta glucan, which increases complement receptor 3 (CR3) binding to the complement fragment iC3b on target cells, could increase mAb mediated cellular cytotoxicity. Both ALM and RTX activate complement resulting in deposition of iC3b on the cell membrane. In CLL cells that are not lysed by complement activation, these iC3b molecules are targets for the effector cells mediating cellular cytotoxicity. We hypothesized that PGG beta glucan (Imprime PPG®, Biothera, Eagan MN) an intravenous formulation of a 1,3/1,6 glucose polymer prepared from a strain of Saccharomyces cerevisiae, would improve the efficacy of therapy with ALM and RTX in patients with CLL by increasing CR3 binding to iC3b and thus enhancing macrophage, neutrophil, and NK cell mediated cytotoxicity. We report the results of a Phase I study of the combination of ALM, RTX and PPG beta glucan in patients with CLL. Methods: The primary aim of this IRB approved study (NCT01269385) was to determine the maximum tolerated dose (MTD) of PGG beta glucan that could be safely combined with ALM and RTX. The MTD was defined as the PGG beta glucan dose level below that which induced dose limiting toxicity in at least one third of patients, or the highest dose level tested if all levels were tolerated. Eligibility for the trial required a diagnosis of CLL by standard (IWCLL-NCI 2008) criteria, no prior treatment for CLL, high risk CLL based on molecular markers, absence of standard indications for initiation of therapy for CLL, and adequate performance status and organ function. High risk CLL was defined as at least one of the following: 17p13-; 11q22-; either unmutated ( Results: Thirteen patients were enrolled from February 2011 to April 2012. The 11 evaluable patients had a median age of 61 years (range 47 – 77), 73% were male, 3 had early stage disease (Rai 0) and 8 had intermediate stage disease (Rai I n = 7, Rai II n = 1). High-risk parameters were 17p- in 4 patients, 11q22- in 3 patients, and unmutated IGHV and expression of ZAP70 and/or CD38 in 4 patients. There were no dose limiting toxicities. One patient had grade 4 febrile neutropenia, with no grade 3–4 anemias or thrombocytopenias, and there were no grade 3–4 non-hematological toxicities. All patients responded to therapy with 7 CR, 1 CCR, 1 nPR, and 2 PR (IWCLL-NCI 2008 criteria). Median follow up was 6.9 months (2.3 – 13.2) and one patient progressed at 9.7 months. No patients have required treatment for progressive disease and there have been no patient deaths. Two patients were not evaluable: One developed neutropenia and therapy was not held per protocol, and the other developed a grade 2 skin reaction to ALM and treatment was stopped. Discussion: The combination of PGG beta glucan with ALM and RTX is well tolerated at a PGG beta glucan dose of 4 mg/kg. All patients responded to therapy with 64% achieving a CR. These data support continuation of this study in a phase II component. Acknowledgement: This study was funded by the University of Iowa/Mayo Clinic Lymphoma SPORE (CA097274) and Biothera. Disclosures: Zent:Biothera: Research Funding; Genzyme: Research Funding; Genentech: Research Funding; Novartis: Research Funding; GlaxoSmithKline: Research Funding. Off Label Use: Phase I study using PGG beta glucan in CLL.