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A phase I dose-escalation trial of ublituximab (TG-1101), a novel anti-CD20 monoclonal antibody (mAb), for rituximab relapsed/refractory B-cell lymphoma patients.
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Background: Anti-CD20 therapy (rituximab or RTX) in treating patients (pts) with B-cell lymphomas has resulted in significant improvement in treatment response and clinical outcomes. Despite advances, pts continue to relapse from, or are refractory to, RTX-based regimens. Ublituximab (UTX) is a novel, chimeric mAb targeting a unique epitope on the CD20 antigen. UTX has been glycoengineered to enhance affinity for all variants of FcγRIIIa receptors, and therefore demonstrates greater ADCC activity than RTX (Le Garff-Tavernier, 2011). UTX displayed greater antitumor activity compared to RTX in NHL in vivo models and in low CD20 expressing tumors (ASH 2011). A phase I trial with UTX used as a single agent in pts with relapsed/refractory CLL reported a response rate of 45%. Herein we report on the phase I dose-escalation of UTX in pts with RTX relapsed/refractory B-cell lymphoma. Methods: Eligible pts have B-cell lymphoma relapsed or refractory to a RTX containing regimen. Pts are required to have measurable/evaluable disease, ECOG PS < 2 and no active hepatitis B/C. The phase I dose-escalation uses a sequential 3+3 design in dose cohorts of 450mg, 600mg and 900mg respectively. UTX is administered once weekly for 4 infusions followed by monthly maintenance therapy. PK and correlative PD data are being collected. Primary endpoint: Maximum Tolerated Dose (MTD) and Dose Limiting Toxicities (DLT). Efficacy is a secondary endpoint. Results: Nine pts (5 FL, 3 MZL, 1 MCL) have been enrolled (3 each cohort). Median age 63; 3/6 (M/F). Median prior Rx = 4 (2-6). RTX refractory (44%). 8/9 pts are evaluable for safety; no DLT’s observed and no Grade 3/4 AE’s to date. 7/9 pts have had at least one response assessment (8 wk scan), which includes: 1 CR (rituximab refractory MZL); 2 PR’s (1 MZL, 1 FL); 2 SD (FL) and 2 PD (1 transformed FL, 1 MCL). PK analysis is ongoing. Conclusions: UTX has been well tolerated to date with no G 3/4 AE’s with demonstrated early clinical activity at all doses. 7/9 patients continue to receive UTX treatment (range 1–25 wks). Enrollment in the 900mg expansion cohort is now open with an emphasis on RTX relapsed/refractory indolent or low CD20-expressing lymphomas. Clinical trial information: NCT01647971.