Ublituximab, a Novel Glycoengineered Anti-CD20 Monoclonal Antibody (mAb), in Combination with TGR-1202, a Next Generation Once Daily PI3kδ Inhibitor, Demonstrates Activity in Heavily Pre-Treated and High-Risk Chronic Lymphocytic Leukemia (CLL) and B-Cell Lymphoma

Introduction: Ublituximab (UTX) is a novel chimeric mAb targeting a unique epitope on the CD20 antigen, glycoengineered to enhance affinity to FcγRIIIa receptors, thereby demonstrating significantly greater ADCC than rituximab. UTX monotherapy in patients (pts) with rituximab relapsed/refractory NHL and CLL has reported a 43% ORR (ASCO 2014). TGR-1202 is a next generation, once daily, oral PI3Kδ inhibitor which notably lacks the hepatotoxicity associated with other PI3Kδ inhibitors, and is active in pts with relapsed and refractory hematologic malignancies (EHA 2014). UTX and TGR-1202 have shown synergistic activity in-vitroin various lymphoid cell lines (Lugano 2013). This Phase 1 trial evaluates safety and efficacy of the combination of a glycoengineered anti-CD20 (UTX) and a PI3Kδ inhibitor (TGR-1202) in pts with heavily pre-treated relapsed or refractory CLL and NHL.

Methods: Eligible pts have relapsed/refractory CLL or NHL with an ECOG PS ≤ 2. A 3+3 design evaluates cohorts of CLL and NHL pts independently with UTX dosed on Days 1, 8, 15 of Cycles 1 & 2 followed by maintenance therapy. UTX starts at 600 mg in Cohort 1 and increases to 900 mg for pts with CLL and is fixed at 900 mg for pts with NHL. TGR-1202 starts at 800 mg QD in Cohort 1 and is increased in subsequent cohorts. An amendment in July 2014 was introduced to include an improved micronized formulation of TGR-1202, starting at 400 mg once daily and increasing in subsequent cohorts. There are no limits on prior therapy, and patients with Richter’s Transformation or who are refractory to prior PI3Kδ inhibitors or BTK inhibitors are eligible. Primary endpoints: Safety and Dose Limiting Toxicities (DLT). Secondary endpoints: Efficacy (ORR, CR rate).

Results: As of August 2014, 21 pts have been enrolled: 8 CLL/SLL, 7 DLBCL, 5 Follicular Lymphoma, and 1 patient with Richter’s Transformation. Median age is 64 years (range 35-82); 12 male/9 female. Median prior Tx = 3 (range 1-9); median ECOG PS = 1. All pts are evaluable for safety. Adverse events have been manageable with no safety concerns noted. Day 1 infusion related reactions (IRR) were the most common treatment related adverse event (48%), with all but one event Grade 1 or 2 in severity, followed by neutropenia (38%), diarrhea (29%), and nausea (29%). Notably, no events of TGR-1202 related hepatotoxicity have been reported to date. All IRR and neutropenia events have been manageable with dose delays. One neutropenia related dose delay in a CLL patient at UTX 600 mg + TGR 800 mg met the criteria for a DLT, necessitating enrollment of additional pts into this cohort. No other DLTs have been reported, including at higher dose levels. Fifteen pts were evaluable for efficacy with 6 pts too early for response assessment. Among evaluable pts, 80% displayed a reduction in tumor burden at first efficacy assessment, despite pts exhibiting a number of high-risk characteristics, including 3/5 CLL pts having 17p/11q deletion and a median of 6 prior lines of therapy amongst pts with FL. Objective responses are summarized below:

Amongst pts with CLL, 2/2 pts with normal cytogenetics achieved a PR including a patient with prior treatment with a BTK inhibitor, while 2/3 pts with presence of 17p/11q deletion achieved a PR, with the remaining patient having SD with a 44% nodal reduction at first assessment.

Conclusions: Preliminary data suggests the combination of UTX + TGR-1202 is well tolerated with early signs of clinical activity in heavily pre-treated and high-risk patient subsets. Enrollment is ongoing with at least 30 patients anticipated.