A Phase I Trial of TGR-1202, a Next Generation Once-Daily PI3Kδ Inhibitor, in Combination with Brentuximab Vedotin, in Patients with Relapsed/Refractory Hodgkins Lymphoma

Introduction: TGR-1202 is a once daily, oral PI3Kδ inhibitor that has demonstrated activity in patients (pts) with relapsed and refractory hematologic malignancies, with a favorable safety and tolerability profile compared to other PI3Kδ inhibitors (Burris, ASCO 2016). Brentuximab vedotin (BV) is a CD30 specific antibody-drug conjugate, which is FDA approved for the treatment of Hodgkin's Lymphoma (HL) and Systemic Anaplastic Large-cell Lymphoma (sALCL). BV has demonstrated impressive response rates in pts with rel/ref disease, however the duration of response is short in pts not achieving a complete response (median PFS of ~6 months for non-CR pts; Gopal et al, Blood 2015). Marked synergy has been demonstrated pre-clinically with TGR + BV, with the combination demonstrating a 3-fold increase in cell death in-vitro and a 55% increase in tumor growth inhibition over either TGR or BV alone in an in-vivo xenograft model of HL (Locatelli et al, ASH 2014). As the combination of TGR + BV displays strong synergy pre-clinically and incorporates non-overlapping mechanisms of activity, a Phase 1 trial evaluating the combination of TGR + BV in pts with rel/ref HL was undertaken.

Methods: Eligible pts have relapsed or refractory HL, have received prior ASCT or at least 2 prior regimens, and have an ECOG PS < 3. Prior BV exposure is allowed. Two dose cohorts for TGR are evaluated (400 and 600 mg) dosed once daily with a fixed dose of BV 1.8 mg/kg on day 1 of each cycle (Cycle = 21 days) until off study. Safety is the primary endpoint evaluated by CTCAE v. 4.0. Efficacy (ORR and duration of response) is a secondary endpoint with responses determined according to response criteria of the International Working Group (Cheson, JCO 2007).

Results: Fourteen pts have been enrolled. Median age is 34 (range 21 - 81); 9 Male/5 Female; Median ECOG PS = 1; with a median of 3 prior therapies (range 2 - 6). Seven pts had prior ASCT. Six pts had previously received BV, and all 6 were refractory to prior BV therapy. All pts are evaluable for safety. The most common AEs regardless of causality were nausea (71%; 0% Gr. 3/4), diarrhea (57%; 7% Gr. 3/4), neutropenia (50%; 43% Gr. 3/4), and rash (43%; 7% Gr. 3/4), followed by cough, dyspnea, and vomiting (36% each, all grades). Peripheral neuropathy was reported in 4 pts (29%), and were all Grade 1/2. Eleven pts were evaluable for efficacy, with 3 discontinuing prior to first efficacy assessment (1 withdrew consent, and 2 due to AEs). The ORR was 64% (7/11), with 45% (5/11) achieving a complete response with a median TTR of 8 weeks. Notably, 50% (3/6) of BV refractory patients responded to TGR-1202 + BV combination therapy (2 CRs, 1 PR). Three responding patients proceeded to stem cell transplant. Of the remaining 4 patients achieving a response, 2 patients remain in CR, and 2 have progressed (at 13 and 16.5 mos respectively).

Conclusions: The combination of TGR-1202 + brentuximab vedotin exhibits an acceptable tolerability profile and is clinically active. Responses were observed in patients with advanced Hodgkin's Lymphoma, including responses in 50% of patients previously refractory to brentuximab vedotin. Further studies evaluating this combination are warranted.