The BCL-2-Specific BH3-Mimetic ABT-199 (GDC-0199) Is Active and Well-Tolerated in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia: Interim Results of a Phase I First-in-Human Study

BCL-2 is highly expressed in indolent non-Hodgkin lymphomas (NHL), mantle cell lymphoma (MCL) and other selected aggressive lymphomas, and is a promising target for therapeutic intervention. The first-generation BCL-2 inhibitor navitoclax showed some activity in indolent lymphoma, but its co-inhibition of BCL-x_L resulted in dose-limiting thrombocytopenia, precluding the full exploration of the potential of BCL-2 inhibition with this drug in NHL. ABT-199 is an orally bioavailable, second-generation BH3-mimetic that inhibits BCL-2 (K_i<0.10 nM), but has 500-fold less activity for BCL-x_L (K_i=48 nM). ABT-199 demonstrated antitumor activity against a variety of human cell lines and xenograft models that include B cell NHL, follicular lymphomas (FL), diffuse large B-cell Lymphoma (DLBCL) and MCL.

This is a phase-I dose-escalation trial using a modified Fibonacci design in patients with relapsed/refractory NHL. The primary objectives of this study are to determine the safety, pharmacokinetics (PK) and maximum tolerated dose (MTD) of ABT-199; to recommend a phase-2 dose; and to assess efficacy and biomarkers in patients with relapsed/refractory NHL. Adult patients requiring therapy, with ECOG performance status £1, and adequate marrow function received ABT-199 on Week 1 Day −7 (W1D-7), followed by continuous once-daily dosing from W1D1, until progressive disease (PD) or unacceptable toxicity. Due to concerns of potential tumor lysis, a strategy of commencing with a 2 to 3 week lead-in period with step-wise increases to the target cohort dose is being evaluated. In the first four cohorts, the starting dose increased from 50 to 200 mg (50, 100, 200, and 200 mg, respectively), with target cohort doses of 200 mg [n=3], 300 mg [n=3], 400 mg [n=4], and 600 mg [n=7]. Evaluations include: adverse events (AE; NCI-CTCAE-V4) and tumor response (IWG 2007 criteria).

To date, 17 patients (median age, 71 [35–85]) have been treated with ABT-199. Median prior therapies were 3 (range, 1–7) and 6 patients had bulky adenopathy (>5cm). Most common AEs (experienced by >2 patients) were nausea (41%), diarrhea (24%), dyspepsia (24%), fatigue (24%), extremity pain (24%); and anemia, constipation, upper respiratory tract infection and cough (18% each). Grade 3 or 4 AEs occurring in >1 patient were anemia (18%) and neutropenia (12%). Treatment-related thrombocytopenia has not been reported and no dose-limiting toxicities (DLTs) have been identified to date. After a single dose administration with a high-fat meal, ABT-199 reached C_max at approximately 7 hrs with a terminal half-life of about 15 hrs. Food increased ABT-199 exposure by approximately 3-fold. With a median follow-up of 2.8 months (range, 1.2 to 10.8), 14 patients remain on study and 3 have discontinued due to PD. In patients who have completed at least a W6 assessment, reductions of >50% in target lesions have been observed in 8/15 patients (53%); 6/6 patients with MCL, 1/2 patients with WM and 1/2 patients with DLBCL. Additionally, 5 FL patients have been evaluated (3 with rituxan-refractory disease) with a median time on study of 6.4 months (range, 3.5 to 10.8). 4/5 FL patients had nodal disease reductions ranging from 18% to 40%.

ABT-199 shows single agent anti-tumor activity in patients with NHL; particularly in MCL. Activity is also observed in DLBCL and WM. To date, no DLTs have been identified and tumor lysis syndrome related to ABT-199 has not been reported. Dose escalation is continuing to identify the optimal dosing regimen and MTD of ABT-199 in NHL. Updated results will be presented.

Seymour:Roche: Advisory Board member Other, Consultancy; Genentech: Advisory Board member, Advisory Board member Other, Consultancy. Anderson:Abbott: Research Funding; Genentech: Research Funding; Walter and Eliza Hall Institute of Medical Research: Employment, receives commercial income related to ABT-199, receives commercial income related to ABT-199 Other. Kipps:Abbott: Consultancy, Research Funding. Wierda:Abbott: Research Funding; Genentech: Consultancy, Research Funding; GlaxoSmithKline: Consultancy, Research Funding; AmGen: Research Funding; Merck: Consultancy; Celgene: Consultancy; Pharmacyclics: Consultancy; Genzyme: Consultancy. Kahl:Abbott: Research Funding; Genentech: Consultancy, Research Funding. Miller:Abbott: Research Funding; Genentech: Research Funding. Darden:Abbott: Employment, owner of Abbott stock Other. Nolan:Abbott: Employment, own Abbott stock Other. Gressick:Abbott: Employment, stock owner Other. Xiong:Abbott: Employment, own Abbott stock Other. Huang:Genentech: Research Funding; Abbott: Research Funding; Walter and Eliza Hall Institiute of Medical Research: Employment, receives commercial income related to ABT-199, receives commercial income related to ABT-199 Other. Chyla:Abbott: Employment, Stock owner Other. Busman:Abbott: Employment, Stock owner Other. Graham:Abbott: Employment, Stock owner Other. Cerri:Abbott: Employment, Stock owner Other. Enschede:Abbott: Employment, own Abbott stocks Other. Humerickhouse:Abbott: Employment, own Abbott stocks Other. Roberts:Abbott: Research Funding; Genentech: Research Funding; Walter and Eliza Hall Institute of Medical Research: Employment, Receives commercial income related to ABT-199, Receives commercial income related to ABT-199 Other.