Safety and preliminary efficacy of venetoclax with decitabine or azacitidine in elderly patients with previously untreated acute myeloid leukaemia: a non-randomised, open-label, phase 1b study.

BACKGROUND: Elderly patients (aged ≥65 years) with acute myeloid leukaemia have poor outcomes and no effective standard-of-care therapy exists. Treatment with hypomethylating agents such as azacitidine and decitabine is common, but responses are modest and typically short-lived. The oral anti-apoptotic B-cell lymphoma 2 protein inhibitor, venetoclax, has shown promising single-agent activity in patients with relapsed or refractory acute myeloid leukaemia and preclinical data suggested synergy between hypomethylating agents and venetoclax, which led to this combination phase 1b study. METHODS: Previously untreated patients aged 65 years and over with acute myeloid leukaemia who were ineligible for standard induction therapy were enrolled into this non-randomised, open-label, phase 1b study. Patients were required to have an Eastern Cooperative Oncology Group performance status of 0-2 and either intermediate-risk or poor-risk cytogenetics. Patients were enrolled into one of three groups for the dose-escalation phase of this study: group A (venetoclax and intravenous decitabine 20 mg/m2 [days 1-5 of each 28-day cycle]), group B (venetoclax and subcutaneous or intravenous azacitidine 75 mg/m2 [days 1-7 of each 28-day cycle]), and group C (a venetoclax and decitabine substudy with the oral CYP3A inhibitor posaconazole, 300 mg twice on cycle 1, day 21, and 300 mg once daily from cycle 1, days 22-28, to assess its effect on venetoclax pharmacokinetics). Dose escalation followed a standard 3 + 3 design with at least three evaluable patients enrolled per cohort; daily target doses of venetoclax for groups A and B were 400 mg (cohort 1), 800 mg (cohorts 2 and 3), and 1200 mg (cohort 4), and 400 mg for group C. The primary endpoints were the safety and pharmacokinetics of venetoclax plus decitabine or azacitidine, and to determine the maximum tolerated dose and recommended phase 2 dose. Secondary endpoints included the preliminary anti-leukaemic activity of venetoclax with decitabine or azacitidine through the analysis of overall response, duration of response, and overall survival. We analysed safety, pharmacokinetics, and anti-leukaemic activity in all patients who received one or more venetoclax doses. The expansion phase of the study is ongoing but is closed to accrual. This trial is registered with ClinicalTrials.gov, number NCT02203773. FINDINGS: 57 patients were enrolled in the study. 23 patients in group A and 22 patients in group B were enrolled between Nov 19, 2014, and Dec 15, 2015, and 12 patients in group C were enrolled between June 14, 2015, and Jan 16, 2016. As of data cutoff on June 15, 2016, the most common grade 3-4 treatment-emergent adverse events were thrombocytopenia (27 [47%] of 57 patients; nine in group A, 13 in group B, and five in group C), febrile neutropenia (24 [42%] of 57; 11 in group A, ten in group B, and three in group C), and neutropenia (23 [40%] of 57; 12 in group A, eight in group B, and three in group C). The most common serious treatment-emergent adverse event in groups A and B was febrile neutropenia (seven [30%] of 23 patients vs seven [32%] of 22), whereas in group C it was lung infection (four [33%] of 12 patients). 49 (86%) of 57 patients had treatment-related adverse events; the most common in groups A and B included nausea (12 [52%] patients vs seven [32%] patients), fatigue (six [26%] patients vs seven [32%]), and decreased neutrophil count (six [26%] patients vs six [27%]), whereas in group C the most common were nausea (seven [58%] of 12 patients), leucopenia (six [50%]), vomiting (five [42%]), and decreased platelet count (five [42%]). The maximum tolerated dose was not reached. The recommended phase 2 dose was 400 mg once a day or 800 mg with an interrupted dosing schedule (safety expansion). In total, four (7%) of 57 patients had died within 30 days of the first venetoclax dose caused by sepsis (group B), bacteraemia (group A), lung infection (group C), and respiratory failure (group A). Tumour lysis syndrome was not observed. Decitabine and azacitidine did not substantially affect venetoclax exposures. Overall, 35 (61%; 95% CI 47·6-74·0) of 57 patients achieved complete remission or complete remission with incomplete marrow recovery. In groups A and B, 27 (60%; 95% CI 44·3-74·3) of 45 patients had complete remission or complete remission with incomplete marrow recovery. INTERPRETATION: Venetoclax plus hypomethylating agent therapy seems to be a novel, well-tolerated regimen with promising activity in this underserved patient population. Evaluation of expansion cohorts is ongoing at 400 mg and 800 mg doses using both hypomethylating agent combinations. FUNDING: AbbVie and Genentech.

Efficacy and Biological Correlates of Response in a Phase II Study of Venetoclax Monotherapy in Patients with Acute Myelogenous Leukemia.

We present a phase II, single-arm study evaluating 800 mg daily venetoclax, a highly selective, oral small-molecule B-cell leukemia/lymphoma-2 (BCL2) inhibitor in patients with high-risk relapsed/refractory acute myelogenous leukemia (AML) or unfit for intensive chemotherapy. Responses were evaluated following revised International Working Group (IWG) criteria. The overall response rate was 19%; an additional 19% of patients demonstrated antileukemic activity not meeting IWG criteria (partial bone marrow response and incomplete hematologic recovery). Twelve (38%) patients had isocitrate dehydrogenase 1/2 mutations, of whom 4 (33%) achieved complete response or complete response with incomplete blood count recovery. Six (19%) patients had BCL2-sensitive protein index at screening, which correlated with time on study. BH3 profiling was consistent with on-target BCL2 inhibition and identified potential resistance mechanisms. Common adverse events included nausea, diarrhea and vomiting (all grades), and febrile neutropenia and hypokalemia (grade 3/4). Venetoclax demonstrated activity and acceptable tolerability in patients with AML and adverse features. SIGNIFICANCE: Venetoclax monotherapy demonstrated clinical activity in patients with AML (relapsed/refractory or unfit for intensive chemotherapy) with a tolerable safety profile in this phase II study. Predictive markers of response consistent with BCL2 dependence were identified. Clinical and preclinical findings provide a compelling rationale to evaluate venetoclax combined with other agents in AML. Cancer Discov; 6(10); 1106-17. ©2016 AACRSee related commentary by Pullarkat and Newman, p. 1082This article is highlighted in the In This Issue feature, p. 1069.

A phase I safety and pharmacokinetic study of ABT-263 in combination with carboplatin/paclitaxel in the treatment of patients with solid tumors.

Bcl-2 family proteins are the key regulators of the intrinsic apoptotic pathway, controlling the point-of no-return and setting the threshold to engage the death machinery in response to chemical damage. Bcl-2 proteins have emerged as attractive targets for anti-cancer drug development. Navitoclax is a selective, potent, orally bioavailable, small molecule Bcl-2 inhibitor. Primary endpoints assessed the safety and pharmacokinetic (PK) interactions between navitoclax in combination with carboplatin/paclitaxel or paclitaxel alone in patients with solid tumors The study comprised two arms, one a combination of navitoclax with paclitaxel and carboplatin, the second with navitoclax and paclitaxel alone. Nineteen patients were enrolled in this study. The most frequently reported treatment-emergent AEs were alopecia (57.9 %), anemia (52.6 %), nausea (52.6 %), constipation (42.1 %), diarrhea (42.1 %), fatigue (42.1 %), neutropenia (36.8 %), thrombocytopenia (36.8 %), vomiting (31.6 %), decreased appetite (31.6 %), dehydration (26.3 %), and hypomagnesaemia (26.3 %). In the light of significant hematological and non-hematological toxicity the study was ended before de-escalation of navitoclax. Only one partial response was obtained at any dose tested, thus lowering doses could not have increased efficacy. It is the combination of toxicity with modest efficacy that led to discontinuation. No apparent PK interaction was observed between navitoclax and carboplatin or paclitaxel and the combination of navitoclax and paclitaxel had modest anti-tumor activity.

A phase I clinical trial of navitoclax, a targeted high-affinity Bcl-2 family inhibitor, in combination with gemcitabine in patients with solid tumors.

PURPOSE: To investigate the safety, optimal dosing, pharmacokinetics and clinical activity of a regimen of navitoclax (ABT-263) combined with gemcitabine in patients with solid tumors. EXPERIMENTAL DESIGN: Patients with solid tumors for which gemcitabine was deemed an appropriate therapy were enrolled into one of two different dosing schedules (21-day dosing schedule: navitoclax administered orally on days 1-3 and 8-10,; and gemcitabine 1,000 mg/m(2) on days 1 and 8; 28-day dosing schedule: navitoclax administrated orally on days 1-3, 8-10, and 15-17; and gemcitabine 1,000 mg/m(2) on days 1, 8 and 15). Navitoclax doses were escalated from 150 to 425 mg. An expanded safety cohort was conducted for the 21-day dosing schedule at the maximum tolerated dose (MTD) of navitoclax. RESULTS: Forty-six patients were enrolled at three U.S. centers. The most common adverse events included: hematologic abnormalities (thrombocytopenia, neutropenia, and anemia), liver enzyme elevations (ALT and AST), and gastrointestinal disturbances (diarrhea, nausea, and vomiting). Dose-limiting toxicities (DLTs) observed in cycle 1 were grade 4 thrombocytopenia (2 patients), grade 4 neutropenia (1 patient), and grade 3 AST elevation (2 patients). The MTD of navitoclax was 325 mg co-administered with gemcitabine 1,000 mg/m(2) for the 21-day schedule. No clinically significant pharmacokinetic drug-drug interactions were observed. There were no objective responses. Stable disease, reported at the end of cycle 2, was the best response in 54 % of evaluable patients (n = 39). CONCLUSIONS: The combination of navitoclax 325 mg with gemcitabine 1,000 mg/m(2) was generally well tolerated and exhibited a favorable safety profile in patients with advanced solid tumors.

Phase II study of single-agent navitoclax (ABT-263) and biomarker correlates in patients with relapsed small cell lung cancer.

PURPOSE: Bcl-2 is a critical regulator of apoptosis that is overexpressed in the majority of small cell lung cancers (SCLC). Nativoclax (ABT-263) is a potent and selective inhibitor of Bcl-2 and Bcl-x(L). The primary objectives of this phase IIa study included safety at the recommended phase II dose and preliminary, exploratory efficacy assessment in patients with recurrent and progressive SCLC after at least one prior therapy. EXPERIMENTAL DESIGN: Thirty-nine patients received navitoclax 325 mg daily, following an initial lead-in of 150 mg daily for 7 days. Study endpoints included safety and toxicity assessment, response rate, progression-free and overall survival (PFS and OS), as well as exploratory pharmacodynamic correlates. RESULTS: The most common toxicity associated with navitoclax was thrombocytopenia, which reached grade III-IV in 41% of patients. Partial response was observed in one (2.6%) patient and stable disease in 9 (23%) patients. Median PFS was 1.5 months and median OS was 3.2 months. A strong association between plasma pro-gastrin-releasing peptide (pro-GRP) level and tumor Bcl-2 copy number (R = 0.93) was confirmed. Exploratory analyses revealed baseline levels of cytokeratin 19 fragment antigen 21-1, neuron-specific enolase, pro-GRP, and circulating tumor cell number as correlates of clinical benefit. CONCLUSION: Bcl-2 targeting by navitoclax shows limited single-agent activity against advanced and recurrent SCLC. Correlative analyses suggest several putative biomarkers of clinical benefit. Preclinical models support that navitoclax may enhance sensitivity of SCLC and other solid tumors to standard cytotoxics. Future studies will focus on combination therapies.