ABT-263 (Navitoclax)

ABT-263 is an orally sellecitive inhibitor of B-cell leukemia 2 (Bcl-2) family of proteins with potential antineoplastic activity. ABT-263 is a small molecular with the formula of C47H55ClF3N5O6S3 and Molecular Weight of 974. As a Bad-like Bh3 minetic, ABT-263 binds to Bcl-2 family proteins Bcl-2, Bcl-xl and Bcl-w, disrupts the interaction between Bcl-2/Bcl-xl /Bcl-w and pro-apoptotic proteins such as Bim, Bad and Bak, which trigger the caspases-initiated cell death pathway to induce apoptosis.

References:

1. Tse et al., ABT-263: A Potent and Orally Bioavailable Bcl-2 Family Inhibitor. Cancer Res. 2008, 68, 3421-3428. 

2. Shoemaker et al., Activity of the Bcl-2 Family Inhibitor ABT-263 in a Panel of Small Cell Lung Cancer Xenograft Models. Clin. Cancer Res. 2008, 14, 3268-3277

Data on the DNA damaging and mutagenic potential of the BH3-mimetics ABT-263/Navitoclax and TW-37.[Pubmed:26958630]

Data Brief. 2016 Jan 16;6:710-4.

Unfortunately, the mutagenic activities of chemotherapy and radiotherapy can provoke development of therapy-induced malignancies in cancer survivors. Non-mutagenic anti-cancer therapies may be less likely to trigger subsequent malignant neoplasms. Here we present data regarding the DNA damaging and mutagenic potential of two drugs that antagonize proteins within the Bcl-2 family: ABT-263/Navitoclax and TW-37. Our data reveal that concentrations of these agents that stimulated Bax/Bak-dependent signaling provoked little DNA damage and failed to trigger mutations in surviving cells. The data supplied in this article is related to the research work entitled "Inhibition of Bcl-2 or IAP proteins does not provoke mutations in surviving cells" [1].

Safety, efficacy, and pharmacokinetics of navitoclax (ABT-263) in combination with irinotecan: results of an open-label, phase 1 study.[Pubmed:26429709]

Cancer Chemother Pharmacol. 2015 Nov;76(5):1041-9.

PURPOSE: The oral Bcl-2 inhibitor navitoclax demonstrated activity in solid and hematologic malignancies as monotherapy and in combination with other cytotoxic agents in preclinical and early clinical studies. We evaluated the safety, pharmacokinetics (PK), and antitumor activity of navitoclax plus irinotecan. METHODS: In this multicenter, open-label, phase 1 dose escalation study, adults with advanced solid tumors received navitoclax (starting dose 150 mg/day) in combination with 1 of 2 irinotecan schedules during a 21-day cycle: a once-every-3-week regimen (Q3W 180, 250, or 350 mg/m(2)) or a once-weekly regimen (QW 75 or 100 mg/m(2)). Enrollment occurred until a maximum tolerated dose (MTD) and/or recommended phase 2 dose (RPTD) was reached. RESULTS: All patients (Q3W, n = 14; QW, n = 17) were evaluable for safety, PK, and efficacy. The most common adverse event in both groups was diarrhea (Q3W 92.9 %; QW 76.5 %), which was the most frequent grade 3/grade 4 adverse event (Q3W 42.9 %; QW 29.4 %). The study was amended to exclude 4 UGT1A1*28 7/7 homozygous patients due to frequent irinotecan-related grade 3/grade 4 diarrhea and/or febrile neutropenia. No apparent PK interactions between navitoclax and irinotecan were observed. The MTD of the combination was exceeded in the Q3W group at the lowest dose administered. In the QW group, the MTD and RPTD for navitoclax were 150 mg when combined with irinotecan 75 mg/m(2). One patient in each group achieved a partial response. CONCLUSION: The RPTD of navitoclax in combination with irinotecan 75 mg/m(2) QW during a 21-day cycle was 150 mg in these heavily pretreated patients.

Safety, efficacy, and pharmacokinetics of navitoclax (ABT-263) in combination with erlotinib in patients with advanced solid tumors.[Pubmed:26420235]

Cancer Chemother Pharmacol. 2015 Nov;76(5):1025-32.

PURPOSE: Navitoclax (ABT-263), a novel, oral Bcl-2 inhibitor, enhances the antitumor effects of chemotherapy in vitro by lowering the apoptotic threshold. This phase I study (NCT01009073) evaluated the safety, pharmacokinetics, and preliminary antitumor activity of navitoclax combined with erlotinib in patients with advanced solid tumors. PATIENTS AND METHODS: An open-label dose escalation study included an arm evaluating navitoclax combined with erlotinib, which included a dose escalation cohort and a planned safety expansion cohort. Patients with documented cancers for whom erlotinib therapy was appropriate received erlotinib 150 mg orally once daily plus navitoclax 150 mg orally once daily, with navitoclax dose escalation via a continuous reassessment method model. RESULTS: Eleven patients were enrolled, including six patients with nonsmall cell lung cancer. Dose-limiting toxicities, most commonly diarrhea, were observed in 4 patients. Navitoclax dosing remained at 150 mg/day because the maximum tolerated dose was exceeded at this starting dose. The planned dose escalation did not occur; no recommended phase II dose (RPTD) was identified, and there was no safety expansion cohort. The most common treatment-related adverse events were diarrhea, nausea, vomiting, and decreased appetite. Pharmacokinetic analysis showed no apparent interactions between co-administered navitoclax and erlotinib. No objective responses were observed; the disease control rate was 27 % (95 % CI, 6-61 %). CONCLUSION: At the erlotinib and navitoclax doses administered, RPTD was not reached, but the safety profile of the combination was consistent with data from monotherapy studies. There were no apparent pharmacokinetic interactions between erlotinib and navitoclax. Three patients had stable disease.

Combination with vorinostat overcomes ABT-263 (navitoclax) resistance of small cell lung cancer.[Pubmed:26575826]

Cancer Biol Ther. 2016;17(1):27-35.

Small cell lung cancer (SCLC) is an aggressive tumor type with high mortality. One promising approach for SCLC treatment would be to utilize agents targeting molecular abnormalities regulating resistance to apoptosis. BH3 mimetic antagonists, such as ABT-737 and its orally available derivative ABT-263 (Navitoclax) have been developed to block the function of pro-survival BCL-2 family members. The sensitivity of SCLC to these drugs varies over a broad range in vitro and in clinical trials. We have previously shown that the expression of Noxa, a BH3-only pro-apoptotic BCL-2 family protein, is a critical determinant of sensitivity to ABT-737. Thus, pharmacological up-regulation of Noxa could enhance cell death induced by the BH3 mimetics. We find that the combination of ABT-263 and a HDAC inhibitor, vorinostat, efficiently induces apoptosis in a variety of SCLC cell lines, including ABT-263 resistant cell lines. Cell death induced by combined treatment is Noxa- and/or BIM-dependent in some cell lines but in others appears to be mediated by down-regulation of BCL-XL and release of BAK from BCL-XL and MCL-1. These results suggest that combination of HDAC inhibitors and BCL-2 inhibitors could be an alternative and effective regimen for SCLC treatment.