A literature review of the patent publications on venetoclax - a selective Bcl-2 inhibitor: discovering the therapeutic potential of a novel chemotherapeutic agent

Discovery of potent and selective Bcl-2 inhibitors with acyl sulfonamide skeleton

The antiapoptotic protein B-cell lymphoma 2 (Bcl-2), overexpressed in many tumor cells, is an attractive target for potential small molecule anticancer drug discovery. Herein, a series of novel derivatives with acyl sulfonamide skeleton was designed, synthesized, and evaluated as Bcl-2 inhibitors by means of bioisosteric replacement. Among them, compound 24g demonstrated equal efficient inhibition activity against RS4;11 cell line compared to positive control ABT-199. Moreover, it showed improved selectivity for Bcl-2/Bcl-xL inhibitory effects, the result of which was consistent with platelet toxicity studies. In vitro and in vivo pharmacokinetic properties of compound 24g had a significantly improved profiles. Taken together, those results suggested it as a promising candidate for development of novel therapeutics targeting Bcl-2 in cancer.

LC-Q-TOF-MS driven identification of potential degradation impurities of venetoclax, mechanistic explanation on degradation pathway and establishment of a quantitative analytical assay method

Venetoclax is a selective orally active Bcl-2 protein inhibitor very recently approved by USFDA to treat chronic lymphocytic leukemia and other hematological malignancies. Postmarketing surveillance of any drug depends on its acceptability based on risk to benefit ratio. When risk outweighs the benefits, withdrawal of an already marketed drug is warranted. Presence of impurity is the primary cause of increased risk in a drug substance or drug product. With the discovery of newer molecules, it is of great importance to establish advanced analytical techniques for quantification of the drugs as well as their related impurities to address the prospective regulatory queries even if it is already in the market. In this study, a quantitative analytical assay method has been developed and validated for quantification of venetoclax in presence of its degradation impurities. A stress study was performed to examine the stability of the drug in hydrolytic, oxidative, thermolytic and photolytic environments. Venetoclax was found to be prone to degradation in acidic hydrolytic and oxidative stress conditions. Three new degradation impurities have been identified and characterized with the help of LC-Q-TOF-MS with accurate mass measurement and their putative structures have been proposed. Furthermore, for the first time, a possible degradation pathway has been established with mechanistic explanation. Moreover, the analytical method developed in this study will be of immense help for routine analysis of quality control and stability study samples of venetoclax in industry and research laboratories.

Development of a Stability-Indicating Analytical Method for Determination of Venetoclax Using AQbD Principles

Venetoclax is an emerging drug for the treatment of various types of blood cancers. It was first approved in 2016 for the treatment of relapsed and refractory chronic lymphocytic leukemia. Later, the indications expanded, and multiple research as well as clinical studies are still conducted involving venetoclax. No analytical method for the determination of venetoclax can currently be found in the literature. We developed a mass spectrometry-compatible stability-indicating ultrahigh-performance liquid chromatography (LC) method for venetoclax. The LC method was developed using analytical quality by design principles. The developed method is able to separate venetoclax and its degradation products. The method was validated in the working point where a linearity range was established and accuracy, repeatability, and selectivity were assessed. Venetoclax is the only Bcl-2 protein inhibitor on the market. It is very effective in combinational therapy, so future drug development involving venetoclax may be expected. A stability-indicating method could aid in the development of new pharmaceutical products with venetoclax.

On the Stability and Degradation Pathways of Venetoclax under Stress Conditions

Venetoclax is an orally bioavailable, B-cell lymphoma-2 (BCL-2) selective inhibitor, used for the treatment of various types of blood cancers, such as chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL). In this study we investigated the degradation of venetoclax under various stress conditions including acidic, basic, oxidative, photolytic and thermolytic conditions. We isolated and identified six of its main degradation products produced in forced degradation studies. The structures of the isolated degradation products were determined by using nuclear magnetic resonance (NMR) spectroscopy, high resolution mass spectrometry (HRMS) and infrared (IR) spectroscopy. Additionally, one oxidation degradation product was identified with comparison to a commercially obtained venetoclax impurity. We proposed the key degradation pathways of venetoclax in solution. To the best of our knowledge, no structures of degradation products of venetoclax have been previously published. The study provides novel and primary knowledge of the stability characteristics of venetoclax under stress conditions. Venetoclax is currently the only BCL-2 protein inhibitor on the market. In addition to single agent treatment, it is effective in combinational therapy, so future drug development involving venetoclax can be expected. A better insight into the stability properties of the therapeutic can facilitate future studies involving venetoclax and aid in the search of new similar therapeutics.

The Incomplete Puzzle of the BCL2 Proteins

The proteins of the BCL2 family are key players in multiple cellular processes, chief amongst them being the regulation of mitochondrial integrity and apoptotic cell death. These proteins establish an intricate interaction network that expands both the cytosol and the surface of organelles to dictate the cell fate. The complexity and unpredictability of the BCL2 interactome resides in the large number of family members and of interaction surfaces, as well as on their different behaviours in solution and in the membrane. Although our current structural knowledge of the BCL2 proteins has been proven therapeutically relevant, the precise structure of membrane-bound complexes and the regulatory effect that membrane lipids exert over these proteins remain key questions in the field. Here, we discuss the complexity of BCL2 interactome, the new insights, and the black matter in the field.