ATG4B inhibitors with a benzotropolone core structure block autophagy and augment efficiency of chemotherapy in mice.

Autophagy is a cell survival mechanism hijacked by advanced tumors to endure a rough microenvironment. Late autophagy inhibitors such as (hydroxy)chloroquine have been used clinically to halt tumor progression with modest success. However, given the toxic nature of these compounds and their lack of specificity, novel targets should be considered. We recently identified a benzotropolone derivative that significantly inhibited the essential autophagy protein ATG4B. Therefore, we synthesized and tested additional benzotropolone compounds to identify a promising ATG4B inhibitor that impairs autophagy both in vitro and in vivo. A compound library containing 27 molecules with a benzotropolone backbone was synthesized and screened for inhibition of recombinant ATG4B. Depending on the benzotropolone compound, inhibition of recombinant ATG4B ranged from 3 to 82%. Active compounds were evaluated in cellular assays to confirm inhibition of ATG4B and suppression of autophagy. Seven compounds inhibited processing of the autophagy protein LC3 and autophagosome formation. Compound UAMC-2526 was selected for further in vivo use because of its fair plasma stability. This compound abolished autophagy both in nutrient-deprived GFP-LC3 mice and in CD1-/- Foxn1nu mice bearing HT29 colorectal tumor xenografts. Moreover, addition of UAMC-2526 to the chemotherapy drug oxaliplatin significantly improved inhibition of tumor growth. Our data indicate that suppression of autophagy via ATG4B inhibition is a feasible strategy to augment existing chemotherapy efficacy and to halt tumor progression.

Novel Ferroptosis Inhibitors with Improved Potency and ADME Properties.

Ferroptosis is a nonapoptotic, iron-catalyzed form of regulated necrosis that is critically dependent on glutathione peroxidase 4 (GPX4). It has been shown to contribute to liver and kidney ischemia reperfusion injury in mice. A chemical inhibitor discovered by high-throughput screening displayed inhibition of ferroptosis with nanomolar activity and was dubbed ferrostatin-1 (fer-1). Ferrostatins inhibit oxidative lipid damage, but suffer from inherent stability problems due to the presence of an ester moiety. This limits the application of these molecules in vivo, due to rapid hydrolysis of the ester into the inactive carboxylic acid. Previous studies highlighted the importance of the ethyl ester and suggested steric modifications of the ester for generating improved molecules. In this study, we report the synthesis of novel ferroptosis inhibitors containing amide and sulfonamide moieties with improved stability, single digit nanomolar antiferroptotic activity, and good ADME properties suitable for application in in vivo disease models.

From human immunodeficiency virus non-nucleoside reverse transcriptase inhibitors to potent and selective antitrypanosomal compounds.

The presence of a structural recognition motif for the nucleoside P2 transporter in a library of pyrimidine and triazine non-nucleoside HIV-1 reverse transcriptase inhibitors, prompted for the evaluation of antitrypanosomal activity. It was demonstrated that the structure-activity relationship for anti-HIV and antitrypanosomal activity was different. Optimization in the diaryl triazine series led to 6-(mesityloxy)-N2-phenyl-1,3,5-triazine-2,4-diamine (69), a compound with potent in vitro and moderate in vivo antitrypanosomal activity.