Discovery of Acylsulfonohydrazide-Derived Inhibitors of the Lysine Acetyltransferase, KAT6A, as Potent Senescence-Inducing Anti-Cancer Agents.

A high-throughput screen designed to discover new inhibitors of histone acetyltransferase KAT6A uncovered CTX-0124143 (1), a unique aryl acylsulfonohydrazide with an IC50 of 1.0 µM. Using this acylsulfonohydrazide as a template, we herein disclose the results of our extensive structure-activity relationship investigations, which resulted in the discovery of advanced compounds such as 55 and 80. These two compounds represent significant improvements on our recently reported prototypical lead WM-8014 (3) as they are not only equivalently potent as inhibitors of KAT6A but are less lipophilic and significantly more stable to microsomal degradation. Furthermore, during this process, we discovered a distinct structural subclass that contains key 2-fluorobenzenesulfonyl and phenylpyridine motifs, culminating in the discovery of WM-1119 (4). This compound is a highly potent KAT6A inhibitor (IC50 = 6.3 nM; KD = 0.002 µM), competes with Ac-CoA by binding to the Ac-CoA binding site, and has an oral bioavailability of 56% in rats.

Haemoglobin degradation underpins the sensitivity of early ring stage Plasmodium falciparum to artemisinins.

Current first-line artemisinin antimalarials are threatened by the emergence of resistant Plasmodium falciparum. Decreased sensitivity is evident in the initial (early ring) stage of intraerythrocytic development, meaning that it is crucial to understand the action of artemisinins at this stage. Here, we examined the roles of iron (Fe) ions and haem in artemisinin activation in early rings using Fe ion chelators and a specific haemoglobinase inhibitor (E64d). Quantitative modelling of the antagonism accounted for its complex dependence on the chemical features of the artemisinins and on the drug exposure time, and showed that almost all artemisinin activity in early rings (>80%) is due to haem-mediated activation. The surprising implication that haemoglobin uptake and digestion is active in early rings is supported by identification of active haemoglobinases (falcipains) at this stage. Genetic down-modulation of the expression of the two main cysteine protease haemoglobinases, falcipains 2 and 3, renders early ring stage parasites resistant to artemisinins. This confirms the important role of haemoglobin-degrading falcipains in artemisinin activation, and shows that changes in the rate of artemisinin activation could mediate high-level artemisinin resistance.

Novel conjugated quinoline-indoles compromise Plasmodium falciparum mitochondrial function and show promising antimalarial activity.

A novel class of antimalarial compounds, based on an indol-3-yl linked to the 2-position of a 4-aminoquinoline moiety, shows promising activity against the malaria parasite, Plasmodium falciparum . Compounds with a quaternary nitrogen on the quinoline show improved activity against the chloroquine-resistant K1 strain. Nonquaternerized 4-aminoquinolines retain significant potency but are relatively less active against the K1 strain. Alkylation of the 4-amino group preferentially improves the activity against the chloroquine-sensitive 3D7 strain. The quinoline-indoles show only weak activity as inhibitors of ß-hematin formation, and their activities are only weakly antagonized by a hemoglobinase inhibitor. The compounds appear to dissipate mitochondrial potential as an early event in their antimalarial action and therefore may exert their activity by compromising Plasmodium mitochondrial function. Interestingly, we observed a structural relationship between our compounds and the anticancer and anthelminthic compound, pyrvinium pamoate, which has also been proposed to exert its action via compromising mitochondrial function.