Agnese Chiara Pippione

Substituted 4-hydroxy-1,2,3-triazoles: synthesis, characterization and first drug design applications through bioisosteric modulation and scaffold hopping approaches

Bioisosterism and scaffold hopping are two widely used approaches in medicinal chemistry for the purpose of lead optimization. The study highlights the physicochemical properties of the 4-hydroxy-1,2,3-triazole scaffold, a less investigated heterocyclic system. Synthetic strategies to obtain different N-substituted 4-hydroxy-1,2,3-triazole isomers are presented, and their role as possible isosteres of the carboxylic acid is discussed. The aim is to use this system to modulate the acidic moieties present in lead compounds and, at the same time, to regiodirect substituents in set directions, through targeted substitution on the three nitrogenatoms of the triazole ring. Through this approach, compounds having enhanced binding affinity, will be sought. Two examples of bioisosteric applications of this moiety are presented. In the first example, a classical bioisosteric approach mimicking the distal (S)-glutamic acid carboxyl group using the 4-hydroxy-1,2,3-triazole moiety is applied, to obtain two promising glutamate analogs. In the second example, a scaffold hopping approach is applied, replacing the phenolic moiety present in MDG-1-33A, a potent inhibitor of Onchocerca volvulus chitinase, with the 4-hydroxy-1,2,3-triazole scaffold. The 4-hydroxy-1,2,3-triazole system appears to be useful and versatile in drug design.

A covalent PIN1 inhibitor selectively targets cancer cells by a dual mechanism of action

The prolyl isomerase PIN1, a critical modifier of multiple signalling pathways, is overexpressed in the majority of cancers and its activity strongly contributes to tumour initiation and progression. Inactivation of PIN1 function conversely curbs tumour growth and cancer stem cell expansion, restores chemosensitivity and blocks metastatic spread, thus providing the rationale for a therapeutic strategy based on PIN1 inhibition. Notwithstanding, potent PIN1 inhibitors are still missing from the arsenal of anti-cancer drugs. By a mechanism-based screening, we have identified a novel covalent PIN1 inhibitor, KPT-6566, able to selectively inhibit PIN1 and target it for degradation. We demonstrate that KPT-6566 covalently binds to the catalytic site of PIN1. This interaction results in the release of a quinone-mimicking drug that generates reactive oxygen species and DNA damage, inducing cell death specifically in cancer cells. Accordingly, KPT-6566 treatment impairs PIN1-dependent cancer phenotypes in vitro and growth of lung metastasis in vivo.

Hydroxytriazole derivatives as potent and selective aldo-keto reductase 1C3 (AKR1C3) inhibitors discovered by bioisosteric scaffold hopping approach

The aldo-keto reductase 1C3 isoform (AKR1C3) plays a vital role in the biosynthesis of androgens, making this enzyme an attractive target for castration-resistant prostate cancer therapy. Although AKR1C3 is a promising drug target, no AKR1C3-targeted agent has to date been approved for clinical use. Flufenamic acid, a non-steroidal anti-inflammatory drug, is known to potently inhibit AKR1C3 in a non-selective manner as COX off-target effects are also observed. To diminish off-target effects, we have applied a scaffold hopping strategy replacing the benzoic acid moiety of flufenamic acid with an acidic hydroxyazolecarbonylic scaffold. In particular, differently N-substituted hydroxylated triazoles were designed to simultaneously interact with both subpockets 1 and 2 in the active site of AKR1C3, larger for AKR1C3 than other AKR1Cs isoforms. Through computational design and iterative rounds of synthesis and biological evaluation, novel compounds are reported, sharing high selectivity (up to 230-fold) for AKR1C3 over 1C2 isoform and minimal COX1 and COX2 off-target inhibition. A docking study of compound 8, the most interesting compound of the series, suggested that its methoxybenzyl substitution has the ability to fit inside subpocket 2, being involved in π-π staking interaction with Trp227 (partial overlapping) and in a T-shape π-π staking with Trp86. This compound was also shown to diminish testosterone production in the AKR1C3-expressing 22RV1 prostate cancer cell line while synergistic effect was observed when 8 was administered in combination with abiraterone or enzalutamide.

Use of human Dihydroorotate Dehydrogenase (hDHODH) Inhibitors in Autoimmune Diseases and New Perspectives in Cancer Therapy

BACKGROUND Human dihydroorotate dehydrogenase (hDHODH, EC 1.3.5.2), a flavindependent mitochondrial enzyme involved in de novo pyrimidine biosynthesis, is a validated therapeutic target for the treatment of autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis. However, human DHODH inhibitors have also been investigated as treatment for cancer, parasite infections (i.e. malaria) and viruses as well as in the agrochemicals industry. OBJECTIVE An overview of current knowledge of hDHODH inhibitors and their potential uses in diseases where hDHODH is involved. METHOD This review focuses on recent advances in the development and application of hDHODH inhibitors, specifically covering the patent field, starting from a brief description of enzyme topography and of the strategies usually followed in designing its selective inhibitors. RESULTS The most important and well-described novelty is the fact that the discovery, in the autumn of 2016, that hDHODH inhibitors are able to induce in vivo myeloid differentiation has led to the possibility of developing novel hDHODH based treatments for Acute Myelogenous Leukemia (AML). CONCLUSION The review will describe a variety of specific inhibitor classes and conclude on recent and future therapeutic perspectives for this target.

Androgen-AR axis in primary and metastatic prostate cancer: chasing steroidogenic enzymes for therapeutic intervention

Androgens play an important role in prostate cancer (PCa) development and progression. Although androgen deprivation therapy remains the front-line treatment for advanced prostate cancer, patients eventually relapse with the lethal form of the disease. The prostate tumor microenvironment is characterised by elevated tissue androgens that are capable of activating the androgen receptor (AR). Inhibiting the steroidogenic enzymes that play vital roles in the biosynthesis of testosterone (T) and dihydrotestosterone (DHT) seems to be an attractive strategy for PCa therapies. Emerging data suggest a role for the enzymes mediating pre-receptor control of T and DHT biosynthesis by alternative pathways in controlling intratumoral androgen levels, and thereby influencing PCa progression. This supports the idea for the development of multi-targeting strategies, involving both dual and multiple inhibitors of androgen-metabolising enzymes that are able to affect androgen synthesis and signalling at different points in the biosynthesis. In this review, we will focus on CYP17A1, AKR1C3, HSD17B3 and SRD5A, as these enzymes play essential roles in all the three androgenic pathways. We will review also the AR as an additional target for the design of bifunctional drugs. Targeting intracrine androgens and AKR1C3 have potential to overcome enzalutamide and abiraterone resistance and improve survival of advanced prostate cancer patients.

Heterocyclic ring cleavage upon collision-induced dissociation of deprotonated 3-hydroxy-1,2,5-oxadiazoles (3-hydroxyfurazans)

A series of 4-substituted 3-hydroxyfurazans were subjected to electrospray ionization tandem mass spectrometry. At low collision energy, oxyisocyanate ([O=C=N-O](-), m/z 58) was formed as the predominant product ion from each deprotonated 3-hydroxyfurazan, indicating cleavage of the heterocyclic ring. The facile energetics of this characteristic fragmentation process was confirmed by density functional computations.