Rational design, synthesis and structure–Activity relationships of a cyclic succinate series of TNF-α converting enzyme inhibitors. Part 1: lead identification

Intricate relationship between SARS-CoV-2-induced shedding and cytokine storm generation: A signaling inflammatory pathway augmenting COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), through its ability to induce cytokine release syndrome, can set up a generalized inflammatory response together with activating multiple inflammatory pathways, which contributes to a dramatic increase in the number of mortalities and morbidities worldwide. Reportedly, the manipulative nature of coronavirus disease 2019 (COVID-19), which targets the immune system, often focuses on specific inflammation-related pathways, usually confined to interleukins and tumor necrosis factor-α (TNF-α), with a great emphasis on therapeutic approaches targeting the inhibition of these inflammatory mediators. The involvement of a disintegrin and metalloprotease 17 (ADAM-17) and matrix metalloproteinase-9 (MMP-9) in the pathogenesis of COVID-19, through their ability to potentiate the cytokine storm during an episode of SARS-CoV-2 infection, often goes unnoticed. In this review, the intricate relationship between ADAM-17 and MMP-9 together with angiotensin-converting enzyme 2 (ACE-2) as the main target for SARS-CoV-2 is highlighted in detail through a compilation of evidence-based literature; thus, we shed light on a proposed inflammatory pathway that COVID-19 may exploit to provoke an inflammatory response of a complex nature. Conclusively, our proposed mechanism acts as a means to developing a therapeutic approach aimed at modulating the intricate communication between ADAM-17 and MMP-9, where a great emphasis on the role of ACE-2 shedding and subsequent elevation in angiotensin II (Ang-II) levels is crucial to understanding the awry inflammatory response in patients with COVID-19. From this concept, designing a therapeutic strategy targeting multiple inflammatory mediators and enzymes simultaneously is another approach to unravel this global pandemic.

Novel methods and strategies in the discovery of TACE inhibitors

INTRODUCTION

Tumor necrosis factor-α (TNF-α) is a key player in inflammation and joint damage in rheumatoid arthritis (RA). One treatment approach to exclude TNF-α from the biological system is by inhibiting tumor necrosis factor-alpha converting enzyme (TACE), the enzyme responsible for the production of its active form. To date, a number of TACE inhibitors have been reported in the literature from various strategies and methods.

AREAS COVERED

The following article presents the design and development strategies for the discovery of novel TACE inhibitors which could be of therapeutic utility for the alleviation of inflammatory conditions. The review is based on literature of the subject from 2005 onward.

EXPERT OPINION

Discovery of a selective TACE inhibitor has remained a major goal for many academic and pharmaceutical industrial research laboratories for quite some time. Identification of selective TACE inhibitors has proved elusive until recently due to structural similarities between TACE and MMPs. The differences in the shape and size of the S1' pocket of TACE and MMPs could be exploited to design selective TACE inhibitors devoid of any MMP inhibitory activity in the near future. It would be a Herculean task to develop a specific TACE inhibitor for clinical treatment of RA because binding subsites of TACE and MMPs are quite similar. However, developments taking place currently in the field as well as in the application of molecular modeling techniques at a wider scale could yet provide clinically useful selective TACE inhibitors in the not too distant future.

Potent, exceptionally selective, orally bioavailable inhibitors of TNF-alpha Converting Enzyme (TACE): novel 2-substituted-1H-benzo[d]imidazol-1-yl)methyl)benzamide P1' substituents

Novel ((2-substituted-1H-benzo[d]imidazol-1-yl)methyl)benzamides were found to be excellent P1' substituents in conjunction with unique constrained beta-amino hydroxamic acid scaffolds for the discovery of potent selective inhibitors of TNF-alpha Converting Enzyme (TACE). Optimized examples proved potent for TACE, exceptionally selective over a wide panel of MMP and ADAM proteases, potent in the suppression of LPS-induced TNF-alpha in human whole blood and orally bioavailable.

Synthesis and structure-activity relationship of a novel, non-hydroxamate series of TNF-alpha converting enzyme inhibitors

A novel series of TNF-alpha converting enzyme (TACE) inhibitors which are non-hydroxamate have been discovered. These compounds use a triazolethione moiety as the zinc binding ligand and exhibit IC50 values from 1.5 to 100 nM in a porcine TACE assay. They also have excellent selectivities over other MMPs.

A new 4-(2-methylquinolin-4-ylmethyl)phenyl P1′ group for the β-amino hydroxamic acid derived TACE inhibitors

A new P1' group for TACE inhibitors was identified by eliminating the oxygen atom in the linker of the original 4-(2-methylquinolin-4-ylmethoxy)phenyl P1' group. Incorporation of this 4-(2-methylquinolin-4-ylmethyl)phenyl group onto different beta-aminohydroxamic acid cores provided compound 18, which demonstrated potent porcine TACE (p-TACE) and human whole blood activity, excellent PK properties, and good selectivity against a variety of MMPs.

Identification of potent and selective TACE inhibitors via the S1 pocket

By focusing on the P1 portion of the piperidine beta-sulfone ligands we identified a motif that induces selectivity and resulted in a series of TACE inhibitors that demonstrated excellent in vitro potency against isolated TACE enzyme and excellent selectivity over MMPs 1, 2, 9, 13, and 14.

Arylisothiocyanato selective androgen receptor modulators (SARMs) for prostate cancer

A new series of androgen receptor targeted agents (ARTA) was prepared and tested in androgen-dependent and -independent prostate cancer cell lines. These agents were bicalutamide analogs with isothiocyanato substituted B-rings. Also, the linker sulfone of R-bicalutamide was maintained or replaced with several alternative linkages including ether, amine, N-methylamine, thioether, and methylene (in this case the product was a racemic mixture) functional groups at the X-position. To expand the structure-activity relationship (SAR) of these arylisothiocyanato AR ligands, B-ring halogenated arylisothiocyanato ligands were also prepared and tested. The arylisothiocyanato AR ligands showed strong binding affinities to AR ranging from 0.6 to 54 nM. Among them, thioether and ether linkages demonstrated high binding affinities (0.6 and 4.6 nM, respectively) and selective cell growth inhibition (approximately 3- to 6-fold) for LNCaP, an androgen-dependent prostate cancer cell line, when compared to the androgen independent prostate cell lines (DU145, PC-3, and PPC-1) and a bladder cell line (TSU-Pr1). However, the ligands were inactive (IC50>100 mM) in a normal monkey kidney cell line (CV-1) that was used as the control for non-specific toxicity.

Synthesis and evaluation of succinoyl-caprolactam γ-secretase inhibitors

The synthesis, evaluation, and structure-activity relationships of a series of succinoyl lactam inhibitors of the Alzheimer's disease gamma-secretase are described. Beginning with a screening hit with broad proteinase activity, optimization provided compounds with both high selectivity for inhibition of gamma-secretase and high potency in cellular assays of A beta reduction. The SAR and early in vivo properties of this series of inhibitors will be presented.

Synthesis and structure–activity relationship of a novel, achiral series of TNF-α converting enzyme inhibitors

A novel series of achiral TNF-alpha converting enzyme (TACE) inhibitors has been discovered. These compounds exhibited activities from 0.35 to 11nM in a porcine TACE assay and inhibited TNF-alpha production in an LPS-stimulated whole blood assay with an IC(50) value of 23nM for the most potent one. They also have excellent selectivities over related metalloproteases including aggrecanases.

Synthesis and structure–activity relationship of a novel sulfone series of TNF-α converting enzyme inhibitors

Replacement of the amide functionality in IM491 (N-hydroxy-(5S,6S)-1-methyl-6-[[4-(2-methyl-4-quinolinylmethoxy)anilinyl]carbonyl]5-piperidinecarboxamide) with a sulfonyl group led to a new series of alpha,beta-cyclic and beta,beta-cyclic gamma-sulfonyl hydroxamic acids, which were potent TNF-alpha converting enzyme (TACE) inhibitors. Among them, inhibitor 4b (N-hydroxy-(4S,5S)-1-methyl-5-[[4-(2-methyl-4-quinolinylmethoxy)phenyl]sulfonylmethyl]-4-pyrrolidinecarboxamide) exhibited IC50 values of < 1 nM and 180 nM in porcine TACE (pTACE) and cell assays, respectively, with excellent selectivity over MMP-1, -2, -9 and -13 and was orally bioavailable with an F value of 46% in mice.

Reverse hydroxamate-based selective TACE inhibitors

Reverse hydroxamate-based selective TACE inhibitors are described. They have potent TACE inhibitory activities and excellent selectivities against MMP-1, 2, 3, 8, 9, 13, 14, and 17. One representative compound, 18 has demonstrated an excellent oral inhibitory activity of the lipopolysaccharide (LPS)-stimulated TNF-alpha production in rats.