Aggrecanase-2 inhibitors based on the acylthiosemicarbazide zinc-binding group

Novel dithiocarbamates selectively inhibit 3CL protease of SARS-CoV-2 and other coronaviruses

Since end of 2019, the global and unprecedented outbreak caused by the coronavirus SARS-CoV-2 led to dramatic numbers of infections and deaths worldwide. SARS-CoV-2 produces two large viral polyproteins which are cleaved by two cysteine proteases encoded by the virus, the 3CL protease (3CL^pro) and the papain-like protease, to generate non-structural proteins essential for the virus life cycle. Both proteases are recognized as promising drug targets for the development of anti-coronavirus chemotherapy. Aiming at identifying broad spectrum agents for the treatment of COVID-19 but also to fight emergent coronaviruses, we focused on 3CL^pro that is well conserved within this viral family. Here we present a high-throughput screening of more than 89,000 small molecules that led to the identification of a new chemotype, potent inhibitor of the SARS-CoV-2 3CL^pro. The mechanism of inhibition, the interaction with the protease using NMR and X-Ray, the specificity against host cysteine proteases and promising antiviral properties in cells are reported.

Targeting Aggrecanases for Osteoarthritis Therapy: From Zinc Chelation to Exosite Inhibition

Osteoarthritis (OA) is the most common degenerative joint disease. In 1999, two members of the A Disintegrin and Metalloproteinase with Thrombospondin Motifs (ADAMTS) family of metalloproteinases, ADAMTS4 and ADAMTS5, or aggrecanases, were identified as the enzymes responsible for aggrecan degradation in cartilage. The first aggrecanase inhibitors targeted the active site by chelation of the catalytic zinc ion. Due to the generally disappointing performance of zinc-chelating inhibitors in preclinical and clinical studies, inhibition strategies tried to move away from the active-site zinc in order to improve selectivity. Exosite inhibitors bind to proteoglycan-binding residues present on the aggrecanase ancillary domains (called exosites). While exosite inhibitors are generally more selective than zinc-chelating inhibitors, they are still far from fulfilling their potential, partly due to a lack of structural and functional data on aggrecanase exosites. Filling this gap will inform the design of novel potent, selective aggrecanase inhibitors.

Molecular Design in Practice: A Review of Selected Projects in a French Research Institute That Illustrates the Link between Chemical Biology and Medicinal Chemistry

Chemical biology and drug discovery are two scientific activities that pursue different goals but complement each other. The former is an interventional science that aims at understanding living systems through the modulation of its molecular components with compounds designed for this purpose. The latter is the art of designing drug candidates, i.e., molecules that act on selected molecular components of human beings and display, as a candidate treatment, the best reachable risk benefit ratio. In chemical biology, the compound is the means to understand biology, whereas in drug discovery, the compound is the goal. The toolbox they share includes biological and chemical analytic technologies, cell and whole-body imaging, and exploring the chemical space through state-of-the-art design and synthesis tools. In this article, we examine several tools shared by drug discovery and chemical biology through selected examples taken from research projects conducted in our institute in the last decade. These examples illustrate the design of chemical probes and tools to identify and validate new targets, to quantify target engagement in vitro and in vivo, to discover hits and to optimize pharmacokinetic properties with the control of compound concentration both spatially and temporally in the various biophases of a biological system.

Modulators of hERAP2 discovered by high-throughput screening

Endoplasmic reticulum aminopeptidase 2, ERAP2, is an emerging pharmacological target in cancer immunotherapy and control of autoinflammatory diseases, as it is involved in antigen processing. It has been linked to the risk of development of spondyloarthritis, and it associates with the immune infiltration of tumours and strongly predicts the overall survival for patients receiving check-point inhibitor therapy. While some selective inhibitors of its homolog ERAP1 are available, no selective modulator of ERAP2 has been disclosed so far. In order to identify such compounds, we screened an in-house focused library of 1920 compounds designed to target metalloenzymes. Structure-Activity Relationships and docking around two hits led to the discovery of selective inhibitors of ERAP2. Amid those, some bind to yet untapped amino-acids in the S1 pocket. Importantly, we disclose also the first activator of small substrates hydrolysis by ERAP2. Inhibitors and activators identified in this study could serve as useful starting points for optimization.

ADAMTS5 promotes murine adipogenesis and visceral adipose tissue expansion

Enhanced expression of the aggrecanase ADAMTS5 (A Disintegrin And Metalloproteinase with Thrombospondin type 1 motifs; member 5) has been observed in adipose tissue (AT) of obese rodents. Here, we have investigated the role of ADAMTS5 in adipogenesis, AT expansion and associated angiogenesis. In vitro differentiation of precursor cells into mature adipocytes was studied using murine embryonic fibroblasts (MEF) derived from wild-type (Adamts5(+/+)) and ADAMTS5 deficient (Adamts5(-/-)) mice, or 3T3-F442A preadipocytes with stable gene silencing of Adamts5. De novo adipogenesis was monitored by injection of 3T3-F442A cells with or without Adamts5 knockdown in Nude mice. Furthermore, Adamts5(+/+)and Adamts5(-/-) mice were kept on a high-fat diet (HFD) to monitor AT development. Adamts5(-/-) MEF, as well as 3T3-F442A preadipocytes with Adamts5 knockdown, showed significantly reduced differentiation as compared to control cells. In mice, de novo formed fat pads arising from 3T3-F442A cells with Adamts5 knockdown were significantly smaller as compared to controls. After 15 or 25 weeks on HFD, total body weight and subcutaneous AT weight were similar for Adamts5(+/+) and Adamts5(-/-) mice, but visceral/gonadal fat mass was significantly lower for Adamts5(-/-) mice. These data were confirmed by magnetic resonance imaging. In addition, the blood vessel density in adipose tissue was higher for Adamts5(-/-) mice kept on HFD. In conclusion, our data support the concept that ADAMTS5 promotes adipogenesis in vitro and in vivo, as well as development of visceral AT and associated angiogenesis in mice kept on HFD.

p-SCN-Bn-HOPO: A Superior Bifunctional Chelator for (89)Zr ImmunoPET

Zirconium-89 has an ideal half-life for use in antibody-based PET imaging; however, when used with the chelator DFO, there is an accumulation of radioactivity in the bone, suggesting that the (89)Zr(4+) cation is being released in vivo. Therefore, a more robust chelator for (89)Zr could reduce the in vivo release and the dose to nontarget tissues. Evaluation of the ligand 3,4,3-(LI-1,2-HOPO) demonstrated efficient binding of (89)Zr(4+) and high stability; therefore, we developed a bifunctional derivative, p-SCN-Bn-HOPO, for conjugation to an antibody. A Zr-HOPO crystal structure was obtained showing that the Zr is fully coordinated by the octadentate HOPO ligand, as expected, forming a stable complex. p-SCN-Bn-HOPO was synthesized through a novel pathway. Both p-SCN-Bn-HOPO and p-SCN-Bn-DFO were conjugated to trastuzumab and radiolabeled with (89)Zr. Both complexes labeled efficiently and achieved specific activities of approximately 2 mCi/mg. PET imaging studies in nude mice with BT474 tumors (n = 4) showed good tumor uptake for both compounds, but with a marked decrease in bone uptake for the (89)Zr-HOPO-trastuzumab images. Biodistribution data confirmed the lower bone activity, measuring 17.0%ID/g in the bone at 336 h for (89)Zr-DFO-trastuzumab while (89)Zr-HOPO-trastuzumab only had 2.4%ID/g. We successfully synthesized p-SCN-Bn-HOPO, a bifunctional derivative of 3,4,3-(LI-1,2-HOPO) as a potential chelator for (89)Zr. In vivo studies demonstrate the successful use of (89)Zr-HOPO-trastuzumab to image BT474 breast cancer with low background, good tumor to organ contrast, and, importantly, very low bone uptake. The reduced bone uptake seen with (89)Zr-HOPO-trastuzumab suggests superior stability of the (89)Zr-HOPO complex.

Inhibition of aggrecanases as a therapeutic strategy in osteoarthritis

Over the last decade, there has been a large effort to target aggrecanases, which are responsible for the degradation of the aggrecan in the extracellular matrix of joints, in order to hopefully lead to new treatments for osteoarthritis. Only a few inhibitors have been effective in explants or rodent models and thus only a few have reached the clinic, none of which have proven to be effective. In this article, a survey of chemical series is described, covering historical and recent inhibitors and highlighting how some of their problems were resolved, with a critical overview of the challenges encountered. A large effort should be undertaken in designing smaller compounds with higher residence times, defining new interaction sites on the aggrecanases and exploiting target flexibility.