RSC Medicinal Chemistry Blog

New, effective and selective COX-2 inhibitors that prevent inflammation have been reported in MedChemComm, in a new HOT article.

Cyclo-oxygenases are enzymes responsible for production of key inflammation-promoting molecules. Most drugs that target COX are non-selective and inhibit both COX-2, present in inflamed tissues, and COX-1, which has important regulatory functions in normal tissues. This can lead to gastro-intestinal side-effects such as ulcers.

Dr Marwa El-Gazzar’s group at the National Centre for Radiation Research and Technology in Cairo synthesized new derivatives of celecoxib, a recently discovered COX-2 selective inhibitor. They tested their effect on COX-2 in vitro to study their structure-activity relationship. Several of the compounds – many of which had sulfonamide moieties – were as effective as celecoxib at inhibiting COX-2, while having no effect on COX-1. These compounds were also the most effective at reducing paw oedema in rat models of inflammation, and had significant analgesic effects – importantly, they were non-toxic and did not cause ulceration.

The designed 1,3,4-thiadiazole derivatives and their proposed orientation into the selectivity site of COX-2.

The group also performed a molecular docking study to gain insight into the compounds’ inhibition mechanism. The compounds were found to strongly bind to the COX-2 active site, making them more effective. They could also enter a small pocket found only in COX-2 to bind to specific residues there – this gave them their selectivity.

The promising results for the reported compounds, as well as the mechanistic insights gained, could prove invaluable in developing new, selective drugs that can successfully treat inflammation without adverse side effects.


Read the full article here:

Synthesis of novel thiadiazole derivatives as selective COX-2 inhibitors
Fatma A. Ragab, Helmi I. Heiba, Marwa G. El-Gazzar,* Sahar M. Abou-Seri, Walaa A. El-Sabbagh and Reham M. El-Hazek
Med. Chem. Commun., 2016, Advance Article
DOI:  10.1039/C6MD00367B

Susannah May is a guest web writer for the RSC Journal blogs. She currently works in the Publishing Department of the Royal Society of Chemistry, and has a keen interest in biology and biomedicine, and the frontiers of their intersection with chemistry. She can be found on Twitter using @SusannahCIMay.

A new way of screening for small molecules using PNA-encoded libraries has been reported in MedChemComm. The technique, by Nicolas Winssinger’s group at the University of Geneva, identifies molecules that bind covalently to specific proteins. It could help to find new potent drugs in future.

DNA or PNA-encoded libraries are becoming a popular technique to easily screen large numbers of small molecules. However, it is often difficult to distinguish covalently binding molecules from those that bind non-covalently but with high affinity. Researchers are especially interested in covalent inhibitors as they permanently deactivate proteins and can make powerful drugs, with examples including aspirin and omeprazole.

Winssinger’s group synthesised two libraries of small molecules that were tagged with PNA “barcodes” and immobilised on a surface to form microarrays. These were incubated with a kinase solution and then washed. The group used a washing procedure which removed kinase bound with high-affinity non-covalent bonds, but left any kinase that was covalently bound to molecules. The DNA-PNA bonds were undamaged by the washing, and allowed easy identification and discrimination of the covalently bound and non-covalently bound molecules.

The method could be combined with other techniques such as next-generation sequencing in future. It promises to be the next step in efficient and rapid drug discovery.


Read the full article here:

Screening for covalent inhibitors using DNA display of small molecule libraries functionalized with cysteine reactive moieties
C. Zambaldo, J.-P. Daguer, J. Saarbach, S. Barluenga and N. Winssinger
Med. Chem. Commun. 2016, 7, 1340-1351

Part of the DNA Encoded Libraries themed collection in MedChemComm.

Susannah May is a guest web writer for the RSC Journal blogs. She currently works in the Publishing Department of the Royal Society of Chemistry, and has a keen interest in biology and biomedicine, and the frontiers of their intersection with chemistry. She can be found on Twitter using @SusannahCIMay.