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New Method for Synthesising Sulphur-Based Medicines Can Boost Drug Discovery Efficiency and Speed

When tested on Celecoxib, an approved drug for arthritis, researchers successfully produced several different pharmacophores that could be used to develop similar drugs.

In every successful drug, there is a special part of it that physically fits into the biochemical pathway that the drug is trying to disrupt. This special segment is called the pharmacophore, defined as the 3D arrangement of a drug’s functional molecule that is necessary to ensure optimal interactions with a biological target. Producing new pharmacophores is a key objective in drug discovery. Of the various kinds of pharmacophores, sulphur-based ones are considered to be highly versatile and promising. However, they are rarely used in practice due to the difficulties faced in producing them.

Finding a way around this problem, scientists at Nanyang Technological University (NTU) have recently designed a novel approach to synthesise sulphur pharmacophores by using pentanidium, a catalyst specially created by the scientists themselves. By demonstrating how these new sulphur pharmacophores could be used to modify and repurpose existing drugs, their method raises hope for developing new therapeutic “weapons” to treat various diseases.

“The process of drug discovery is akin to finding the right key to a lock – it involves testing drug candidates with different pharmacophores until a certain combination proves to be effective in modulating a biological pathway. We essentially developed a method that could allow us to make many different types of sulphur-based pharmacophores that are compatible with different drug compounds. This is a valuable addition to the toolkit of drug discovery programmes,” said Professor Tan Choon Hong, Chair of School of Physical and Mathematical Sciences and lead author of the study.

More than half of existing drugs today are chiral, which means that they cannot be superimposed on their mirror image and therefore exist in either a left- or right-handed form that are mirrors of each other. While they possess the same chemical makeup, chiral molecules have different arrangements of their atoms, implying that they can behave drastically different from one another. For instance, one could induce therapeutic effects for a disease, whereas the other could be inactive or even cause toxicity. Therefore, drug developers have long endeavoured to synthesise pharmacophores in their desired single forms to eliminate the risk of side effects. Unfortunately, this remains to be a challenging task. Medicinal chemists, who are keen to use sulphur-based compounds as pharmacophores, still struggle in synthesising sulphur-based pharmacophores into only either the single left- or right-handed form. Present methods largely focus on producing only one type of pharmacophore.

In the current study, the NTU researchers have reported that their approach can generate a series of sulphur-based pharmacophores with sufficient variation to improve the efficiency and success of the drug discovery process. To generate the sulphur pharmacophores, Prof. Tan and colleagues first added a sulphur compound to an acyl chloride and thiolate. They then used pentanidium – a catalyst developed by the NTU scientists in a previous study – to induce asymmetric synthesis, a chemical reaction that results in just a single form, rather than a mixture of both forms being produced.

To demonstrate the value of their approach, the researchers tested their synthesis method on the arthritis drug Celecoxib. Their experiment led to the development of several different pharmacophores that could be used to develop similar drugs.

“Our approach not only allows us to make variations of pharmacophores to speed up drug discovery but also allows us to pair a pharmacophore with an existing drug and see how it alters the drug’s function. This is exciting to the medicinal chemist because you can now improve on existing drugs or develop new therapies without having to start from scratch,” added Prof. Tan. [APBN]

Source: Zhang et al. (2022). Synthesis of chiral sulfinate esters by asymmetric condensation. Nature.