Organic Chemists Fighting Blindness


Background - Why is this important?

Picture showing child holding Mectizan
Picture showing child holding Mectizan

© Zul Mukhida/Sightsavers
Onchocerciasis, also known as river blindness, causes debilitating skin disease and is the second-leading infectious cause of blindness. Today 140 million people in Africa are at risk of infection.

This Neglected Tropical Disease (NTD) is caused by wolbachial bacteria that live within the nematode worm, Onchocerca volvulus. When the worms that have infected a person die, they release the bacteria, leading to severe itching and the destruction of the tissue in the human eye resulting in blindness. Globally, over 37 million people are infected, often living in poor, rural African communities but there is an effective drug that only needs to be taken twice a year; Ivermectin (MectizanTM) is a broad spectrum anti-parasitic medicine that kills the larvae and prevents them from causing damage.

What did the organic chemists do?

Modern synthetic organic chemistry played a crucial role in the discovery and manufacture of the highly effective drug Ivermectin. Specifically, organic chemistry helped to convert a natural product, Avermectin, which was less effective into the highly effective drug, Ivermectin.

A reaction called catalytic hydrogenation, was used to change one of the five carbon-carbon double bonds in the chemical structure of avermectin into a single bond. Changing this one bond alters the 3D shape of the molecule hence improving its safety and efficacy making it a more effective drug against the spread of the disease.

Avermectin and Ivermectin

Catalytic Hydrogenation of Avermectin

The transformation of the double carbon-carbon bond into a single bond is tricky, because the other double bonds in the avermectin molecule must be left unchanged for the drug to work. By using a specific catalyst called Wilkinson's catalyst, the reaction can take place. Wilkinson's catalyst is one of the prototype organometallic catalysts, (Ph3P)3RhCl, which is named after the British chemist and 1973 Nobel Laureate, Sir Geoffrey Wilkinson. 

What was the impact?

In collaboration with the World Health Organisation, Ivermectin has been used in over 200 million people worldwide.

Catalysis was recognized with the 2001 Nobel Prize for chemistry (Knowles, Noyori and Sharpless) and it is still an important area of new chemistry research today. It has been used in the manufacture of many other medicines but scientists are still restricted in the types of new molecules that can be made in the laboratory. Fortunately, new research into organic synthesis is underway in many UK universities which allows medicinal chemists to design new drugs for cancer, heart disease, diabetes and infections.


Related Links

Link icon Sightsavers
Sightsavers work with partners to eliminate avoidable blindness in the developing world

Link icon Merck
The Merck (Mectizan) Donation Program provides free treatment for river blindness (onchocerciasis) in endemic countries worldwide

Link icon UNICEF
UNICEF partners with Merck & Co. to fight onchocerciasis, a neglected tropical disease


External links will open in a new browser window



Also of interest

Switch

Catalysis at the flick of a switch

14 March 2012

A nanoswitch that can be turned on or off by copper(I) ions can be used to control an organic reaction



Cells dividing

One-pot synthesis creates anticancer candidates

03 January 2012

A rapid, high-yield approach produces indole alkaloid natural product analogues that can interfere with cell division



Telephone

‘Dial a molecule’ approach controls antibiotic production

11 August 2011

The structure of the pacidamycin antibiotics can be refined by genetic tinkering


Contact and Further Information

Dr Anne Horan
Programme Manager, Life Sciences
Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, CB4 0WF
Tel: 01223 432699