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Asked by anon-196311 to Sebastian, Paddy, Lee, Jennifer, Fiona, Eleanor on 11 Mar 2019.
Question: do you know what thalidomide is and if so what is it used for now
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Sebastian Cosgrove answered on 11 Mar 2019:
Thalidomide was a drug that was used to treat morning sickness during pregnancy, and was given to pregnant women during the 50s and 60s. This actually led to thousands of babies being born with birth defects, in that their limbs did not form correctly during the pregnancy. The reason for this is because the molecule thalidomide exists in two almost identical forms, called optical isomers (or enantiomers). If you look at two optical isomers they look identical, but they are the mirror images of each other, and we give them the labels R or S. Your hands are example of enantiomers. Hold them out in front of you – they are the same but they are reflections of each other. You have an R and an S hand!
R isomers and S isomers can have dramatically different biological effects, and this was demonstrated in a dramatic fashion by thalidomide. One of the isomers did in fact treat morning sickness, but the other one was what caused the severe birth defects.
The case of thalidomide revolutionised drug discovery, because once it was determined what caused the birth defects, all drugs had to be tested in both forms of optical isomers. This is a challenge, because chemically it can be extremely hard to distinguish between optical isomers and still poses one of the greatest challenges in synthetic chemistry today!
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Fiona Scott answered on 12 Mar 2019:
Thalidomide is a drug product (chemical structure here: http://www.chemspider.com/Chemical-Structure.5233.html) which was known for being withdrawn as an anti-sickness drug for pregnant women in the 1960s. What wasn’t known at the time was that the drug contained two “mirror images” of the same molecule, called “enantiomers”. Much like how you can’t fit your right hand in a left glove, one of the enantiomers caused the desired anti-sickness effect while the other caused learning and physical deformities in the babies of the mothers. There is now a “thalidomide generation” who were affected by this drug. BBC’s Call The Midwife included this in one of their series and it was very powerful (and difficult) to watch at times.
This case study completely changed how drugs are assessed before going into patients and chemists are a lot more careful when their drugs involve enantiomers to be sure to separate them into their two different forms. Of the 70 or so molecules I’ve made so far, only one has the potential to form enantiomers.
Thalidomide is now being used as part of other drug structures to treat prostate cancer, as well as in PROTAC technology, a new way to treat diseases that previously weren’t thought treatable. They won’t be used in pregnant women for obvious reasons but drug repurposing like this is becoming increasingly popular as a way to get more drugs to the market.
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