The creation and early use of thalidomide is one of the most famous, tragic disasters in drug development history.

It was prescribed to pregnant people for morning sickness in the late 1950s and early 1960s. But it was later discovered that taking thalidomide while pregnant caused serious birth defects.

Once the danger was discovered, thalidomide was pulled from shelves. It’s a landmark story in the stakes of drug safety screenings, and one of the most famous international scandals in modern medicine. So it may come as a shock to hear that we’re still using thalidomide.

Yeah, turns out thalidomide is good for more than just treating nausea. And part of the reason we’ve resurrected the drug has to do with the very same drug testing procedures that it inspired. [♪ INTRO] Now, for starters, it’s pretty hard to overstate just how dangerous thalidomide is during pregnancy. In the ‘50s and ‘60s, it caused at least 10,000 children to be born with severe congenital health problems, from deformed arms to issues with their organs like heart or kidneys.

Up to 40% of these were fatal, and that doesn’t even include countless more thalidomide-affected pregnancies that ended in miscarriages. Once thalidomide’s connection with birth defects were discovered, most countries banned the drug entirely in 1961 and 1962. And one of the legacies of this tragedy is that we realized we needed to step up drug safety standards.

For example, all drugs must now be tested for harm to fetuses in at least two types of animals. More safety is clearly a good thing, but it does have side effects. Those safety measures are a part of what makes developing new drugs very expensive.

Today, a brand new drug costs a company between hundreds of millions and billions of dollars. This high price tag is why pharmaceutical companies and researchers are so interested in using old drugs for new tricks. And as it happens, researchers knew about thalidomide’s potential for treating other conditions, almost right away.

See, just a couple years after thalidomide was banned, a doctor in Israel found it was an effective treatment for Hansen’s Disease, which is also known as leprosy. Decades later, it was approved by the FDA and is still used today to treat complications of that disease. More discoveries followed, with thalidomide shown to be an effective treatment for HIV, lupus, Crohn's disease, and more.

And the reasons thalidomide works in these cases may in fact be linked to why it causes those awful birth defects. Thalidomide binds to a protein called cereblon, which plays a vital role in the developing limbs and organs as a fetus grows. But the interaction between thalidomide and this protein also reduces how many inflammatory molecules get produced.

In particular, a molecule called TNF-alpha. TNF-alpha is essential for our immune systems, but too much can have negative effects, so regulating it can help treat some diseases like autoimmune conditions. In the 1990s, interest in thalidomide started to really ramp up.

In particular, researchers thought maybe it could even help treat cancer. TNF-alpha can both help and hurt the body’s fight against cancer. For instance, it has a role in helping our immune system target some cancer cells.

However, some types of cancer can evade TNF-alpha, or the cancer cells cause a lot of inflammation themselves, and quickly throw this balance off. And that’s why a drug that regulates it can help. But in addition to all that, thalidomide has another trick up its sleeve.

It’s called anti-angiogenesis. Angiogenesis just means the formation of new blood vessels, so anything that causes anti-angiogenesis is just blocking those vessels from growing. Which honestly doesn’t sound like a great thing, since blood vessels are essential for bringing oxygen and nutrients to anything they supply with blood.

But you know what needs to grow a bunch of blood vessels to get bigger? Cancer. Which means that a drug that can prevent new blood vessels from forming can help slow down tumors.

It’s not perfect, though. There are some side effects from this feature of thalidomide, including potential nerve damage. But despite the tradeoffs, the trials investigating cancer treatment with thalidomide were overall pretty successful, showing that it can work against cancers of the esophagus, kidneys, and pancreas, among others.

In 2006 the FDA approved it to treat multiple myeloma, a cancer of the white blood cells. Now, of course, despite all this success, thalidomide does still cause those birth defects. So when it’s prescribed, there is a rigorous safety program that comes along with it.

In the US, thalidomide is controlled under a Risk Evaluation and Mitigation Strategy, REMS program, by the FDA. This means they verify everyone who gets the drug isn’t pregnant already, knows the risks associated, and uses multiple methods of birth control. They also evaluate the risk of medication being mixed up between people in a household, or even being shared inadvertently through intercourse or blood and sperm donations.

Thalidomide can be spread through at least some body fluids so even if you personally aren’t going to become pregnant, you still need to be careful. The program seems to have worked pretty well. When quizzed about the risk of birth defects, over 98% of patients knew the correct answers.

A 2007 study notes that zero new cases of birth defects from thalidomide have been reported in the United States since the drug was approved in 1998! The story of thalidomide is a lesson in the importance of drug safety testing. But it also illustrates that while a certain medication might have nasty side effects, it might still have a crucial role to play in how we treat other illnesses.

As I'm making this video, I'm actually taking chemotherapy right now. And it's wild. They give you the chemo, but before they do they dress up to make sure none of it gets on their skin because it’s dangerous for people.

And then they put it in my veins. Sorry if that's how you found out I have cancer. It's a pretty treatable kind.

We're doing good. And when this works, repurposing something we’ve already studied can be an efficient way to develop new treatments. So here’s to second chances, thalidomide.

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If you’d like to learn more about becoming a patron, head on over to Patreon.com/scishow, and thank you so much for watching and learning with us. [♪ OUTRO]