– The drug “Skyrizi” is advertised in the US as a treatment for 3 seemingly different afflictions – 1) plaque psoriasis, Crohn’s disease, and psoriatic arthritis. How is that possible?


My post is not meant as an ad for that drug.

In the US, we are bombarded with TV ads for drugs, and this drug has some catchy songs they play while advertising stuff. But I noticed that the same drug was advertised to 3 different audiences for 3 different afflictions.

Are these 3 afflictions somehow medically related? How does this one drug solve issues for 3 (to the layman, seemingly) different medical diagnoses?

In: 4

All of those afflictions are caused by an overactive immune system, and Skyrizi works by dampening that immune response. By turning down that reponse, the symptoms for those conditions can improve. That’s why the side effects are so severe. If you turn off your immune system, you’re much more likely to get sick from other diseases.

Some drugs have multiple effects on the body, and have approved usages for multiple ailments. Cymbalta, an antidepressant, has been shown to have pain relieving properties, and is ideal for a depression patient that also has arthritis. Pseudoephedrine is a cold medicine and nasal spray, and is administered via IV to stroke patients to raise their blood pressure and prevent a second stroke. Viagra was first discovered while being investigated as a cardiac medicine; it was only moderately effective as a cardiac medicine but the males in the trial noticed a certain side effect it became famous for

The immune system is sort of like an army defending the body. There are types of cells that are constantly on surveillance, checking various parts of the body looking for invaders. When they find one (like bacteria, viruses, parasites, or fungi, for example), they set off a series of events to try and get rid of the attacker. They’ll call backup quickly – there’s the first line of attack (the innate immune system), where a bunch of soldiers come and try and blow things up to try and get rid of the invaders, but might cause damage to the area. They’ll also take pictures of the invaders and send the info back to HQ to try and get some specialty soldiers (the adaptive immune system) who are really good at fighting those specific invaders without destroying everything else in the way. The immune system is super smart and really really good at what it does.

But sometimes, the surveillance team that’s checking everyone’s IDs to see who might be an invader gets confused. Sometimes they think that perfectly normal cells in the body are actually invaders. When this happens, we call it an autoimmune disease – the immune system is attacking things it shouldn’t be. This is bad, because then normal areas of the body get attacked and damaged – for plaque psoriasis, it’s the skin, for Crohn’s disease the intestines, and for psoriatic arthritis it’s the joints.

Medicines that help patients with autoimmune diseases try and stop the immune response from going ham on perfectly normal cells. A bunch of different medications work to try and slow down the body’s attack process, (the inflammatory pathway) and they can focus on different parts of the response. Some drugs try and stop the bombs that the soldiers throw, some try and block the soldiers themselves, some try and jam the communication systems that the surveillance team uses to call for backup. Skyrizi (risankizumab) is a type of medication in a class called biologics (i.e. big molecules), specifically a monoclonal antibody. Antibodies are the specialty soldiers that are good at fighting off specific invaders. In this case, they’ve designed the antibody to fight off one of the molecules in the inflammatory pathway called IL-23a – basically these soldiers attack the walkie-talkies that the immune system uses and it stops the body from calling in the backup soldiers. The walkie-talkies in this case (IL-23a) are all used to call backup in psoriasis, Crohn’s disease, and psoriatic arthritis, so this medication helps for all of them.

Of course, if the surveillance team’s walkie-talkies have a double-agent team that is trying to disable them (Skyrizi), then the surveillance team might miss out on *actual* invaders. Many of these drugs that work on the immune system can make people more susceptible to infections. Also the body might eventually find out about these double agents, and develop their own specialty soldiers (antibodies) to try and take out the Skyrizi soldiers! This is why sometimes a person will do really well on a medication for years, but then the medication no longer works. It’s a constantly evolving battle!