Interleukin-23 (IL-23) sits upstream in the chain of signals that produces a psoriasis plaque. It is the messenger that keeps a particular group of immune cells alive and pumping out IL-17, which in turn tells skin cells to overgrow and pulls inflammation into the skin.
Risankizumab is a lab-made antibody that binds the p19 part of IL-23 and takes it out of circulation. Cut the supply line and the whole downstream cascade winds down.
Two practical consequences follow from acting upstream rather than at the end of the chain. First, the effect builds more slowly than with an IL-17 blocker but goes deeper and lasts longer — which is why one injection can hold for three months. Second, because it does not block IL-17 directly, it does not carry the yeast infection problem that comes with Cosentyx, and it does not worsen inflammatory bowel disease. In fact it treats it.
There is no known interaction with alcohol, and no special sun precautions beyond ordinary skin care. There are no significant drug-drug interactions to worry about — biologics like this are broken down like proteins, not by the liver enzymes that cause most drug interactions.
If you are being treated for Crohn's disease or ulcerative colitis rather than psoriasis, the label requires liver enzymes and bilirubin before starting. For psoriasis it does not.
IL-23 blockers build slowly and then hold. Expect visible thinning of plaques by 4 weeks, substantial clearing by 8 to 12 weeks, and your best result at around 16 weeks — which is roughly when the third injection is due.
If you are still substantially flaring at 16 weeks on the full schedule, that is the point to discuss switching, not before.
Scalp psoriasis usually follows the body but can lag a few weeks. Nail psoriasis takes far longer — six months to a year — because the damaged nail has to grow out. Do not judge nails at 16 weeks.
Psoriatic arthritis joint symptoms typically improve over the first few months. IL-23 blockers tend to be stronger on skin than on joints, so if your arthritis is the dominant problem, say so early.
One characteristic of this class: the response is durable. Many people stay clear across the whole 12 weeks, and long-term data show clearance holding for years rather than gradually slipping.
Skyrizi controls psoriasis; it does not cure it.
Because the drug lingers in your system, the disease does not come back the moment you stop. Most people go months — often three to six, sometimes longer — before plaques return in a meaningful way. It comes back gradually, not as a rebound flare, and it usually returns to roughly the severity you had before rather than something worse.
If you restart later, risankizumab generally works again. Antibodies against the drug that meaningfully block its effect are uncommon.
Some people ask whether they can stretch the interval to reduce cost or exposure. That is a conversation to have with your dermatologist, not a decision to make alone — but it happens, and it is not unreasonable in someone who has been clear for a long time.
If you stop because it is not working, sensible alternatives are Tremfya, an IL-17 blocker like Cosentyx, or the oral drug Sotyktu.