The itch won’t quit. So you scratch. Then your skin burns, cracks, and flares. If you have atopic dermatitis (AD), you know the cycle all too well.
Maybe you’ve tried steroid creams or other ointments, but they don’t help enough. Scientists have searched for a new approach – one that targets the root cause of itch.
Now, that treatment is here.
In December 2024, the FDA approved nemolizumab (Nemluvio) for people 12 and older with moderate-to-severe AD that hasn’t improved with prescription creams or ointments. But this drug didn’t make it to market overnight. It took years of research, clinical trials, and expert review to get here.
Here’s how it happened.
Step 1: The Science Behind Nemolizumab
In the early 2010s, scientists at Chugai Pharmaceutical Co. in Japan zeroed in on a potential way to stop chronic itch at its source. They focused on interleukin-31 (IL-31), a protein known for triggering inflammation and itching. Because of this link, researchers often call it the “itch cytokine.”
Cytokines are messengers that help regulate the body’s immune system. IL-31 tells nerves and cells to trigger itching. This can be helpful – it makes you flick away a mosquito or scratch off something harmful. But when the signal won’t turn off, the itch itself becomes the problem.
People with AD tend to have high levels of IL-31 all the time, which scientists think explains why their skin itches nonstop. Earlier studies also showed that when researchers gave IL-31 to mice, dogs, or humans, they started scratching.
That raised a key question: If you block IL-31, can you stop the itch? To test that theory, scientists created a drug that could do just that.
Nemolizumab is a biologic medication called a monoclonal antibody – a lab-made protein that targets certain parts of your immune system. In this case, it blocks IL-31 from attaching to its receptors (IL-31RA).
By doing this, the drug disrupts the itch-scratch cycle. With less IL-31 activity, nerves don’t send itch signals to the brain, and inflammation goes down. This not only reduces itching but also allows the skin to heal, which helps prevent future flares.
Step 2: Early Testing
Nemolizumab is a shot you give yourself once a month or every other month. It comes in a prefilled injector pen that you can get shipped directly to your home.
But before doctors could prescribe it, scientists had to prove it worked and wouldn’t cause harm.
They ran lab tests and animal studies (in mice and monkeys) to see if the drug reduced itching and whether it caused any serious side effects. Only when they passed this stage could they move to research in humans.
Step 3: Testing in People
Clinical trials are studies that test new drugs in volunteers. They follow strict rules and medical guidelines. Scientists run them in phases to make sure a treatment is safe and works before approval.
Nemolizumab went through three phases:
Phase I. Researchers tested nemolizumab in a small group of people with and without atopic dermatitis. At this stage, they checked how the body processed the drug. The results were promising. There were no major safety concerns, and some people with AD said they felt less itchy.
Phase II. Researchers focused on safety and effectiveness in a larger group. Hundreds of people with moderate-to-severe AD took part.
One study lasted 12 weeks, and another lasted 24 weeks. In both, people who got monthly doses of nemolizumab had less itching and clearer skin than those who got a placebo (a look-alike treatment with no active ingredient).
People in both groups could use their standard topical treatments during the study.
Phase III. The ARCADIA 1 and 2 trials followed more than 1,100 people with moderate-to-severe AD for about a year. This included adults and adolescents ages 12 to 17. All had symptoms that weren’t well controlled by skin creams or ointments.
Many people taking nemolizumab felt less itchy within the first week. By week 16:
- 36%-38% had clear or almost-clear skin, compared to 24%-26% in the placebo group.
- 42%-44% had a 75% improvement in AD severity, compared to 29%-30% in the placebo group.
- 34%-36% reported better sleep, compared to 16%-20% in the placebo group.
These trials confirmed that nemolizumab provided meaningful relief and better quality of life for people with AD without serious side effects.
How safe was nemolizumab in clinical trials?
Studies found no major safety concerns. Serious side effects were rare, and most people continued using the drug.
The most common side effect was headache. Like with any shot, some people had redness, swelling, or pain where the needle went in, which usually went away in a few days.
Some people also reported:
- Muscle or joint pain
- Upset stomach
- Worsening eczema or skin irritation
- Hives or other mild rashes
- Colds or stuffy nose
Serious reactions were rare, but a small number of people:
- Had asthma flares during treatment
- Experienced facial swelling, a possible sign of allergic reaction
If you try nemolizumab, your doctor will watch for serious problems after your first dose. But if your face or lips swell while taking any drug, get medical help right away.
It’s unknown whether nemolizumab is safe for pregnant people. But early animal studies show blocking IL-31 doesn’t seem to affect pregnancy, breastfeeding, or growth and development in baby monkeys.
Step 4: Checking by Experts
Even if a drug looks promising in studies, it doesn’t get approved right away. The FDA’s Center for Drug Evaluation and Research (CDER) carefully reviews all the data to make sure it’s ready for use. CDER scientists include doctors, chemists, and other medical specialists.
This process helps the FDA set guidelines on how to use nemolizumab safely.
How long did FDA approval take?
From discovery to FDA approval, the process took more than 10 years. Here’s a look at key milestones:
- 2004: Scientists discover IL-31.
- 2010s: Researchers develop nemolizumab to block IL-31.
- 2011-2012: First human studies begin.
- 2017: A major study shows nemolizumab is safe and works well.
- 2018-2023: More clinical trials test long-term safety and benefits.
- August 2024: FDA approves nemolizumab for prurigo nodularis.
- December 2024: FDA approves nemolizumab for atopic dermatitis.
Step 5: Watching Over Time
Even after FDA approval, experts keep a close watch on a drug’s safety and effectiveness. This is called postmarket surveillance. It helps catch any side effects that didn’t show up in earlier trials.
Doctors and researchers report any new problems to the FDA, and the agency updates safety guidelines when needed. If serious issues come up, the FDA alerts the public. In some cases, they might even pull an approved drug from the market if they find it’s harmful.
So far, no new safety concerns have been reported with nemolizumab.
Should You Try Nemolizumab?
If other AD treatments haven't worked, nemolizumab might be worth exploring. It’s been well-studied, proven effective, and carefully reviewed for safety. Talk to your doctor to see if it’s right for you.
Each new medicine builds on past treatments, making care safer and better. Researchers spent years testing nemolizumab before the FDA approved it. But the work isn’t over – experts will keep studying the drug to make sure it remains a reliable treatment.
