Activated phosphoinositide 3-kinase delta (PI3K-delta) syndrome (APDS) is a rare, inherited condition that affects your immune system. It's caused by a change (variant) in one of two genes, PIK3CD or PIK3R1, that help control a protein called PI3K-delta. This protein normally helps manage the growth and function of certain immune cells. In APDS, PI3K-delta becomes overactive, which throws the immune system off balance.
People with APDS often deal with repeated sinus, ear, and lung infections, swollen lymph nodes, an enlarged spleen, and other immune-related problems. Some also develop autoimmune conditions, digestive issues, lung scarring (bronchiectasis), or a higher risk of certain lymphomas. Because APDS is genetic, it's usually confirmed through blood testing that looks for a PIK3CD or PIK3R1 variant.
Joenja (leniolisib) is a prescription medicine and the first treatment designed to target the underlying cause of APDS rather than just its symptoms. The FDA first approved Joenja in 2023 for people who are 12 years and older with APDS and then expanded the approval in September 2026 to include children as young as 4 years who weigh at least 27 kg (about 60 lbs).
This article covers how Joenja works, who it's approved for, how it's taken, and what clinical studies found. You may also want to read about the side effects and interactions of Joenja in a separate article.
How Does Joenja Work for APDS?
PI3K-delta is part of a family of related proteins that help control how immune cells called B cells and T cells grow, mature, and respond to threats. A variant in the PIK3CD gene causes PI3K-delta itself to become overactive, while a variant in PIK3R1 removes a normal "brake" on PI3K-delta, leading to the same kind of overactivity. Either way, PI3K-delta stays switched on too much of the time.
This overactivity confuses B cells and T cells. Instead of maturing normally, many of these cells get stuck at earlier, less useful stages, while others wear out and stop working well before they should. The result is an immune system that struggles to fight off certain infections while also overreacting in ways that cause swollen lymph nodes and other signs of excess immune tissue growth (lymphoproliferation).
Joenja works by fitting into the active site of PI3K-delta and blocking it. In lab studies, Joenja was much more selective for PI3K-delta than for related proteins in the same family (PI3K-alpha, PI3K-beta, and PI3K-gamma), which may help limit its effects on unrelated processes in the body. By blocking PI3K-delta, Joenja reduces activity further down an internal signaling chain that normally tells B and T cells how much to grow and divide. Taking Joenja seems to reduce markers of this overactivity in B cells, helping many B and T cells return to more typical patterns of growth and function.
Is Joenja Right for Me?
Joenja is approved for the treatment of APDS in adult and pediatric patients 4 years and older who weigh 27 kg (about 60 lbs) or greater.
To be considered for Joenja, you'll first need a confirmed diagnosis of APDS, meaning genetic testing has identified a variant in PIK3CD (sometimes called APDS1) or PIK3R1 (APDS2). Your health care provider will also look at your overall health, current symptoms, and any treatments you've already tried, as APDS can be managed in different ways depending on how it's affecting you.
Joenja hasn't been studied in children younger than 4 years or in anyone who weighs less than 27 kg.
How Do I Take Joenja?
Before you start Joenja, your health care provider will check whether you are pregnant (if you're someone who can become pregnant) because Joenja may cause harm to a fetus.
Joenja is a tablet you take by mouth twice a day, about 12 hours apart. It can be taken with or without food. Your dose depends on your age and weight:
| Age | Body Weight | Dose |
|---|---|---|
| 4 years to less than 12 years | 27 kg to less than 38 kg | 40 mg twice daily |
| 4 years to less than 12 years | 38 kg to less than 45 kg | 50 mg twice daily |
| 4 years to less than 12 years | 45 kg or greater | 70 mg twice daily |
| 12 years and older | Any weight | 70 mg twice daily |
If you miss a dose by more than six hours, skip it, and take your next dose at the usual time. If you vomit within an hour of taking Joenja, take another dose as soon as you can. If it's been more than an hour since you took Joenja, just wait and take your next scheduled dose when you normally would.
Don't stop taking Joenja or change your dose on your own, even if you're feeling well. Talk to your health care provider first.
How Was Joenja Studied for APDS?
The approval for people 12 years and older was based mainly on a clinical trial called Study 2201. This was a 12-week study comparing Joenja to a placebo (a look-alike tablet with no medicine in it). Neither the participants nor the study team knew who was taking Joenja and who was taking the placebo until the study ended. This helps keep the results from being influenced by expectations.
The study enrolled 31 people with APDS, aged 12-54 years. Participants were assigned by chance to one of two groups: 21 people received Joenja 70 mg twice daily, and 10 people received a placebo. At the start of the study, participants were in their 20s on average, with roughly equal numbers of male and female participants.
Most study participants were White, with only small numbers of Asian, Black, or other races represented. About 70% of the participants were not Hispanic or Latino, more than 20% did not report their ethnicity, and less than 10% were Hispanic or Latino. Most participants had the PIK3CD gene variant (APDS1) rather than PIK3R1 (APDS2). Many were also taking other treatments for APDS, such as glucocorticoids or immunoglobulin replacement therapy, and they continued these throughout the study.
Researchers tracked two main measures: how much participants' swollen lymph nodes shrank, based on imaging scans (CT or MRI), and how much the percentage of "naive" B cells, a healthier, less worn-out type of immune cell, increased out of participants' total B cells, based on blood tests.
For children aged 4 years to less than 12 years, Joenja's dosing and safety were studied separately in a small, eight-patient study that didn't compare Joenja to a placebo. Instead, researchers used blood tests to confirm that this age group absorbed and processed Joenja similarly to older patients.
What Are the Main Benefits of Joenja Based on Studies?
After 12 weeks, both of the study's main measures showed a clear benefit for Joenja over the placebo.
Lymph node size. People taking Joenja saw their swollen lymph nodes shrink more than people taking the placebo did. Overall, 26% of people taking Joenja had their swollen lymph nodes go away completely, and the rest had at least a partial reduction in size. In the placebo group, some people had a partial improvement, but many showed little change, and one person's lymph nodes continued to grow.
Naive B cells. The percentage of naive B cells out of total B cells increased by about 37 percentage points in the Joenja group compared to the placebo group. This is a sign that the immune system was starting to make and maintain healthier B cells, rather than getting stuck with older or less functional ones.
Your results may differ from what was seen in clinical studies.
Are There Additional Potential Benefits of Joenja Based on Studies?
Beyond the two main measures, researchers also looked at many other changes:
Spleen size. People taking Joenja had a bigger decrease in spleen size than those taking the placebo. Among people who started the study with an enlarged spleen, 38% of those taking Joenja saw it return to a normal size within 12 weeks, compared with 20% of those taking the placebo.
Immunoglobulin M (IgM) levels. IgM, an antibody that's often elevated in APDS, dropped by an average of about 208 mg/dL in the Joenja group, compared with only about 10 mg/dL in the placebo group.
T-cell balance. Many people with APDS have an imbalance between two types of T cells, often labeled CD4+ and CD8+. In the Joenja group, this balance moved closer to what's typically seen in a healthy immune system.
Low blood cell counts (cytopenias). Among people who started the study with low blood cell counts, such as anemia, 82% of those taking Joenja saw improvement, compared with 60% of those taking the placebo.
Reported quality of life. Formal quality-of-life surveys didn't show a clear difference between groups. But study investigators reported that 70% of the people taking Joenja, compared with 44% taking the placebo, noticed improvements in things such as energy levels and tolerance for physical activity.
Your results may differ from what was seen in clinical studies.
How Long Were the Studies? Is There Longer-Term Data?
The placebo-controlled part of Study 2201 lasted 12 weeks. Because APDS can worsen over time, it wasn't considered fair to keep people on a placebo much longer than that.
After the initial 12 weeks, participants could continue taking Joenja in an open-label extension, meaning everyone knew they were getting the active medicine. Looking at everyone who has taken Joenja in clinical trials and afterward, most people have been treated for well over a year: 66% were treated for about two years or longer, and some people have now been taking Joenja for more than five years. This longer-term experience is where much of what's known about Joenja's safety over time comes from.
Is There Any Cost Assistance Available for Joenja?
Joenja requires a prescription and is typically prescribed by an immunologist or another specialist experienced in treating APDS.
Pharming, the drugmaker of Joenja, offers a patient support program that can help with insurance questions, connect you with financial assistance if you qualify, and provide ongoing support from a dedicated care team. You can learn more at joenja.com or by calling 877-796-2737.