The Food and Drug Administration has approved the first medicine for young children with activated phosphoinositide 3-kinase delta syndrome, or APDS, extending a treatment already used in teenagers and adults down to patients as young as 4. The FDA approval, announced September 11, clears Joenja (leniolisib) for children ages 4 to 11 who weigh at least 27 kilograms, in new 40-milligram and 50-milligram twice-daily doses.
APDS is an ultra-rare, inherited immune disorder caused by mutations in the PIK3CD or PIK3R1 genes. It leaves patients prone to recurrent respiratory infections, swollen lymph nodes and enlarged spleens, and carries an elevated lifetime risk of lymphoma. Leniolisib, made by the Dutch biotech Pharming Group, works by blocking the overactive PI3K-delta enzyme at the center of the disease. It was first approved in 2023 for patients 12 and older; this decision is the first to cover the youngest APDS patients in the United States.
A small bridging study, not a new trial
The pediatric approval does not rest on a fresh placebo-controlled trial. Instead, regulators relied on a pharmacokinetic bridging study, known as LE3301, that measured drug levels in just eight children weighing more than 27 kilograms and found no clinically meaningful difference in how the drug is processed compared with patients 12 and older. Efficacy evidence for younger patients leans on extrapolation from the original 12-week, placebo-controlled trial in older patients, which showed reduced lymph node swelling and increased levels of protective naive B cells within its 85-day study period. That is a small sample by the standards of a pediatric drug approval, and it is worth noting plainly: the FDA's decision for 4-to-11-year-olds is grounded far more in dosing science than in a dedicated efficacy trial for that age group.
Reported side effects in the studies included stomach pain, respiratory infections, diarrhea, headache and cough. A separate application covering children weighing between 13 and 27 kilograms was submitted to the FDA in July and remains under review.
"Our immediate priority is to support physicians and families in navigating the access pathway so treatment can start as quickly and responsibly as possible."
Leverne Marsh, Chief Commercial Officer, Pharming Group
The company says Joenja will become available through its specialty distribution network in October. For families of younger children with APDS, who previously had no approved therapy targeting the disease's underlying cause, the approval marks a first option — one regulators and physicians will likely watch closely as more real-world pediatric data accumulate.
