Biopharmaceutical company Pharming Group N.V. (Euronext Amsterdam:PHARM) (NASDAQ:PHAR) revealed on Monday that the US Food and Drug Administration (FDA) has issued a Complete Response Letter for its supplemental New Drug Application (sNDA) seeking approval of Joenja (leniolisib) for children aged 4 to 11 with activated phosphoinositide 3-kinase delta syndrome (APDS), a rare primary immunodeficiency.

The FDA cited concerns about potential underexposure in lower-weight paediatric patients and requested additional pharmacokinetic data to reassess dosing, as well as further data and clarification on one analytical method used in production batch testing. Approval of Joenja for patients aged 12 years and older remains unaffected.

Pharming said it plans to work closely with the FDA, address the clinical pharmacology and manufacturing issues, and request a Type A meeting to determine next steps for resubmission. The sNDA was supported by Phase III data showing improvements in lymphadenopathy and naïve B cells over 12 weeks, with mild to moderate adverse events and no drug-related serious adverse events. The application received Priority Review in October 2025.

There are currently no approved treatments globally for children under 12 with this condition.