Alpelisib in Pediatric and Adult Patients With Lymphatic Malformations Associated With a PIK3CA Mutation.

Eligibility Criteria

• 1. Signed informed consent and assent (when applicable) from the participant, parent, legal authorized representative or guardian.
• 2. Participant must be willing to remain at the clinical site as required by the protocol and be willing to adhere to study restrictions and examination schedules.
• 3. Participant has a physician confirmed and documented diagnosis of a symptomatic LyM at the time of informed consent (Note: the physician must confirm that the LyM cannot be included under the PROS diagnostic criteria).
• 4. Participant is not considered as a candidate for or is not willing to receive non-drug therapies including but not limited to sclerotherapy, embolization, and surgery until the completion of Week 24 in Stage 1 and 2.
• 5. Participant has evidence of a somatic mutation(s) in the PIK3CA gene prior to randomization.
• 6. Participant has at least one measurable LyM lesion confirmed by BIRC assessment prior to randomization.
• 7. Participants must be able to ingest study drug (either in tablet form or as a drinkable suspension \[Groups 1 to 4\] or granules or as an oral suspension \[Group 5\]) as assessed within 7 days before study treatment start. Drug administration via feeding tubes is allowed.
• 1. Participant has a physician-confirmed and documented diagnosis of PROS at the time of informed consent.
• 2. Participant has a physician-confirmed and documented diagnosis of a Central Conducting Lymphatic Anomaly, General Lymphatic Anomaly, Gorham-Stout disease, Kaposiform lymphangiomatosis at the time of informed consent.
• 3. Participant has a known history of Stevens-Johnson syndrome, erythema multiforme, or toxic epidermal necrolysis at the time of informed consent.
• 4. Participant has an established diagnosis of type I diabetes mellitus or uncontrolled type II diabetes mellitus at the time of informed consent.
• 5. Participant had previous treatment with alpelisib and/or any other PI3K inhibitors with treatment duration longer than 2 weeks at the time of informed consent.