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

Key inclusion 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 theprotocol and be willing to adhere to study restrictions and examination schedules.

3. Participant has a physician confirmed and documented diagnosis of a symptomatic LyMat the time of informed consent (Note: the physician must confirm that the LyMcannot be included under the PROS diagnostic criteria).

4. Participant is not considered as a candidate for or is not willing to receivenon-drug therapies including but not limited to sclerotherapy, embolization, andsurgery 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 torandomization.

6. Participant has at least one measurable LyM lesion confirmed by BIRC assessmentprior to randomization.

7. Participants must be able to ingest study drug (either in tablet form or as adrinkable 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 viafeeding tubes is allowed.

Key exclusion criteria:

1. Participant has a physician-confirmed and documented diagnosis of PROS at the timeof informed consent.

2. Participant has a physician-confirmed and documented diagnosis of a CentralConducting 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, ortoxic epidermal necrolysis at the time of informed consent.

4. Participant has an established diagnosis of type I diabetes mellitus or uncontrolledtype II diabetes mellitus at the time of informed consent.

5. Participant had previous treatment with alpelisib and/or any other PI3K inhibitorswith treatment duration longer than 2 weeks at the time of informed consent.

Other inclusion/exclusion criteria may apply