This is a multicenter pharmacokinetic (PK) subtrial to investigate the PK profile of KVD900 (sebetralstat) in adolescent patients 12 to 17 years of age with Hereditary Angioedema (HAE) type I or II.

Inclusion Criteria:

• Male or female adolescent patient 12 to 17 years of age at the time of enrollment and during sample collection in this PK subtrial.
• Patient is currently participating in KVD900-302.
• Patient must provide signed informed consent or assent (when applicable), and a legally authorized representative (LAR) must also provide signed informed consent when applicable.
• Patient and LAR are willing and able to provide samples per the requirements of the protocol, including willingness to complete forms and the electronic Diary, obtain and return samples in a timely manner, and obtain samples while within the required age limit.

Exclusion Criteria:

• Patient has a history of any bleeding disorder or currently taking any anti-coagulant or anti-platelet agent.

Data will not be shared until all global regulatory filings are complete.