A Phase III, Crossover Trial Evaluating the Efficacy and Safety of KVD900 (Sebetralstat) for On-Demand Treatment of Angioedema Attacks in Adolescent and Adult Patients With Hereditary Angioedema (HAE)

Inclusion Criteria:

• Male or female patients 12 years of age and older.

• Confirmed diagnosis of HAE type I or II at any time in the medical history.

• Patient has access to and ability to use conventional on-demand treatment for HAEattacks.

• If a patient is receiving long-term prophylactic treatment with one of theprotocol-allowed therapies, they must be on a stable dose and regimen for at least 3months prior to the Screening Visit (except for danazol, which requires a stabledose and regimen for 6 months prior to the Screening Visit). Patient must be willingto remain on a stable dose and regimen for the duration of the trial.

• Patient's last dose of attenuated androgens other than danazol was at least 28 daysprior to randomization.

• Patient:

1. has had at least 2 documented HAE attacks within 3 months prior to screening orrandomization; or

2. is a completer of the KVD824-201 trial within 3 months prior to randomizationand meets all other entry criteria to enroll in KVD900-301

• Patients must meet the contraception requirements.

• Patients must be able to swallow trial tablets whole.

• Patients, as assessed by the Investigator, must be able to appropriately receive andstore IMP, and be able to read, understand, and complete the electronic diary (eDiary).

• Investigator believes that the patient is willing and able to adhere to all protocolrequirements.

• Patient provides signed informed consent or assent (when applicable). A parent orlegally authorized representative (LAR) must also provide signed informed consentwhen required.

Exclusion Criteria:

• Any concomitant diagnosis of another form of chronic angioedema, such as acquiredC1-inhibitor deficiency, HAE with normal C1-INH (previously known as HAE type III),idiopathic angioedema, or angioedema associated with urticaria.

• A clinically significant history of poor response to bradykinin receptor 2 (BR2)blocker, C1-INH therapy or plasma kallikrein inhibitor therapy for the management ofHAE, in the opinion of the Investigator.

• Use of angiotensin-converting enzyme (ACE) inhibitors after the Screening Visit orwithin 7 days prior to randomization.

• Any estrogen containing medications with systemic absorption (such as oralcontraceptives including ethinylestradiol or hormonal replacement therapy) within 7days prior to the Screening Visit.

• Patients who require sustained use of strong cytochrome P450 3A4 (CYP3A4) inhibitorsor inducers.

• Inadequate organ function, including but not limited to:

1. Alanine aminotransferase (ALT) >2x upper limit of normal (ULN)

2. Aspartate aminotransferase (AST) >2x ULN

3. Bilirubin direct >1.25x ULN

4. International normalized ratio (INR) >1.2

5. Clinically significant hepatic impairment defined as a Child-Pugh B or C

• Any clinically significant comorbidity or systemic dysfunction, which in the opinionof the Investigator, would jeopardize the safety of the patient by participating inthe trial.

• History of substance abuse or dependence that would interfere with the completion ofthe trial, as determined by the Investigator.

• Known hypersensitivity to KVD900 or placebo or to any of the excipients.

• Prior participation in trial KVD900-201.

• Participation in any gene therapy treatment or trial for HAE.

• Participation in any interventional investigational clinical trial (with theexception of KVD824-201), including an investigational COVID-19 vaccine trial,within 4 weeks of the last dosing of investigational drug prior to screening.

• Any pregnant or breastfeeding patient.