Extension Study of Oral PHA-022121 for Acute Treatment of Angioedema Attacks in Patients with Hereditary Angioedema

Key Inclusion Criteria:

1. Signed and dated informed consent form

2. Diagnosis of HAE type I or II

3. For participants from Study C201, received at least one dose of study drug (including the non-attack visit) in Study C201. For participants from Study C306,participant was randomized (and for adolescent participants 12 to <18 years receiveda dose of study drug in a non-attack state at Visit 1) and completed Study C306,with 2 attacks treated, or after closure of that study by the Sponsor.

4. In the opinion of the Investigator, the participant (and parent/caregiver foradolescent participants) is willing and able to comply with the protocol.

Key Exclusion Criteria:

1. Pregnancy or breast-feeding

2. Any other systemic disease or significant disease or disorder that would interferewith the patient's safety or ability to participate in the study

3. Use of lanadelumab for long-term HAE prophylactic therapy within 12 weeks prior toenrollment in Part A.

4. For Part A: Use of C1-esterase inhibitor, oral kallikrein inhibitors, attenuatedandrogens, anti-fibrinolytics, or monoclonal HAE therapy within a defined periodprior to enrolment. For Part B: If a participant is receiving long-term prophylactic therapy with one ofthe following medications indicated for HAE: plasma-derived C1-INH, danazol at lessthan or equal to 200 mg/day, anti-fibrinolytics, berotralstat, or lanadelumab, theymust be on a stable dose and regimen for at least 3 months before screening andintends to remain on the same dose for the duration of the study.

5. History of alcohol or drug abuse within defined period, or current evidence ofsubstance dependence or abuse

6. Participation in any other investigational drug study within defined period

7. Discontinued from parent study after enrollment for any study drug-related safetyreason.

8. Use of concomitant medications that are potent CYP3A4 inhibitors (e.g.,clarithromycin, erythromycin, itraconazole, ketoconazole, ritonavir, grapefruit) orpotent CYP3A4 inducers (e.g., phenytoin, rifampicin, St. John's Wort).