A Study of Lanadelumab (SHP643) in Chinese Participants With Hereditary Angioedema (HAE)

Inclusion Criteria:

1. Be of Chinese descent, defined as born in China and having Chinese parents and Chinese maternal and paternal grandparents.
2. The participant is male or female and greater than or equal to (>=) 12 years of age at the time of informed consent.

Documented diagnosis of HAE Type I or Type II based upon all of the following:

1. Documented clinical history consistent with HAE (subcutaneous [SC] or mucosal, nonpruritic swelling episodes without accompanying urticaria).
2. Diagnostic testing results obtained during screening by a laboratory (approved by the sponsor) that confirm HAE Type I or Type II: C1 esterase inhibitor (C1-INH) functional level <40% of the normal level. Participants with functional C1-INH level 40% to 50% of the normal level may be enrolled if they also have a C4 level below the normal range. Participants may begin participating in the run-in period before these diagnostic results are available. Participants may be re-tested if results are incongruent with clinical history or believed by the investigator to be confounded by recent long-term prophylaxis (LTP) use.
3. At least one of the following: Age at reported onset of first angioedema symptoms less than or equal to (<=) 30 years, a family history consistent with HAE Type I or Type II, or C1q within normal range.

Attack rate:

• At the time of enrollment, participants must experience at least 1 investigator-confirmed HAE attack per 4 weeks during the run-in period.

The participant (or the participant's parent/legal guardian, if applicable) has provided written informed consent approved by the institutional review board (IRB)/ institutional ethical committee (IEC).

• If the participant is an adult, be informed of the nature of the study and provide written informed consent before any study-specific procedures are performed.

OR

• If the participant is a minor (that is <18 years of age), have a parent/legal guardian who is informed of the nature of the study provide written informed consent (that is, permission) for the minor to participate in the study before any study-specific procedures are performed. Assent will be obtained from minor participants.

1. Males, or non-pregnant, non-lactating females who are fertile and sexually active and who agree to be abstinent or agree to comply with the applicable contraceptive requirements of this protocol for the duration of the study, or females of non-childbearing potential, defined as surgically sterile (status post hysterectomy, bilateral oophorectomy, or bilateral tubal ligation) or postmenopausal for at least 12 months.
2. Agree to adhere to the protocol-defined schedule of assessments and procedures.

Exclusion Criteria:

1. Concomitant diagnosis of another form of chronic, recurrent angioedema, such as acquired angioedema, HAE with normal C1 esterase inhibitor (C1-INH) (also known as HAE Type III), idiopathic angioedema, or recurrent angioedema associated with urticaria.
2. Participation in a prior lanadelumab study or use any lanadelumab prior to the study.
3. Dosing with investigational drug or exposure to an investigational device within 4 weeks prior to entering to screening.
4. Exposure to angiotensin-converting enzyme inhibitors or any estrogen-containing medications with systematic absorption (such as oral contraceptives or hormonal replacement therapy) within 4 weeks prior to screening.
5. Exposure to androgens (that is, danazol, methyltestosterone, testosterone) within 2 weeks prior to entering the run-in period.
6. Use of LTP therapy (defined as continued use) for HAE (C1-INH, attenuated androgens, or anti-fibrinolytics) for adult participants within 2 weeks prior to entering the run-in period. Adolescent participants (>=12 to <18 years of age) who are on LTP therapy for HAE are allowed to enter the study.
7. Use of short-term prophylaxis for HAE 7 days prior to entering the run-in period. Short-term prophylaxis is defined as fresh frozen plasma (FFP), C1-INH, attenuated androgens, or antifibrinolytics used to avoid angioedema complications from medically indicated procedures. Note: Currently, C1-INH therapies are not available in China.
8. Any of the following liver function abnormalities: alanine aminotransferase (ALT) greater than (>) 3* upper limit of normal (ULN), or aspartate aminotransferase (AST) > 3* ULN or bilirubin > 2* ULN (unless the bilirubin is a result of Gilbert's syndrome).
9. Pregnancy or breast feeding.
10. Participant has any condition that in the opinion of the investigator or sponsor, may compromise their safety or compliance, preclude successful conduct of the study, or interfere with interpretation of the results (example, history of substance abuse or dependence, significant pre-existing illnesses or major comorbidity the investigator considers may confound the interpretation of the study results).