• Age ≥18 years at the time of signing informed consent.

• Provided written informed consent and any authorizations required by local law and be willing to comply with all study requirements for the duration of the study.

• Have a documented diagnosis of HAE-1/HAE-2 (Type I or II) based upon ALL of the following (a, b, AND c):

‣ Documented clinical history consistent with HAE (SC or mucosal, non-pruritic swelling episodes without accompanying urticaria).

⁃ Diagnostic testing (historical documentation or during Screening, with option of one repeat test) that confirms 2 of the following:

• C1-INH antigen level \<50% the lower limit of normal (LLN).

∙ C1-INH functional level \<50% LLN.

∙ C1-INH function ≥50% but ≤60% and a pathogenic mutation in the SERPING1 gene.

∙ Complement factor C4 level below the LLN.

⁃ Have at least one of the following:

• Age ≤30 years at reported HAE onset.

∙ A family history consistent with HAE-1/HAE-2.

∙ Complement component 1q within the normal range.

• Experienced ≥1 Investigator-confirmed HAE attack in the first 4 weeks of Screening or ≥2 Investigator-confirmed HAE attacks in 8 weeks of Screening.

• Have access to, and the ability to use, at least one acute HAE therapy to treat HAE attacks (eg, plasma-derived or recombinant C1-INH concentrate or a BK2-receptor antagonist) that has previously been shown to be effective for the participant.

• Participants must be deemed medically appropriate for on-demand treatment as the sole medicinal management for their HAE during the study, per Investigator.

• Women of childbearing potential must have a negative serum pregnancy test during Screening and a negative urine pregnancy test on Study Day 1 before study drug administration and must agree to use acceptable contraceptive methods if engaged in sexual activity of childbearing potential (refer to Section 13.2.2) from the time of signing the informed consent form (ICF) until the EOS Visit or 1 month after study drug administration, whichever is longer.