This Phase 3 study aims to evaluate the efficacy and safety of NTLA-2002 compared to placebo in participants with HAE.

This is a multinational, multicenter, double-blind, placebo-controlled study in which approximately 60 participants will be randomized in a 2:1 ratio to receive a single IV infusion of NTLA-2002 or placebo. After the Primary Observation Period (Week 1 through Week 28), participants will have the option to receive a blinded, single IV infusion of the opposite treatment. Following the Primary Observation Period, participants will enter the Long-Term Observation Period (76 weeks), for a total of 104 weeks. Including the Screening and Run-In Period, prior to the first blinded dosing, the total study duration is approximately 28 months.

Inclusion Criteria:

1. Age ≥16 years
2. Clinical history consistent with HAE-C1INH-Type 1 or -Type 2
3. Ability to provide evidence of HAE attacks (confirmed by the Investigator) to meet the screening requirement
4. Must agree to refrain from the use of long-term prophylactic therapies from the start of the screening period through the end of the Primary Observation Period. PI must be in agreement that it is medically acceptable for the participant to do so.
5. Must have access to, and the ability to use, on-demand medication(s) to treat potential angioedema attacks
6. Adequate chemistry and hematology measures at screening
7. Must agree not to participate in another interventional study for the duration of this trial.
8. Must be capable of providing signed informed consent. Participants 16 to < 18 years of age, whose legal guardian provides informed consent, must provide assent.
9. Must agree to follow contraception requirements

Exclusion Criteria:

1. Concurrent diagnosis of any other type of recurrent angioedema or HAE with normal C1-INH
2. Have known negative reaction or hypersensitivity to any lipid nanoparticles (LNP) component.
3. Any condition that, in the Investigator's opinion, could adversely affect the safety of the subject.
4. Unwilling to comply with study procedures.