The goal of this long-term extension (LTE) study is to evaluate the safety and efficacy of pegtibatinase in patients with classical homocystinuria (HCU). Patients who are active in the Phase 1/2 COMPOSE study or those who complete the 24 weeks of blinded treatment in the Phase 3 HARMONY are eligible to participate.

Participants will be in this clinical study for a minimum of 108 weeks including:

• a treatment period of up to 104 weeks
• a 4-week safety follow-up period

Overall Design:

This is a global, multicenter, single-arm, open-label study. Participants who meet all eligibility criteria may transition from other pegtibatinase studies and enroll into this LTE study for long-term safety, efficacy, and clinical assessments of pegtibatinase treatment.

All participants will follow a protocol of self-administration of pegtibatinase unless exempted. During the study, pegtibatinase pharmacokinetic assessments will be conducted. An optional protein tolerance modification (PTM) sub-study will also be conducted for eligible participants.

Inclusion Criteria:

• Participants active in the COMPOSE study or who completed the 24-week blinded period on study intervention (pegtibatinase or placebo) in the Phase 3 HARMONY study

Exclusion Criteria:

• Participant permanently discontinued from study intervention treatment in a previous pegtibatinase study due to serious AE (SAE) or intolerance

Requests for clinical trial data, including language stating its intended use, should be directed to datarequest@travere.com. If approved, the requested information will be provided to the requestor after signing a data access agreement. Requests can be made following completion of the study and full publication of the study data in a peer reviewed journal for up to 36 months following its publication. Travere reserves the right to decline or recommend modifications to a request if it does not comply with the data sharing policy or if it is determined that the request is made by a biased source.

Requests can be made following completion of the study and full publication of the study data in a peer reviewed journal for up to 36 months following its publication.

Requires submission and approval of intended use and a data sharing agreement.