The purpose of this study is to evaluate the long-term safety and tolerability of MBX 2109 in patients with hypoparathyroidism who completed the 12-week treatment period in the Phase 2 study, MBX-2H1002.

This study is to investigate the long-term safety and tolerability of MBX 2109 administered once weekly to patients with hypoparathyroidism. Additionally, the ability of MBX 2109 to maintain serum calcium levels within the normal range without the need for active vitamin D and to reduce elemental calcium supplements to ≤600 mg/day.

Key Inclusion Criteria:

1. Must have completed the Week 12 Visit in MBX-2H1002 Study.

2. Is an adult ≥18 years of age at the time of the Screening visit of this extension study.

3. Has a diagnosis of one of the following types of hypoparathyroidism for at least 26 weeks prior to the

   Screening visit:

   1. Postsurgical chronic hypoparathyroidism
   2. Idiopathic hypoparathyroidism
   3. Autoimmune hypoparathyroidism

4. Can comprehend and is willing to sign an informed consent form (ICF), and abide by the study restrictions, study visits, and procedures.

5. In the opinion of the investigator, must be able to successfully demonstrate reconstitution and self-administration of study drug.