An Extension Study of KRN23 in Adults With X-Linked Hypophosphatemia

An Open-Label, Long-Term, Extension Study to Evaluate the Safety and Efficacy of KRN23 in Adult Subjects With X-Linked Hypophosphatemia

The primary purpose of this study is to assess the safety and efficacy of repeated subcutaneous (SC) injections of KRN23 in adult subjects with X-Linked Hypophosphatemia (XLH).

Inclusion Criteria:

1. Satisfactory completion of KKP's sponsored KRN23-INT-001 clinical trial
2. eGFR ≥ 60 mL/min
3. Corrected Ca < 10.8 mg/dL
4. For female of child-bearing potential, a negative serum pregnancy test
5. A willingness to utilize adequate contraception and not become pregnant [or to have their partner(s) become pregnant] during the study
6. Additional inclusion criteria apply

Exclusion Criteria:

1. Subject experienced a safety-related event in the KRN23-INT-001 study
2. Pregnant or lactating female subject or pregnant or female planning to become pregnant during the study
3. Receipt of a live (attenuated) vaccine (except for influenza vaccines) during the course of the KRN23-INT-001 study and/or of this study
4. Condition which could present a concern for either the subject's safety or difficulty with data interpretation
5. Additional exclusion criteria apply