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

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