A Repeated Study of KRN23 in Adults With X-Linked Hypophosphatemia

A Phase I/II, Open-Label, Repeat-Dose, Dose-Escalation Study 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). A Bone Substudy will evaluate the effects of single-blind KRN23 versus Placebo on bone mineral density and bone quality.

Main Inclusion Criteria:

1. 18 years or older
2. Clinical diagnosis of XLH
3. TmP/GFR < 2.0 mg/dL
4. GFR ≥60 mL/min
5. Corrected Ca <10.8 mg/dL
6. A willingness to utilize adequate contraception and not become pregnant[or to have their partner(s) become pregnant] during the study
7. Additional inclusion criteria apply

Main Exclusion Criteria:

1. Have any sign of active infectious disease or have had an infection requiring treatment with antibiotics within 3-weeks of Screening
2. History of known immunodeficiency
3. Pregnant or lactating females subjects or female planning to be become pregnant during the study
4. Receipt of a live (attenuated) vaccine (except for influenza vaccines) within 3-months of Screening, and/or during the study
5. Use of pharmacologic vitamin D metabolite or its analog, phosphate, calcimimetics, and ingestion of aluminum hydroxide antacids within 10-days prior to Screening and/or dosing
6. Use of any supplement containing phosphate, calcium and/or vitamin D within 10-days prior to Screening and/or dosing
7. Condition which could present a concern for either the subject's safety or difficulty with data interpretation
8. Additional exclusion criteria apply