An Open-Label, Multi Center, Single-Cohort, Post-Marketing Phase 4 Study to Evaluate the Efficacy, Pharmacodynamics, and Safety of the Anti-FGF23 Antibody, KRN23, in Adult Chinese Patients With Tumor-Induced Osteomalacia (TIO)
The purpose of this study is to assess the safety, pharmacokinetics and efficacy of KRN23 in adult Chinese patients with TIO
• Have a clinical diagnosis of TIO based on evidence of excessive FGF23 that is not amenable to cure by surgical excision of the offending tumor (documented by Investigator)
• Male or female Chinese patients aged ≥18 years at the time of signing the informed consent form
• Have a fasting serum phosphorus level \< 2.5 mg/dL (0.81 mmol/L) at Screening
• Have a serum iFGF23 level ≥ 100 pg/mL by Kainos assay at Screening
• Have a TmP/GFR \< 2.5 mg/dL at Screening
• Have an estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73m2(using CKD-EPI formula) at Screening. Subjects with an eGFR ≥ 30 but \< 60 mL/min at screening will be considered eligible so long as in the opinion of the Investigator the decline in renal function is not related to nephrocalcinosis
• Have a corrected serum calcium level \< 10.8 mg/dL (2.69 mmol/L) at Screening (Corrected serum calcium = serum calcium in mg/dL + 0.8 × \[4 - serum albumin in g/dL\])
• Have a negative pregnancy test at Screening and be willing to have additional pregnancy tests during the study (female patients of child-bearing potential only)
• Be willing to use an effective method of contraception while participating in the study (sexually active patients of child bearing potential) and for 12 weeks after last dose of study drug. Women of non child bearing potential are defined as permanently sterile (i.e. due to hysterectomy or bilateral oophorectomy) or postmenopausal (defined as at least 12 months postcessation of menses without an alternative medical cause). Postmenopausal status of female patients will be confirmed with a Screening serum follicle stimulating hormone (FSH) level \>40 mIU/mL
⁃ Be willing to provide access to prior medical records to determine eligibility including imaging, biochemical, and diagnostic, medical, and surgical history data
⁃ Provide written informed consent after the nature of the study has been explained, and prior to any research-related procedures
⁃ Be willing and able to complete all aspects of the study, adhere to the study visit schedule and comply with the assessments (in the opinion of the Investigator)