Clinical Data Functional Measurements: 6 Minute Walk Test (6MWT) and Patient Reported Outcomes (PROs)Patients with walking impairment at baseline (defined by < 80% predicted normal walk distance in 6MWT) in the bi-weekly dosing group achieved a mean increase of 84 meters (p<0.001) at 40 weeks (n=14), and 97 meters (p<0.001) at 64 weeks (n=7).Functional disability scores were measured with the Pediatric Orthopedic Society North America/Pediatric Outcome Data Collection Instrument (POSNA/PODCI). When evaluating the Global score of all five domains in those patients with substantial impairment at baseline (n=28, defined as baseline scores < 40 or one standard deviation below the normalized score of 50), a mean improvement of +17.5 (p< 0.0001) was observed at 40 weeks. Though the magnitude of these changes in functional measurements are substantial, any conclusions must be tempered by the fact that these data are from an uncontrolled, open-label study.Safety and TolerabilityThe most common treatment-related adverse events reported by preferred term was injection site reaction in 33% of patients. All of these reactions were considered mild. All other treatment-related adverse events were also considered mild. There was one serious adverse event considered possibly treatment-related. This was a previously reported patient with fever and muscle pain who improved without complication and is still in the trial. There have been no deaths or discontinuations from the study for any reason. No clinically meaningful changes were observed in mean serum calcium, urinary calcium and in serum intact parathyroid hormone. None of the patients had serum phosphorus levels above the upper limit of normal at any time point. No clinically significant changes were observed in renal ultrasounds pre- and post-treatment.Phase 2 Adult Extension StudyThe open-label, long-term extension study enrolled 20 adult patients with XLH who had previously participated in the phase 1 INT-001 or INT-002 studies of KRN23. All patients had at least a 12-month KRN23 treatment break before enrolling in the extension study. Patients who had resumed oral phosphate and active vitamin D therapy between studies (65%) completed a 21-day washout period. All patients began KRN23 treatment at the last dose received in the INT-001 or 002 study with an option to titrate during the first 12 weeks. An analysis of 24-week data is being presented. Metabolic MeasuresPatients treated with KRN23 demonstrated increased serum phosphorus at 24 weeks of treatment, and maintained levels in the low normal range. Renal phosphate reabsorption (TmP/GFR) and serum 1,25 dihydroxy vitamin D levels also increased from baseline to 24 weeks.Patient-Reported Outcomes and Physical FunctionAt baseline, 19 of 20 patients had worst pain scores measured by the Brief Pain Inventory Question 3 (BPI-Q3) of > 4, classified as moderate to severe pain. The mean BPI-Q3 score was significantly reduced from baseline (p=0.0268; 1.1 point reduction from 6.6 at baseline to 5.5 at 24 weeks). These patients also demonstrated significant improvements in BPI pain interference (p=0.0009) and pain severity (p=0.0141) scores.WOMAC pain, stiffness and physical function domain scores were significantly reduced at 24 weeks in these patients. Patients demonstrating the greatest improvements in stiffness (WOMAC stiffness responders) and pain (BPI-SF worst pain responders) had greater improvements in mobility tests, including the Timed Up and Go (TUG test for balance and agility) and the 6MWT. Mean patient TUG scores improved by 2 seconds (p=0.04) at week 24. At baseline, nearly all patients (19/20) were impaired in walking (defined by < 80% predicted normal walk distance in 6MWT). The mean increase in distance walked was 25 meters (p=0.05) from baseline.Safety and TolerabilityThe most common adverse events were arthralgia (30%), nasopharyngitis (25%), back pain (20%), injection site reaction (20%), and pain in extremity (20%).