Additional Relevant Details
Before KRN23 treatment and after washout with any oral phosphate treatment, the mean serum phosphorus level was 1.7 mg/dL, well below the lower limit of normal of 2.5 mg/dL. After KRN23 treatment began, six of the eight patients achieved serum phosphorus levels that entered the normal range. The dose continues to be titrated up in one of the two patients whose serum phosphorus levels have increased but not entered the normal range. Renal phosphate reabsorption (TmP/GFR) and serum 1,25 dihydroxy vitamin D levels also increased in seven of the eight patients. One patient did not demonstrate an improvement in these markers. Overall, the improvement in serum phosphorus and other bone mineral metabolism measures observed in this study to date is generally consistent with what has been observed in studies of KRN23 in pediatric and adult patients with X-linked hypophosphatemia (XLH).Of the eight patients enrolled, the two patients who completed 24 weeks of treatment showed an improvement in bone mineral density, and one of these two patients showed early evidence of fracture resolution, determined via bone scan. Additional bone data will be available in the second half of 2016.