Ultragenyx Pharma (RARE) Announces Positive Interim Data from KRN23 Phase 2 in TIO

September 19, 2016 6:29 AM EDT

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Ultragenyx Pharmaceutical Inc. (Nasdaq: RARE) announced positive interim data from the Phase 2 study of KRN23 for the treatment of tumor-induced osteomalacia (TIO). Interim data at 24 weeks from the first eight patients, including one patient with epidermal nevus syndrome (ENS), demonstrated that KRN23 improved serum phosphorus levels and bone metabolism measures. Ultragenyx is conducting the Phase 2 study under a collaboration and license agreement with Kyowa Hakko Kirin to develop and commercialize KRN23. These data were presented today at the American Society for Bone and Mineral Research (ASBMR) 2016 Annual Meeting.

“Patients with TIO have substantial hypophosphatemia, osteomalacia and fractures,” said Emil D. Kakkis, M.D., Ph.D., Chief Executive Officer and President of Ultragenyx. “These data support that KRN23 could potentially reverse some of these symptoms and improve bone health in patients.”

Mean serum phosphorus, renal phosphate reabsorption (TmP/GFR) and serum 1,25 dihydroxy vitamin D levels increased over 24 weeks of treatment. 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. The mean serum phosphorus level entered the normal range within one week of treatment, and was maintained in the low normal range from week 10 to week 24 of treatment. 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 seven patients who responded, six patients showed an improvement in bone mineral density at 24 weeks of treatment. Bone turnover markers, including Procollagen type 1 N-terminal propeptide (P1NP) and C-telopeptide of type I collagen (CTX-1), showed a statistically significant increase. One patient completed 48 weeks of treatment, at which time bone biopsies indicated an improvement from severe osteomalacia at baseline to mild osteomalacia at 48 weeks. The same patient showed resolution of four fractures at 24 weeks of treatment, determined by bone scan as previously disclosed. Bone mineral density for this patient improved 2% and 3% in the lumber spine and total hip, respectively. Bone biopsy and bone scan data for additional patients will be available at a later date.

Adverse events occurred in all patients. Treatment-related adverse events were observed in three patients (38%), and included Vitamin D deficiency and rash as previously disclosed, and dysgeusia, all mild in grade. There was one serious adverse event of neoplasm progression, which occurred in one patient with pre-existing metastatic spindle sarcoma who did not respond and has discontinued treatment. No injection site reactions were observed. Two patients had restless leg syndrome, one of whom had symptoms suggestive of worsening pre-existing restless leg syndrome. No clinically meaningful changes were observed in mean serum calcium, urinary calcium and in serum intact parathyroid hormone.

Conference Call Details

Ultragenyx will host a conference call on Monday, September 19 at 11am ET during which Dr. Kakkis will discuss results of the KRN23 studies being presented at the ASBMR Annual Meeting. The live and replayed webcast of the call will be available through the company's website at http://ir.ultragenyx.com/events.cfm. To participate in the live call by phone, dial 855-797-6910 (USA) or 262-912-6260 (international) and enter the passcode 83882106. The replay of the call will be available for one year.

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