Dive Brief:
- The Food and Drug Administration has approved Crysvita, developed by Ultragenyx Pharmaceutical Inc. and Kyowa Hakko Kirin Co. Ltd., for the treatment of a rare form of rickets, known as X-linked hypophosphatemia (XLH). It is Ultragenyx's second approval in six months.
- UltraGenyx said it expects Crysvita to have a net price of $160,000 and $200,000 per patient per year, but that could fluctuate since the dose is based on bodyweight of the patient.
- XLH affects around 3,000 pediatric and 9,000 adult patients. As part of the approval, Ultragenyx gets a Rare Pediatric Disease Priority Review Voucher (PRV). This is the 14th voucher to be issued by the FDA, and is a valuable asset for the company.
Dive Insight:
The approval of Crysvita (burosumab-twza) heralds the first Food and Drug Administration-approved treatment to reach the market for XLH, a rare inherited form of rickets that leads to lower-extremity deformity, delayed growth, decreased height and increased risk of fractures. Unlike other forms of rickets, vitamin D therapy is not effective.
By binding excess levels of fibroblast growth factor 23 and normalizing phosphorus levels, Crysvita helps to correct the underlying disease. In clinical trials, 94% of adults and 94-100% of children receiving Crysvita reached normal phosphorus levels. Crysvita treatment, in both adults and children, also improved X-ray findings.
Crysvita's mechanism "leads to sustained improvements in phosphate metabolism with concurrent repair of the skeleton, even after prior treatment with conventional approaches," said Tom Carpenter, the lead study investigator and director of the Yale Center for X-Linked Hypophosphatemia, in an April 17 statement.
"Most importantly, the dosing regimen for Crysvita is far less burdensome than for currently available therapies," Carpenter added. "I expect it to revolutionize the care of patients with XLH."
According to Leerink analyst Joseph Schwartz, Ultragenyx expects a gradual build-up for Crysvita, but much of the challenge will be identifying patients given that diagnosis is challenging in adults.
"Towards this end, Ultragenyx [has] developed a field team (30 patient diagnosis liaisons) to increase the awareness of XLH and identify new XLH patients," Schwartz wrote in an investor note. "Separately, Ultragenyx [has] deployed 32 UltraCare liaisons to provide a comprehensive centralized in-house support program to provide financial assistance to get [patients] on Crysvita once identified."
The next step is expected to be filings in key Latin American markets.
"Latin America is especially important since Ultragenyx will commercialize burosumab while paying Kyowa Hakko Kirin a low single-digit royalty on net sales. Ultragenyx … anticipates approval [in Latin America] next year while utilizing named patient sales in the meantime with FDA's approval despite named patient sales falling out of favor," Schwartz wrote in his note.
This is not Ultragenyx's first PRV.
PRVs are a sort of 'thank you' to developers of rare disease drugs, and provide a regulatory fast pass that allow companies to cut the review time by the FDA for a New Drug Application to six months. Like the 'get out of jail free' cards in the board game Monopoly, PRVs may be kept until needed, or sold. Their value is rather more than $50, though – Ultragenyx received a priority review voucher for U.S. approval of its rare pediatric disease drug Mepsevii (vestronidase alfa), and sold it to Novartis AG for $130 million in December 2017.
Kyowa Kirin International PLC has been granted conditional marketing authorization in Europe for Crysvita. The first commercial launch is expected in Germany in the second quarter of 2018, followed by other European countries.