Ultragenyx shares surge as blockbuster hopeful burosumab continues to perform in pivotal study

Emil Kakkis, Ultragenyx

Just in time for its R&D day today, Ulytragenyx $RARE and its partners at Kyowa Hakko Kirin outlined updated 48 week data on burosumab, which is on track to get a likely FDA approval in the spring.

Moving the goal line out to 48 weeks, from 24, researchers say that 84% of patients suffering from X-linked hypophosphatemia — or XLH — and on the drug from the start of the trial hit their goal on serum phosphorus levels, which was the primary endpoint. And 89% of the switchovers from the placebo group also hit their marks on the biomarker for efficacy.

Two measures of stiffness and physical function also reflected positive results for the drug, alongside an improvement in fracture healing.

The therapy, initially developed by Kyowa Hakko Kirin, is a monoclonal IgG1 antibody that targets FGF23, a hormone linked to the reduction of serum levels of phosphorus and active vitamin D.

This drug is central to Ultragenyx’s narrative. The biotech just scored an approval for Mepsevii, a drug that treats rare cases of mucopolysaccharidosis type VII . But it’s the burosumab launch after the April 17 PDUFA date that has everyone’s attention on Wall Street. The biotech has been setting up a small, 30-person sales force as it begins to handle what Ultragenyx execs hope will be a substantial portfolio of rare disease drugs.  And burosumab has peak sales figures of $1 billion tied to it.

A number of analysts are looking for Ultragenyx to use today’s presentation to investors as a chance to explain in more detail how the company plans to leverage the gene therapy platform it acquired with the Dimension buyout earlier in the year.

The biotech’s shares surged 6% on the latest data readout.

“This longer term data on symptom improvement and fracture healing support burosumab’s potential value in treating serious disease symptoms and promoting bone healing in adult patients with XLH,” said Ultragenyx CEO Emil Kakkis in a statement. “The continued clinical improvements in patients and the new data demonstrating a significant decrease in pain medication use after treatment with burosumab provide further support for the potential value in the treatment of adults with XLH.”

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Research Scientist - Immunology
Recursion Pharmaceuticals Salt Lake City, UT
Director of Operations
Atlas Venture Cambridge, MA

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