Children whose dwarfism was due to achondroplasia had few treatment options other than surgery to treat spinal or limb complications. There is now a drug available that could prevent some of these problems from occurring in the first place. The FDA has approved a BioMarin Pharmaceutical therapy that targets the genetic mutation at the root of the hereditary disease.
The application for approval for the drug Vosoritide is valid for children from 5 years of age who suffer from achondroplasia and who still have open growth plates. The decision is made three months after the European Commission has approved the drug, which is sold under the name “Voxzogo” for children from 2 years of age until the growth plate closes.
BioMarin of San Rafael, Calif., Said in an investor presentation that as the first approved drug to target the underlying cause of achondroplasia, Voxzogo has the potential to become a blockbuster seller. Chief Commercial Officer Jeff Ajer said he expected the drug to eclipse sales of the company’s enzyme replacement therapy Vimizan, which had sales of $ 544.4 million last year.
“I believe Voxzogo has the greatest long-term sales potential compared to previously approved products, including Vimizan, our largest marketed product to date,” Ajer said on a conference call on Friday.
Several proteins regulate bone development. Achondroplasia is caused by a mutation in the gene responsible for producing fibroblast growth factor receptor 3 (FGFR3), a protein that downregulates bone growth. The mutation leads to overactivity of this protein, which in turn leads to people with short limbs and an average height of about four feet. While achondroplasia doesn’t usually affect mental abilities, it may require surgery to correct spinal deformities or straighten bent legs, according to the National Organization for Rare Disorders.
FGFR3 is balanced in the body by a peptide called a C-type natriuretic peptide (CNP). Voxzogo is an analog of this peptide. The FDA approval of the BioMarin drug is based on the results of a phase 3 study in 121 children aged 5 and over. These participants were randomly given either a once-daily injection of the study drug or a placebo. The aim of the study was to measure the annualized growth rate, which is the rate of height gain, after one year of treatment.
Study results showed that children who received the BioMarin drug got an average of 1.57 centimeters taller compared to those who received a placebo. Side effects included injection site reactions, vomiting, and a drop in blood pressure. A drop in blood pressure is listed as a warning on the label of the medicine.
BioMarin estimates that 21,000 children worldwide – including around 3,000 in the United States – have achondroplasia and are eligible for treatment with Voxzogo. The company has set a wholesale price of $ 899 per vial, which Ajer says is on par with wholesale prices in France and Germany. One vial is the equivalent of a daily dose of Voxvogo and, at wholesale prices, annual therapy costs exceed $ 320,000. Using rebates and rebates, BioMarin calculates that the average revenue per U.S. patient will be about $ 240,000 per year. Voxzogo is still under regulatory review in Japan, Brazil and Australia.
Other companies want to challenge BioMarin on achondroplasia. A peptide drug from Ascendis Pharma is in mid-stage clinical development. Pfizer has a mid-stage biological drug candidate through the $ 340 million acquisition of Therachon in 2019. Tyra Biosciences raised nearly $ 173 million when it went public in September to fund the development of its small molecule FGFR3 inhibitor. Although the focus of biotechnology is on blocking the role of FGFR3 in cancer, it also plans to develop its lead drug candidate for achondroplasia.
Voxzogo received FDA approval on Friday as part of the agency’s accelerated approval path, which allows earlier approval of drugs for serious illnesses with limited treatment options. These faster decisions based on a surrogate endpoint – an indication that a drug may be working – require a post-marketing study to confirm the benefit to the patient. To meet this requirement, BioMarin plans to leverage its ongoing open-label extension studies, which will compare participants to the available natural history of patients who have had the disease. The main goal will be to determine the final adult size.
Hank Fuchs, President of BioMarin’s Global Research and Development, said BioMarin’s post-market study plans place the company in a good position to collect the adult height data needed to translate accelerated approval into one converting full approval and helps fend off potential competitors. Fuchs stated that once BioMarin is fully approved, the annualized growth rate will no longer be available as a surrogate endpoint for accelerated approval. This means that subsequent achondroplasia drugs must meet the same adult height threshold that BioMarin must show for full FDA approval.
“I think the expectation is that in the future hundreds of patients will have to cross the finish line at full adult size before any followers can enter this market,” said Fuchs. “We feel really good about the post-marketing requirement because it sets a pretty high bar for subsequent approvals.”
BioMarin said Voxzogo will be available to US patients by the end of December, if not sooner.
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