The FDA gave the go-ahead to a pair of rare disease therapies this week, both marking the first-ever approvals for developers Rigel Pharmaceuticals and Ultragenyx.
Rigel got a green light from the FDA for chronic immune thrombocytopenia (ITP) therapy Tavalisse (fostamatinib), although there was a sense of déjà vu as it prematurely published a press release on its website trumpeting the milestone last week, causing a surge in its share price before the mistake was spotted.
All’s well that ends well however, with the US regulator giving its blessing to the first-in-class oral spleen tyrosine kinase (SYK) inhibitor after a lengthy and often turbulent development pathway, including a failed phase III trial in ITP. Rigel said it intends to launch Tavalisse (fostamatinib) in the US in May and – so far – hasn’t revealed what it intends to charge for the drug. It also plans to submit the drug in Europe before the end of the year and in Canada in 2019.
ITP is a disease caused by low platelet counts that lead to bruising, bleeding and fatigue. According to the company, Tavalisse targets the underlying autoimmune cause of the disease by impeding platelet destruction, providing “an important new treatment option for adult patients with chronic ITP”. At the moment ITP is treated using drugs to boost platelet counts, steroids to reduce the immune response and surgery to remove the spleen, but a sizeable proportion of patients don’t respond to those therapies.
Fostamatinib was being developed as a treatment for rheumatoid arthritis by AstraZeneca (AZ), but the big pharma company returned rights to the drug in 2013 after disappointing phase III trials. Rigel is also developing it for additional indications, including autoimmune haemolytic anaemia and IgA nephropathy.
Ultragenyx’s FDA approval was for Crysvita (burosumab), which has become the first approved drug for adults and children ages one year and older with X-linked hypophosphatemia (XLH), a rare, inherited form of rickets that affects around 3,000 children and 15,000 adults in the US.
The symptoms, which also include impaired bone growth, dental problems and severe pain, are linked to low blood phosphate levels.
Ultragenyx already has one approved drug on the market – mucopolysaccharidosis type VII therapy Mepsevii (vestronidase alfa), which got the nod from the FDA last November – but analysts say Crysvita is likely to be a much larger market opportunity with blockbuster sales potential. The company has set the annual price of the drug at $160,000 for a paediatric patient and $200,000 for adults.
Piper Jaffray analyst Christopher Raymond said that the FDA approval is for a broader group of patients than in Europe, where Crysvita was approved in February only for use in paediatric patients. He’s predicting sales could reach $336m in 2022.
Ultragenyx has also picked up a second rare paediatric disease priority review voucher for the approval, having sold the first one for $130m.