Active ingredient: fostamatinib
Disease: Chronic immune thrombocytopenia
Peak sales estimate: $300 million
Approved: 17 April, 2018
Company: Rigel Pharmaceuticals
The scoop: This is a phoenix from the flames story for Rigel: Back in 2016, the biotech saw its shares plummet when a second phase 3 trial for fostamatinib missed its primary endpoint. That came a few months after its first phase 3 trial notched a barely positive result in immune thrombocytopenia (ITP).
But less than two years later, Rigel officially won FDA approval for the drug, now known as Tavalisse. A snafu with the website appeared to confirm the approval before the FDA officially had.
It’s now green-lighted to treat thrombocytopenia in adult patients with ITP, a rare disease that causes the immune system to attack and destroy platelets, the blood cells responsible for clotting, which causes excessive bruising, bleeding and fatigue.
But clinical issues in other indications abound: Just before its approval, the California biotech said its drug was unable to hit its primary endpoint in a proof-of-concept study involving patients with IgA nephropathy (IgAN), an orphan autoimmune disease of the kidneys.
It did, however, suggest that the drug had shown some evidence of efficacy in a subgroup of more seriously ill IgAN patients, but this was still a setback for the company’s longer-term ambitions for fostamatinib.
The drug, once seen as a rheumatoid arthritis hopeful before being rejigged for orphan indications, has also been in phase 2 trials for warm antibody autoimmune hemolytic anemia, but IgAN is considered to be the largest of all three target and now approved indications—all of which are fairly rare—and affects an estimated 82,500 to 165,000 people in the U.S. alone.
Tavalisse, which targets the underlying cause of the disease by preventing destruction of platelets, is the first in a new class of oral spleen tyrosine kinase (SYK) inhibitors.
During its 2016 slump, the company saw its market share worth just $200 million, but since approval it’s more than doubled. — Ben Adams