The Food and Drug Administration has approved a leukemia drug developed by Rigel Pharmaceuticals, giving the 26-year-old biotechnology company its second marketed medicine.
The pill, which will be sold as Rezlidhia, has been cleared for use in adults whose relapsed or refractory acute myeloid leukemia has specific genetic mutations the drug targets, the company said in a statement Thursday.
The target mutations are to an enzyme known as isocitrate dehydrogenase-1, or IDH1 for short. About 6% to 9% of AML patients’ cancers have mutations in the IDH1 gene, which is associated with poor clinical outcomes. Rezlidhia is designed to bind to the IDH1 enzyme and block its activity.
Rigel’s approval was based on a mid-stage study of 151 patients. Thirty-five percent of the 147 who were evaluated for efficacy had either a partial or complete response to treatment. On a median basis, their responses lasted 26 months.
The most common side effects were liver toxicity and differentiation syndrome, a complication in leukemia patients that can be fatal if untreated. Rigel said the condition was “manageable” in most cases by interrupting dosing or administering steroids. Still, the FDA put its strictest warning on Rezlidhia’s labeling, cautioning of the risk of differentiation syndrome and counseling physicians to withhold the drug if the side effect is suspected.
Rigel plans to disclose the price of Rezlidhia later this month, chief commercial officer Dave Santos said on a conference call.
Rigel was formed in 1996 and is best known for Tavalisse, a medicine approved in 2018 for a rare autoimmune condition. It bought rights to the drug now known as Rezlidhia in August through a licensing deal with Forma Therapeutics, a biotech Novo Nordisk acquired in September. That deal included an initial $2 million payment and potentially $233 million in additional payouts tied to various milestones.
The approval of Rezlidhia sets the stage for Rigel to compete with a similar treatment known as Tibsovo. Tibsovo was developed by Agios Pharmaceuticals and approved in 2018. Agios sold rights to the drug, as well as the rest of its cancer business, to French drugmaker Servier in 2020.
Rigel’s share prices jumped about 35% in early trading on Friday, but at $0.93 apiece, its shares are in danger of being delisted from the Nasdaq stock exchange. Its stock has lost nearly two thirds of its value over the last year, and the company has only reported two profitable quarters in the last three years. It laid off 16% of its workforce in October and reported a third quarter loss of $19 million on $22.4 million in total revenue.
Rigel’s pipeline includes five experimental drugs that are partnered with Eli Lilly, Kissei, Daiichi Sankyo and BerGenBio. Two of them were part of a nearly $1 billion alliance the company formed with Lilly last year.