Mirum gets iBAT inhibitor Livmarli across the FDA finish line for rare pediatric liver condition

Children with Alagille syndrome (ALGS) will soon have a treatment available for the itchiness and skin lesions that accompany the rare liver disease. That'll likely bring a windfall to newly commercial drugmaker Mirum Pharmaceuticals. 

On Wednesday, the FDA approved Mirum's Livmarli, a minimally absorbed ileal bile acid transporter (iBAT) inhibitor. The drug, taken in capsule form, is the first medication approved for the disease, which affects between 2,000 and 2,500 children in the United States.

ALGS is a genetic disorder that leaves bile ducts narrow, malformed and fewer in number, causing bile to accumulate and leading to inflammation and liver damage. Cholestatic pruritus, the itchy sensation which accompanies the disorder, is an unrelenting condition that interrupts sleep and causes bleeding and scarring of the skin from scratching.

“Many children ultimately require major surgical interventions such as liver transplantation,” Binta Kamath, pediatric hepatologist at the Hospital for Sick Children in Toronto, said in a statement Wednesday.

Livmarli represents the first approved treatment in ALGS, which could be a lucrative market, Evercore ISI analyst Josh Schimmer wrote to clients last month. He expects the ALGS market will be worth $500 million annually at the start of Mirum's commercialization efforts.

Annual cost of the treatment for an average-sized patient will be $391,000, which is 56% higher than the estimate of Evercore. A similar iBAT inhibitor treatment, Albireo Pharma’s Bylvay, goes for $385,000 yearly. Two months ago, the FDA signed off on Bylvay for the treatment of pruritus in all subtypes of another liver condition, familial progressive intrahepatic cholestasis (PFIC). 

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Mirum also is conducting a study of Limvarli against PFIC at a three-times higher dose, while Albireo is evaluating Bylvay at a higher dose in an ALGS trial, Schimmer notes.

"It will be interesting to see how these play out considering the already-high price points," Schimmer wrote. "Livmarli may be able to move into PFIC as a second-line option, with a range of dose options whereas Bylvay may struggle to gain inroads in ALGS."

With its approval for Livmarli, Mirum also scored a lucrative priority review voucher (PRV). The FDA uses PRVs to encourage the development of treatments for rare, underserved diseases. Earlier this month, Albireo sold its PRV for Bylvay for $105 million.  

For development and marketing efforts outside the U.S., Mirum has inked deals with Takeda, GC Pharma of South Korea and CANbridge Pharmaceuticals of China.

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Once touted as a potential blockbuster, Livmarli traveled a long road to approval. In 2014, Lumena sold the drug to Shire for $260 million, but its value plummeted when it flunked two trials, including one in ALGS. Promising early data from another trial convinced Mirum that Livmarli was worth a $120 million gamble, so the company scooped up the rights from Shire.

“Since the first study’s initiation more than a decade ago, we have dreamed of today,” Roberta Smith, president of the Alagille Syndrome Alliance, said in a statement. “Until now, patients have had limited-to-no treatment options to address the severe and unrelenting itch.”