Mirum Pharmaceuticals Launches with $120 Million Series A and Phase 3-Ready Candidate for Rare Liver Diseases

~ Financing led by NEA. Drug candidate licensed from Shire for Alagille syndrome (ALGS) and progressive familial intrahepatic cholestasis (PFIC) ~

4.9 million adults—2% of adults in the US—have a diagnosed liver disease, according to the CDC. Liver disease can be caused by multiple external factors, including alcohol and chemical abuse and viruses, and by inherited factors. Alagille syndrome (ALGS) is a rare genetic disorder that can affect the liver in addition to numerous other organs including the heart, eyes and kidneys as well as the skeleton. Patients with ALGS have fewer than the normal number of small bile ducts inside the liver, which causes a build up of bile—a condition called cholestasis—which in turn leads to liver damage and liver disease.

ALGS is transmitted in an autosomal dominant fashion, meaning a child can get it from only one parent. Each child of a parent with an autosomal dominant mutation has a 50% chance of inheriting the mutated gene. In contrast, progressive familial intrahepatic cholestasis (PFIC) is transmitted in an autosomal recessive fashion, meaning both parents must have a copy of the mutated gene, and there’s a 25% chance that a child will inherit both.

San Diego-based Mirum Pharmaceuticals announced its launch today with $120 million in Series A financing and a global license from Shire SHPG to develop maralixibat, a Phase 3-ready candidate to treat rare cholestatic liver diseases. and volixibat, an early stage liver disease candidate. Both compounds are inhibitors of the apical sodium dependent bile acid transporter (ASBT), an important intestinal and liver protein that carries bile acids. The financing was led by New Enterprise Associates (NEA) with participation from Deerfield Management, Frazier Healthcare Partners, Novo Holdings, Pappas Capital, RiverVest Venture Partners and Rock Springs Capital. In exchange for global rights, Shire will receive an undisclosed upfront payment and equity stake in Mirum, in addition to potential future milestone payments and royalties. Mirum plans to initiate Phase 3 confirmatory studies in patients with ALGS and PFIC in 2019.

Maralixibat has had a volatile clinical history, beginning with its creation by Lumena Pharmaceuticals, which was acquired by Shire in 2014 for $260 million. The candidate performed poorly in clinical studies and was thought by many to have no future. New interim analysis from the Phase 2b “ICONIC” study of maralixibat in ALGS patients, however, showed reductions in bile acids and pruritus (itchy skin associated with liver disease) compared to placebo. Additionally, a subset of patients with the PFIC2 type of PFIC responded to maralixibat with a sustained (greater than two years for some) reduction or normalization of serum bile acids and reduction of pruritus. The FDA awarded Breakthrough Therapy designation to Shire in 2016 for the drug, then known as SHP625, for patients with PFIC2. Mirum will present the data at a liver diseases conference next year.

Further, Mirum’s CEO Mike Grey, is the former CEO of Lumena, and he has brought the band back together to develop maralixibat. Mirum’s team includes co-founders, management and advisors from Lumena as well as from Tobira Therapeutics, another company focused on liver diseases that was acquired by Allergan AGN in 2016. NEA, Pappas Capital and RiverVest were early investors in Lumena, while Frazier Healthcare was an early investor in Tobira.

The interim data we are announcing today from the Phase 2b ICONIC study in ALGS conducted by Shire underscores my continued confidence in maralixibat and its potential to help patients with these severely debilitating liver diseases. The study leveraged an improved trial design and in its interim analysis, patients taking maralixibat had reductions in bile acids and pruritus compared to placebo. Additionally, in a single-arm, open-label Phase 2 study, a subset of patients with PFIC2 responded to maralixibat, with a sustained (>2 years for some) reduction or normalization of serum bile acids and reduction of pruritus. These results led to the FDA’s Breakthrough Therapy designation for patients with PFIC2. These clinical studies demonstrate the potential of maralixibat to significantly impact patients’ lives.

– Mike Grey, Chairman and CEO, Mirum Pharmaceuticals.

John Carroll writes in Endpoints News that the price Mirum paid Shire for maralixibat was “somewhat less than what it sold for,” according to Mr. Grey, when Shire acquired Lumena. Mr. Carroll continued, “It’s unlikely that anyone knows more about this drug than Grey, who never gave up on it.”

The substantial investment we have made in Mirum and the outstanding syndicate of savvy biotech investors underscores the value we ascribe to maralixibat, as well as our confidence in the company’s management team to execute on an aggressive development plan. Mike and his team are seasoned biotech veterans with a deep knowledge of the drug, the disease biology and the patient populations they hope to help.

– Ed Mathers, partner, NEA, and board member, Mirum Pharmaceuticals.

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