Rare disease companies often focus on developing just a few products — or even only one — before they’re ultimately acquired.
“Over the past handful of years now, there were a number of these single-product, rare disease companies, and their end goal really almost had to be to get acquired,” said Chris Peetz, CEO of Mirum Pharmaceuticals. “Because a single rare disease product oftentimes is just not big enough to support all the infrastructure it takes to commercialize the medicine.”
Mirum’s approach, however, is different, building a larger and more diverse portfolio of several rare disease therapies. The company acquired biotech Bluejay Therapeutics in January, adding the late-stage monoclonal antibody for hepatitis D, brelovitug, to its pipeline.
Mirum scored its first FDA approval in 2021 with Livmarli, which treats cholestatic pruritus in patients with the rare genetic liver condition Alagille syndrome.
By focusing on “these underserved, smaller medicines that can have a huge impact for patients in these rare disease settings,” Peetz said the company “set the tone about what's been different about Mirum over time.”
In 2023, Mirum then bought Travere Therapeutics’ bile acid product portfolio, which included the rare disease medications Cholbam and Chenodal.
Peetz said Mirum’s strategy has been “finding these opportunities that, on their own, maybe don't stand alone as a company, but as we can accumulate more of them together, it turns into a really attractive business model, on top of that really important patient impact.”
A focused strategy
Big pharma companies acquiring rare disease biotechs is nothing new. In recent years, Sanofi gobbled up Blueprint Medicines, Gilead Sciences snapped up CymaBay Therapeutics, and AstraZeneca snagged Amolyt Pharma.
However, part of Mirum’s strategy is that it isn’t a big pharma company and instead is solely focused on rare diseases.
“The concept that we were working under is that there are quite a few misunderstood clinical programs in development that are in bigger companies that get lost, either because the big company thinks it's too small or doesn't understand the data from rare, less studied settings,” Peetz said.
With Mirum, he said, “the whole idea was, we can start a company around this and look for opportunities that are deprioritized in bigger companies.”
Mirum isn’t alone in this approach. For instance, California-based rare disease biotech BioMarin, which already has eight commercial therapies, added to its pipeline and portfolio when it bought the rare disease company Amicus Therapeutics in December for $4.8 billion.
There’s also a brand-new player in the game courtesy of two former BioMarin executives who’ve teamed up to form Mendra, a biopharma aimed at advancing rare disease medicines using AI to accelerate patient identification, clinical trial enrollment and access to global markets. The venture is backed by an $82 million oversubscribed Series A financing round.
Skirting rare disease roadblocks
Last year, the FDA indicated new flexibility in approval pathways for ultra-rare diseases, when Stealth BioTherapeutics landed an FDA nod for the Barth syndrome treatment Forzinity, despite having very few trial participants. The agency also proposed a “plausible mechanism” pathway for approving personalized therapies “where a randomized trial is not feasible,” prioritizing rare diseases that are fatal or can cause severe disabilities in children.
Despite notching some wins, rare disease drug innovation has faced several FDA roadblocks.
The agency’s rare pediatric priority review voucher program, which aimed to incentivize product development for rare pediatric diseases, expired at the end of 2024 and is still in limbo after the Senate failed to pass a massive spending package that included funding for Immigration and Customs Enforcement along with the voucher program.
Rare disease developers hit another snag in January when a Senate committee blocked the FDA’s new National Priority Voucher program, which intends to shorten FDA review time to just one to two months.
While Mirum took advantage of the priority review voucher program for its Livmarli approval, having a wider and deeper drug portfolio will mean that it’s less reliant on narrow FDA approval pathways. Stealth BioTherapeutics and the Barth syndrome community held its collective breath for months as it waited to find out whether the FDA would approve its only drug using a more flexible approach.
Peetz said a more diversified strategy is also an advantage on the funding side for companies looking to get acquired. He noted that it was “still challenging” for single product disease companies to get funded because of the economic downturn in the financial markets. However, he believes those conditions could “create more opportunity for Mirum to be a partner of choice for companies that don't want to take a single product forward in a rare setting.”
