BioCryst acquires Astria for $700 million, giving it a chance to beat bigger rivals in rare disease HAE space

Patients who want to prevent episodes of swelling caused by the rare disease hereditary angioedema can choose injectable drugs, with dosing schedules ranging from every two weeks to every two months. BioCryst Pharmaceuticals aims to provide patients with less frequent dosing through its $700 million acquisition of Astria Therapeutics. Astria Therapeutics is a biotech company whose primary asset is providing patients with the option of as few as two injections per year.

BioCryst is already a player in the field of hereditary angioedema (HAE), a rare genetic disorder that causes episodes of swelling in various parts of the body and can be life-threatening when it affects a patient's airway. The Durham, North Carolina-based company markets Orladeyo, a once-daily drug approved to prevent HAE attacks. The drug is a small molecule designed to block kallikrein, a protein that plays a role in episodes of swelling.

Astria is developing an injectable kallikrein inhibitor called navenibart. The Boston-based biotech company designed the antibody to be selective for its target and have a long half-life, allowing for less frequent dosing. Earlier this year, Astria began a global Phase 3 clinical trial. Placebo-controlled studies tested a starting dose of 600 mg, followed by 300 mg every three months; 600 mg every six months; or 600 mg every three months. The primary objective was to measure the number of HAE episodes during six months of treatment. Astria said it expects preliminary results in early 2027.

BioCryst develops drugs to treat rare diseases, but HAEs are important in its portfolio as Orladeyo is its best-selling product. In addition to Orladeyo's current use to treat HAE patients 12 years and older, the FDA is expected to make a decision on December 12 regarding an oral granular formulation of the drug for children 2 to 11 years of age.

The HAE treatment market is becoming increasingly competitive. Dominant is Takeda Pharmaceutical's Takhzyro, a kallikrein inhibitor approved by the FDA in 2018 for the prevention of HAE. The antibody drug is given as a subcutaneous injection every two weeks, but the dose may be extended to every four weeks in some patients.

This summer, two new HAE prevention drugs received FDA approval, providing patients with alternatives to Takeda's drugs. CSL Behring was the first to approve Andembry in June, an antibody designed to block factor XIIa, a protein that plays a role in swelling attacks in HAE. This CSL medication is injected once a month. In August, Ionis Pharmaceuticals received regulatory approval for Dawnzera, an antisense oligonucleotide designed to target messenger RNA to provide instructions for prekallikrein, the precursor to kallikrein. Dawnzera is given as an injection every month or every two months.

BioCryst said in an investor presentation that three to six months of injectable navenibart could make Astria's drug the first choice for injectable HAE treatments. In addition to reducing the frequency of injections, navenibart has shown the potential to match or even beat Takeda's drug in efficacy. Acknowledging the limitations of cross-trial comparisons, results from navenibart's Phase 1b/2 trial showed that three- and six-month injections reduced HAE attack rates by an average of 92% and attack-free rates by 50%. These measures are the best results for currently available injectable HAE prevention products.

BioCryst chief commercial officer Charlie Gayer said on an Oct. 14 conference call that HAE patients' needs for efficacy can largely be met by existing products. Those who do not achieve adequate efficacy with one product can choose another.

“But the market is not looking for higher efficacy, it’s looking for reduced dose burden,” Geyer said. “That's what Navinibat has the potential to deliver when given every three to six months. Again we saw in market research that very low to no injection site pain at three months really got patients' attention and we think that was the tipping point for them to switch.”

Orladeyo was discovered and developed internally by BioCryst, which had sales of $437.6 million last year. BioCryst estimates the drug will generate $550 million in revenue in 2025, a figure that does not include the European Union, where Italy's Neopharmed Gentill has rights after a deal was struck this summer. BioCryst expects revenue from its HAE portfolio to reach $1.0 billion in 2029 and then $1.8 billion in 2033.

BioCryst is continuing internal research and development in other areas. The next therapeutic candidate in its pipeline is BCX17725, a protein drug in early-stage development to treat Netherton syndrome, a rare inflammatory skin disease for which there is currently no FDA-approved treatment. By acquiring Astria, BioCryst acquires a late-stage asset that will continue to drive revenue growth when Orladeyo sales begin to level off. CEO Jon Stonehouse described navenibart as “the perfect next product for our company.”

Astria's purchase price is $8.55 in cash and 0.58 shares of BioCryst common stock, based on BioCryst's 20-day average share price as of October 8. The terms value Astria stock at about $13 per share, which is a 53% premium to the stock's closing price the day before the deal was announced. BioCryst has also secured up to $550 million in debt financing through funds managed by Blackstone. BioCryst said in a regulatory filing that part of the debt financing will be used for the cash portion of the acquisition of Astria.

The transaction, which still requires regulatory and Astria shareholder approval, is expected to close in the first quarter of 2026. Upon completion of the transaction, Astria CEO Jill Milne will join BioCryst's board of directors, and Astria shareholders will own approximately 15% of the combined company. Astria's pipeline includes STAR-0310, an antibody designed to block the inflammatory protein OX40 as a potential treatment for atopic dermatitis. STAR-0310 does not fit with BioCryst's rare disease strategy, and the biotech plans to pursue strategic alternatives for this early-stage asset.

“We think it's a very interesting product, but it's not a rare disease and would work better in the hands of people with this condition [atopic dermatitis] area,” Stonehouse said.

Photo: Francesco Carta fotografo, Getty Images