BioCryst’s $700 million acquisition of Astria gives it a chance to beat its biggest competitors in rare HAE diseases

Patients who want to prevent swelling caused by hereditary angioedema, a rare disease, can choose from injectable medications with dosing schedules ranging from every two weeks to every two months. BioCryst Pharmaceuticals aims to offer patients even less frequent doses through the $700 million acquisition of Astria Therapeutics, a biotech whose core asset could offer patients the option of receiving just two injections per year.

BioCryst is already a player in hereditary angioedema (HAE), a rare inherited disease that causes attacks of swelling in various parts of the body that can be life-threatening when they affect a patient’s airways. The Durham, North Carolina-based company markets Orladeyo, a once-daily pill approved to prevent HAE attacks. This medication is a small molecule designed to block kallikrein, a protein that plays a role in swelling attacks.

Astria is developing an injectable kallikrein inhibitor called navenibart. The Boston-based biotech designed this antibody to provide selectivity to its target as well as a long half-life that allows for less frequent dosing. Earlier this year, Astria launched a global Phase 3 clinical trial. The placebo-controlled program is testing an initial 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 is to measure the number of HAE attacks during the six-month treatment period. Astria said it expects preliminary results in early 2027.

BioCryst develops drugs for rare diseases, but HAE is high in its portfolio thanks to Orladeyo, which is its best-selling product. In addition to Orladeyo’s current use to treat HAE patients ages 12 and older, an FDA decision is expected by Dec. 12 regarding an oral granule formulation of the drug for children ages 2 to 11.

The HAE treatment market is becoming increasingly competitive. Takeda Pharmaceutical dominates with Takhzyro, a kallikrein inhibitor approved by the FDA in 2018 for HAE prophylaxis. This antibody medication is administered by subcutaneous injection every two weeks, although the dosage can be extended to every four weeks for some patients.

Two new HAE prophylactic drugs won FDA approval over the summer, providing patients with alternatives to Takeda’s drug. CSL Behring was the first to approve Andembry, an antibody designed to block factor XIIa, a protein that plays a role in HAE swelling attacks, in June. This CSL medication is given as a monthly injection. In August, Ionis Pharmaceuticals received a regulatory green light for Dawnzera, an antisense oligonucleotide designed to target messenger RNA that provides instructions for pre-kallikrein, a precursor to kallikrein. Dawnzera is injected every month or two.

Navenibart injections for three or six months could make the Astria drug the first-choice injectable treatment for HAE, BioCryst said in an investor presentation. In addition to reducing injection frequency, navenibart showed potential equal to, or even greater than, Takeda’s drug in terms of effectiveness. Recognizing the limitations of cross-trial comparisons, results from Navenibart’s Phase 1b/2 trial showed that the three- and six-month injections resulted in an average 92% reduction in HAE attack rate and a 50% attack-free rate. These measurements are the best results displayed by injectable HAE prophylaxis products currently available.

Speaking on an Oct. 14 conference call, Charlie Gayer, BioCryst’s chief commercial officer, said the efficacy needs of HAE patients are largely met by available products. Those who do not obtain sufficient effectiveness with one product can choose another.

“But the market is not looking for more effectiveness, but a less restrictive dosage,” Gayer said. “That’s what Navenibart has the potential to deliver with dosing every three to six months. And what we saw again in our market research is that that three-month profile with very little to no pain at the injection site is really something that’s catching the attention of patients and we think it’s a turning point toward what will get them to change.”

Orladeyo, which was discovered and developed in-house by BioCryst, accounted for $437.6 million in revenue last year. BioCryst estimates revenue for the drug in 2025 will be $550 million, a figure that excludes the European Union, where Italian company Neopharmed Gentill holds the rights following a deal reached over the summer. BioCryst projects that its HAE portfolio could reach $1 billion in revenue in 2029 and then exceed $1.8 billion in 2033.

BioCryst continues its internal R&D in other areas. The next therapeutic candidate in development is BCX17725, a protein drug in early development for Netherton syndrome, a rare inflammatory skin disease for which there are currently no FDA-approved treatments. With the acquisition of Astria, BioCryst acquires a later-stage asset that will continue to drive revenue growth as Orladeyo sales begin to stabilize. CEO Jon Stonehouse described Navenibart as “the perfect next product for our business.”

The Astria acquisition consists of $8.55 in cash and 0.58 shares of BioCryst common stock, a price based on BioCryst’s 20-day average share price as of October 8. These terms value Astria’s shares at approximately $13 each, representing a 53% premium to the stock’s closing price the day before the deal was announced. BioCryst also secured up to $550 million in debt financing with funds managed by Blackstone. A portion of the debt financing will be applied to the cash portion of the Astria acquisition, BioCryst said in a regulatory filing.

The transaction, which still requires approval from regulators and Astria shareholders, is expected to close in the first quarter of 2026. Upon closing, 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 BioCryst’s rare disease strategy and the biotech plans to pursue strategic alternatives for this asset at an early stage.

“We think it’s a really interesting product, but it’s not a rare disease and it’s better that it’s in the hands of someone in this field. [atopic dermatitis] region,” Stonehouse said.

Photo: Francesco Carta photographer, Getty Images