Fasenra (benralizumab) Receives FDA Approval for Hypereosinophilic Syndrome
The FDA expanded the indications for AstraZeneca's drug, approving it for the treatment of hypereosinophilic syndrome in patients over 12 years old. The decision is based on Phase III data showing a 65% reduction in the risk of disease exacerbations compared to placebo.
Not just a rare disease: How Fasenra's approval for HES reshapes the competitive landscape of the eosinophilic biologic market
[The Gist]: What's really happening
On May 13, 2026, the FDA approved AstraZeneca's Fasenra (benralizumab) for the treatment of hypereosinophilic syndrome (HES) in patients over 12 years old. At first glance, this is a niche approval for an orphan disease with a prevalence of 0.3–6.3 cases per 100,000 people. But in reality, this is less a clinical event and more a strategic maneuver in the three-way war between AstraZeneca, GSK, and Sanofi/Regeneron for dominance in the rapidly growing segment of biologics targeting eosinophils. The HES treatment market, valued at $1.2 billion in 2025, is projected to grow to $1.74 billion by 2035. And Fasenra now has an indication that its main competitor, Dupixent, lacks.
Timeline and Context
Fasenra's path to this approval was far from smooth. The drug debuted in 2017 as a treatment for severe eosinophilic asthma and by 2025 had reached sales of $920 million in the first half of the year. However, a series of setbacks followed.
In February 2025, the FDA rejected an application for the drug in chronic rhinosinusitis with nasal polyps, despite positive results from the OSTRO study. In April 2026, the FDA again denied AstraZeneca's registration for this indication. And in late September 2025, the RESOLUTE study in COPD failed to achieve statistical significance on the primary endpoint. Three failures in eighteen months. For a brand with blockbuster ambitions, this was a critical moment.
The HES approval, based on results from the Phase III NATRON study, becomes a much-needed strategic comeback. In this trial involving 133 patients, Fasenra reduced the risk of first exacerbation by 65% compared to placebo (HR 0.35; 95% CI: 0.18-0.69; P=0.0024). The results were published in Nature Medicine on March 31, 2026, providing scientific credibility.
But the timeline also includes important context: GSK beat AstraZeneca by getting Nucala approved for HES several years earlier, as well as for CRSwNP in 2025. Meanwhile, Dupixent dominates with sales of $5.7 billion in 2025, far ahead of both Nucala ($1.4 billion) and Fasenra ($1.3 billion). HES is one of the few areas where Fasenra now has a clear competitive advantage.
Who Wins and Who Loses
Winners:
- AstraZeneca: This is the fifth approved indication for Fasenra, after asthma and EGPA. HES gives the drug a niche where it is not playing catch-up. Unlike attempts to enter the CRSwNP market, where Dupixent is deeply entrenched, here AstraZeneca can compete on equal footing.
- HES patients: Diagnosing HES is difficult—patients often suffer for years from fatigue, skin rashes, abdominal pain, and neurological symptoms before receiving the correct diagnosis. The NATRON study showed sustained improvement in fatigue scores on the PROMIS Fatigue scale, a meaningful patient-centered endpoint. A once-monthly subcutaneous injection is more convenient than traditional high-dose corticosteroid therapy with its cumulative toxicity.
- AstraZeneca's portfolio: Fasenra is the company's second-largest respiratory product. Expanding indications supports revenues, while the ternary asset toazoraliad moves into focus as a potential long-term replacement.
Losers:
- GSK: Nucala was the first anti-IL-5 drug on the HES market, but Fasenra's mechanism of action is fundamentally different: it is a cytolytic antibody targeting the alpha chain of the IL-5 receptor, causing eosinophil depletion rather than just inhibition. Now AstraZeneca can claim superior biology. Nucala still leads in overall sales ($930 million over nine months in 2025), but the window of opportunity is narrowing.
- Sanofi/Regeneron: Although Dupixent does not directly compete in HES (it is not approved for this disease), every new indication for Fasenra or Nucala creates an ecosystem of specialized care where physicians become more familiar with eosinophil biology and start prescribing these IL-5-targeted drugs. This expands the market but also increases competitive pressure.
- Generic dasatinib manufacturers: Dasatinib is a second-line option for some forms of HES, and its market share in the $1.2 billion segment may decline as first-line biologics become more widely used.
What the Media Misses
Most coverage focuses on the efficacy endpoint of "65% risk reduction." But the real insight lies in the study design and unmet patient needs.
Non-obvious insight: The inclusion criteria for NATRON required patients to already be on stable background HES therapy—typically corticosteroids. The primary endpoint measured not complete remission, but time to the need to increase that therapy. This means Fasenra is essentially approved as a steroid-sparing agent. What's the deeper meaning here? AstraZeneca's strategy is not just about suppressing eosinophils—it addresses a real clinical problem that physicians understand well: long-term corticosteroid use causes cataracts, osteoporosis, diabetes, and avascular necrosis. By positioning Fasenra as a means to reduce cumulative steroid dose, the company directly appeals to these fears without bearing the burden of explicitly proving this in the registration study. This is a smart way to give the drug clinical significance without requiring a much longer overall survival study—which would be nearly impossible for a rare disease like HES.
The second omission concerns the global regulatory trajectory: Fasenra is already approved for HES in Chile. AstraZeneca appears to be using a "wave approval" strategy—first small markets, then the FDA, now applications will be filed with the EMA and PMDA (Japan). This creates a sense of growing momentum, even if each individual regulatory decision is not guaranteed.
Forecast: Next 30 Days and 90 Days
30 days (by mid-June 2026):
AstraZeneca is expected to announce the commercial price for the HES indication in the US. Since both Nucala and Fasenra are already on the market, price competition will be moderate—likely both companies will set a list price in the range of $45,000–55,000 per year. A key event will be inclusion in guidelines: the American Society of Clinical Oncology (ASCO) and the American Academy of Allergy, Asthma & Immunology (AAAAI) may update their recommendations to include benralizumab, accelerating adoption.
In parallel, GSK will likely publish new data on Nucala in HES to counter the NATRON results. This will be a publication battle that sets the narrative at physician conferences through summer 2026.
90 days (by mid-August 2026):
A real-world evidence (RWE) analysis using data from the HES registry or the Truven Health MarketScan database is likely. These data will show whether patients are switching from oral corticosteroids and dasatinib to Fasenra and how persistent adherence is. If RWE confirms a long-term steroid-sparing effect, Fasenra could capture over 25% of the US HES market by the end of 2026.
The broader picture: The failure in COPD and the rejection for CRSwNP mean that AstraZeneca must maximize every remaining niche. Expect aggressive lobbying for inclusion of Fasenra in formularies for HES patients, as well as an accelerated EMA submission by fall 2026. If European approval comes within the next six months, the projected HES market growth to $1.74 billion by 2035 may even be an underestimate—especially if improved diagnostics identify more patients than current epidemiological models suggest.
— Editorial Team
