Amgen and AstraZeneca’s inflammatory disease drug Tezspire has clinched a phase 3 win in eosinophilic esophagitis (EoE) as the partners eye another challenge to Sanofi and Regeneron’s incumbent Dupixent.
A phase 3 EoE trial for Tezspire has hit all primary and key secondary endpoints, Amgen and AZ announced Thursday.
By targeting an upstream driver of inflammation, Tezspire demonstrated statistically significant improvements in both histologic remission—defined by a low count of peak eosinophils in the esophagus—and swallowing difficulties compared to placebo at week 24, according to the companies. For both Tezspire doses tested, the treatment effects on the study’s co-primary endpoints lasted through week 52, the companies added.
The success from the phase 3 Crossing trial positions the anti-TSLP biologic to potentially expand into its third inflammatory disease indication beyond severe asthma and chronic rhinosinusitis with nasal polyps (CRSwNP). Amgen and AZ said they will share the study’s results with regulatory authorities and with the scientific community at an upcoming medical meeting.
If approved, Tezspire would open a new front in its rivalry with Dupixent, which became the first medicine specifically indicated for EoE in 2022. Compared with Tezspire’s upstream targeting of TSLP, Dupixent works downstream in the immune cascade by blocking IL-4 and IL-13 signaling pathways.
EoE is a chronic inflammatory disease of the esophagus, which can lead to esophageal narrowing and difficulty swallowing, known as dysphagia. The disorder is estimated to affect more than 470,000 people in the U.S., with increased prevalence in the past few years, according to Amgen and AZ.
Before biologics are introduced, first-line treatment of EoE typically centers on three methods, frequently referred to as the “3Ds”—drugs, diet and dilation. For drugs, proton pump inhibitors such as omeprazole and swallowed topical corticosteroids like fluticasone are common options. During the Crossing trial, patients were allowed to remain on those background medications.
“Despite the availability of first-line therapies or dietary interventions, many patients with eosinophilic esophagitis still experience substantial burden, including difficulty swallowing food, and emotional and daily-life impacts of the disease,” Arjan Bredenoord, M.D., a gastroenterologist at the Amsterdam University Medical Center in the Netherlands and primary investigator of the Crossing trial, said in an Aug. 27 statement.
“The impressive results from the Crossing trial sustained over 52 weeks demonstrate that [Tezspire], taken every four weeks, could provide a new approach to treating this disease, with the potential to help more patients achieve remission and symptom improvement,” he added.
In addition to the primary endpoints measured at week 24 and the key secondary endpoints evaluated at week 52, Crossing also hit other goals, including endoscopic disease features and histologic severity and extent at weeks 24 and 52, plus endoscopic response, inflammatory remission and total endoscopic remission at week 52.
Tezspire’s trial win now gives AZ another shot at EoE after its anti-IL5 antibody Fasenra failed to make the cut. Back in 2022, the British pharma reported mixed results from the phase 3 Messina trial, in which Fasenra achieved better histological disease remission compared to placebo but came up short on the dysphagia symptoms metric.
Besides EoE, Tezspire is undergoing phase 3 development—the Journey and Embark trials—in chronic obstructive pulmonary disease (COPD).
First approved by the FDA for severe asthma in late 2021, Tezspire generated $1.9 billion in combined sales for Amgen and AZ in 2025, up from nearly $1.3 billion the year before.
With a much broader label beyond inflammatory conditions affecting the airway, Dupixent brought in $17.8 billion in 2025 global sales.
Meanwhile, against the backdrop of Tezspire’s first-in-class wins, drugmakers are developing more anti-TSLP agents. GSK recently launched phase 3 tests of its twice-yearly candidate felcorekibart (GSK5784283) for COPD and asthma after buying the long-acting drug in 2024.
Last year, Roche licensed a TSLPxIL-33 bispecific antibody from China’s Qyuns Therapeutics in a deal potentially worth more than $1 billion. Qyuns also out-licensed a TSLPxIL-13 bispecific candidate to Windward Bio, which secured $165 million in crossover financing in May to help advance a twice-yearly anti-TSLP candidate into phase 3. Sanofi is also developing a TSLPxIL-13 bispecific nanobody called lunsekimig, which recently hit goals in a pair of midstage studies for asthma and CRSwNP.