AZ, Amgen’s first-in-class asthma drug gets breakthrough status

AstraZeneca and partner Amgen have picked up a breakthrough designation from the FDA for tezepelumab, a drug that AZ claims could be a “best in disease” therapy for severe asthma.

Tezepelumab is a thymic stromal lymphopoietin (TSLP) targeting antibody that would slot into AZ’s key respiratory portfolio alongside Fasenra (benralizumab), the company’s interleukin-5 inhibitor antibody, which was approved for severe asthma in Europe in January but just failed a test in chronic obstructive pulmonary disease (COPD).

The new candidate is in a phase III programme called PATHFINDER – due to report results from 2020 – and according to AZ chief executive Pascal Soriot has shown remarkable activity in mid-stage testing, reducing several key asthma biomarkers including blood eosinophils, fractional exhaled nitric oxide (FENO) and immunoglobulin levels as well as cutting asthma attacks.

Drugs like Fasenra and GlaxoSmithKline’s rival IL-5 inhibitor Nucala (mepolizumab) have emerged as an important treatment option for people with severe asthma characterised by high levels of eosinophils. However, the FDA’s BTD for tezepelumab is for patients “without an eosinophilic phenotype, who are receiving inhaled corticosteroids/long-acting beta2-agonists with or without oral corticosteroids and additional asthma controllers,” says AZ.

Because it acts further upstream in the inflammatory cascade responsible for asthma, tezepelumab could be suitable for a broader range of patients than Fasenra and Nucala, and also potentially Sanofi and Regeneron’s new candidate Dupixent (dupilumab), an IL-4 and IL-13 inhibitor that is already approved for atopic dermatitis. Dupixent was filed for asthma in the US in March and is due for an FDA verdict by 20 October, but some analysts have said they also expect Dupixent to be used mainly in patients with eosinophilic asthma.

Tezepelumab new status comes on the back of the phase IIb PATHWAY study which showed a significant reduction in the annual asthma exacerbation rate compared with placebo in a broad population of severe asthma patients irrespective of patients’ characteristics at enrolment. Around 10% of all asthma patients are thought to have severe symptoms making them eligible for antibody therapies.

“Tezepelumab is exciting because it has the potential to treat a broad population of severe asthma patients, including those ineligible for currently-approved biologic therapies,” said Sean Bohen, AZ’s chief medical officer.  The BTD “will help us bring tezepelumab to patients as quickly as possible,” he added.

Biologic drugs for asthma are predicted to make several billions of dollars in sales at peak, and there are already signs of string growth for some new products. Nucala made £245m ($317m) in the first six months of the year, with later entrant Fasenra bringing in $86m. Analysts have suggested tezepelumab could be a blockbuster in its own right.