AstraZeneca halts a pair of lung cancer trials over a safety scare

AstraZeneca's headquarters in London--Courtesy of AstraZeneca

AstraZeneca ($AZN) is pressing pause on trials combining two of its most important pipeline cancer treatments after tracking reports of lung disease, halting enrollment as it gathers more information.

The company is testing a combination of AZD9291 and durvalumab, formerly MEDI4736, in two studies involving patients with non-small cell lung cancer. Late last month, AstraZeneca hit the brakes on enrollment in both trials due to an increase in reports of interstitial lung disease, which can lead to dangerous scarring and impaired pulmonary function. The pauses are temporary, the company stressed in an emailed statement, and patients already enrolled in the study will be given new consent forms to ensure they understand the risks before choosing whether keep getting treatment.

Such a spike in lung disease never cropped up in trials on AZD9291 and durvalumab as individual agents, AstraZeneca said, and the company has no plans to change its development plans for each treatment as a monotherapy.

But any concerns about combined safety are particularly resonant for AZD9291 and durvalumab, two treatments whose future value is strongly tied to their potential in treatment cocktails. Durvlumab, an antibody that works by leading an immune attack on cancers, is part of a blockbuster class of medicines expected to dominate the oncology market in large part because of their potential in combination therapies. If AstraZeneca's contender has a safety overhang, it could eventually cede ground to rival therapies from Merck ($MRK), Bristol-Myers Squibb ($BMY) and others.

As for AZD9291, in development on its own for lung cancer, the drug is racing with a similar candidate from Clovis Oncology ($CLVS), with each headed toward FDA approval next year. Any worries over AZD9291's safety in combination with other therapies could give an edge to Clovis' treatment, called rociletinib.

AstraZeneca is counting on its oncology pipeline--and the aforementioned two drugs in particular--to do much of the heavy commercial lifting over the next few years. In 2014, while trying to shake off Pfizer's ($PFE) buyout interest, the U.K. drugmaker promised to deliver annual revenue above $45 billion by 2023, a watermark that requires $3 billion a year from AZD9291 and $6.5 billion from durvalumab.