By Michael Erman

NEW YORK (Reuters) – Drugmaker Bristol-Myers Squibb Co said on Friday it was pulling the application to have its immunotherapies Opdivo and Yervoy approved in Europe as an initial treatment for advanced lung cancer, after regulators there balked at changes to the design of its clinical trials.

The drugmaker said it had no plans to refile the application in the European Union. Lung cancer is the most lucrative oncology market.

According to Bristol, Europe’s Committee for Medicinal Products for Human Use (CHMP) said it was not possible to assess the data from the company because of “multiple protocol changes” the company made in its trial. The combination is still under review by the U.S. Food and Drug Administration (FDA), which granted the company priority review for the drugs as a treatment for first line non-small cell lung cancer earlier this month. The FDA is expected to decide on the treatment by May 15.

Opdivo is one of Bristol’s top-selling drugs, with analysts expecting $7 billion in sales for 2019. But the company’s sales of the drug has slowed in recent years as it has been eclipsed by Merck & Co’s rival drug Keytruda.

Keytruda is already approved to treat newly diagnosed advanced lung cancer in both the United States and Europe. Analysts estimate Merck’s 2019 sales of Keytruda were around $11 billion last year.

Bristol-Myers said it still plans to file applications to get Opdivo plus Yervoy and limited chemotherapy approved as an initial treatment for lung cancer in the United States, Europe and elsewhere.

The process of getting Opdivo and Yervoy approved as a first line treatment for lung cancer has been an albatross for Bristol-Myers.

The European regulator balked after the company adjusted its clinical trials in Feb. 2018 in order to test the drugs’ effectiveness using a new biomarker called Tumor Mutational Burden. (TMB)

The company already withdrew an application last year to have the combination approved in the United States based on the TMB data after discussions with regulators.

Shares of Bristol closed down 1.3 percent in the New York Stock Exchange on Friday. The company is scheduled to report earnings next week.

(Reporting by Michael Erman; editing by Jonathan Oatis and David Gregorio)