資料來源：https://www.reuters.com/article/us-merck-co-fda-idUSKCN12P06Q

Merck & Co has won U.S. approval to market its immunotherapy Keytruda for use in previously untreated lung cancer patients two months ahead of schedule, making it the only such drug cleared for first-line treatment.

The green light from the Food and Drug Administration (FDA), announced by the U.S. drugmaker late on Monday, confirms Merck's leading position in the hot area of medicines that fight tumors by harnessing the body's immune system.

Keytruda's latest approval is for treating first-line metastatic non-small cell lung cancer (NSCLC) in patients with high-levels of a protein called PD-L1, which makes them more receptive to immunotherapy.

The FDA had set a target date of Dec. 24 for deciding on this new use.

Expectations for Keytruda, which works by taking the brakes off the immune system, have been building since its success in treating selected untreated patients. Annual sales of the drug are now expected to reach $8.1 billion in 2021, according to consensus forecasts compiled by Thomson Reuters.

Rival Bristol-Myers Squibb's drug Opdivo failed in a late-stage trial for the same indication. Bristol had tried to make Opdivo work irrespective of PD-L1 levels. In the event, it disappointed comprehensively in a major study.

Keytruda and Opdivo, along with Roche's rival immunotherapy Tecentriq, are already approved for lung cancer patients who have undergone previous chemotherapy.

Keytruda had originally only been cleared in this second-line setting for patients with high PD-L1 levels but the FDA also expanded this on Monday to allow for treatment where PD-L1 expression is just 1 percent or more.

Immunotherapy drugs are used additionally in melanoma, Hodgkin lymphoma and cancers of the bladder, kidney, head and neck, but lung cancer, the world's biggest cancer killer with an annual death toll of 1.6 million, is the biggest potential market.

Although doctors are allowed to prescribe medicines for not yet approved uses, the FDA's first-line clearance of Keytruda could greatly increase the number of patients taking the drug.

Leerink analyst Seamus Fernandez said the news should cement Merck's position as leader in the first-line lung cancer field for at least the next 12 to 18 months, after when the battle is likely to shift to new combination therapies.

Only a quarter to a third of non-small cell lung cancer patients have tumors with at least 50 percent of cells producing PD-L1, making them suitable for first-line Keytruda, so around 70 percent of the market is still up for grabs.

As a result, the race is now on between Merck, Bristol, Roche and AstraZeneca to find smart ways for combining treatments, either by adding chemotherapy or using two different immunotherapies in tandem.

Merck's first-line approval was based on data from a late-stage study which showed Keytruda achieved superior progression-free and overall survival compared to chemotherapy in patients whose tumors expressed high levels of PD-L1.

(Editing by Lisa Shumaker and Jane Merriman)