Drug maker Merck & Co Inc, whose medicine Keytruda has received approval for treating serious skin cancer type melanoma, was shown in a clinical trial to shrink tumors in roughly half of patients of advanced lung cancer with high protein levels used by tumors for evading the disease-fighting cells of the patients’ body.

As the trial has showed progressive result, the company has filed an application seeking approval from the US Food and Drug Administration (FDA) for its drug to treat the patients with non-small cell lung cancer (NSCLC), whose ailment has significantly worsened despite earlier treatment.

Keytruda, which is also called pembrolizumab, is part of a new class of medications designed especially for helping the immune system fend off cancer by obstructing a protein named Programmed Death receptor (PD-1), or an associated target called PD-L1.

The company said that its FDA filing of lung cancer treatment is for those patients who are suffering with both squamous and non-squamous NSCLC.

Nearly 160,000 Americans lose their life annually due to lung cancer.

For the Phase 1 study, Merck involved 495 patients with NSCLC and found that 45 percent of them having high PD-L1 levels responded to Keytruda as compared to 16.5 percent of patients having PD-L1 levels between one percent and 49 percent.

The response rate, which intends tumor shrinkage of at least 30 percent, was recorded 10.7 percent for patients having PD-L1 level below one percent.

Problems related to thyroid are one of the main side effects of Keytruda. One patient had lost his life due to pneumonitis or lung inflammation, which was witnessed in 3.6 percent of trial patients.

The Merck results, which were published in the New England Journal of Medicine, were presented during a meeting of the American Association for Cancer Research.