Programmed cell death 1 (PD-1) inhibition with pembrolizumab is showing early promise for some patients with advanced non-small-cell lung cancer, according to preliminary findings published in the New England Journal of Medicine.

The research was published to coincide with the annual meeting of the American Association for Cancer Research, held in Philadelphia.

The study involved 495 patients in the advanced stages of non-small-cell lung cancer. All of the patients received infusions of pembrolizumab every two to three weeks. The researchers also analyzed their tumor samples to measure levels of PD-L1.

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Of the whole study group, 19 percent responded to the treatment, meaning their tumors shrank by at least 30 percent, lead author Edward Garon, M.D., an associate professor of medicine at the University of California, Los Angeles, told HealthDay.

But among patients with PD-L1 activity in at least half their tumor cells, 45 percent responded to the drug. After about a year of follow-up, most of the study patients with high PD-L1 levels were still alive, Garon said.

The most common side effects were fatigue, skin rash, and appetite loss. But about 10 percent of patients had more severe side effects, Garon said. Nine developed serious cases of pneumonitis of grade 3 or greater, including one patient who died.

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“In conclusion, we have shown the efficacy and safety of pembrolizumab for previously treated and previously untreated patients with non-small-cell lung cancer,” the authors write.

“Prospective testing of PD-L1 expression is feasible and retrospectively identified patients with an enhanced likelihood of having a clinical benefit from treatment with pembrolizumab.”

The research was supported by Merck Sharp & Dohme, a subsidiary of Merck.


  1. Garon, Edward B., MD, et al. “Pembrolizumab for the Treatment of Non-Small-Cell Lung Cancer.” The New England Journal of Medicine. DOI: 10.1056/NEJMoa1501824. [epub ahead of print]. April 19, 2015.