• Merck's monoclonal antibody therapy Keytruda reduced the risk of early stage lung cancer progressing or death by 24% in patients who had undergone surgery, according to clinical trial data.
• The 200-milligram intravenous injections are administered once every three weeks for a total of 18 injections over the course of a year.
• Keytruda helps activate the body's immune system to fight cancer. It's FDA approved as a therapy for numerous other cancer types.
• Merck plans to submit the data on early stage lung cancer to the FDA as soon as possible.

Merck's antibody therapy for early stage lung cancer patients who have previously undergone surgery to have tumors removed reduced the risk of the disease progressing or the patient dying by 24%, according to clinical trial data released Thursday.

Keytruda is a monoclonal antibody treatment that helps activate the body's immune system to fight off non-small cell lung cancer, the most common form of the disease. The 200-milligram intravenous injections are administered once every three weeks for a total of 18 injections over the course of a year.

Merck's head of global clinical development, Dr. Roy Baynes, described the reduced risk of the cancer returning as significant and clinically meaningful. Baynes also expects Keytruda to improve patients' overall survival rate, though he said the data is not mature enough yet to draw a definitive conclusion in that regard.

"When you treat a tumor early, it takes quite a long time for bad outcomes to translate into death," Baynes said. "So the trial is too immature at this point to comment on overall survival, although we would say that the overall survival is directionally favorable at this time."

The clinical trial for early stage lung cancer patients post-surgery evaluated more than 1,000 people randomized into two groups, 590 who received the treatment and 587 who received a placebo. Patients who received Keytruda were disease for more than four years at the median, about a year longer than those in the placebo group. The trial included patients who received chemotherapy and those who hadn't.

Merck plans to submit the data to the Food and Drug Administration as quickly as possible, spokesperson Melissa Moody said. The approval process can take eight to 12 months, according to Baynes. Keytruda was first approved by the FDA in 2014 to treat melanoma and has become a blockbuster drug for Merck that is now used to treat numerous other types of cancer.

Baynes said significant progress has been made in treating lung cancer with immune therapy. He noted that in the case of metastatic lung cancer, where the disease has advanced to other areas of the body, Keytruda in combination with chemo has improved the five-year survival rate to 40%. Typically, the survival rate is only 5%.

Lung cancer is the leading cause of cancer death globally with more than 1.7 million people succumbing to the disease in 2020, according to the World Health Organization. People diagnosed with non-small cell lung cancer normally undergo surgery to remove the tumors if the disease is caught at an early stage. After surgery, patients undergo either observation or receive chemotherapy. Risk factors include a history of smoking and asbestos exposure among others.

However, half of all patients with early stage non-small cell lung cancer have the disease return within five years after removing the tumors and most of them see the cancer return in two years, according to Dr. Mary O'Brien, a co-principal investigator in the trial and an oncologist at Royal Marsden Hospital in London. Patients live with the constant fear and anxiety that the cancer will return, she said.

Keytruda stops cancer cells from shutting down the body's defense system. Cancer cells have a protein that binds to a receptor on T cells, which tricks them into not going on the attack. The Keytruda monoclonal antibody binds to this receptor instead, foiling the cancer's trick and allowing the immune system to fight the disease.

Baynes said the drug is generally well tolerated, though there are side effects associated with the immune system kicking into gear. An example is thyroid toxicity, which occurs when the thyroid releases too much hormone into the body. In more serious but rare cases, patients can develop pneumonitis, an inflammation of the lung tissue, he said. Thyroid toxicity is treated with antithyroid medication and pneumonitis with steroids.

Merck's Keytruda sales totaled $17.2 billion in 2021 or about 35% of the company's $48.7 billion in total revenue for the year. CEO Rob Davis told investors on Merck's fourth-quarter earnings call that using Keytruda to prevent cancer from returning in patients is a major area of future growth for the company.

While the cancer immune therapy is a major area of clinical research, the FDA has only approved one treatment so far to prevent lung cancer from returning in patents who have undergone surgery. The agency approved Tecentriq, made by Genentech, last October.

Clarification: This story has been updated to note that Keytruda is administered through intravenous injection, and one possible side effect is thyroid toxicity.