Pfizer on Friday, announced that the US Food and Drug Administration (FDA) have approved the expanded use of the cancer drug Xalkori (crizotinib). The drug is used to treat patients with advanced small cell lung cancer with a rare mutation called ROS-1.

Pfizer’s Xalkori is the only drug available for one percent of lung cancer patients with a rare mutation. Xalkori restricts the activity of ROS-1 protein, preventing the growth of non-small cell lung cancer (NLCLC). The drug was approved in 2011 and is used twice-a-day. A diagnostic kit is also developed by the company, to identify patients with ROS-1 mutated lung cancer.

“Xalori is the first and only FDA approved treatment for patients with ROS-1 positive NSCLC,” stated the USFDA.

In 2014, clinical trials revealed that the drug helps in reducing the size of tumors in 36 out of 50 patients, with a 72 percent success rate. FDA’s Richard Pazdur, M.D., said that the expanded use of Xalkori will provide a valuable treatment option for patients with the rare and difficult to treat ROS-1 gene mutation by giving health care practitioners a more personalized way of targeting ROS-1 positive NSCLC.

Pfizer stated that more than 8,000 patients have been treated with the drug, since it was approved in the US. The company also added that the European Medicines Agency (EMA), is reviewing an application that would expand the marketing to treatment of adult patients with ROS-1-positive advanced NSCLC. Xalkori is priced at $14,336/month — the pricing before any discounts or rebates offered by manufacturers to insurers and other payers.

There are about 1.5 million new cases of  non-small lung cancer cases every year, but about 15,000 are affected by ROS-1 gene alterations. The USFDA stated that lung cancer is the leading cause of cancer-related deaths in the United States, with an estimated 221,200 diagnoses and 158,040 deaths in 2015, according to National Cancer Institute.