The U.S. Food and Drug Administration on Friday approved Xalkori (crizotinib) to treat certain patients with late- non-small cell lung cancers, who have a form of genetic mutation.

 Xalkori is a Pfizer drug, and it works by targeting specific genes found certain patients. This gene is called the abnormal anaplastic lymphoma kinase (ALK) gene and is present in about 1 to 7 percent of non-small cell lung cancer patients.

This gene stimulates cancer cells and cause new growth. However, Xalkori works to block the proteins produced by this gene.

It's another example of how we're using molecular medicine to subtype lung cancer into more specific and treatable diseases, said Dr. Roy Herbst, a lung cancer expert who is chief of medical oncology at Yale University, to the Washington Post.

Xalkori, a twice-daily pill, is being approved along with a companion diagnostic test that will help determine if a patient has the abnormal gene. It's the second such targeted therapy approved by the FDA this year.

The approval of Xalkori with a specific test allows the selection of patients who are more likely to respond to the drug, said Dr. Richard Pazdur, director of the Office of Oncology Drug Products in the FDA's Center for Drug Evaluation and Research, in a statement. Targeted therapies such as Xalkori are important options for treating patients with this disease and may ultimately result in fewer side effects.

The FDA approved the drug under its accelerated approval program. This program speeds up the clearance of therapies showing promising early results.

But the drug will come with a high financial cost to society, as Forbes reported that Pfizer said it will cost $9,600 a month, or $115,000 for patients who take Xalkori for a year.

In clinical trials, the average duration of treatment was between 22 and 32 weeks, but because the drug appears to extend patients' lives, many may be on it for far longer than that, Forbes noted.

The trend in oncology research continues towards targeted therapies, said Alberto Gutierrez, director of the Office of In Vitro Diagnostic Device Evaluation and Safety in the FDA's Center for Devices and Radiological Health, also in a statement. This test is an example of the important role companion diagnostics play in determining that the safest and most effective treatments are promptly delivered to patients living with serious and life-threatening diseases.

The most common side effects reported in patients taking Xalkori included vision disorders, nausea, diarrhea, vomiting, swelling (edema), and constipation.