The therapy requires a patient's T-Cells, one type of white blood cells, to be harvested and modified. These engineered cells are designed to be attracted to a certain protein in tumor cells in order to kill them. Due to the complex nature of the procedure, a healthcare professional will have to go through training to be able to administer the pricey treatment -- The Wall Street Journal says it will cost patients around $373,000.

Kite Pharma conducted a multicenter clinical trial involving 101 adults with relapsed large B-cell lymphoma to convince the FDA to give the therapy its approval. The tumors in 72 percent of the test subjects shrunk and even disappeared completely in 51 percent of the subjects. Despite being effective, the therapy can only be used if a patient has relapsed or failed to respond to at least two different kinds of treatment. That's because Yescarta could cause pretty severe and life-threatening side effects, including anemia and low white blood cell counts. The worst possible reaction to the therapy? It's none other than death: according to The WSJ, Kite Pharma determined that the deaths of two of its test subjects were related to the treatment.