Iovance Biotherapeutics has developed a 'living drug' made up of immune cells from patients' own tumors. The therapy involves taking the immune cells from the patient's tumor, growing them in the lab, and then infusing them back into the body. The massive influx of immune cells zeros in on and attacks cancer cells, and in some cases, appears to wipe out every last one. The drug doesn't work for everyone, but it can still be a lifesaver for some patients. It has been approved in the US for advanced melanoma.