Bristol-Myers Squibb Co and bluebird bio Inc said on Friday their experimental therapy for a type of multiple myeloma met the main goal in a mid-stage study. Shares of bluebird rose 5.5% to $83.75 in trading after the bell. The study evaluated the efficacy and safety of the therapy, Ide-cel, in patients who had received three prior treatments for multiple myeloma, a cancer of the white blood cells, the companies said. Patients across three doses of the therapy had an overall response rate of 73.4%. The therapy also demonstrated a median progression free survival of 8.6 months, the companies said in a statement.The therapy belongs to a class of drugs known as chimeric antigen receptor T-cell therapy or CAR-T, which involves drawing white blood cells from a patient, processing them in the lab to target cancer, and infusing the cells back into the patient. The drug targets a protein linked to multiple myeloma known as BCMA. The safety profile of the therapy was consistent with the data in prior studies, the companies said. "We are encouraged by these data, especially the outcomes observed at the highest target dose," Kristen Hege, senior vice president of oncology and cell therapy development at Bristol-Myers said in a statement.