Bristol-Myers Squibb Co. and bluebird bio Inc. said its experimental blood cancer treatment ide-cel reduced the disease and extended life in patients during a mid-stage study.

The companies were evaluating the chimeric antigen receptor T cell, or CAR-T cell, therapy in patients with relapsed and refractory multiple myeloma who have received at least three prior treatments. Multiple myeloma is an incurable blood cancer that forms in plasma cells, which are responsible for producing antibodies.

The companies evaluated three doses of the CAR-T cell therapy in the open-label phase 2 study, dubbed as KarMMa. Ide-cel achieved the primary goal of reducing the disease in patients, also known as the overall response rate, across all dose groups.

The treatment also met the key secondary endpoint of the study by leaving no detectable cancer, known as complete response.

CAR-T cell therapies are a complex and expensive form of cancer treatment that takes a patient's own immune cells and modifies them to fight cancer when infused back into the body.

The U.S. Food and Drug Administration has approved Novartis AG's Kymriah and Gilead Sciences Inc.'s Yescarta to treat certain cancers. Both CAR-T cell therapies cost upward of $300,000.