Experimental Cancer Therapy Holds Great Promise — But at Great Cost

Soon after she received the treatment, Karen Koehler’s brain swelled. Her blood pressure plummeted. As she fell into a coma, her husband and sister sat at her bedside — urging the doctors to keep pushing her farther along the razor’s edge between life and death.

Koehler was undergoing a promising — and terrifying — experimental therapy that her oncologists hoped could rid her body of cancer entirely. It’s called CAR-T therapy, and it works by engineering the patient’s own immune cells to attack cancer.

One of the hallmarks of CAR-T: It has to nearly kill you if it’s going to save you.

The treatment induces such sudden and severe side effects that it can take a small army of top specialists to keep patients alive while their newly engineered immune systems attack their cancer cells. The result: CAR-T remains so risky, so complex, and so difficult to manage that experts warn it’ll be years before it’s available to most patients who would stand to benefit — even though two drug makers, startup Kite Pharma and pharmaceutical giant Novartis...