Eight years ago, a Dutch oncologist, John Haanen, set out to change melanoma treatment by arranging one of the largest and most rigorous trials ever for a cell therapy technique originally

devised in the mid-’80s. He could not have picked worse timing.

Months after the trial began, European regulators approved the first PD-1 inhibitor, a groundbreaking immunotherapy. Patients clamored for it. “We had to wait,” Haanen said. 

As the years passed, though, his study accrued patients who had exhausted PD-1s and provided a crucial lens on whether the decades-old approach, known as TIL therapy, could help patients who