The Food and Drug Administration on Wednesday approved a futuristic new approach to treating cancer, clearing a Novartis therapy that has produced unprecedented results in patients with a rare and deadly cancer.

The treatment, called a CAR-T, is made by harvesting patients’ white blood cells and rewiring them to home in on tumors. Novartis’s product is the first CAR-T therapy to come before the FDA, leading a pack of novel treatments that promise to change the standard of care for certain aggressive blood cancers.

Novartis’s therapy is approved to treat children and young adults with relapsed acute lymphoblastic leukemia. It will be marketed as Kymriah.

In a clinical trial, Kymriah left 83 percent of participants cancer-free after three months, results oncologists have hailed as a major advance for patients with few other options. The most frequent side effect was an inflammatory storm called cytokine release syndrome, a reaction to CAR-T that can prove fatal in some patients but is commonly controlled with immunosuppressant drugs.

“I think this is most exciting thing I’ve seen in my lifetime,” said Dr. Tim Cripe, an oncologist with Nationwide Children’s Hospital, at an FDA meeting on Kymriah in July.

Now the question now turns to price. Novartis did not immediately disclose how much it intends to charge for Kymriah, but analysts expect it to cost as much as $700,000 for a course of treatment, and the Swiss drug maker has already come under pressure from a patient advocacy group.

In what is perhaps an effort to assuage cost concerns, Novartis said Wednesday that it is working with Medicare on a system in which the government would only pay for CAR-T treatments if patients respond within a month.

Unlike well-understood pills and commonly injected biotech drugs, CAR-T presents a radical new paradigm for doctors, regulators, and payers. Each dose is custom-tailored for an individual patient, requiring a complex process in which human cells must be safely ferried across the country, reliably re-engineered, and soundly returned.

And it remains unclear is just how lucrative a business opportunity Kymriah presents, whatever the price. There are about 3,100 new cases of ALL each year, but roughly 70 percent can be pushed into remission by standard therapy. That could leave just a few hundred patients who might be eligible for Novartis’s therapy, casting doubt on whether the company can get an outsize return on what will be a substantial manufacturing investment.

Republished with permission from STAT. This article originally appeared on August 30, 2017