US regulators have approved the first cancer drug that uses a patient’s own cells to fight cancer. But the drug is priced at $475,000.

Oncologists described the drug, made by Novartis and marketed as Kymriah, as revolutionary, but critics say the first-of-its-kind cancer treatment could usher in a new class of ultra-expensive medications.

Kymriah will be a one-time, intravenous treatment patients receive after scientists at Novartis engineer a patient’s own immune cells (T-cells) to fight cancer. The drug will treat acute lymphocytic leukemia, the most common type of childhood cancer in the US.

Currently, standard treatments push about 85% of children into remissions of five years or longer, according to the American Cancer Society. Kymriah would treat patients who don’t respond to standard treatment, probably only a few hundred children and young adults per year.

“This is a brand new way of treating cancer,” said Dr Stephan Grupp of Children’s Hospital of Philadelphia, who led the Novartis study. Grupp treated the first patient using the new immunotherapy procedure: a girl who was near death but is now cancer-free five years and counting. Grupp described the drug as “enormously exciting”.

Though the price may be shocking to many, analysts will probably view the $475,000 price tag as conservative. A British study suggested the “upper bound” for a drug like Kymriah could be $649,000.

Critics countered that the Novartis treatment only proved drug pricing in America was “completely broken”.

“While Novartis’s decision to set a price at $475,000 per treatment may be seen by some as restraint, we believe it is excessive,” said David Mitchell, the president of Patients for Affordable Drugs. Mitchell said Novartis should not “get credit” for bringing an expensive drug to market “and claiming they could have charged people a lot more”.

Mitchell’s group met Novartis the day before the drug’s approval – and price – was announced.

“Instead of a discussion about how to arrive at a fair price for its new CAR-T drug, Novartis spent most of the meeting explaining why it needs to charge an astronomical price,” Mitchell said.

In a conference call Wednesday, Bruno Strigini, Novartis’s head of oncology, said the $475,000 price was an attempt to balance patient access to the drug with ensuring a return on the company’s investment, Stat News reported.

The company’s CEO, Joseph Jimenez, said in a statement: “Five years ago, we began collaborating with the University of Pennsylvania and invested in further developing and bringing what we believed would be a paradigm-changing immunocellular therapy to cancer patients in dire need. With the approval of Kymriah, we are once again delivering on our commitment to change the course of cancer care.”

The drug company also said in the statement that it was collaborating with Medicare on a plan in which the government would only pay for the treatments if patients responded to them by the end of the first month.

Patients for Affordable Drugs calculated that before Novartis collaborated with University of Pennsylvania, American taxpayers invested roughly $200m into “foundational” research on CAR-T cell therapies, as the new immunotherapy treatment is known.

The FDA approved Novartis’ drug following a study of 63 patients that found 83% who took the medication went into remission. However, it is unclear how long the benefits of the treatment may last; some patients relapsed months later.

Further, patients could also experience extreme and even life-threatening side effects. One side effect, cytokine release syndrome, can cause high fevers, diarrhea and vomiting. Another, neurological toxicities, can cause delirium, loss of balance and difficulty speaking and understanding.

Additionally, patients will almost certainly have to travel to receive the treatment. Novartis individually edits patients’ cells. Anyone seeking treatment will need to travel to one of 32 sites around the country for their cells to be collected and mailed to Novartis in New Jersey, Stat News reported.

The Associated Press contributed to this report