Dive Brief:

  • Fate Therapeutics on Thursday reported new results from two early-stage studies testing two types of experimental leukemia treatments that use natural killer cells, an emerging form of cancer immunotherapy.
  • Four of nine patients who received one Fate NK cell therapy showed evidence of a response, as did one of three who got a different type of NK cell therapy. There were no instances of the neurological or immune-related side effects seen with other forms of cell therapy and there were also no side effects that would prevent testing of higher doses, according to the company.
  • The results are the latest piece of evidence suggesting NK cell therapies could eventually become an effective, off-the-shelf treatment for blood cancer — a strategy being pursued by Fate, Nkarta Therapeutics, Takeda and others. But lingering questions remain. Wall Street analysts, for example, noted the responses Fate observed weren't "deep" and most occurred in patients who may have been easier to treat.

Dive Insight:

Unlike the CAR-T cell therapies approved for a handful of blood cancers, natural killer cell therapies rely on NK cells, the body's front-line defenders, to seek out and attack tumors.

Their developers aim to prove they're safer than their CAR-T counterparts, more convenient and potentially able to broaden the cell therapy's reach to more cancers. Some efforts are even underway to combine NK cell therapies with other medicines, among them CAR-T treatments.

Research into NK cell treatments remains early, and the field has significant hurdles still to overcome, like proving how potent their effects are and how long they last. It's unclear what role they'll play in cancer care. But encouraging signs are emerging, most notably from a lymphoma treatment developed by the MD Anderson Cancer Center.

The field's progress has led to the launch of multiple startups and elevated the profile of biotechs like Fate and Nkarta Therapeutics, the most advanced, publicly traded companies developing the technology. NK cells are "becoming a very important tool and cell type within this fight against cancer," said CRISPR Therapeutics CEO Sam Kulkarni in an interview after the biotech formed a broad partnership with Nkarta last week.

Both Fate and Nkarta have begun with acute myeloid leukemia, for which there is a history of "naked," or non-engineered donor, NK cells being successfully used to treat patients with the disease. The biotechs aim to prove engineered versions that are mass-produced as "off-the-shelf" therapies can be just as effective or better than NK cell transplants.

Donor NK cell transplants are meant to "bridge" patients to potentially curative stem cell transplants, and have historically produced response rates of roughly 30% to 35% in relapsed or refractory disease, according to Stifel analyst Benjamin Burnett.

Fate is using induced, pluripotent stem cells to make its treatments, while Nkarta is using donor cells. Fate is further along and has two candidates in its pipeline. One, called FT516, is essentially an engineered naked NK cell administered along with a cytokine drug meant to boost its effects. The other, FT538, is modified with certain characteristics to increase its potency.

Thursday's update, from Phase 1 studies testing each as a monotherapy, marked the most comprehensive update for each. Positively, the response rates appeared in line with what's been observed in academic tests, have lasted as long as six months and haven't led to side effects that would stop Fate from testing higher doses. One of the four patients with the best response was able to undergo a stem cell transplant. The other three responses are ongoing.

"Our biggest takeaway," wrote Burnett, is that FT516 "is able to at the very least recapitulate the efficacy of a naturally derived NK cell."

But on a conference call Thursday, several analysts questioned the strength of those responses, as none of the patients showed full evidence of disease in remission. They also observed the responders were patients who had gone through fewer prior treatments than others and had lower numbers of cancerous cells in the bone marrow at the start of the study. Such patients are "arguably easier to treat," wrote SVB Leerink analyst Daina Graybosch.

Fate executives argued responses could evolve to become stronger as time goes on. That'll be critical to watch, as will the results when Fate moves on to test higher doses in more patients. The company aims to test up to a three-times higher dose of FT516 and even higher than that for FT538. Fate also plans to study FT538 alongside the antibody drug Darzalex.

Shares in Fate rose by nearly 9% in morning trading Friday. 

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