- Nkarta reported its first results from early-stage studies testing two different blood cancer treatments that harness natural killer cells, an emerging form of cellular immunotherapy.
- Three of five acute myeloid leukemia patients treated with the highest dose of one Nkarta therapy, and eight of the 17 who could be evaluated, responded to treatment, according to a statement. Five of six non-Hodgkin lymphoma patients who received the highest dose of another Nkarta treatment, and seven of 10 overall, responded. Nkarta now will test a higher dose as well, CEO Paul Hastings said in an interview.
- There were no instances of the immune or neurological side effects often associated with other engineered cell therapies, an important distinction for NK cell treatments. The most common side effects were infections as well as depleted white and red blood cell counts, which is "what you would expect" after the chemotherapy regimen used to prepare these patients for treatment, according to Hastings.
Nkarta is one of the leading companies in the push to develop immunotherapies based on "natural killer," or NK cells, part of the body’s first line of defense against foreign invaders.
Early clinical results from programs at MD Anderson Cancer Center and German biotech Affimed as well as Fate Therapeutics have shown promise treating some blood cancers without the potentially dangerous side effects observed with so-called CAR-T therapies. As "off-the-shelf’" drugs derived from donor cells or pluripotent stem cells, NK cell treatments could also be more convenient than personalized cell therapies, which are logistically complex to manufacture.
Still, NK cell therapies have more to prove before they can become a viable alternative to treatments like Gilead’s Yescarta and Novartis’ Kymriah. Clinical studies are early and haven’t yet proven how long-lasting the effects of NK cell treatments are or how well they compare to CAR-T.
Nkarta’s first human results don’t change that narrative as its studies haven’t gone on long enough and the company hasn’t treated enough patients to draw true comparisons to CAR-T. However, its findings do build on the early evidence supporting the potential for NK cell therapies in leukemia and lymphoma.
One treatment, NKX101, is being developed for acute myeloid leukemia, for which donor NK cells have a history of being used to "bridge" patients to curative stem cell transplants. At the highest tested dose so far, three of five patients who’d previously received a median of three prior treatments were driven into remission. Two of them had "full" complete responses, meaning no disease was detected after treatment. One patient became eligible for a transplant. Another is three months out. Although followup is short, none have relapsed, according to Hastings.
The CEO said the data "exceeds the published literature" for donor NK cell treatment, which, according to research last May from Stifel analyst Benjamin Burnett, is associated with a 30% to 35% response rate in relapsed or refractory disease.
Meanwhile, three of six lymphoma patients on the highest dose of the other treatment, NKX019, had complete responses as well. All of those responses are ongoing and one patient was treated six months ago, Hastings said. CAR-T therapies have established about a 70% response rate and 50% remission rate in B-cell lymphomas, Burnett wrote. Some 30% to 35% of those remissions last at least six months, a key hurdle for cell therapies to meet.
"Time will tell" how long the responses hold up, Hastings said. "We are hopeful."
Nkarta didn’t see any responses among four patients with myelodysplastic syndrome. However, the company now will test higher doses in leukemia and lymphoma patients as it seeks to "maximize the durability and efficacy we’re already seeing," Hastings said.
So far, the safety profile is enabling Nkarta to test multiple doses of its treatment and could lead it to evaluate its NK cell therapies alongside other drugs in earlier lines of care. Nkarta also plans to study NKX101 in solid tumors and NKX019 in patients who have previously received CAR-T treatment, Hastings said.
Nkarta will report data on patients given a higher dose of each treatment later this year, the CEO added.
Company shares climbed more than 94%, to about $15 apiece, in early trading Monday.