What happened

Shares of Nkarta (NKTX -6.48%) were down more than 34% as of 12:30 p.m. on Tuesday after the clinical-stage biotech announced disappointing trial results for an acute myeloid leukemia (AML) therapy.

So what

Nkarta focuses on engineering allogeneic, off-the-shelf natural killer (NK) cell therapies to treat cancer, as a way to improve the body's immune response to cancer cells.

On Tuesday, the company announced early-stage results for AML therapy NKX101. The company said that among the six patients with relapsed/refractory AML, four achieved a complete response, including just two with complete responses with measurable residual disease negativity. The low response isn't a surprise since that frequently has been a problem for AML therapies.

There was another concern coming out of the study. While the company said the therapy was generally well tolerated, there were cases where some limited CAR-T-like toxicities were observed. That may be a greater concern since CD33, the cancer protein that is the target in AML therapies, is also found in healthy cells.

Now what

Investors could have more reason to be concerned. On June 22, six executives sold a total of 4,033 shares of Nkarta, including CEO Paul Hastings, who sold 1,704. While company insiders often sell stock for various reasons, the timing of the sales, combined with the recent trial results, isn't ideal.

In the first quarter, the company said it had $332.1 million in cash, enough to fund operations into 2025. Fortunately, it has other possibilities in its pipeline. NKX101 is also being studied to treat liver cancer, and NKX019 is in early trials to treat B-cell malignancies, including relapsed/refractory non-Hodgkin lymphoma. The company also has two pre-clinical programs that it is partnering on with CRISPR Therapeutics.