The CRISPR trial is designed to see whether the T cells can be edited to make them more effective. Researchers snipped out two genes that theoretically should enhance the cells’ ability to bind to the cancer cells; a third excised gene should take a natural immune system brake off the T cells.

Edward A. Stadtmauer, the Penn blood cancer specialist who led the study, said, “This trial is primarily concerned with three questions: Can we edit T cells in a specific way? Are the resulting cells functional? And are these cells safe to infuse into a patient? This early data suggest that the answers to all three questions may be yes.”

The results, which Stadtmauer will present Saturday at a blood cancer convention, show that the edited T cells multiplied, persisted, and homed in on the myeloma cells. However, one patient’s cancer progressed, one has stable disease, and the third was treated too recently to evaluate.

Over the next four years, the trial aims to treat 18 patients with advanced myeloma, sarcoma, and melanoma.

Penn gene therapy pioneer Carl June, who led the studies behind the world’s first T-cell cancer therapy, stressed that CRISPR is not being used to directly alter the patients’ genomes. Last year, a Chinese researcher was denounced as reckless after he claimed to have used CRISPR to alter the genetic code of two human babies to make them immune to the AIDS virus.