The first human trials of the controversial gene editing technology called CRISPR has officially started in the US.

Researchers at the University of Pennsylvania are conducting a powerful experiment on cancer patients. As NPR reports, one patient had multiple myeloma and another one had sarcoma. Both the patients had relapsed after undergoing the standard treatment.

CRISPR is a technique in which modifications are made at the DNA level, with the potential to cure many diseases. A Chinese scientist, He Jiankui, used the technique to edit genes in human embryos that are now the world’s first CRISPR twins.