The boy who underwent an experimental transplant at a University of Minnesota hospital has died, his doctors announced Friday.

Twelve-year-old Eric Blue received an umbilical cord blood transplant at the Amplatz Children’s Hospital in April in an attempt to cure him of HIV and leukemia. He died July 5, the Associated Press reported.

The donor’s cells began attacking tissues in the boy’s body last month. He would have been the second person cured of both diseases by such a transplant, the Star Tribune reported.

Blue’s identity was kept private until Friday, when his mother released his name.

The procedure was designed to allow Blue to stop taking the antiretroviral drugs required to keep HIV at bay.

Dr. Michael Verneris, a University transplant specialist, told the Star Tribune his patient was “incredibly brave and courageous.”

“The promise we made to the child … was that we were going to learn from this, and we still are learning,” Verneris said.