LONDON – He Jiankui has faced up to critics and defended his work in creating what are claimed to be the world's first CRISPR/Cas9 gene-edited babies. Addressing the second International Summit on Human Gene Editing in Hong Kong Wednesday, He said he is "proud" of altering the CCR5 gene of twin girls given the pseudonyms Lulu and Nana, inserting a naturally occurring mutation that blocks infection by the HIV virus. (See story this issue.)