He Jiankui, an associate professor at Southern University of Science and Technology in Shenzhen, China, addressed a packed hall of around 700 people attending the Human Genome Editing Summit at the University of Hong Kong. The professor said that he had successfully altered the DNA of twin girls born to an HIV-positive father.
A total of eight volunteer couples - HIV-positive fathers and HIV-negative mothers - had signed up to the trial, with one dropping out before it was halted.
"I must apologise this result was leaked unexpectedly," said He. "The clinical trial was paused due to the current situation," he added.
But the geneticist said that he is proud of his work.
"For this case, I feel proud. I feel proudest," He said, when challenged by several peers at the conference.
"This study has been submitted to a scientific journal for review," He said. He did not name the journal and said his university was unaware of his study.
He, who said his work was self-funded, shrugged off concerns that the research was conducted in secrecy, explaining that he had engaged the scientific community over the past three years.
In videos posted online this week, He said he used a gene-editing technology known as CRISPR-Cas9 to alter the embryonic genes of twin girls born this month.
He said gene editing would help protect the girls from infection with HIV, the virus that causes AIDS.
But scientists and the Chinese government have denounced the work that He said he carried out, and a hospital linked to his research suggested its ethical approval had been forged.
The conference moderator, Robin Lovell-Badge, said the summit organisers were unaware of the story until it broke this week.
CRISPR-Cas9 is a technology that allows scientists to essentially cut and paste DNA, raising hope of genetic fixes for disease. However, there are concerns about safety and ethics.
More than 100 scientists, most in China, said in an open letter on Tuesday the use of CRISPR-Cas9 technology to edit the genes of human embryos was dangerous and unjustified. "Pandora's box has been opened," they said.
He's research focuses on genome sequencing technology, bioinformatics and genome editing, according to his biography on the summit's website.
He received his PhD at Rice University in Houston, Texas, and worked as a postdoctoral research fellow in Stephen Quake lab at Stanford University according to the site.
'I must apologise this result was leaked unexpectedly,' He Jiankui said. 'The clinical trial was paused due to the current situation.'