By Gerry Shih and Carolyn Y. Johnson

The Washington Post

HONG KONG — He Jiankui, the Chinese researcher who claimed this week to have helped produce the world’s first genetically altered babies, said Wednesday there was another “potential pregnancy” involved in his study as he defended a procedure that has shaken the scientific world.

Appearing in public for the first time since revealing he had successfully altered the DNA of twin girls while they were embryos to make them resistant to HIV infection, the Stanford-trained bioengineering professor said he felt “proud” of his work and its implications for public health in the face of nearly universal condemnation.

“We should, for millions of families with inherited disease, show compassion,” he told a packed audience at the Second International Summit on Human Genome Editing in Hong Kong. “If we have this technology, we can make it available earlier. We can help earlier those people in need.”

He’s scientific talk chronicled the development of this line of research, from early mouse experiments to primates and eventually a human clinical trial. He said that eight couples were enrolled in the trial, but one dropped out. All had fathers with well-controlled HIV and mothers who were not infected.

There were 31 embryos created through in vitro fertilization, and 70 percent were successfully edited. He showed data indicating that he had not detected unintended genetic changes caused by CRISPR/Cas-9, the gene-editing tool that he used — although it remains to be seen whether outside scientists will find the evidence convincing.

The disclosure this week of He’s research — carried out in southern China mostly under a shroud of secrecy — has sparked urgent debate about the ethics of gene-editing and raised the prospect of a future in which parents produce “designer babies” with selectively improved traits like intelligence or strength.

Midway during He’s talk, Nobel Laureate David Baltimore said the study resulting in the birth of two girls showed “there has been a failure of self-regulation in the scientific community.”

The ethics of the procedure are complicated by the fact that targeting specific segments of DNA may not be fully precise or carry side effects that are difficult to predict.

He said Wednesday he was “against genome-editing for enhancement” and that he would conduct the experiment on his unborn daughter if she were at risk with HIV infection. He said he worked with seven couples and 31 embryos, more than 20 of which were edited. Aside from “Lulu” and “Nana,” two apparently healthy girls that have been born, there is another mother in the study in the “early stages” of pregnancy, he said.

He’s work came to light this week on the eve of the Hong Kong conference after the Associated Press and MIT Technology Review published extensive on-camera interviews with the researcher, whose lab posted videos about the breakthrough on YouTube. The revelation was stunning, not only because the genomics field had declared a voluntary international moratorium on editing embryos three years ago, but also because it came before He’s work was peer-reviewed or published in a journal.

He opened his appearance Wednesday by apologizing for news about his work “leaking” before it passed peer review. He said the work has been submitted to a journal, but he did not specify which publication.

Asked why he had kept his work secret, He said he talked openly about his research at conferences, including at Berkeley, and had consulted with “several experts” in the United States at Stanford and in China as he moved into clinical trials. He did not name those people.

Amid repeated questions about the ethics and methodology of his experiment, He said he found volunteers through a social network of HIV carriers and explained, line by line and over 70 minutes, the implications of the study to seek their informed consent. When asked if he had considered the implications of carrying out the procedure on the behalf of two unborn girls with potentially unknown physical or emotional consequences, He said he could not answer the question.

He, seated and speaking calmly throughout, said he saw profound value in what he had accomplishment, having visited villages in China where a third of the population was ravaged by AIDS and having helped an HIV-infected father produce a daughter.

“I feel proud,” He said. “I feel proudest because the father thought he lost hope for life. When the baby was born, he sent a message at the first saying I will work hard for and take care of my two daughters for the second half of his life.”

He said his job was to be “transparent, open, and share the knowledge I accumulated to society, to the world, and then, let society decide what it should do in the next step.”

Born in China’s Hunan Province, He graduated from the University of Science and Technology of China in 2006 and pursued a Ph.D. at Rice and postdoctoral research at Stanford.

In 2012, he was recruited by a Chinese government-backed Thousand Talents Plan, which aims to bring leading international experts in science and technology to the country.

This week, hundreds of Chinese scientists signed two letters condemning He’s research as “crazy” and calling on the government to explicitly ban the practice of implanting edited embryos from reproduction.