Researchers in China have confirmed they have for the first time in medical history succeeded in creating genetically modified human embryos. The team hopes their efforts will one day allow doctors to eradicate genetic diseases from fetuses before birth, but many feel that manipulating human DNA may open up Pandora’s box.

Using the gene-editing CRISPR technology, a team of researchers at Sun-Yat-sen University in Guangzhou, China were able to edit out the gene responsible for a potentially fatal blood disorder, Sky News reported. Although the study only resulted in a small fraction of the 86 edited embryos actually containing the replacement genomes, the accomplishment still marks the first time such a project was conducted on human subjects.

For the majority of the embryos, the CRISPR technology did not work at all, and in a small fraction of the embryos the gene editing caused unintended genetic mutations. Others ended up with edited genes in only some cells but not the others. The scientists admit that the technology is not yet ready for real life application and, as reported by MIT Technology Review, the team did not attempt to establish a pregnancy in any of the fetuses for ethical reasons.

“If you want to do it in normal embryos, you need to be close to 100 percent,” explained Junjiu Huang, one of the researchers involved in the study, as reported by Sky News. “That’s why we stopped. We still think it’s too immature."

According to Huang, the tests were conducted on “non-viable” embryos that would have otherwise been unable to survive. They were obtained from fertility clinics in the local area.

The goal of gene editing embryos is to repair faulty genes which may lead to genetic mutations and diseases before the fetus is born. Theoretically, by editing genes in the earliest stage of life scientists can better ensure that all subsequent copies of the gene contain the same repair, The Washington Post reported.

Current CRISPR technology has enabled researchers to cure genetic diseases in living adult mice, but this has never been replicated in humans. CRISPR technology is also at the root of new HIV treatment studies, with the aim of changing the DNA of HIV-positive individuals to mirror those of the naturally immune and therefore offer a lifetime resistance to the disease without a need for medication.

The goal of gene editing may be genuine, but many feel that this approach to treating genetic diseases oversteps the line of what science can and should do.

George Daley, a stem cell biologist at Harvard Medical School, told the online journal Nature that the results from this Chinese study serve as a “stern warning” that this technology is nowhere near ready for testing to “eradicate disease genes.” Others believe that even when the technology does become ready for use, it should still not be implemented.

“Changing a genetic sequence could lead to unexpected problems that would be passed down from one generation to another while triggering other defects or diseases,” biologist Zhao Shimin told Sky News. “Massive, uncontrolled use of DNA editing could lead to the extinction of the human race."

Opponents to genetic editing of human fetuses also bring up the worry of “designer Babies.” More precise methods of editing technology mean that scientists will not be limited to picking and choosing the diseases children may inherit but also the physical traits.

"I think it's pretty inevitable that we'll get to a point where it's scientifically possible…" Dr David King, from the campaign group Human Genetics Alert, told the BBC. "But that does not mean to say it's inevitably the way we have to go as a society."

Source: Liang P, Xu Y, Zhang, X, et al. CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes. Protein & Cell. 2015.