Susan Walsh / AP

Scientists urge caution on human gene editing

Conference concludes it would be 'irresponsible' to use powerful tools for gene editing until consequences are known

An international group of scientists and ethicists said this week that it would be “irresponsible” to use a powerful tool for editing human genes until more is known about the consequences and ethics of passing genetic changes to future generations.

At the close of the three-day International Summit on Human Gene Editing in Washington, D.C., participants urged caution in moving forward with “any clinical use” of human gene editing — “unless and until the relevant safety and efficacy issues have been resolved” and “broad societal consensus” is reached on the issue. They also said the practice should take place only under “appropriate regulatory oversight.”

Tools to precisely edit genes inside living cells, especially a cheap and easy-to-use mechanism called CRISP-Cas9, are transforming biology. Potential treatments include a possible cure for sickle-cell anemia, and new ways to fight HIV and cancer. But this so-called germline editing — which can involve manipulating sperm, eggs or embryos — wouldn’t affect only a patient, but also his or her descendants.

And depending on how gene editing is used, it also could alter human heredity — possibly to create "designer babies" — raising ethical questions that triggered three days of debate among the scientists, policymakers and ethicists from 20 countries at the Washington summit.

The question gained urgency after Chinese researchers in April made the first attempt to alter genes in human embryos, an experiment that showed scientists don't yet know how to do that safely and effectively.

The Washington summit's participants endorsed treatment-related gene editing research, and said laboratory research on germline editing "is clearly needed and should proceed" with appropriate oversight as international debate continues.

A panel of participants at the Washington summit offered what geneticist Eric Lander of the Broad Institute of Massachusetts Institute of Technology and Harvard called "a framework for deciding if and when" the reproductive use of gene editing ever moves forward.

"As scientific knowledge advances and societal views evolve, the clinical use of germline editing should be revisited on a regular basis," the panel concluded. It urged the sponsors of this week's summit — scientific academies of the United States, Britain and China — to create an international forum to help "establish norms concerning acceptable uses of human germline editing."

First-step testing of an initial gene editing therapy, using older tools, has already begun in people.

Sangamo Biosciences of Richmond, California, is developing an HIV treatment that involves pulling immune cells from patients' blood, editing a gene that boosts resistance to the virus, and then returning those cells to the bloodstream. So far 80 HIV patients have received the therapy in first-stage testing, with good results so far, said Sangamo senior scientist Fyodor Urnov.

Next year, Sangamo plans a clinical trial that would take step further and inject a gene editing tool directly into the body in an attempt to target hemophilia B, a blood disorder.

"We're at the beginning of this story now," cautioned Dr. Adrian Thrasher of University College London, where researchers recently used edited immune cells to treat a 1-year-old leukemia patient. "What we'll see over the next five years or so is increasing clinical trials."

The Chinese attempt used embryos too abnormal to ever have developed into fetuses. The researchers aimed to correct a gene defect that triggers a deadly disease, but only a few embryos were fully corrected and others had alterations in the wrong spots.

Critics say changing human inheritance could have consequences not foreseeable for several generations, and could pass genetic alterations to descendants without their consent. A mistake could have irreversible consequences.

"It's a radical rupture with past human practices," said Marcy Darnovsky of the Center for Genetics and Society, a nonprofit based in Berkeley, California.

There is also the question of what is permissible to alter, whether it’s just deleting a gene that causes a devastating disease in a family, or enhancing future children to be smarter, more attractive or more athletic.

"I'm skeptical about the 'Brave New World' scenario," said Dr. George Daley of Boston Children's Hospital, noting that such enhancements involve more genes than anyone can guess.

One of the scientists who discovered powerful tools for altering genes is not convinced that the case has been made for using the technology on human sperm, eggs and embryos.

"The tools are not ready," biologist Emmanuelle Charpentier of the Max Planck Institute for Infection Biology in Berlin and Umea University, Sweden, told Reuters on Wednesday during the Washington summit.

"As long as they are not perfect and ready, I think it's good to have this ban against editing the germline,” Charpentier said.

Charpentier and colleague Jennifer Doudna of the University of California at Berkeley did pioneering work on developing the CRISPR-Cas9 system, a technology that can strategically delete specific stretches of DNA and add in genes.

She said she would need very strong convincing about the immediate benefits of editing human germline cells. "For the moment,” she said, “I don't see any."

Al Jazeera and wire services

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