A tool to edit human genes is nowhere near ready to use for pregnancy, but altering early embryos as part of careful laboratory research should be allowed as scientists and society continue to grapple with the ethical questions surrounding this revolutionary technology, organizers of an international summit concluded Thursday.

"It would be irresponsible" to edit human sperm, eggs or early embryos in a way that leads to pregnancy, said Nobel laureate David Baltimore of the California Institute of Technology, who chaired the summit.

Tools to precisely edit genes inside living cells, especially a cheap and easy-to-use one called CRISP-Cas9, are transforming biology, and potential treatments created by them promise to do such things as cure sickle-cell anemia or fight HIV and cancer.

But depending on how it's used, it also could alter human heredity '€” maybe create "designer babies" '€” raising ethical questions that triggered three days of debate by scientists, policymakers and ethicists from 20 countries. This so-called germline editing '€” manipulating sperm, eggs or early embryos '€” wouldn't affect just one sick person but his or her descendants.

The question gained urgency after Chinese researchers 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 summit's organizers endorsed treatment-related gene editing research, and said lab research on germline issues "is clearly needed and should proceed" with appropriate oversight.

Here are some takeaways from the high-profile summit:

REAL-WORLD USE OF ANY KIND IS YEARS AWAY

First-step testing of an initial gene editing therapy has begun in people.

Sangamo Biosciences is developing an HIV treatment '€” pulling immune cells from patients' blood, editing a gene that boosts resistance to the virus and returning those cells. 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 takes a next step and injects a gene editing tool directly into the body, an attempt to target hemophilia B, a blood disorder.

SCIENTIFIC QUESTIONS ABOUT EDITING HUMAN EMBRYOS

The Chinese attempt used embryos too abnormal to ever have developed into a fetus. 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.

But it may be feasible to gene edit sperm-producing cells that in some men don't do their job, something a University of Pittsburgh researcher is exploring.

ETHICAL ARGUMENTS

Critics say changing human inheritance could have consequences not foreseeable for several generations, and would pass genetic alterations to future generations 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.

Then there's the question of what is permissible to alter: Just deleting a gene that causes a devastating disease in a family? Or enhancing future children to be smarter, prettier or more athletic? The latter triggers fear of eugenics.

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

GLOBAL IMPACT

If treatment-related gene editing eventually pans out, another question is how poor countries will afford it.

"Even if gene editing becomes a useful strategy for HIV cure, the cost may make access to such treatments impossible for people living in low-resource countries," said Keymanthri Moodley of Stellenbosch University in South Africa. (kes)(+)

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