He says he used a technology known as CRISPR to edit sections of the human genome, performing the procedure on embryonic humans. The technology, which selectively "snips" and trims areas of the genome and replaces it with strands of desired DNA, has previously been used on adult humans and other species. CRISPR technology has only recently been used to treat deadly diseases in adults, and limited experiments have been performed on animals.
In a December 2018 letter signed by 150 Chinese scientists, He was condemned for ignoring ethical guidelines. The letter called the gene manipulation a "Pandora's box," and said, "The biomedical ethics review for this so-called research exists in name only. Conducting direct human experiments can only be described as crazy."
In the April letter, the scientists drew attention to scientific questions surrounding germline editing that, in their view, must be addressed before scientists proceed. These include how artificial changes to an embryo's genes "might interact with existing human genetic diversity when these new alterations are passed on to future generations."
Clinical germline editing is currently banned in the United States and in 30 or so other countries throughout the world, including China.
"Before this status quo is revisited, it is vital that extensive discussions and engagement take place among all major stakeholders, including members of the scientific, medical, patient, caregiver, policy, legal, ethical, and faith communities," the letter reads.
These stakeholders must be consulted before any more germline editing takes place, they say, and "effective and easily accessible mechanisms" must be developed "for reporting potential violations."
The scientists in the April letter noted the potential for gene editing in somatic cells which do not result in births or the passing on of manipulated traits.
"In somatic cells, certain types of gene editing will likely have important scientific and medical applications, including their use to treat patients living with genetic disorders such as sickle cell anemia, beta-thalassemia, blindness, muscular dystrophies, and hemophilia, as well as cancer and many other diseases," the scientists wrote.
Azar has not yet issued a response to the April letter.
CNA spoke to John DiCamillo, an ethicist at the National Catholic Bioethics Center, in early 2017. He explained that somatic cell gene editing may be morally legitimate when used for "a directly therapeutic purpose for a particular patient in question, and if we're sure we're going to limit whatever changes to this person."
He pointed to gene therapy trials for disorders such as sickle cell disease and cancer that show promise for treating difficult disorders.
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Editing sperm, eggs, or early embryos, however, presents serious concerns, he said. Manipulating sperm and ova requires removing them from a person's body; if conception is achieved with these cells, it is nearly always through in vitro methods. This practice of in vitro fertilization is held by the Church to be ethically unacceptable because it dissociates procreation from the integrally personal context of the conjugal act.