Wednesday, 8 July 2026,

Katarina Harasimov carries out base editing in Niakan’s laboratory at the Loke Centre for Trophoblast Research, University of Cambridge. Loke Centre for Trophoblast Research, University of Cambridge.

Base editing now edits single DNA bases in human embryos with remarkable accuracy. Ethical and safety challenges mean clinical use remains distant.

According to CNN

Pioneer methods of gene editing are already being used in clinical practice and saving lives, easing the suffering from severe genetic diseases. At the same time, the number of patients receiving such treatments is growing, while there is a risk that mutated genes could be passed on to their children.

Scientific consensus – and legislation in seventy countries – has for many years recognized that using powerful germline DNA editing technologies, which can be passed on irreversibly to future generations, is too dangerous.

A new study indicates that editing the DNA of human embryos can occur with unprecedented precision, hinting at the possibility of editing hereditary traits in the near future. However, scientists warn that many obstacles remain before this becomes safe for living embryos.

Six years ago I thought that using gene editing in human embryos was unimaginable.

– Amander Clark

Research, usually donated by patients who underwent IVF, is now strictly regulated by most countries and is typically allowed only for 14 days after the embryo’s creation. Public opinion on embryo editing often reflects ethical considerations and concerns, beyond medical safety, due to the possibility of creating “designer” babies with desired traits.

The CRISPR-Cas9 technology has transformed science, enabling modification of genes in living organisms for biotechnological and medical purposes. In 2020, two inventors of this technology received the Nobel Prize in Chemistry, and in 2023 the U.S. FDA approved the first two gene therapies for sickle cell anemia – a complex inherited blood disorder that significantly affects the African American community.

However, CRISPR-Cas9 can be a “rough” tool: during DNA editing, breaks in both strands occur, and in some cases this leads to significant and unpredictable changes, including the loss of an entire chromosome.

A notable case is Chinese scientist He Jiankui, who in 2018 announced the birth of two girls after editing embryos to increase resistance to HIV. For this he was sentenced to three years in prison in 2019 (later released). He did not respond to a request for comment.

Modern, more precise forms of CRISPR, notably base editing, can change one nucleotide pair at a time.

Base editing was first used in 2022 in a clinical trial to modify immune cells in a teenager in the United Kingdom after other treatments had failed. Since then, eight children and two adults have received such treatment. Last year, base editing was used to treat an infant with a severe CPS1 deficiency, a rare and dangerous genetic disease.

Two new studies used this method to edit embryos at the earliest stage of development, which were donated for scientific purposes after IVF. Both groups found that the method’s precision reduces the likelihood of off-target chromosomal abnormalities.

Base editing can precisely change one nucleotide pair to another in the human genome – about 3 billion base pairs – it’s an incredible achievement.

– Kathy Niakan

Niakan and her team used base editing to better understand how a key gene functions in embryonic development. They found that the NANOG gene – named after the mythical land Tir Na Nog – plays an important role in forming the first cells that later become the embryo and placenta. This study was published on June 25 in the journal Nature.

According to Niakan, base editing marks a significant step compared with traditional CRISPR-Cas9, as the risk of unforeseen chronic damage and chromosomal errors is much lower: “Base editing can precisely change one nucleotide pair to another in the human genome; this is an incredible achievement.”

In another study, Dietrich Egli of Columbia University used base editing to insert one of two mutations into recently fertilized eggs. One of the targets was the PCSK9 gene, which regulates cholesterol, and the other – HBG, which encodes the fetal form of hemoglobin. He noted that the study was accepted for publication in a peer-reviewed journal.

Despite progress, Egli emphasizes: the path to clinical use is still far away. Even in the absence of significant chronic chromosomal damage, two major problems remain: mosaicism and the so-called off-target effects, when editing is not present in all cells of the embryo, which creates a risk for the entire organism.

The problem of mosaicism is not solved; they do not fully understand the long-term effects of intervention, and there is no way to run pregnancy trials without actual pregnancy and a baby.

– Laurie Zoloth

These questions go even deeper when it comes to enabling the possibility of “creating” babies with desirable traits that in the future could reduce the risk of cardiovascular diseases; in such a scenario the benefits could be driven by lifestyle or medications in a hypothetical future.

– Laurie Zoloth

A recent public opinion survey on embryo research in four countries showed support for using genome editing in embryos to prevent severe or life-threatening conditions in the United Kingdom, the Netherlands, and Spain; in Italy, this percentage was 46%.

We do not want to ban research,” stated the head, emphasizing the importance of proper frameworks for a new scientific direction that protect both research and society.

– Laurie Zoloth

Ethical and social considerations remain important alongside scientific progress. Experts say it’s essential to proceed with caution, continue the discussion, and develop regulatory frameworks to ensure a balance between innovation and public safety. The question of whether embryo editing could cross from treatment to the potential creation of “designer” babies remains open, as does the future impact of these technologies on inequality among people from different socio-economic backgrounds.

Ultimately, the scientific community emphasizes a responsible approach: real use of genetic editing in human offspring requires not only technical mastery but also clear ethical norms and robust regulatory mechanisms to safeguard both science and society.