Science that gives humans more say over their destinies

David Liu has been having a good run.

On May 15, the New England Journal of Medicine published what has become a high-profile case of a 5-month-old boy called KJ with a deadly genetic disorder, who became the first to receive a personalized CRISPR gene-editing treatment. The therapy was built on base editing, a technology developed in Liu’s lab nearly a decade ago.

The therapy was created to correct the single-letter genetic mutation that was shutting down KJ’s ability to eliminate ammonia from his liver, a condition known as CPS1 deficiency. Half of the babies with this disorder die in the first week of life. KJ not only survived but began recovering.

This was the first of two recent landmark events involving science developed by Liu, the Thomas Dudley Cabot Professor of the Natural Sciences, and his team. Liu, who is also an HHMI investigator, won the 2025 Breakthrough Prize for his work on base editing and prime editing, technologies that enable the correction or replacement of virtually any genetic mutation. 

“There’s a lot of confidence in base editing technology based on the 17 previous base editing clinical trials and thousands of research publications, but it doesn’t change the fact that you still realize the stakes are very high for this patient and their family,” said Liu of KJ’s case. “This story is a powerful testament to the fact that the editing technology, the delivery technology, the manufacturing, the animal models, and the regulatory approval are all robust enough to make this huge team effort happen fast enough to save Baby KJ.”

A chemical biologist by training, Liu has long believed that scientific discovery gives humans the opportunity to have more say over their own lives.

Just a week after KJ’s story made headlines, Prime Medicine, a biotech company Liu co-founded, announced the first clinical results of its therapy for chronic granulomatous disease (CGD), a rare and severe immune disorder.

For the first time, an adult human had been treated with a prime-edited medicine. Prime editing enables even more versatile and precise rewriting of DNA.

The patient was missing two base pairs in a particular gene that encodes an enzyme essential for immune system function. The adult patient responded positively: Early data showed restoration of the missing enzyme activity and no serious adverse effects.

“This is the Alyssa Tapley moment for prime editing,” Liu said, referring to the first patient successfully treated with base editing in the U.K. “The scientists at Prime Medicine succeeded in taking out the patient’s bone marrow, editing it with prime editing, and then transplanted the patient’s edited bone marrow back into his body.

“Until now, the only curative treatment for CGD is transplantation of another person’s bone marrow into the patient, which puts patients at significant risk of rejection or of graft-versus-host disease in which the donor’s immune system attacks the patient’s own tissue,” he added. “So prime editing provides an especially elegant and effective solution, by prime editing the patient’s own bone marrow to fix the disease-causing deletion and then returning it to the patient.”

In KJ’s case, the treatment was developed on an emergency timeline by a coalition of academic researchers and companies across the U.S., led by University of Pennsylvania physician scientists Kiran Musunuru and Rebecca Ahrens-Nicklas.

Liu’s lab played a vital role in developing base editing almost exactly eight years ago and advising the team on which base editor would be likeliest to correct KJ’s mutation effectively while minimizing the risk of unwanted side effects.

“It normally takes many years to go from a genetic diagnosis of a new mutation to a clinical treatment,” Liu said. “This time, it happened in less than seven months.”

While base editing and prime editing technologies each offer their own strengths, their shared promise is a future in which previously untreatable genetic diseases can be reversed with a bespoke treatment.

Prime editing, introduced by Liu’s group in 2019, acts like a molecular word processor, capable of search-and-replace corrections to DNA. It opens the door to treating thousands of genetic mutations behind conditions like sickle cell disease, progeria, and Tay-Sachs.

Both KJ’s case and the CGD breakthrough illustrate what Liu has long championed: the translation of fundamental science into tools that can change lives — safely, swiftly, and equitably.

“Genetic diseases are a consequence of the chemical structure of our DNA, so they will always be a part of humanity. Our mission is to make possible a future in which these types of gene editing treatments are routine, so that people are no longer so beholden to the misspellings in our DNA,” Liu said. “We can finally have some say in our genetic features.”

Liu credited early grants from the National Institutes of Health and other public agencies for enabling high-risk, high-reward ideas like gene editing. Basic science and future breakthroughs are in grave danger due to Washington’s cuts to scientific research, Liu warned.

“It’s easy to forget that every translation of science into a societal benefit began as a basic science project where initially there may not have been any obvious pathway to benefit society,” Liu said. “A basic science investigation into repetitive sequences of DNA found in bacteria turned into the discovery of CRISPR and now into dozens of uses of gene editing to benefit patients with terrible diseases, demonstrating the critical importance of basic science to humanity. Basic science must be supported if we want our children to have the opportunity to live better lives.”

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