Understanding CRISPR
CRISPR is an innovative technology that is reshaping lives and creating significant impacts in healthcare. CRISPR, an acronym for “Clustered Regularly Interspaced Short Palindromic Repeats,” is present in prokaryotes—tiny, single-celled organisms devoid of organelles. These sequences are situated within the genomes of prokaryotes, which organize a cell’s DNA in clusters.
As a gene editing mechanism, CRISPR is employed to alter particular segments of DNA to address serious illnesses. It is especially effective as it assists in protecting the body from viral infections by integrating the foreign DNA into its own genome, which enables it to identify and eliminate the virus in subsequent encounters. Notably, when compared to other gene editing techniques, CRISPR is significantly more accurate and simpler to program, facilitating an easier process for redesigning sequences. While alternative gene-editing techniques generally utilize a single protein, CRISPR operates on RNA-guided targeting paired with the Cas9 enzyme.
The Mechanism Behind CRISPR
CRISPR functions by leveraging a natural defense system found in bacteria that enables them to recognize and eradicate viral attackers. When a virus invades a bacterial cell (a prokaryote), the bacterium retains a snippet of the invader’s DNA within its own genome, serving as a genetic “memory.” This allows the bacterium to identify and react more efficiently to future infections.
In the context of gene editing, this mechanism is modified with two essential elements: the Cas9 enzyme, which acts as molecular scissors to sever DNA, and guide RNA, which guides Cas9 to the specific genetic sequence necessitating alteration. Once the DNA is cleaved, the natural repair processes of the cell commence, allowing researchers to implement modifications to the genetic material.
Unlike previous tools that depended on challenging-to-reprogram proteins, CRISPR’s RNA-guided framework is more adaptable, easier to create, and highly accurate. This ease of use and precision has enabled CRISPR to find applications in medicine, agriculture, manufacturing, and microbiology—such as engineering microorganisms to boost product yields. However, as this article discusses, as capabilities expand, so do ethical issues, particularly concerning germline editing and genetic enhancement.
First Patient of a Tailored CRISPR Treatment
In February 2025, the first individualized CRISPR therapy was administered for a baby named KJ to address a deficiency in Carbamoyl Phosphate Synthetase 1 (CPS1)—an enzyme critical for converting ammonia (which is generated during protein breakdown) into urea. A team spearheaded by Dr. Rebecca Ahrens-Nicklas and Dr. Kiran Musunuru at the Children’s Hospital of Philadelphia created this treatment following years of gene editing research and collaboration with other medical professionals.
Their efforts concentrated on conditions affecting the urea cycle, leading to harmful ammonia accumulation that can damage organs such as the brain and liver. They customized the treatment specifically for KJ’s variant of CPS1 deficiency, utilizing preclinical research on analogous cases.
So far, the only CRISPR treatments authorized by the U.S. FDA have been for more prevalent diseases like sickle cell disease and beta thalassemia, affecting tens or hundreds of thousands of individuals. In KJ’s situation, his treatment was formulated within six months after his birth, aimed specifically at his particular CPS1 variant. The team developed a base editing approach administered through lipid nanoparticles to his liver to rectify the defective enzyme.
The February treatment marked the first of three doses; KJ received the subsequent doses in March and April 2025. Following his final dose, he has not faced any serious adverse effects, shows improved tolerance to dietary protein, and requires diminished medication to regulate ammonia levels. While he will need continuous monitoring, Ahrens-Nicklas indicates that the outcomes thus far are encouraging.
Ethical Issues Surrounding CRISPR
Like any pioneering technology, CRISPR presents intricate ethical dilemmas. Although its main objective is to edit somatic cells to treat ailments, it can also be applied to gametes, venturing into the contentious area of germline editing. Modifying DNA that will be passed on to future generations is often regarded as unethical—particularly when performed for trait enhancement rather than disease treatment.
In light of these apprehensions, scientists have temporarily halted germline editing until its ethical and