Introduction to CRISPR
CRISPR is a groundbreaking innovation that is reshaping lives and making significant impacts in the healthcare sector. CRISPR, which signifies “Clustered Regularly Interspaced Short Palindromic Repeats,” is present in prokaryotes—tiny, single-celled organisms lacking organelles. These sequences are situated in the genomes of prokaryotes, which organize a cell’s DNA in clusters.
As a tool for gene editing, CRISPR is employed to alter specific DNA segments to address serious illnesses. It is particularly valuable as it assists the body in combating viral infections by integrating the foreign DNA into its own genome, thereby enabling recognition and destruction of the virus in subsequent encounters. What stands out is that, when compared to other gene editing techniques, CRISPR offers far greater precision and ease of programming, facilitating a more straightforward sequence redesign process. While traditional gene-editing methods often depend on a single protein, CRISPR utilizes RNA-guided targeting alongside the Cas9 enzyme.
How CRISPR Works
CRISPR operates by leveraging a natural defense mechanism found in bacteria, which allows them to detect and eliminate viral threats. When a virus penetrates a bacterial cell (a prokaryote), the bacterium incorporates a portion of the invader’s DNA into its own genome as a genetic “memory.” This allows the bacterium to identify and respond more efficiently to subsequent infections.
In gene editing, this mechanism is modified using two essential components: the Cas9 enzyme, which acts like molecular scissors to sever DNA, and guide RNA, which directs Cas9 to the specific genetic sequence requiring modification. After the designated DNA is cut, the cell’s inherent repair processes take control, enabling researchers to implement changes to the genetic code.
In contrast to previous tools that depended on hard-to-revise proteins, CRISPR’s RNA-guided approach is more adaptable, simpler to design, and highly accurate. This combination of simplicity and precision has facilitated the application of CRISPR in various fields including medicine, agriculture, manufacturing, and microbiology—such as designing microbes to enhance product yields. However, as this article discusses, with extended capabilities come increasing ethical dilemmas, especially concerning germline editing and genetic enhancement.
World’s First Patient of a Personalized CRISPR Treatment
In February 2025, the world’s inaugural personalized CRISPR treatment was administered to a baby named KJ to assist in addressing a deficiency in Carbamoyl Phosphate Synthetase 1 (CPS1)—an enzyme vital for converting ammonia (produced during protein metabolism) into urea. A team led by Dr. Rebecca Ahrens-Nicklas and Dr. Kiran Musunuru at the Children’s Hospital of Philadelphia devised this treatment after extensive research on gene editing and collaborations with other healthcare professionals.
Their research concentrated on conditions impacting the urea cycle, resulting in harmful ammonia accumulation, which can harm organs such as the brain and liver. They customized the treatment specifically for KJ’s type of CPS1 deficiency using preclinical studies on similar variants.
To date, the only CRISPR therapies granted approval 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 instance, his treatment was formulated within six months post-birth to target his specific CPS1 variant. The team developed a base editing therapy delivered using lipid nanoparticles to his liver to rectify the impaired enzyme.
The February treatment constituted the first of three doses; KJ received the subsequent two in March and April 2025. By the time of his last dose, he had not encountered any severe side effects, exhibited improved tolerance to dietary protein, and needed less medication to regulate ammonia levels. Although he will require continuous monitoring, Ahrens-Nicklas indicates that the outcomes so far appear promising.
Ethical Considerations of CRISPR
As with any pioneering technology, CRISPR evokes intricate ethical inquiries. While its main objective is to edit somatic cells for disease treatment, it can also be applied to gametes, venturing into the contentious area of germline editing. Modifying DNA intended for inheritance by future generations is often regarded as unethical—particularly when performed for enhancing traits instead of addressing health conditions.
In light of these issues, scientists have temporarily suspended germline editing until its ethical and social consequences are more comprehensively understood. The unpredictability of genetic alterations, coupled with the permanence of these changes across generations, raises vital questions regarding where to establish boundaries. What started as an innovative concept has evolved into a powerful reality, sparking debates over who is entitled to define its parameters.
CRISPR’s significant cost and sophisticated infrastructure demands make it more accessible in affluent, developed countries—especially in the West. As treatments remain costly, access becomes restricted to the wealthy, exacerbating socioeconomic disparities. The potential