A gene editing tool using a system known as CRISPR-Cas9 has recently been approved by the U.S. Food and Drug Administration (FDA) for sickle cell disease. The drug is known as Casgevy and the media has hailed this treatment as a ‘cure’ for sickle cell anemia patients. While it is still unclear if the drug completely cures these patients, clinical trials show exciting efficacy.
Sickle cell disease is a genetic blood disorder affecting thousands of US citizens. Many of these patients are African American and Hispanic. In sickle cell disease, hemoglobin, a protein in red blood cells that helps carry oxygen throughout the body, is mutated. As a result, blood cells change shape in the form of a sickle, giving the disease its name. Unfortunately, the mutated cells cause disruption of blood flow and prevent other blood cells from delivering oxygen to the body. This disease is extremely rare and can lower the quality of life in patients. Previously, there were limited treatments options including transfusions and medications for pain management. However, Casgevy provides a new option to help treat the patient and relieve pain for over a year after a single treatment.
One-time treatment using Casgevy improved life quality for sickle cell patients. A single-arm trial was conducted at multiple health centers in adults and adolescents. These patients were screened for two vaso-occlusive crises (VOCs) which are described as severely painful events due to a lack of oxygen delivery from sickle cell blood cells blocking blood flow. The primary measure of success in the trial was the number of VOCs after treatment. In total, 44 patients received Casgevy and 33 were able to follow up and be evaluated. Of the 33 patients that made it through the trial, 29 of them did not experience any VOCs for 12 months. This is a 93.5% success rate based on the number of patients that were analyzed. All 44 patients were able to successfully undergo treatment without any graft rejection. In addition, researchers concluded that this treatment was not only effective, but safe with few side effects. The most common side effects included low platelet and white blood cell count, nausea, abdominal pain, vomiting, headache, itching, and mouth sores.
Based on this clinical trial, the UK approved Casgevy for sickle cell disease last month (November). The US recently approved this drug last week and signifies great advances in healthcare. The clustered regularly interspaced short palindromic repeats (CRISPR) – Caspase (Cas)9 system used for Casgevy is a way to edit genes. This technology has the capability to cut out and add genes within your DNA. For the development of this gene editing tool, Drs. Emmanuelle Charpentier and Jennifer A. Doudna were awarded the 2020 Nobel Prize in Chemistry. It has quickly become a tool to help scientists manipulate the genome and control gene expression in experiments. Therefore, this technology will help progress scientific research. More importantly, it has the power to edit gene expression in patients with debilitating diseases such as sickle cell disease. This technology could be applied to a variety of genetic disorders and could eventually help cure genetic disease. Overall, Casgevy is a major advance forward to treating sickle cell disease and improving patient quality of life.
Recently, FDA, CRISPR-Cas9, Casgevy, Emmanuelle Charpentier, Jennifer A. Doudna, Nobel Prize in Chemistry
