--- title: CRISPR Gene Editing Is Being Tested in Human Patients description: Editing genes in patients could lead to cures for a number of devastating genetic diseases, including vision disorders and sickle cell anemia canonical: https://time.com/5642755/crispr-gene-editing-humans/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2019-08-06T10:00:49.000Z article:modified_time: 2026-10-13T08:56:01.263Z article:section: Health og:title: CRISPR Gene Editing Is Being Tested in Human Patients. Here’s What You Need to Know og:description: Editing genes in patients could lead to cures for a number of devastating genetic diseases, including vision disorders and sickle cell anemia og:url: https://time.com/5642755/crispr-gene-editing-humans/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltfe699e887851501d/698a00d7457a52179cd6297a/gettyimages-845814134.jpeg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 6000 og:image:height: 3375 og:image:alt: Genetic manipulation and DNA modification concept. og:type: article twitter:card: summary_large_image twitter:title: CRISPR Gene Editing Is Being Tested in Human Patients. Here’s What You Need to Know twitter:description: Editing genes in patients could lead to cures for a number of devastating genetic diseases, including vision disorders and sickle cell anemia twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltfe699e887851501d/698a00d7457a52179cd6297a/gettyimages-845814134.jpeg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 video:duration: 02:22 video:published: 2016-06-22 section: science topics: CRISPR, gene editing, DNA, genome, molecular scissors, genetic mutations, HIV, Huntington's disease, malaria, Zika, heritable changes genre: explainer tones: informative, optimistic, accessible, brief emotions: hope (medium), curiosity (medium), excitement (low) sentiment: positive audience: general public, science students, health-curious viewers, technology enthusiasts products: CRISPR content_suitability: health controversy [01:35-01:45] transcript_source: publisher captions transcript_reviewed: not applicable ---  # CRISPR Gene Editing Is Being Tested in Human Patients, and the Results Could Revolutionize Health Care > Sponsored content. 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Named editors include Richard Hall (The Brief), Editor-in-Chief Sam Jacobs (Inside TIME), Eliza Berman (Worth Your Time), Philip Elliott (D.C. Brief), Justin Worland (Future Proof) and Harry Booth (In the Loop). Health Matters is written by TIME's health desk. #### How do I sign up for a TIME newsletter? Go to time.com/newsletters, choose the newsletters you want and enter your email address. There is no cost and no subscription requirement. ### Sources * TIME Newsletters: [time.com/newsletters](/c/time-nl-network-2026q3/newsletters?i=645e870b-48d2-41eb-8427-3a1e8355df6d&cr=time-nl-network-2026q3-v1) ## Video: How CRISPR DNA-Editing Works [Watch (HLS stream): How CRISPR DNA-Editing Works](https://cdn.jwplayer.com/manifests/xeP3Y87P.m3u8) (2:22)  _Published 2016-06-22. A brief guide to a ground-breaking new technology._ Description, summary, key points, chapters, key quotes, questions and transcript, where present, were produced automatically from the video or its captions and were not reviewed. ## Summary The video gives a brief explanation of CRISPR gene editing, starting with what DNA and the genome are. It describes CRISPR as a programmable, man-made molecule with molecular scissors that can find and cut target DNA, with repairs either by the body or by scientists patching in corrected letters. It notes that edits made in eggs, sperm or embryonic cells are permanent and passed to future generations. The video closes by listing examples of early uses, such as cutting out HIV and altering mosquitoes to reduce the spread of malaria and Zika. ## Key points - Every cell in the body carries a copy of the genetic code called the genome, made up of DNA. (00:07) - The genome is described as a book made up of three billion letters arranged in sequences that form DNA words. (00:19) - Computers have deciphered the entire human genome and identified genetic mutations behind diseases that currently have no cure. (00:42) - CRISPR is a man-made molecule that can be programmed to find mutated or diseased DNA. (00:57) - CRISPR is equipped with a pair of molecular scissors that can snip a target DNA section from the genome. (01:16) - If changes occur in eggs, sperm, or embryonic cells, they will be permanent and passed on to future generations. (01:35) - CRISPR is being used to cut out the HIV virus and to eliminate Huntington's disease from the brain. (01:53) - Scientists have used CRISPR to alter a mosquito's genome so it is less likely to spread malaria and Zika. (01:57) ## Chapters - [00:00 to 00:57] What DNA and the genome are. The video introduces DNA and the genome as the genetic code carried by every cell, and notes that computers have deciphered the human genome. - [00:57 to 01:35] How CRISPR finds and cuts DNA. CRISPR is presented as a programmable molecule with molecular scissors that can locate and snip target DNA, with the body or scientists repairing the cut. - [01:35 to 02:22] Heritable changes and early applications. The video explains that edits in reproductive or embryonic cells are passed on, then lists early uses against HIV, Huntington's disease and malaria and Zika. ## Key quotes - [00:57] narrator: "With Crisper we can edit DNA." - [01:35] narrator: "If this happens in eggs, sperm, or embryonic cells, the changes will be permanent and passed on to future generations." - [02:07] narrator: "Chrisper could lead to a new world of treatments, curing diseases and even eliminating them." ## Questions this video answers - What is DNA and what does the genome consist of? [00:03] - What is CRISPR and how is it programmed? [00:57] - How does CRISPR edit DNA once it finds its target? [01:16] - What happens when DNA edits occur in eggs, sperm, or embryonic cells? [01:35] - What are some early uses of CRISPR mentioned in the video? [01:53] ## Content suitability - health controversy [01:35-01:45]: Describes permanent genetic changes passed to future generations, a topic that can be sensitive.  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Aug 6, 2019 10:00 AM UTC A brief guide to a ground-breaking new technology.  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Aug 6, 2019 10:00 AM UTC It’s only been seven years since scientists first learned how to precisely and reliably splice the human genome using a tool called[ CRISPR](https://time.com/4379503/crispr-scientists-edit-dna/?iid=toc%5F062316), making it possible to think about snipping out disease-causing mutations and actually cure, once and for all, genetic diseases ranging from sickle cell anemia to certain types of cancer and even blindness. Doctors are plunging ahead in search of ways to use the relatively new technology to start treating patients. In China last November, scientist Jiankui He stunned—and dismayed—the genetic community when he announced he had already used CRISPR, which many believe still hasn’t been proven either safe or effective in human patients, to[ permanently alter the genomes of twin girls](https://time.com/5466967/crispr-twins-lives/) to be immune to HIV infection. He’s experiment was criticized because he edited the twins’ cells when they were embryos, therefore ensuring that every one of their cells is now changed, including their reproductive ones, which means their edited genomes can be passed on to their children, despite the fact that experts can’t be sure what the long term effects of such lasting modifications might be. Editas Medicine and Allergan recently[ announced](http://ir.editasmedicine.com/news-releases/news-release-details/allergan-and-editas-medicine-initiate-brilliance-phase-12) a more acceptable form of gene editing, one that would change genetic defects in cells that don’t get passed onto the next generation. They are enrolling patients born with a congenital vision disease into what will be the first test in the U.S. of whether CRISPR can fix a mutation in the cells of a living human body. Other ongoing trials, including one from partners Vertex Pharmaceuticals and CRISPR Therapeutics that is treating blood diseases, rely on treating patients’ cells outside of their body and introducing them back to the body, where, in theory, they would outnumber the diseased cells. In the Editas study, CRISPR will be introduced directly into the eye where it will repair the genetic mutations in the patients’ vision cells and potentially cure them of their disease. The illness, called Leber congenital amaurosis 10 (LCA10), is caused by a single mutation in the CEP290 gene, which is critical for building the outer portion of photoreceptor cells that sense and translate light into signals that travel through the optic nerve and into the brain where they are interpreted as sight. The mutation prevents the photoreceptors from sensing light, which contributes to low vision or blindness. The fact that LCA10 is a single-gene disease make it an ideal target for early CRISPR therapies. Scientists can design CRISPR to act as molecular scissors to snip a cell’s DNA in specific, pre-determined locations — in this case around the aberrant CEP290 gene — and remove it. Without the mutation, the normal protein can be made and the photoreceptor cells can function as they should. “We are going in and cutting out the mutation,” says Charles Albright, chief scientific officer of Editas. “Hopefully that will restore the normal protein to normal levels and let patients sense light again, and that sensation of light can turn into vision.” Scientists agree that CRISPR holds great promise in giving researchers unprecedented power to snip out abnormal stretches of DNA, But there are still significant questions about how safe and effective CRISPR gene editing will be once it’s unleashed in the human body. CRISPR works well enough in the lab, in a dish of human cells, but as with any technology, there are glitches. Some studies have shown that the gene editing goes awry once in a while, splicing incorrect places in the genome. Then there is the bigger question of what longer term, unanticipated effects man-made edits to the human genome might have. But, if the CRISPR gene editing works, it would be a one-time fix for a genetic disorder that currently can’t be treated at all. “This is a super cool idea, and it has a ton of potential,” says Dr. Steven Schwartz, professor of ophthalmology at the University of California Los Angeles Stein Eye Institute, who is not involved in the study. The genetic editing would essentially eliminate the genetic mutation that these people had been born with, and depending on how early the treatment is given, could not only restore, but possibly preserve their vision. Some children with the condition are born with limited sight and eventually go blind, so Editas and Allergan plan to eventually include children as young as three years old in the study if the first doses appear safe. The trial will hopefully answer many questions could be critical for the future of CRISPR-based therapies. Studying the technique in patients will give doctors clearer answers about dosing the therapy, as well as potential side effects. Albright says the treatment will be provided during outpatient surgery, in which the surgeon will inject the molecular gene editing machinery under the retina. The CRISPR mechanics will be encased in a deactivated adenovirus built specifically to deliver its splicing payload to photoreceptor cells. Even if they unload the CRISPR in other cells, says Albright, it’s not biologically dangerous since the gene is only mis-coded in the photoreceptor cells. To track if the CRISPR did its job, the research team will assess the patients’ vision with a special test designed for those with low vision, and will record video of the patients working through a maze in which they have to avoid obstacles and heed instructions such as stop signs. The scientsits also plan to use imaging to try to track whether the photoreceptors cells have actually been rebuilt. ## Learning From Human Studies The trial is just one of a few underway to test the powerful CRISPR technology around the world. One of the most promising, for example, is studying whether gene editing can treat, and effectively cure, blood disorders such as beta thalassemia and sickle cell anemia. In beta thalassemia, the hemoglobin part of red blood cells, which is supposed to pick up oxygen from the lungs and distribute it to the cells in the rest of the body, doesn’t work properly. Patients need to be transfused with donors blood regularly, and even with these transfusions, complications can occur if the dose isn’t right and iron levels in the blood cells spike, which can lead to organ damage and even death. In sickle cell disease, a mutation in the gene that makes hemoglobin causes the red blood cells to collapse into a sickle shape, which makes it more difficult for the cells to flow smoothly through the body’s arteries and veins. Blockages caused by the misshapen blood cells can lead to severe pain and strokes. The biotech company CRISPR Therapeutics, founded by one of the technology’s co-developers, has engineered a solution to treat both conditions that relies on genetic modifications connected to the production of fetal hemoglobin. Normally fetal hemoglobin, which provides the developing fetus with oxygen via the blood while in utero, is shut off about six months after birth, and genes for adult hemoglobin are turned on. While it’s not clear why adult hemoglobin replaces the fetal version, researchers say that they have not seen any significant differences between the two types when it comes to the ability to transport oxygen to the body’s cells. However, since the genes for adult hemoglobin don’t produce healthy red blood cells in people with beta thalassemia and sickle cell disease, one treatment strategy is to introduce genetic changes that turn on fetal hemoglobin again. In CRISPR Therapeutics’ trials for each disease, doctors remove patients’ bone marrow cells, which contain the stem cells that make all blood cells, treat these stem cells outside of the body with CRISPR to turn on the fetal hemoglobin genes, then give patients strong chemotherapy to remove their existing, diseased bone marrow stem cells and replace them with the CRISPR-edited cells. Because these cells are now altered to make fetal hemoglobin, hemoglobin levels eventually rise back to normal levels for beta thalassemia patients, and the red blood cells now have a normal shape in those with sickle cell. For people with beta thalassemia, the gene editing therapy could mean the end to a lifetime of transfusions, and for sickle cell patients, a first-ever treatment. “When we make this change \[with gene editing\], the notion is that this is a transformative, one-time cure for life for these diseases,” says Samarth Kulkarni, CEO of CRISPR Therapeutics. Kulkarni won’t reveal much about how far along the trials are, but says that the first patient with beta thalassemia who was treated with CRISPR has not needed transfusions in four months. He hopes to enroll 45 people in this first study of the gene editing treatment for each disease, but plans to review the safety of the therapy after the first 17 people have been treated. The preliminary results “are an encouraging sign,” he says. “But these are early days still.” Early, but promising. ## Transcript [00:00] To understand CRISPR gene editing, let's start with [00:03] what is DNA. Handed down [00:07] from generation to generation, every cell in your body [00:11] carries a copy of your genetic code called your [00:14] genome. It's made up of DNA. It's [00:19] like a book that describes A book made up of three [00:22] billion letters arranged in different sequences that [00:26] make up DNA words. These words can influence the [00:29] traits that you take on, athletic, intelligent, [00:37] gifted. Recently, [00:42] computers have deciphered the entire human genos [00:45] and have identified genetic mutations behind diseases [00:48] that currently have no cure [ MUSIC ] [00:57] With Crisper we can edit DNA. Crisper is a man- made [01:01] molecule that can be programmed to find mutated or [01:05] diseased DNA. [ MUSIC ] [01:16] It's also equipped with a pair of molecular scissors. So [01:19] once Crisper finds it's target DNA, it can snip that [01:23] section from the genome. [ MUSIC ] [01:30] Sometimes the body can repair itself. Other [01:35] times, scientists can patch it with corrected letters. If [01:41] this happens in eggs, sperm, or embryonic cells, the [01:45] changes will be permanent and passed on to future [01:48] generations. Crisper is already showing promise. [01:53] It's being used to cut out the HIV virus. Eliminate [01:57] Huntington's disease from the brain and even alter a [02:00] mosquito's genome so it's less likely to spread malaria [02:03] and zikka. Chrisper could lead to a new world of [02:07] treatments, curing diseases and even eliminating them. [02:11] So future generations won't ever have to suffer from [02:14] them again. 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