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Genetics

Genes, Proteins, and DNA

The human body is made up of trillions of cells.

Each cell has a copy of your genome—the total collection of all your genes and DNA.

Genes are instructions that every cell in your body uses to make the proteins they need to function.

Genes can be found in long chains of molecules called deoxyribonucleic acids (DNA) that are twisted together into the shape of a double helix.

There are 4 DNA molecules that are identified by the letters A, T, C, and G. Combinations of these letters make up the genetic instructions that our cells use to make proteins.

Illustrations of genes and proteins

DNA Mutations and Disease

Our genes can also be a source of disease.

Small breaks in our DNA are incredibly common and are normally uneventful. DNA breaks can happen from sunlight, for example, or during cell divisions that happen as we grow. Our cells have built-in DNA repair processes that constantly fix these breaks as they occur.

However, breaks are sometimes repaired incorrectly, creating what is known as a mutation. Mutations can occur spontaneously or be passed down from our parents. Mutations can also change how our cells function, and may lead to serious diseases such as sickle cell disease (SCD), Leber congenital amaurosis 10 (LCA10), cancer, and many others.

Chain of DNA broken out into sequence.

Genomic Medicine: Revolutionizing the Development of Medicines

Genomic medicine is a developing field of medical research that harnesses recent advances in genetics to develop new medicines for diseases. In fact, we are at an inflection point where we are seeing the first real genomic medicines emerge to help patients.

Advances in the scientific fields of cell therapy and gene therapy have paved the way for the success of gene editing, which in turn is now expanding and accelerating the development of a new class of genomic medicines.

Genomic medicine addresses diseases using cell therapy, gene therapy, and gene editing.

This field genetically addresses diseases by using gene editing and gene therapy technologies, which are different in a few key ways.

In gene editing, a mutated gene is revised, removed, or replaced at the DNA level. In gene therapy, the effect of a mutation is offset by inserting a “healthy” version of the gene, and the disease-related genes remain in the genome. Both approaches may provide a durable benefit to patients, and both gene therapy and gene editing, alone or in combination, may lend themselves to the development of transformative genomic medicines.

Editas Medicine is working to develop genomic medicines for a range of diseases, many of which do not currently have medicines available. We are a gene editing company, and use the terms “gene” and “genome” editing interchangeably to refer to our CRISPR technology.

CRISPR Gene Editing

CRISPR (pronounced “crisper”) is an acronym for “Clustered, Regularly Interspaced, Short Palindromic Repeats,” and refers to a recently developed gene editing technology that can revise, remove, and replace DNA in a highly targeted manner. CRISPR is a dynamic, versatile tool that allows us to get to and edit nearly any location in the genome, and has the potential to help us develop medicines for people with a wide variety of diseases. We view CRISPR as a “platform” technology because of its ability to target DNA in any cell or tissue.

CRISPR uses a combination of 2 types of molecules to edit disease-related genes or to modify cells: a nuclease (the gene editor) and guide RNA (which helps the nuclease find the right place to edit).

CRISPR’s ability to only edit intended DNA targets and avoid off-target editing is known as its specificity. Achieving high levels of specificity requires the right combination of nuclease and guide RNA.

Nuclease

Protein that edits DNA

Nuclease: a protein that edits DNA.

Editas Medicine works with CRISPR nucleases, Cas9 (both aureus Cas9 and pyogenes Cas9) and Cas12a, including enhanced forms of each.

Guide RNA

Molecule that shows the nuclease where to edit

Guide RNA: a molecule that shows the nuclease where to edit.

Editas Medicine creates and tests thousands of guide RNAs to identify guides with the highest levels of specificity.

About the Cas9 Nuclease

Cas9 is able to locate, bind to, and edit targeted genes. It is an essential tool for the research and development of genomic medicines and has the potential to facilitate solutions for many diseases.

About the Cas12a (Cpf1) Nuclease

Cas12a—also known as Cpf1—greatly expands the range of ways that CRISPR gene editing can be used to produce genomic medicines. It provides researchers with more options for where and how to edit DNA and makes use of a shorter guide RNA than Cas9. Our team is continuing to evaluate the best uses for each nuclease.

We’re Developing Many CRISPR Medicines

Using CRISPR gene editing technology, we are pioneering the possible and developing a broad class of transformative genomic medicines for people living with serious diseases.

We are working on making medicines where editing occurs inside the body (in vivo CRISPR medicines), as well as ex vivo CRISPR cell medicines where editing occurs outside the body and edited cells are administered to patients (ex vivo CRISPR cell medicines).

Editas Medicine’s In Vivo Advances

We’re using in vivo technology to develop a wide range of genome editing medicines. Our initial work on in vivo editing is focused on ocular diseases, or diseases of the eye.

Editas Medicine is working to create medicines that treat a number of ocular diseases, including LCA10.

  • Leber congenital amaurosis, or LCA, is a group of inherited retinal degenerative disorders caused by mutations in at least 18 different genes
  • LCA is the most common cause of inherited childhood blindness with 3/100,000 children around the world affected
  • Symptoms of LCA appear within the first years of life, resulting in significant vision loss and potential blindness
  • Symptoms include:
    • Significant vision loss
    • Rapid involuntary eye movement
    • No measurable electroretinogram activity due to loss of photoreceptor cells (the cells in the eye that take in light and help us see)
  • The most common form of the disease, LCA10, accounts for approximately 20-30 percent of all LCA patients
  • LCA10 is caused by mutations in the CEP290 gene
  • There are currently no treatment options available for LCA10

Our approach to developing a medicine for the treatment of LCA10 is to eliminate a prominent disease-causing mutation in the CEP290 gene. Editing out the mutation may restore normal protein expression and the function of photoreceptor cells in the eyes—cells that are critical for normal vision. The medicine we’re developing is called EDIT-101 (AGN-151587).

Usher Syndrome 2A (USH2A)

  • Usher syndrome is a condition characterized by partial or total vision and hearing loss that worsens over time
  • Estimated to be responsible for 3%-6% of all childhood deafness and approximately 50% of all cases where children are both deaf and blind
  • Usher Syndrome is divided into 3 types (1, 2, and 3), depending on when symptoms develop
    • Types 1 and 2 are most common
  • Mutations in many different genes have been implicated in the 3 types of this syndrome, including (but not limited to) the USH2A gene
    • Approximately 30% of Usher syndrome 2 cases are caused by a mutation in exon 13 of the USH2A gene

We hope to stop vision loss and improve vision for patients who have USH2A caused by a mutation in exon 13 by editing the USH2A gene. More than 4000 patients are estimated to have mutations in this gene.

Retinitis Pigmentosa

  • Symptoms of retinitis pigmentosa usually begin in childhood, and include loss of night vision and loss of peripheral (side) vision
  • Retinitis pigmentosa is estimated to affect between 1/3000 and 1/4000 people globally
  • Retinitis pigmentosa can be caused by mutations in more than 50 genes
  • There are currently no treatment options available for retinitis pigmentosa

Retinitis pigmentosa is a set of rare inherited retinal disorders that cause a gradual loss of vision. We believe that gene editing may be well suited to intervene in certain specific types of retinitis pigmentosa by addressing the underlying genetic mutations that drive the disease, enabling the persistence of vision.

Editas Medicine’s In Vivo Advances

We’re using CRISPR to develop many medicines. Right now, we’re working on developing medicines to treat cancers and blood diseases.

The applications for CRISPR technology in cancer are vast. Right now, we’re exploring potential uses for 2 types of CRISPR medicines: autologous ex vivo CRISPR cell medicines, which work with cells from a patient’s own body, and allogeneic ex vivo CRISPR cell medicines, which use cells from a universal cell population that can be edited and then given to any patient who needs it, without needing the patient to donate cells first. Both approaches may be used to modify immune cells to improve their ability to recognize and destroy tumors.

Editas Medicine is developing CRISPR medicines for 2 major blood diseases: SCD and beta-thalassemia.

Sickle Cell Disease

  • A disease that affects the shape and function of the body’s red blood cells, the cells that carry oxygen throughout the body
  • In SCD, the red blood cells are misshapen, in a sickle shape instead of the disc shape. The abnormal shape causes the cells to block blood flow causing pain and early death
  • There are an estimated 100,000 people in the United States currently living with SCD
  • Usually begins in early childhood. Early symptoms include:
    • Low red blood cell counts
    • Infections
    • Pain
    • Fatigue
    • Delayed growth and development
  • The current standard of care is to manage symptoms and complications; there are currently no approved treatments for SCD

Beta-thalassemia

  • A blood disorder that reduces the body’s production of hemoglobin, a protein that carries oxygen to all of the body’s cells
  • Classified into 2 types based on severity of the disorder:
    1. Thalassemia major (more severe; also known as Cooley’s anemia)
    2. Thalassemia intermedia (less severe)
  • Thousands of babies around the world are born with this disorder each year
  • The symptoms and age where they start are different for each type of beta-thalassemia. General symptoms include:
    • Low red blood cell counts and anemia
    • Growth problems
    • Bone abnormalities
    • In more severe cases: yellowing of the skin and eyes and delayed puberty