In November 2015, the use of gene editing technology to treat an 11-month-old child with leukemia was reported in news articles in Nature and in Science. Because of the human-interest value of this story, it was also reported in Time magazine and in the New York Times.

Data from this first-in-humans clinical use of the therapy will be presented at the 57th American Society of Hematology (ASH) Annual Meeting in Orlando, FL in early December 2015.

The young patient was treated with a complex cellular immunotherapy regimen developed by Cellectis (Paris, France and New York, NY). Cellectis’ platform involves production of allogeneic (rather than autologous) chimeric antigen receptor (CAR) T-cells to create an “off-the-shelf solution” to cellular immunotherapy for cancer, potentially simplifying manufacturing and standardization of therapies.

We have discussed CAR T-cell therapies on this blog, and—in more detail—in two book-length reports published by Cambridge Healthtech Institute (CHI). These are our 2014 Cancer Immunotherapy report, and our new November 2015 report, Gene Therapy: Moving Toward Commercialization.

CAR T-cell therapies directed against the B-cell antigen CD19, being developed by Novartis/University of Pennsylvania, Juno Therapeutics, and Kite Pharma, have demonstrated impressive clinical results against B-cell leukemias and lymphomas. However, in order to avoid immune incompatibility, CAR T-cell must be constructed and manufactured using autologous T-cells derived from the patient to be treated. This is an expensive and laborious process. Hence the rationale for allogeneic CAR T-cell therapy.

Cellectis uses gene editing in construction of its allogeneic CAR T-cells. Specifically, the company first modifies T-cells from healthy donors with an anti-CD19 CAR gene construct, similar to the methods used by other companies that are developing anti-CD19 CAR cellular immunotherapies. Cellectis then uses gene editing based on transcription activator-like effector nucleases (TALENS) to disrupt expression of the T-cells’ TCR (T-cell receptor) genes. It is the TCRs of the transplanted T cells that recognize the patient’s own cells as foreign, and thus attack them. Cellectis also uses TALENS gene editing to disrupt expression of a gene for another cell-surface protein, CD52. CD52 is present on mature lymphocytes, and is the target of the monoclonal antibody drug alemtuzumab (Genzyme’s Lemtrada). Researchers can then use alemtuzumab to prevent host-mediated rejection of the HLA mismatched CAR19 T cells. Cellectis’ “Talen engineered universal CAR19 T cells” can thus in principle be used to treat any patient with B-ALL (B-cell acute lymphoblastic leukemia), instead of autologous anti-CD19 CAR T-cells.

The treatment of the young patient, Layla Richards of London, was on a compassionate use basis. She had refractory relapsed B-ALL, and was expected to die shortly. Meanwhile, Cellectis had a universal CAR19 (UCART19) cell bank in the same hospital in which Layla was being treated. The cell bank had been characterized in detail, in preparation for submission for regulatory approval and Phase 1 testing.

Prior to administration of the UCART19 cells, the patient received lymphodepleting chemotherapy (including administration of alemtuzumab). After getting the UCART19 cells in June 2015 (near her first birthday), Layla went into remission, and has no trace of leukemia. After about three months she had a bone marrow transplant to help her immune system recover, and is now at home. However the follow-up period since her treatment has only been 5 months. Therefore, Layla’s doctors do not yet know how durable the remission will be. The key question is how long the UCART19 cells can survive in the body and prevent recurrence of leukemia.

Gene editing companies and their technologies discussed in our November 2015 report

Our November 2015 gene therapy report includes a chapter (Chapter 8) that focuses on gene-editing technologies and on companies that are developing therapies based on these technologies. The gene-editing technology that has been getting the most attention from the scientific and financial communities is known as CRISPR/Cas9. The other two technologies discussed in Chapter 8 are TALENS and zinc-finger nucleases (ZFN). The basic principle of these gene-editing technologies is that a “molecular scissors” makes a specific double-strand break in a deleterious DNA sequence. This break is either repaired in such a way as to disrupt the gene by forming deletions or mutations, or—if a suitable donor DNA is provided—the deleterious gene is replaced with a desired, functional gene sequence.

Gene-editing specialty companies discussed in our report based on CRISPR/Cas9 technology include Editas Medicine (Cambridge, MA) (which also utilizes TALENS), Intellia Therapeutics (Cambridge MA), CRISPR Therapeutics (Basel, Switzerland; Stevenage, U.K.; and Cambridge MA), and Caribou Biosciences (Berkeley, CA). Sangamo BioSciences (Richmond, CA), which is also discussed in our report, is a pioneer in ZFN technology.

Despite the predominant focus on CRISPR/Cas9 technology and companies in the biotechnology and venture capital communities, the first clinical studies involving gene editing have used Sangamo’s ZFN technology. These studies are in the field of HIV/AIDS. They involve ex vivo treatment of HIV-infected patients’ T-cells with a specific ZFN-based vector, in order to render the patients resistant to further manifestations of the disease.

Meanwhile, Editas has developed a vector designed to enable the company to move its CRISPR/Cas9 technology into the clinic. Editas’ first clinical program will be a potential treatment for a form of the genetically-driven retinal disease, Leber congenital amaurosis (LCA). (This is a different form of LCA than the one being targeted by Spark Therapeutics, which we discussed in our November 16, 2015 article on this blog).

bluebird bio (Cambridge, MA) is also pursuing a gene-editing technology program based on homing endonucleases and MegaTAL enzymes. This research and preclinical-stage program came to bluebird via its 2014 acquisition of Precision Genome Engineering Inc. (Seattle WA).

Cellectis is not the only company that is combining CAR T-cell therapies with gene-editing technology. In May 2015, Editas formed a collaboration with Juno Therapeutics to pursue research programs that combine Editas’ genome editing technologies with Juno’s CAR and TCR T-cell technologies.

Conclusions

Despite the great deal of excitement about gene-editing technologies and companies (especially CRISPR/Cas9) these are early days for development of therapies based on these technologies. Despite the almost miraculous results in the treatment of Layla Richards, it is only one case, and the follow-up period has been short. Nevertheless, this one case may open the way for this therapy to be used in other “desperate situations” where there is no time, or it is not possible, to use a patient’s own T cells. And that a similar technique may be used to treat people with other blood cancers, and eventually people with solid tumors.

For more information on our November 2105 gene therapy report, or to order it, see the CHI Insight Pharma Reports website.

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