Genome Editing: A Revolutionary Technology With Wide Applications in Therapeutics, Drug Discovery, Agriculture and Animal Biotechnology
DNA sequencing technologies have become efficient and inexpensive and have increased our understanding of the genome. Nonetheless, several genomic functions of complex disease pathways and other cellular function pathways cannot be elucidated with sequencing alone, as it was demonstrated that mere presence of DNA sequence does not necessarily translate to function, other epigenetic factors, activator and repressors are important for the gene function. Simple monogenetic diseases that are well characterized and well-studied such as sickle cell anaemia with a single genetic mutation do not have a cure yet. Hence, with advanced gene editing technologies, scientists have been able to study complex diseases and cellular pathways that improved understanding of the genome as well as develop gene-editing based therapy for several genetic as well as acquired diseases.
Gene editing broadly refers to a suite of methods that use programmable endonuclease to target a specific site in the genome that can induce double-stranded break (DSB) which are then repaired by disrupting or modifying the target sequence. There are four major classes of gene editing technologies, including meganuclease and their derivatives, Zinc Finger Nucleases (ZFNs), Transcription Activator-Like Effector Nucleases (TALENs), and Clustered Regularly Interspaced Short Palindromic (CRISPR)-associated nuclease Cas9. These nucleases can be broadly divided into two classes based on their mode of DNA recognition; ZFN, TALEN and meganucleases bind to DNA via protein-DNA interaction, whereas Cas9 binds to DNA with a short guide RNA (g RNA) by Watson-Crick base-pairing. Moreover, transposons are used as gene editing tools that can integrate desired genes into the host genome by using their inherent ‘cut and paste’ process. The global genome editing market, based on technology type is segmented into ZFN, TALEN, CRISPR and Others [rAAV(recombinant adeno-associated virus), piggybac transposon, homing endonuclease, TARGATT, RTDS (Rapid Trait Development System), ARCUS].
The genome editing application are classified into basic research, agriculture/plant biotechnology, animal biotechnology and drug discovery & development. Genome editing technologies have revolutionized basic and applied research and CRISPR was named as one of the breakthrough technologies of 2015 by Science magazine of American Association for the Advancement of Science (AAAS). Meganucleases and ZFN are older technologies, developed in the late 1990s which have more mature market than CRISPR technology. Later in 2010, TALEN was developed which was touted as the next generation gene editing technologies until CRISPR was elucidated in 2012. Although CRISPR was historically known, the mechanism and application for gene editing were elucidated by Dr Jennifer Doudna and Dr Emmanuel Charpentier in 2012, since then the technology has been licensed by various biotechnology and pharmaceutical companies globally for various applications for its simplicity and efficiency and more importantly inexpensive nature of the technology. Presently, there are varieties of gene editing tools that are well characterized with a thorough knowledge of their mechanisms which are transforming the way research is conducted and products developed across global life science sector with a wide range of applications in agriculture, animal biotechnology, drug discovery and development and therapeutics.
Genome editing technologies are being rapidly adopted for therapeutics and drug discovery and development. Majority of gene editing companies, pharmaceutical and biotechnology companies are focusing in these fields. ZFN-based therapeutics was developed by Sangamo Biosciences which is currently in phase 2 clinical trials for HIV treatment. Using TALEN-mediated gene editing technology, Cellectis developed UCART19 (Chimeric Antigen Receptor known as CAR T-cells) therapeutic candidate intended for treating paediatric acute B lymphoblastic leukaemia which is in Phase I study at the University College, London. A study led by scientists from several institutions and St. Jude Children’s Research Hospital demonstrated that CRISPR/Cas9 genome editing can be used to alleviate hereditary haemoglobin deficiencies like beta-thalassemia and sickle cell disease. The scientists edited patient-derived hematopoietic stem and progenitor cells (HSPCs) which produced physiological levels of hemoglobin that reduced sickle cell morphology when differentiated into red blood cells. Besides therapeutics, a comprehensive collection of cell lines and animal models are available from companies such as Horizon Discovery Group, Thermo Fisher Scientific for various diseases and cellular & metabolic pathways to aid and enhance drug discovery and development.
Genome editing technologies have proliferated in agriculture field for developing non-transgenic plants. In addition, CRISPR and TALEN have been used to develop other improved traits in crops such as rice, potato, soybean and these crops are exempted from GMO labelling, creating opportunities in the agriculture sector. In plant sector, the other technologies dominated. Many agricultural giants such as Monsanto and Syngenta have adopted and are exploring possibilities of gene editing technologies. For example, Monsanto signed licensing agreement with TargetGene Biotechnologies, granting Monsanto an exclusive license to TargetGene’s proprietary T.GEE platform to advance plant breeding and biotechnology pipelines. Researchers at Syngenta have partnered with Precision BioSceinces, Inc. to develop advanced agricultural products using Precision’s proprietary ARCUS gene editing technology to insert gene of interest in the corn genome. CIBUS is one of the pioneers of gene editing in plant biotechnology, which developed SU Canola crop that is commercially available in U.S. using their proprietary gene editing technology RTDS.
Animal biotechnology is burgeoning with the development of hornless cow, disease resistant pigs, more meat yielding cow and more recently micro pigs and super muscly beagles. In animal sector, research is confined to academic and government institutes, few companies such as Recombinetics and Genus Plc have adopted CRISPR and TALEN for gene editing in animals.
With the breakthrough emergence of genome editing technologies such as ZFN, TALEN and CRISPR, the genome editing market received abundant investments from both private and public sector. According to analysis by IQ4I, about $1.3 billion has been invested in gene-editing technologies since January 2015. Funding in CRISPR-Cas9 technology alone is estimated to be $588 million since January 2015. The investments were mainly for therapeutics and drug discovery and development. It is also evident that there have been no investments either in the public sector or public sector for ZFN or TALEN technologies since January 2015. CRISPR is being adopted swiftly by scientists for basic and applied research inspite of the patent disputes associated with the technology as it is more efficient, simple and inexpensive. According to industry experts and IQ4I analysis, CRISPR is poised to be dominating technology until another advanced gene editing is introduced.
Some of the major companies in the genome editing market are Applied Stemcell (U.S.), Cellectis S.A. (France), Genscript (U.S.), Horizon Discovery Group (U.K.), Merck KGaA (Germany), Origene Technologies (U.S.), Sangamo Biosciences (U.S.), System Biosciences (U.S.), Thermo Fisher Scientific (U,S,) and Transposagen BioPharmaceuticals (U.S.).Other companies include GE Healthcare (U.K.), Agilent Technologies (U.S.) New England Biolabs (NEB) (U.S.), Integrated DNA Technologies (IDT) (U.S.), Lonza (Switzerland), Addgene (U.S.), Precision Biosciences (U.S.), Bluebird Bio (U.S.), Editas Medicine (U.S.), Caribou Bioscience (U.S.), CRISPR Therapeutics (Switzerland), ERS Genomics (Ireland) and Takara Bio (Japan).