Human Gene Editing: Prevention, Cure, or Enhancement?
"CRISPR Cas9" by National Institutes of Health (NIH) is licensed under CC PDM 1.0
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Summary: Germline gene editing is no longer the sci-fi fantasy of futurists. It is getting closer to becoming safe and effective enough for the prevention and treatment of hereditary disease mutations. Drawing the line between disease and natural variation is controversial, filled with ethical questions of autonomy, distributive justice, and engineered evolution. Universal policy frameworks are needed to safeguard the misuse of gene-editing.
When science moves faster than the law, moral lines become blurred by grey areas and controversy. This manifested in 2018 with Dr He Jiankui, the scientist who edited the CCR5 gene of twin girl embryos born alive to an HIV-positive father, attempting to make them resistant to HIV infection. Though the scientific community roundly condemned Jiankui, it became clear that temporising moratoria on germline gene-editing will not put a stop to the growing number of independent practitioners marketing unapproved experimental interventions to vulnerable patients. Since the Asilomar Conference on Recombinant DNA in 1975, the scientific community has not been idle in engaging both the public and lawmakers to organize professional and legal standards for genomic research. Yet current enforceable international standards vary and have not been enough to stabilize the slippery slope between human embryo research, and germline gene-editing for clinical use.
Gene-editing makes it possible to swap out harmful genes for beneficial ones, such as in the case of mutated CCR5’s resistance to HIV. CCR5 codes for a protein receptor on white blood cells, which are destroyed by the HIV virus. Yet by tampering with this receptor, it is possible for individuals to become susceptible to other infectious agents, as white blood cells are the frontline immune defences. Unintended effects such as these, as well as the possibility of off-target effects, are what keep germline gene-editing as an experimental technique for now.
However, strides are being made in improving the safety and efficacy of CRISPR-Cas9, the DNA-cutting and pasting technology behind gene-editing. In 2016, a Chinese group became the first to inject a person with cells that contain CRISPR-Cas9-edited genes during a clinical trial, to treat aggressive lung cancer. Somatic cell editing in this way does not raise as many ethical questions as germline gene modifications.
Ethical arguments made against germline editing include the disregard for the unborn child’s autonomy. Yet many healthcare practices, such as maternal and child vaccination, quitting smoking, and alcohol abstinence during pregnancy, are decided by the parents, and intended solely for their child’s right to health. Similarly, all states have an obligation to ‘ensure to the maximum extent possible the survival and development of the child’, as is universally ratified in the UN Convention on the Rights of the Child (the USA being the only non-ratifying country).
"Designer Babies - CRISPR Explained" by Kurzgesagt - In A Nutshell is licensed under CC BY-NC-ND 4.0
About 6% of babies born have a significant birth defect of genetic or partially genetic origin. In addition, many diseases of monogenic inheritance, and susceptibility to infection can trace their roots to editable gene locations. Although other reproductive options exist, such as preimplantation genetic diagnosis, which screens IVF-made embryos for gene mutations before selection, they cannot select against all heritable mutations. In the UK, for example, 20% of women undergoing IVF can produce only one viable embryo, so they do not have the option of selecting other embryos, should their sole embryo harbour a significant mutation. Gene-editing would be able to swap out the mutated gene for a natural variant.
When cases are clearly delineated by mutated and natural gene variants, the consensus is on developing germline gene-editing technology as a possible cure. Yet there is sometimes no objective way of drawing clear lines between ‘difference’ and ‘disease’. For instance, is the potential of editing the Klotho gene, found to be implicated in Alzheimer’s disease when mutated, limited only to preventing Alzheimer’s, or could it be extended to boost the IQ within families with low-normal IQ, which does not classify as mental disability? Many denounce this as an enhancement, yet this context is not entirely different from using donor oocytes or sperm from individuals with above-average intelligence, beauty, or physical strength, which is permitted and routinely pursued.
Public opinion on this matter is varied. People are fairly accepting of genetic engineering used to prevent genetic disorders. A survey last year by the Royal Society indicated that the UK public is “cautiously optimistic” about using genetic engineering to improve human health. 76% said they supported inheritable gene-editing to correct genetic disorders. A different survey in 2018 found only slightly more mixed attitudes in the American public, where 60% said they approved of genetic modification in babies to reduce the risk of the development of serious diseases. Many agree that there is a need to improve education and communication. The Dialogue on Science, Ethics and Religion at the American Association for the Advancement of Science is one example.
But what about the cost of gene editing? The CRISPR-Cas9 system created such a stir partly because it is cheaper than existing methods of gene-editing – it is already used in academic laboratories for less than £50 each. However, high licensing fees for CRISPR patents mean gene therapies can be remarkably expensive – since the therapy is permanent and one-off, drug companies may charge large amounts (approximately £500,000-£1 million). Even in the US, many insurers refuse to cover such treatments. In the developing world, where infectious disease is a disproportionate burden, it is hard to see the drive for gene-editing where public health and already available medicines may solve the problem – treatment for HIV antiretrovirals costs approximately £100 per person per year (£8000 over a lifetime), but currently any gene therapy approved (not yet available for HIV though) costs a minimum of £500,000.
Germline gene-editing comes with as much debate and controversy as it does potential for transformative therapy. Its ethical aspects are as important as its technical feasibility. Hence, policymaking that intends to have impact and adherence must address these issues in tandem, and it is high time for such policy deliberation.
Cyranoski, D. (2019, February 26th). The CRISPR-baby scandal: what’s next for human gene-editing. Nature https://www.nature.com/articles/d41586-019-00673-1?fbclid=IwAR3Xb-ZPVajC473SHexlENd1_q1ydCpn7xwC-CaWmqZF2M4xe0YyYEzNxrQ
Cyranoski, D. (2016, November 15th). CRISPR gene-editing tested in a person for the first time. Nature https://www.nature.com/news/crispr-gene-editing-tested-in-a-person-for-the-first-time-1.20988
The Royal Society (2018, March 7th). UK public cautiously optimistic about genetic technologies https://royalsociety.org/news/2018/03/genetic-technologies/
About the authors:
Randa Abu-Youssef graduated from medical school in Alexandria, Egypt. She is currently studying clinical neuroscience as a 1st year PhD student at Cambridge University.
Charlie Fraser is a 3rd year philosophy student at St John's College, Cambridge. In his spare time he likes to watch videos of things fitting together perfectly.
Pippa Sayers is a 2nd year medical student at Queens' College, Cambridge. Her great pleasures in life are attending lectures in pyjamas, rowing, aggressively brightly coloured trainers, and inter-disciplinary conversation.
Tokino Takahashi is a 1st year medical student at Emmanuel College, Cambridge.
Gayatri Vijapurkar is a 1st year medical student at Murray Edwards College, Cambridge.
Muhammed Afolabi is an Assistant Professor at the London School of Hygiene and Tropical Medicine’s Department of Clinical Research