CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool

CRISPR Ethics: Moral

Considerations for Applications of a

Powerful Tool

Carolyn Brokowski

and Mazhar Adli

1 - Department of Emergency Medicine, Yale School of Medicine, 464 Congress Avenue, New Haven, CT 06519-1362, USA

2 - Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, 1340 Jefferson Park Avenue,

Charlottesville, VA 22908, USA

Correspondence to Mazhar Adli: [email protected]

https://doi.org/10.1016/j.jmb.2018.05.044

Edited by Prashant Mali

Abstract

With the emergence of CRISPR techno logy, targeted editing of a wide variety of genomes is no longer an

abstract hypothetical, but occurs reg ularly. As application areas of CRISPR are exceeding beyond research

and biomedical therapies, new and existing ethical concerns abound throughout the global community about

the appropriate scope of the systems' use. Here we review fundamental ethical issues including the following:

1) the extent to which CRISPR use should be permitted; 2) access to CRISPR applications; 3) wheth er a

regulatory framework(s) for clinical research involving human subjects might accommodate all types of human

genome editing, including editing of the germline; and 4) whether international regulations governing

inappropriate CRISPR utilization should be crafted and publicized. We conclude that moral decision making

should evolve as the science of genomic engineering advances and hold that it would be reasonable for

national and supranational legislatures to consider evidence-based regulation of certain CRISPR applications

for the betterment of human health and progress.

Introduction

The CRISPR (Clustered Regularly Interspaced

Short Palindromic Repeats)-Cas9 (CRISPR-associ-

ated protein 9) system (“CRISPR” or “the system”)is

the most versatile genomic engineering tool created

in the history of molecular biology to date. This

system's ability to edit divers e genome types with

unprecedented ease has caused considerable ex-

citement and alarm throughout the international

biomedical community.

CRISPR appears to offer considerable promise in

a wide variety of disease contexts. For example,

around the world at least 15 clinical trials—focused

on multiple myeloma; esophageal, lung, prostate,

and bladder cancer; solid tumors; melanoma;

leukemia; human papilloma virus; HIV-1; gastroin-

testinal infection; β-thalassemia; sickle-cell anemia;

and other diseases— involving CRISPR appli cations

have been developed [1–3]. Moreover, as of May,

2018, in China at least 86 individuals have had their

genes altered as part of clinical trials [4].

While significant public support exists for thera-

peutic applications [5], ethical (moral) and safety

concerns about certain areas of CRISPR applica-

tions, such as ger mline editing, are apparent around

the world [6]. Notably, such discussions commenced

during the Napa Valley meeting of 2015 when a

leading group of CRISPR–Cas9 developers, scien-

tists, and ethicist s met to examine the biomedical,

legal, and ethical aspects of CRISPR systems [7].

From this meeting, more extensive deliberations

were solicited, and the United States (US) National

Academies of Sciences, Engineering, and Medicine

(NASEM or “The Committee”) invited the Chinese

Academy of Sciences and the United Kingdom's

(UK) Royal Society to participate in the International

Summit on Human Gene Editing [8]. The goal of this

meeting was to examine when, where, and how the

technology might be applied in humans. This

discussion continued in February of 2017 when a

multidisciplinary committee of the NASEM published

a comprehensive report examining numerous as-

pects of human genome editing [9].

KDC YJMBI-65762; No. of pages: 14; 4C:

Review

Please cite this article as: C. Brokowski, M. Adli, CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool, J. Mol. Biol.

(2018), https://doi.org/10.1016/j.jmb.2018.05.044

To date, the NASEM report provides perh aps the

most influential, extensive analysis examining wide-

ranging concerns about human genome editing [10].

Importantly, the Committee favored somatic genome

editing, but did not permit genomic modification for

any kind of enhancement [9, 11]. Also, though

impermissible at present, the Committee concluded

cautiously that human heritable genome editing, the

modification of the germline with the goal of creating

a new person who could potentially transfer the

genomic edit to future generations, would be

permissible under certain conditions: “In light of the

technical and social concerns involved … heritable

genome-editing research trials might be permitted,

but only following much more research aimed at

meeting existing risk/benefit standards for authoriz-

ing clinical trials and even then, only for compelling

reasons and under strict oversight.” [9] Although by

law, US federal funding cannot be used to support

research involving human em bryos [12–14], the

NASEM report suggests that when technical and

safety risks are better understood then clinical trials

involving germline editing might begin [9].

In this review, we aim to summarize fundamental

ethical concerns about CRISPR use in general, but

the list is not exhaustive. First, we briefly review

CRISPR systems and their applications in editing

genomes and epigenomes. Second, we describe

how complexities of CRISPR science affect those of

CRISPR ethics and vice versa. Third, we assess

several key ethical considerations. Notably, while

some of these concerns are specific to CRISPR

technology, many, such as research on human

embryos, have been debated long before the

CRISPR revolution [15]. Moreover, since CRISPR

is still a maturing technology, novel applications in

the future may raise new ethical quandaries meriting

further attention and dissection. Fourth, it is impor-

tant to point out that, though morality and law often

overlap, significant differences exist. Although law

may affect ethics and vice versa, we focus mostly on

ethics. Finally, while discussing these issues, we

assume no position on any topic; our account is

merely descriptive. Therefore, we mak e no attempt

to settle any of the controversies presented herein.

CRISPR systems and their uses

Different CRISPR systems in genome editing

CRISPR is a natural bacterial defense system

against invading viruses and nucleic acids. Over

billions of years, multiple CRISPR-type immune

systems have evolved. Naturally occurring CRISPR

systems are typically classified by their repertoires of

CRISPR-associated (cas) genes, which are often

found adjacent to the CRISP R arrays [16, 17].

Although the characterization is yet to be finalized,

two major classes of CRISPR–Cas adaptive immune

systems have been identified in prokaryotes [18–20].

This division is based on the organization of effector

modules. Class 1 CRISPR–Cas systems employ

multi-protein effector complexes and encompass

three types (I, III, and IV). By contrast, Class 2

systems utilize single protein effectors and encom-

pass three other types (II, V, and VI). Although various

natural CRISPR–Cas systems have been repurposed

for genome editing, due to its robust gene-editing

efficiency and broader genome-targeting scope owing

to its simple NGG PAM sequence requirement, the

Cas9 from Streptococcus pyogenes (spCas9) is

currently the most commonly used CRISPR–Cas9

protein. It is worth noting that multiple efforts are

underway to discover novel Cas9 variants or re-

engineer the existing Cas9 proteins, which will have

less dependence on the stringent PAM-sequence

requirement [21, 22].

CRISPR goes beyond genome editing

The DNA-editing capacity of CRISPR–Cas9 is due

to the ability of the WT Cas9 protein to cause double-

stranded breaks at the target site that is determined

by the custom-designed short guiding RNA [23]. The

repair of DNA breaks frequen tly results in indels, due

to the non-homologous end joining (NHEJ) repair

mechanism. However, when a complementary tem-

plate is available, homology-directed repair (HDR)

machinery can use it and thereby achieve more

precise gene editing. Notably, a single-point mutation

in either of the two catalytic domains of Cas9 results

in a nickase Cas9 (nCas9), whereas mutations in

both domains (D10A and H840A for spCas9)

diminish Cas9's catalytic activity, resulting in dead

Cas9 (dCas9) [24]. Interestingly, the application

areas of modified Cas9 proteins are exceeding that

of WT Cas9 [25]. Such uses are largely possible

because the nCas9 or dCas9 can still be guided to

the target sequence [26]. Researchers employed

these Cas9 variants for unique purposes. For

example, tandem targeting of nCas9 has been

utilized to improve targeting specificity [27, 28].

More recently, this enzyme has been used as the

base platform for second generation genome-editing

tools called “base editors” [29, 30] Base-editing

technology employs cytidine or adenine deaminase

enzymes to achieve the programmable conversion of

one base into another (C to T or A to G). Most

importantly, the targeted base transition happens

without DNA double-stranded breaks [29, 31].We

recently utilized this technology to edit the universal

genetic code and introduced a “stop” codon in the

genes [32].

In addition to nCas9, researchers uti lized the

guidable capacity of dCas9 as a platform to recruit

various effector proteins to a specific locus in living

cells. Generally, these activities ca n be classified as

2 Review: CRISPR Ethics

Please cite this article as: C. Brokowski, M. Adli, CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool, J. Mol. Biol.

(2018), https://doi.org/10.1016/j.jmb.2018.05.044

epigenetic editing (to alter locus-specific epigenetic

information), gene regulation (to turn the activities of

single or multiple genes on or off), chromatin imaging

(to label and monitor chromatin dynamics in living

cells), and manipulation of chromatin topology (to

alter 3D chromatin structure in the nuclear space)

[33].

CRISPR research is progressing at a rapid pace.

Recently, scientists have a lso uncovered new

CRISPR–Cas systems (Cas13) that can target RNA

instead of DNA [34, 35]. By enabling targeted RNA

recognition and editing, these newer RNA-targeting

CRISPR tools have their unique applications ranging

from biomedical and biotechnological to the detection

of nucleic acids [36, 37]. Although many ethical

concerns are related to the catalytic activities of WT

Cas9—partly because it permanently alters the

genetic information—some of these activities of

catalytically inactive dCas9, nickase-Cas9-based

platforms, such as base editors and recently discov-

ered RNA-targeting Cas proteins, may raise compa-

rable moral issues depending on the duration of the

exerted effect and the purpose of the experiments.

Detailed discussion of such issues, however, is

beyond the scope of this review (Table 1).

CRISPR ethics and science:

Uncomfortable bedfellows

Moral decisions, especially in biomedicine, are

empirically informed and involve assessing potential

risk-benefit ratios—attempting to maximize the latter

while minimizing the former. To navigate ethical

decision making, it is critical to consider the range of

possible outcomes, the probabilities of each instantiat-

ing, and the possible justifications driving the results of

any one. The ethical concerns about CRISPR genome

engineering technology are largely due to at least three

important reasons.

First, there are concerns about the power and

technical limitations of CRISPR technology. These

include the possibilities of limited on-target editin g

efficiency [38, 39], incomplete editing (mosaicism)

[40, 41], and inaccurate on- or off-target editing [42,

43]. These limitations have been reported in CRISPR

experiments involving animals and human cell lines.

However, the technology is evolving at an unprece-

dented pace. As m ore efficient and sensitiv e

CRISPR tools are developed, many of these con-

cerns may become obsolete. Yet for the sake of this

review, we mention these limitations as one of the

principal worries about widespread CRISPR utiliza-

tion. Second, it is unclear whether modified organ-

isms will be affected indefinitely and whether the

edited genes will be transferred to future generations,

potentially affecting them in unexpected ways.

Combined with technical limitations and the com-

plexities of biological systems, making precise

predictions about the future of an edited organism

and gauging potential risks and benefits might be

difficult, if not impossible. Thus, uncertainty resulting

from these factors hinders accurate risk-benefit

analysis, complicating moral decision making.

Finally, the skeptical view is that even if the genome

is edited as expected and the desired functional output

is achieved at the given time, the complex relationship

between genetic information and biolo gical phenotyp es

is not fully understood. Therefore, the biological

consequence of editing a gene in germline and/or

somatic cells may be unclear and unpredictable

depending on the context. Many biological traits are

determined by the complex regulatory actions of

numerous genes. Hence, is it difficult, if not impossible,

to “design” a biological phenotype at the whole-

organism level. Across biological outcomes, whether

in normal or in disease development, it is uncommon

that a single gene is the only factor shaping a complex

biological trait. Other genetic regulatory factors such as

additional genes or distal regulatory elements (e.g.,

enhancer or repressor elements), as well as environ-

mental and epigenetic factors, contribute to the

emergence of a biological phenotype. To argue that

modifying a gene changes a desired phenotype (under

certain conditions) implies at least a reasonable

understanding of other independent variables contrib-

uting to the phenotype's instantiation. But this under-

standing is still far from complete in many normal and

disease processes [44, 45]. Given the uncertainty

regarding how gene expression and modification

influence complex biological outcomes, it is difficult to

appraise potential risk and benefit. This ambiguity

creates a challenge on its own and is one of the sources

obscuring efficient ethical deliberation and decision

making.

Nevertheless, regulations governing ce llular- and

gene-therapy research may facilitate the safe devel-

opment and oversight of some clinical trials involving

CRISPR-based-editing applications. In the United

States, for instance, cellular- and gene-therapy

products, including many CRISPR applications, at

this time are defined generally by the Food and Drug

Administration as biological products and are regu-

lated by the Food and Drug Administration's Center

for Biologics Evaluation and Research/Office of

Cellular, Tissue , and Gene Therapies [46–48].

Although the r isks and benefits of many such

therapies increasingly are better understood [49],

questions regarding safety and effi cacy remain.

Thus, future advancements likely will con tinue to

improve the benefits of this revolutionary technology,

while minimizing the potential risk s. Regardless of

the uncertainty posed by novel CRISPR technologies

and applications, in several locations around the

world significant regulatory frameworks exist by

which risks may be monitored and contained.

However, wherever such infrastructure and oversight

are lacking, safety and privacy risks might increase.

3Review: CRISPR Ethics

Please cite this article as: C. Brokowski, M. Adli, CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool, J. Mol. Biol.

(2018), https://doi.org/10.1016/j.jmb.2018.05.044

Ethical concerns

To what extent should CRISPR experimentation

be permitted in basic and pre-clinical biomedical

research?

Although it is less than a decade old, CRISPR–

Cas9 has demonstrated unprecedented potential to

revolutionize innovation in basic science. From viruses

and bacteria [50, 51], to simple model organisms, such

as Drosophila melanogaster (fruit fly) [52], Anopheles

gambiae (mosquito) [53], Saccharomyces cerevisiae

(budding yeast) [54], Hydra magnipapillata (hydra)

[55], Caenorhabditis elegans (round worm) [56],

Danio rerio (zebra fish) [57], and Arabidopsis thaliana

(rockcress) [58], to larger animals such as pigs [59],

cattle [60], and monkeys [61], and even human

Table 1. Risk-benefit considerations in CRISPR technology

Benefit(s) Risk(s)/Harm(s)

Basic and pre-clinical research • New model organisms and cell lines

• Increased gene-editing efficiency

• High-throughput screens

• Novel drug targets

• Access to totipotent cells

• Identification of novel signaling,

regulatory, and developmental pathways

• Development of novel gene-editing

approaches (base editing and RNA targeting)

• Knowledge advancement

• Experimentation involving human embryos is

controversial and illegal in some countries

• Potential for privacy and confidentiality breaches

Translational and

clinical medicine

• Immunotherapy

• Organoids

• Novel drug targets

• Artificial intelligence

• Modification of pathological genes

• Novel therapeutics and fertility

applications

• Procreative liberty

• Ability to “fix” single base changes

• Knowledge advancement

• Potential for equitable access

• Serious injury, disability, and/or death to research

participant(s) and/or offspring

• Blurry distinction between therapeutic and

enhancement applications, leading to potential

subtle or obvious exacerbation of inequalities

• Misapplications

• Eugenics

• Potential for inequitable access and exacerbation

of inequalities

Non-therapeutic

applications

• Enhancement to augment select faulty

or normal human characteristics

• Fortification of crops and livestock

• Successful control of pests, invasive

species, and reservoirs (gene drives)

• Disease/infection control (e.g., malaria,

dengue fever, Lyme and Chagas

disease, schistosomiasis)

• Ecosystem alteration to protect

endangered species (gene drives)

• Safety

• Crop cultivation

• Knowledge advancement

• Eugenics

• Exacerbation of racism and inequality

• Theoretical risk for damage to ecosystems

• Theoretical risk of misuse

Access to CRISPR

technology

• Inexpensive (technology itself)

• Widely available

• Profit, economic growth

• Innovation

• Price gouging

• Prohibitively expensive applications

Regulations for

clinical research involving

human subjects

• Established framework in some

countries to manage research risks

• Legal mechanisms for redress

already exist, depending on location

• Lack of appropriate supervisory infrastructure,

oversight, and/or regulatory framework

in many nations

• Unclear how to supervise the research even in

some countries with regulatory oversight

• Over-regulation might hinder progress

National and international

regulations, law, and policy

• Prevention against misuses of technology

• Safeguard against risky, potentially

harmful conditions

• Potential to encroach on individual, scientific,

and societal autonomy

• Limit discovery and progress

• Difficult enforcement

• Lack of uniformity may create inconsistencies

in applications of laws/regulations

4 Review: CRISPR Ethics

Please cite this article as: C. Brokowski, M. Adli, CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool, J. Mol. Biol.

(2018), https://doi.org/10.1016/j.jmb.2018.05.044

zygotes [62, 63], CRISPR experimentation has led to

novel, important findings. Such benefits include at least

the following: increased overall efficiency in gene

editing compared with previous genomic engineering

techniques like transcription activator-like effector

nucleases (TALENs) and zinc finger nucleases

(ZNFs) [64]; significant insights into the evolutionary

transformation of fish fins into tetrapod limbs [65];

investigation into new organisms [66]; genetic and

epigenetic screens [67, 68]; the creation of novel cell

lines [69]; high-throughput screens and libraries [70];

the elucidation of novel genomic and epigenomic

regulatory pathways [71, 72]; insights into the devel-

opment of butterfly coloring and patterning [73];the

functional characterization of key genes and molecular

signaling pathways [74, 75]; and drug-targeting

screens [76, 77]. Data from such experimenta tion

provide essential clues and understanding that pro-

mote biomedical discovery, advancement, and the

basis for potential medical benefits.

One of the major controversies about CRISPR

technology emerges from its possible application in

hum an embryos. This controversy is not about

CRISPR itself, but instead is largely due to the lack of

clarity about the status of the human embryo. Although

some in the scie ntific community main tain that it is

ethically impermissible to exper iment on human

embryos a fter 14 days [78, 79], it is impossible for

any one party—whether it is a government, laboratory,

funding agency, panel of experts, court, religious

organization, or other group—to decide the status of

a human embryo [80, 81] and whether and precisely

when it has “personhoo d” [82]: Is the entity merely a ball

of cells whose status is like that of human skin, which

sheds regularly without further ado? Or does the entity

hold complete personhood status—with irreducible,

inalienable moral rights and to whom we owe important

directed duties? Or is the embryo's status characterized

optimally as something in between? And if so, which

moral rights might this entity hold, and which duties

might we owe to it? Despite this perplexing complexity,

decisions one way or the other must be executed,

because proceeding with research or failing to do so

has important consequences: Banning or significantly

limiting research on human embryos stymies progress

at least by making unavailable or curtailing an option to

investigate the therapeutic potentials of stem cells and

the biology of totipotent cells, which currently are not

known to be present in any other viable human tissue

sources. Totipotent cells can divide indefinitely and

have the capacity to develop into all tissue types.

Depending on how the status of the embryo is

appraised, however, the ban also could save it from

potentially unjust, lethal research-related harms. Even

if the research is justified because of its potential benefit

to the embryo itself and/or to others, the embryo as

such cannot give informed consent at the time of the

research, since the entity is not sufficiently developed.

But from the research, it could experience potentially

life-altering consequences—good or bad—that may

extend throughout the lifespan and future generations.

By contrast, promoting such investigation may

facilitate the development of novel in vitro fertilization

techniques and advances for conditions such as

spinal cord injury [83], Parkinson's disease [84],

burns [85], cardiomyopathy [86], and other ailments

that might be ameliorated by approaches involving

regeneration. Taken together, countries must con-

tinue to decide as the science progresses whether

and how to legalize experimentation on human

embryos. Current positions across the globe vary

widely—from outright banning of the research to

illegalizing its federal funding only (while still allowing

private funding for research and the research itself)

to authorizing federal monies for experimentation

[4, 6, 87, 88].

To what extent should CRISPR use be permitted

in translational and clinical medicine?

CRISPR is significantly benefitting, and is likely to

improve, immunotherapy [89], organoid engineering

and development [90], in vivo drug target identifica-

tion [91], machine learning and artificial intelligence

[92], and disease-gene modification in viable human

embryos [62]. The system offers nearly boundless

potential to promote progress in combating HIV [93],

hemophilia [94], cancer [95], Duchenne muscular

dystrophy [96], amyotrophic lateral sclerosis [97],

sickle-cell anemia [98], cystic fibrosis [99], infertility

[100], and any number of novel diseases. The

potential both for gaining knowledge and for devel-

oping treatments in humans seems nearly endless.

However, such knowledge and treatment acquisition

are not without potential risk. With experimentation

involving somatic cells, risk assessment seems at least

comparable to that which arises in regularly practiced

biomedical testing. The chief objective of phase-2

oncology trials, for example, is to evaluate the efficacy

of a new drug or device [101]. Study participants may

assume significant harms, including possible irrevers-

ible side effects and death [102, 103].Inmany

countries, respect for autonomy permits assuming

such risk with the requirement that informed consent

occurs before enrollment in the research, regardless of

whether individuals are enrolling themselves or their

dependents. If this risk is considered morally (and

legally) permissible, then it would seem unjustified and

unreasonable to not allow risk posed by investigations

involving CRISPR-based genome engineering. At the

time of this writing, there is no empirical support

suggesting that CRISPR experimentation would nec-

essarily pose greater risk: the overall risk profile of

CRISPR experimentation in human subjects remains

unknown.

It could be argued, however, that heritable germ-

line editing might present additional risk, because it

involves not only the research participant but also

5Review: CRISPR Ethics

Please cite this article as: C. Brokowski, M. Adli, CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool, J. Mol. Biol.

(2018), https://doi.org/10.1016/j.jmb.2018.05.044

potentially his or her descendants. Of course, whether

germline engineering technologies introduce risk be-

yond that which might be present in more common

testing scenarios is an empirical matter. For instance, it

is well established that routinely used chemotherapies

have mutagenic properties: alkylating agents, including

cisplatin and cyclophosphamides, cause DNA adducts

and crosslinks; antimetabolites, such as hydroxyurea,

gemcitabine, and 5-fluorouracil, are nucleoside ana-

logs and inhibit thymidine synthase; topoisomerases,

such as etoposide, cause topoisomerase II inhibition,

leading to double-stranded breaks in DNA; and

anthracyclines, like doxorubicin, cause DNA intercala-

tion [104]. Therefore, significant exp osure to any of

these agents increases the probability of both incurring

genetic mutations and passing on these unintended

genomic alterations to future generations. Whether the

risk level presented by such exposure is greater than,

equal to, or less than that presented by CRISPR

experimentation must be quantitatively determined by

empirical evidence. It is also an empirical matter

whether CRISPR introduces risk that is statistically

significant beyond that which is incurred in the daily

experience of a healthy individual with little-to-no

exposure to mutagenic agents. Thus, to determine

with confidence whether it is exceptionally risky to

involve humans in CRISPR translational and clinical

research, possible research-related risks must be

compared with those in other potentially dangerous

experimental and every-day contexts. This is difficult,

however, given that CRISPR technology is new and

that robust, reliable data about CRISPR risk in human

subjects are unavailable. Nevertheless, decision mak-

ing about assuming risk in studies and therapeutics

should be considered according to legal infrastructure,

national and possibly international regulatory agencies,

and ultimately navigated by research participants and/

or their legally authorized representative(s).

Important questions also arise about whether

experiments involving heritable germline editing

yield reliable, interpretable data. One objection is

that such experiments are unlikely to be controlled

and/or predicted [105] because it could be impossi-

ble to analyze or understand the results from such

experimentation until considerable time (decades or

even generations) passes [106]. As previously

noted, the central concern here is the uncertainty

in the causal connection between gene expression/

modification and the potential involvement of other

factors shaping biological outcomes in the future.

Another risk, shared globally, is posed by the

greater society. It is possible, for instance, that

allowing CRISPR germline editing, even if only for

medical purposes, might in some respect(s) lead to

the return of eugenics, whose proponents believed

that the human population can be improved by

controlled breeding to increase the occurrence of

“desirable”, heritable characteristics [107].Unfortu-

nately, historically, this selective weeding of people

with “bad” genes and breeding of those with “good”

ones resulted in many atrocities, including the forced

sterilization of individuals and the propagation of

racially discriminatory policies—both of which were

backed by state authorities and even educated elites

in different societies. In the notorious case Buck v. Bell

[108], for example, the United States Supreme Court

(“the Court”) upheld a Virginia statute permitting the

compulsory sterilization of individuals, such as Carrie

Buck, who were considered “mentally unfit.” Buck was

an economically disadvantaged woman who was

labeled as “feebleminded” like her other family

members of past generations. She was committed

to the Virginia Colony for Epileptics and Feeble-

Minded and was forcibly sterilized [109]. Unfortunate-

ly, however, the evidence of the case strongly

indicates that Buck, like the others in her family, was

normal and that the Court erred gravely [110].Its

decision, authored by eugenics proponent Associate

Justice Oliver Wendell Holmes, led to the sterilization

of 50,000 Americans, set a precedent for the Nazi

racial hygiene program, and is yet to be overturned

[111]. Hence, history reveals that egregious, system-

atic mistakes are always possible.

To what extent should CRISPR use be permitted

for non-therapeutic purposes?

Impor tant et hical questions also arise in non-

therapeutic contexts including enhancement of

crops, livestock, gene drives, and human features

[112].

Certain areas of CRISPR applications, such as the

enhancement of crops and livestock, are likely to

significantly impact society and humanity at large. In

2016, the United Nati ons Food and Agriculture

Organization estimated that 795 million people in the

world were undernourished [113]. And according to

the World Health Organization, 2 billion people are

unable to obtain key nutrients like iron and vitamin A

[114]. A bundant evidence demonstrates that

CRISPR–Cas systems could be used to improve

nutrient content in foods [106, 115–123]. In principle,

CRISPR has the potential to fortify foods efficiently for

individuals who are suffering from a lack of basic

nutrients. Why not decrease malnutrition by maximiz-

ing access to foods of higher quality? Promoting

benefit in this way carries moral weight at least

comparable to any other ethical concern raised

herein, especially given the very large number of

those who are nutrient-deprived. Nevertheless, with

this benefit arise worries about “accessibility” to these

product(s); this issue is discussed further below.

“Gene drive technology” is another CRISPR appli-

cation with unprecedented potential to directly benefit

andsavemillionsoflives[124]. In using gene drives,

researchers employ CRISPR to speed up genetic

recombination such that a “gene of interest” is rapidly

distributed to the entire population much faster than in

6 Review: CRISPR Ethics

Please cite this article as: C. Brokowski, M. Adli, CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool, J. Mol. Biol.

(2018), https://doi.org/10.1016/j.jmb.2018.05.044

a typical Mendelian inheritance rate. Therefore, this

application has the potential to edit the genome of an

entire population or even an entire species. Using

CRISPR-mediated gene drives, investigators have

demonstrated that a gene allele providing a parasite-

resistance phenotype in mosquitos could quickly

spread through the population in a non-Mendelian

fashion [111, 125]. This highly cost-effective technol-

ogy has many potential benefits and applications for

public health, species conservation, agriculture, and

basic research [126]: Gene drives may provide a

fundamental tool to fight against deadly diseases such

as malaria [127–129], dengue fever [130],Chagas

and Lyme disease [131], and schistosomiasis [132].

This application also may control and/or alter a wide

variety of animals (e.g., rodents and bats), invasive

plant pests, and reservoirs [133, 134]. Thus, the

technology has unprecedented power that may save

millions of lives each year. However, it is also

important to consider the expected and unexpected

risks. Once applied, gene drives will eventually affect

every individual of the entire species. Knowing this,

researchers are developing and incorporating key

safety “off-switch” features such as novel ways to (i)

control, (ii) inhibit, and (iii) reverse/eliminate gene

drive systems from the population in case of an

unexpected or emergency event [134–137].

Furthermore, were it possible, would it be it morally

permissible to employ CRISPR techniques to en-

hance human features such as height, muscle mass,

vision, or cognitive factors like learning aptitude and

memory? Answering this question is problematic

largely because of the difficulty with deciding about

what “counts” as pathology vs. what is merely a minor

or even moderate deviation from the “norm” in a given

context. Moreover, accurately characterizing norms in

the first place is often very difficult. Hence, “medical

necessity” often becomes ambiguous, and the bound-

ary between “therapy” and “enhancement” can be

murky. For example, a gene-editing approach may

allow for a reduction in bad cholesterol, thus leading to

a healthier life style. Whether this hypoth etical

scenario, which may benefit both the individual and

society in the long run, should be classified as

enhancement or a medical need is unclear.

Aside from concerns about well characterizing

medical necessity, positive moral liberties are granted

and backed by legal rights in many countries, especially

in the West. Should medical enhancement by CRISPR

technologies be considered a form of free speech and/

or expression? [138] If so, how, if at all, might these

rights be limited, and why? Who has and/or should

have the authority to decide?

Who should have access to CRISPR technology

and/or its products?

Benefits from CRISPR innovation raise concerns

and controversies about fairness and distributive

justice across all layers of society. These matters are

not specific to CRISPR technology, but may apply to

all other technologies arising from academic re-

search. Like many novel biomedical advancements,

new CRISPR applications are expected to be

profitable for patent holders. At least the initial prices

of CRISPR-bas ed products, such as gene therapy,

are likely to be costly [139]. To this end, an ethical

question is whether the high price-tag will make the

CRISPR product available to only the world's elites.

Since much of the funding for CRISPR characteri-

zation and development was provided by grants

from government funds and thus taxpayers' money

[140–151], it is morally problematic to deny poten-

tially lifesaving benefits of the technology to the very

individuals who funded much of its development in

the first place. Moreover, even if it were affordable for

some, there may be economic harms associated

with high-price purchases. For instance, those

needing CRISPR-based applications to maintain a

reasonable quality of life, or even life itself, might be

forced to ma ke painful economic choices about

whether to spend funds on therapuetics, food, or

other essential living necessities. While this problem is

not unique to genomic engineering advancements,

allowing price gouging to continue unaddressed is

unhelpful and potentially allows physical, psycholog-

ical, and economic harms to continue. Encouraging

the establishment of anti-price-gouging laws, where

possible, could ameliorate some of these concerns

[152].

As discussed in the previous section, CRISPR

may be used to fortify foods. Those residing in some

of the most impoverished areas of the world are

positioned to benefit the greatest from the se

products. How might such individuals gain access

to CRISPR-modified foods, especially in places with

armed combat and rogue governments? How, if at

all, could companies benefit such that reaching out

to these populations mig ht be desirable and/or

lucrative?

Limiting human genome editing? Somatic

versus germline editing

As noted above, obvious applications of CRISPR

technology are cell and gene therapies. To date, gene

therapy mostly involves the use of genome-

engineering technologies to edit somatic cells to

treat genetic diseases. Clinical t rials involving

CRISPR-based gene therapy are already under

way. Although clinical gene and cell therapies have

had major road blocks in the past, due to unanticipat-

ed injuries and death [153, 154], significant safety

improvements have been implemented over the last

decade [155]. With the advances of CRISPR technol-

ogy and safer delivery approaches, t herapeutic

applications of gene therapy are on the rise [156].In

the United States and elsewhere, federal regulations

7Review: CRISPR Ethics

Please cite this article as: C. Brokowski, M. Adli, CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool, J. Mol. Biol.

(2018), https://doi.org/10.1016/j.jmb.2018.05.044

provide the needed legal and ethical frameworks,

through the institutional review board system, to

potentially minimize and manage po tenti al risks

[156–160].

At present, there is considerable excitement

about such experimentation in the United States. In

January of 2018, for example, the US National

Institutes of He alth launched the Somatic Cell

Genome Editing program, seeking “to improve the

delivery mechanisms for target ing gene editing tools

in patients, develop new and improved genome

editors, develop assays for testing the safety and

efficacy of the genome editing tools in animal and

human cells, and assemble a genome editing toolkit

containing the resulting knowledge, methods, and

tools to be shared with the scientific community”

[161].

Heritable genome editing, by contrast, is perhaps

the CRISPR systems' greatest discussed controver-

sy. Recently, professional scientific and medical

societies, industry organizations, and CRISPR pio-

neers together have released g reater than 60

statements and reports about whether such editing

in humans is morally permissible [6]. Most state-

ments hold that heritable germline experimentation

should be prohibited currently, although reports from

the Netherlands [162], the United Kingdom [163],

Spain [164], and the United States [9] suggest that

editing could be permissible if certain requir ements

were satisfied. The NASEM Committee's report on

germline editing, for example, specified that the

following provisions must be met for human her itable

germline research to commence: “the absence of

reasonable alternatives; restriction to preventing a

serious disease or condition; restriction to editin g

genes that have been convincingly demonstrated to

cause or to strongly predispose to that disease or

condition; restriction to converting such genes to

versions that are prevalent in the population and are

known to be associated with ordinary health with little

or no evidence of adverse effects; the availability of

credible preclinical and/or clinical data on risks and

potential health benefits of the procedures; ongoing,

rigorous oversight during clinical trials of the effect s

of the procedure on the health and safety of the

research participants; comprehensive plans for long-

term, multigenerational follow up that still respect

personal autonomy; maximum transparency consis-

tent with patient privacy; continued reassessment of

both health and societal benefits and risks, with

broad ongoing participat ion and input by the public;

and reliable oversight mechanisms t o prevent

extension to uses other than preventing a serious

disease or condit ion” [9]. Although fears about

misuse in this context abound, it is important to

point out that there are reasonable arguments

supporting heritable germline editing in research,

such as the protection of defective embryos [165],

the elimination of certain diseases that might be

obliterated optimally early in embryonic develop-

ment, and the exerc ise of free speech and/or

expression [138].

Should international regulations governing

CRISPR use be crafted and promulgated?

Although ethics statements are important, by

themselves, they provide little force. Typically, if

ethics guidelines are infringed, the consequences

suffered by the violator(s) are fairly minimal com-

pared to those arising when in violation of certain

laws. Violations of ethics statements may lead to

loss of funding, the retraction of a publication(s), job

loss, and mistrust among the biomedical community.

By contrast, punishments by law may lead to heavy

fines and potentially incarceration. Given the signif-

icant potential promise, the dark history of eugenics,

the potentially serious transgenerational risks, and

the theoretical potential for misuse, it is reasonable

for the global community to consider instantiating

national and supranational regulations, if not revising

older agreements such as the Geneva [166] and the

United Nations Conventions on Biological and Toxin

Weapons, [167] to reflect changes in genomic

engineering technologies. While doing so likely will

not eliminate all risks, it is arguably one of the few

options available to reasonably control and/or

minimize them.

Conclusions and future directions

CRISPR technology continues to mature, and

existing systems are being engineered to contain

innovative capabilities; excitingly new CRISPR sys-

tems with novel functions are still being discovered.

The potential benefits of such revolutionary tools are

endless. However, like any powerful tool, there are also

associated risks raising moral concerns. To make truly

informed decisions about areas of ethical controversy,

well-controlled, reproducible experimentation and clin-

ical trials are warranted. Currently, this is difficult

because many international laws discourage or

ban such research and/or inhibit its funding for

certain types of investigation. Thus, widespread

data about benefits and risks are unavailable. It is

critical, however, for countries to examine their

reasoning behind these prohibitions to ensure that

they are not simply arising out of fear and without

reasonable justification.

Going forward, many support establishing an

organization that will decide how best to address the

aforem entioned ethical complexities. Recently, a

group of European scientists founded the Association

for Responsible Research and Innovation in Genome

Editing (ARRIGE) to examine and provide guidance

about the ethical use of genome editing [168, 169].

Furthermore, Jasanoff and Hurlbut [170] recently

8 Review: CRISPR Ethics

Please cite this article as: C. Brokowski, M. Adli, CRISPR Ethics: Moral Considerations for Applications of a Powerful Tool, J. Mol. Biol.

(2018), https://doi.org/10.1016/j.jmb.2018.05.044

advocated for the development of an international,

interdisciplinary “global observatory for gene editing.”

Briefly, they argued that deliberations about moral

issues in gene editing should not be dominated by the

scientific community, but instead should include a

“network of scholars and organizations similar to

those established for human rights and climate

change. The network would be dedicated to gathering

information from dispersed sources, bringing to the

fore perspectives that are often overlooked, and

promoting exchange across disciplinary and cultural

divides” [170].

As the technology evolves, so will discussions

about ethical and legal frameworks circumscribing

its uses. The above-mentioned platforms present

interesting ideas for furthering debates and potential

resolutions. The research and ethical guidelines

from national and international organizations, where

diverse disciplines of societies contribute, will be

critical for federal funding agencies and institutional

review boards to enforce and regulate, to minimize

the potentials risks and maximize the potential

benefits of CRISPR technology. However, it is likely

that the enforcement of research laws and ethical

guidelines ultimately will be assumed by govern-

ments and their legal systems, principal investiga-

tors, and institutional review boards.

Acknowledgment

We are thankful to all the Adli lab members. The

research in Dr. Adli's lab is supported through local

funds from University of Virginia School of Medicine

and federal grants from National Institutes of Health/

National Cancer Institute 1R01 CA211648-01.

Author Contributions: M.A. and C.B. conceptu-

alized the study and wrote the manuscript.

Received 18 March 2018;

Received in revised form 30 May 2018;

Accepted 30 May 2018

Available online xxxx

Keywords:

CRISPR–Cas9;

research ethics;

genome editing;

genetic engineering;

bioengineering

Abbreviations used:

CRISPR, Clustered Regularly Interspaced Short

Palindromic Repeats; Cas9, CRISPR-associated protein 9;

NASEM, US National Academies of Sciences, Engineering,

and Medicine.

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