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50 G. M. Ferreira et al.
interactions upon protein alteration. The PyMOL software (https://pymol.org/2/)
makes it possible to visualize, analyze, and generate images of protein structures.
This tool enables the creation of high-quality molecular graphics, facilitating the
visual comparison and analysis of structural differences between the original and
altered proteins. By integrating visual representation with quantitative analysis, a
comprehensive understanding of the effects of protein modification can be achieved.
To further highlight the importance of these strategies for understanding protein
behavior and function, time must be devoted to analyzing changes in protein shape
[7]. With the transition to these new topics, consider delving deeper into mechanics
and molecular biology, illuminating the intricacies that lie at the heart of life
itself [8].
These articles authored by Zhou et al. [9] Schreeck et al. [10] and Schwab and
Schaeffeler [11] represent pivotal contributions from a prominent research group
within the field of pharmacogenomics. Their collective research endeavors have
illuminated crucial facets that shape the landscape of personalized medicine and
drug development. In their comprehensive exploration, Zhou and colleagues [6]
delve into the intricate realm of rare-variant pharmacogenomics, elucidating the
manifold challenges and promising opportunities that accompany the study of
genetic variations in drug response. Their insights provide valuable guidance for
navigating the complexities inherent in tailoring pharmacotherapy to individual
genetic profiles. Similarly, Schreeck et al. [10] offer invaluable insights into the
realm of pediatric medicine and drug development within the context of pharmacogenomics. Their work underscores the importance of considering genetic factors in
pediatric populations to optimize drug ef ficacy and safety, thereby advancing the
field toward more tailored and effective therapeutic interventions for children.
Furthermore, the seminal contribution by Schwab and Schaeffeler [11] highlights
the foundational significance of pharmacogenomics in the broader context of personalized therapy. By emphasizing the pivotal role of genetic variation in drug
response, they lay the groundwork for a paradigm shift toward precision medicine,
wherein treatment strategies are tailored to individual genetic profiles to optimize
therapeutic outcomes. Collectively, these articles not only contribute to the
expanding body of knowledge in pharmacogenomics but also serve as guiding
beacons for future research directions. They underscore the imperative of integrating
genetic insights into clinical practice, fostering a deeper understanding of individualized drug response and paving the way for more effective and personalized
therapeutic approaches.
3 Pharmacogenomics in Drug Development
The drug development process is onerous and expensive. A cross-sectional study
estimated that the pharmaceutical industry spends around US$ 19 million per pivotal
benefit trial and US$ 41 thousand per patient [12]. However, around 90% of clinical
trials fail to find a candidate drug with good efficacy and safety profiles. In 40–50%
3 A Brief Introduction to Pharmacogenomics and Personalized Medicine in... 51
of cases, the failure is due to lack of efficacy, while 30% of trials fail due to
unmanageable toxicity [13].
Additionally, the real-world efficacy and safety profiles differ from the
pre-marketing phase. Many patients experience adverse drug reactions (ADRs),
which are harmful and unintended reactions that result from medication use
[14]. Approximately 8.3% of primary care patients have been affected with at least
one ADR, of which 77% were nonpreventable [15]. Other patients experience
treatment failure, even after adhering properly to treatment [16].
Recently, the pharmaceutical industry shifted the research and development
(R&D) strategy from exploring drugs to treat chronic diseases to precision medicine
models, where the investigational drug is aimed at specific targets and populations
based on genetic information [17]. In this context, pharmacogenetics can be a useful
tool for drug develo pment.
Pharmacogenetics is the science that studies the impact of genetic variation on
drug response, i.e., drug efficacy and safety. The term was first mentioned in 1959 by
Friedrich Vogel in his book Modern Problems of Human Genetics [18] in reference
to the hypothesis that genetic variation in drug-metabolizing enzymes plays a role in
drug response. It was only after the development of technologies such as polymerase
chain reaction (PCR) that pharmacogenetics started to be studied more profoundly,
on a molecular level. After the completion of the Human Genome Project, in 2003,
which sequenced around 90% of the human genome, [19] there was an increase in
the number of studies that explored how single-nucleotide variations (SNVs) in
DNA-affected drug response.
Pharmacogenomics and pharmacogenetics are terms that are often used interchangeably, although they are different concepts. Pharmacogenetics studies the
impact of single variants on drug response, while pharmacogenomics focuses on
the integral effect of multiple variants in genes involved in different parts of PK and
PD [1]. As genomics research proliferates, pharmacogenomics emerges as a rapidly
evolving field with significant potential in drug development. The majority of
genetic variations influencing drug response are located within genes encoding
proteins involved in drug pharmacokinetics (PK) and pharmacodynamics (PD).
PK-related proteins encompass enzymes and drug transporters crucial for drug
absorption, distribution, metabolism, and excretion (ADME), while PD involves
receptors and other proteins mediating both desired therapeutic effects and undesirable adverse events. Consequently, numerous genes may impact drug response,
rendering pharmacogenomics applicable across various stages of drug development,
from preclinical to clinical studies. There are several main databases and sources for
obtaining information related to pharmacogenomics, particularly regarding genetic
variations of specific targets. Some of the key databases and sources include the
following.
• PharmGKB (Pharmacogenomics Knowledge Base): PharmGKB is a comprehen-
sive resource that curates information on how genetic variation affects drug
response. It provides data on pharmacogenomic associations, drug pathways,
and clinical guidelines.
52 G. M. Ferreira et al.
• DrugBank: DrugBank is a widely used database that provides comprehensive
information on drug targets, pharmacology, and drug–drug interactions. It
includes data on genetic variations that influence drug metabolism and response.
• ClinVar: ClinVar is a public archive of reports on the relationships between
human variations and phenotypes, with a focus on clinically relevant information.
It includes data on genetic variants associated with drug response and adverse
reactions.
• PubMed: PubMed is a vast database of biomedical literature, including
pharmacogenomic studies and reviews. It can be searched to find research articles
on genetic variations of specific drug targets and their implications for drug
response.
• GWAS Catalo g (Genome-Wide Association Studies Catalog): The GWAS Cata-
log provides a curated collection of published genome-wide association studies,
including those related to pharmacogenomics. It can be used to identify genetic
variants associated with drug response traits.
To search for information about genetic variations of certain drug targets, one can
follow these step-by-step guidelines (Fig. 3.1).
1. Identify the drug target of interest: Determine the specific protein or genetic locus
targeted by the drug for pharmacological effect.
2. Access relevant databases: Utilize databases such as PharmGKB, DrugBank,
ClinVar, PubMed, and GWAS Catalog to search for information related to the
genetic variations of the target.
3. Perform a search: Use keywords related to the drug target and pharmaco-
genomics, along with terms specifying genetic variations such as single nucleo-
tide polymorphisms (SNPs) or gene mutations.
4. Review search results: Examine the search results to identify relevant studies,
reports, and databases containing information on genetic variations associated
with the drug target.
5. Evaluate the evidence: Assess the quality and relevance of the evidence presented
in the retrieved information, including the study design, sample size, statistical
significance, and clinical implications.
6. Interpret findings: Consider the implications of identified genetic variations on
drug response, including potential effects on drug efficacy, toxicity, and
recommended dosage.
In the pre-clinical phase, for instance, pharmacogenomics can help identify
potential drug targets based on genetic variants associated with the pathophysiology
of diseases. Using pharmacogenomics, targeted drugs can be designed considering a
specific genetic profile. This targeted approach increases the likelihood of treatment
success and reduces the risk of adverse reactions.
Genetic variations in the PCSK9 can impact its protein expression or enzymatic
activity. Commonly, these alterations can lead to increased PCSK9 activity,
resulting in higher degradation of the low-density lipoprotein receptor (LDLR).
Consequently, this hampers the cells’ ability to remove LDL cholesterol from the
3 A Brief Introduction to Pharmacogenomics and Personalized Medicine in... 53
Fig. 3.1 Step-by-step to
search for information about
genetic variations of certain
drug targets
bloodstream, leading to elevated plasma LDL cholesterol levels characteristic of
familial hypercholesterolemia (FH). Chemically, variations in the PCSK9 gene may
alter the amino acid sequence of the PCSK9 protein. These changes can affect the
protein’s structure, stability, and function, influencing its enzymatic activity and
interaction with the LDL receptor. To gather information about these variations,
genetic analyses like sequencing of the PCSK9 gene can be conducted. This helps in
pinpointing specific mutations or polymorphisms within the gene associated with
modified PCSK9 function. Additionally, functional studies can be carried out to
evaluate the impact of these variations on PCSK9 activity and LDL receptor
degradation in cell-based or animal models. It is essential to recognize that these
variations manifest genetically as mutations, resulting in changes in the chemical
composition of the PCSK9 protein. The refore, modeling of these mutated proteins is
crucial to grasp the structural and functional implications of these genetic changes.
Simply seeking the wild-type PCSK9 structure in the Protein Data Bank (PDB)
would not suffice in addressing the complexities introduced by genetic variations, as
it does not account for the specific amino acid sequence alterations associated with
54 G. M. Ferreira et al.
mutations. Hence, computational modeling approaches are indispensable to comprehend the effects of these variations on protein structure and function, aiding in the
development of targeted therapies like PCSK9 inhibitors for treating familial
hypercholesterolemia.
Another step where pharmacogenomics can be useful is in clinical trial phase
1. Phase 1 clinical trials are designed to elucidate the PK profile of investigational
drugs in healthy volunteers [20]. By sequencing the participants and using genomic
information from healthy volunteers, pharmacogenomics can help to identify possible biomarkers of safety for the investigational drug. An unpublished survey from
the Industry Pharmacogenomics Working Group (I-PWG) from 2017 revealed that
79% of pharmaceutical companies that are members of this group sequenced their
clinical trial participants for performing pharmacogenomic studi es of their investigational molecules, especially in the oncology area [2]. Exploring pharmacogenomics well ahead during phase 1 can help to better characterize the PK profile.
It can also be very useful in subsequent phases 2 and 3, by improving participant
selection and stratification for understanding the safety and efficacy outcomes
observed during these phases.
Gefitinib is a successful example of the application of genomics in phase 3 clinical
trials. Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor
(EFGR-TKI) used to treat nonsmall cell lung cancer (NSCLC). EFGR specific
gene mutations are reported in about 10–20% of NSCLC patients. Some studies
reported that the efficacy of gefitinib was enhanced in patients carrying EGFR
mutations compared with patients with no mutations [21]. Clinical trials were
performed to test this hypothesis, such as the Iressa Survival Evaluation in Lung
Cancer (ISEL) trial. This phase 3 study pre-selected patients with EGFR mutations
and verified that these mutations were predictive of gefitinib-related treatment effect
over placebo on overall survival [22]. After several clinical trials, it was a consensus
that gefitinib should be used in selected patients harboring these mutations, which is
why NSCLC patients should now be genetically screened to verify if ge fitinib
therapy is indicated or not.
For more information on how pharmacogenomics can be applied to drug development, the reader is referred to excellent reviews on this topic [17, 23].
4 Case Studies of Genomics-Based Drug Design
Genomics-based drug design is a rapidly developing field that aims to use genomic
data to design drugs that are tailored to the unique genetic profile of everyone. Case
studies have shown the potential of this approach in predicting cancer cell sensitivity
to drugs based on genomic and chemical properties [24]. Additionally, genome
sequence variability has been shown to predict drug precautions and withdrawals
from the market, highlighting the importance of genomics in drug development and
safety [25].
3 A Brief Introduction to Pharmacogenomics and Personalized Medicine in... 55
Despite earlier efforts in genomics-based drug discovery, the overall clinical
efficacy of developed drugs has remained unimpressive, owing in large part to the
heterogeneous causes of disease [26]. However, recent technological and analytical
advances in genomics have made it possible to rapidly identify and interpret the
genetic variation underlying disease, leading to the development of personalized
medicine [26].
Pharmacogenomics, the study of an individual’s response to drugs as a result of
their genetic makeup, has been merged with pharmacology and genomics to produce
safe and effective drugs that are customized to the unique genetic profile of each
individual [3]. The implementation of personalized medicine in clinical practice
requires the inte gration of genomic data with clinical data, such as electronic medical
records [3].
Advances in genomics have also facilitated drug development by providing
genetic and genomic knowledge for target identification, understanding the biological relevance of a drug target, and prioritizing drug targets [27]. The CRISPR -Cas9
library screening approach has been used to detect survival-essential and drugresistance genes via gain or loss of function, enabling genomic screening for gene
activation or inhibition [28].
Predicting the response of a specific cancer to therapy is a primary goal in modern
oncology, aiming for personalized treatment. Large-scale research has revealed
relationships between genomic alterations and drug responses. Computational
approaches have been proposed to predict sensitivity based on genomic features
and the chemical properties of drugs. Machine learning models were developed to
predict the response of cancer cell lines to treatment, based on both the genomic
features of the cells and the chemical properties of the drugs [24].
The work reported by Spahn and colleagues [29] is one important example of a
potential personalized medicine pipeline. In this work, the authors simulated different FGFR2 mutants identified on patient-derived cholangiocarcinoma samples. They
demonstrated the ability of lenvatinib (an unspecific first-generation inhibitor) to
more efficiently interfere in mutant-harboring lines, in comparison to the wild-type,
in agreement with patient treatment data. The supporting in silico modeling, using
long MD simulations, suggests that lenvatinib can adapt better to FGFR2 kinase
mutations’ binding sites than specific inhibitors, such as infigratinib or pemigatinib.
This study highlights how different computational approaches can inform bed-side
decisions, but more importantly, generate a framework that informs recidivists of
common mutations/cases.
The genomic revolution has been transforming the field of medicine, enabling a
more precise approach to drug discovery and development. With a deeper understanding of human genes and their functions, pharmacogenomics emerged, which
harnesses advanced techniques to identify markers that determine a patient’s
response to specific treatments. This approach, centered on an individual’s genetic
profile, promises to optimize therapies, enhancing outcomes across various medical
specialties and leading the way for more personalized treatments. However, the
adoption of this new perspective demands ethical reflection and clear guidelines for
its implementation in clinical practice [30].
56 G. M. Ferreira et al.
In conclusion, genomics-based drug design has shown potential in predicting
cancer cell sensitivity to drugs and predicting drug precautions and withdrawals
from the market. Recent technological and analytical advances in genomics have
made it possible to rapidly identify and interpret the genetic variation underlying
disease, leading to the development of personalized medicine. The implementation
of personalized medicine in clinical practice requires the integration of genomic data
with clinical data. Advances in genomics have also facilitated drug development by
providing genetic and genomic knowledge for target identification and
prioritization [26].
4.1 Challenges and Opportunities in Genomics
and Personalized Medicine for Drug Design
Genomics and personalized medicine have opened new opportunities and challenges
in drug design. The use of genomic data in drug design has an immediate impact on
structural proteomic/genomic projects, as well as on rational drug design [31]. The
widespread application of personal genome sequencing in clinical settings for
predictive and preventive medicine has been limited due to the lack of comprehensive computational analysis pipelines [32]. However, recent technological and
analytical advances in genomics have made it possible to rapidly identify and
interpret the genetic variation underlying disease, leading to the development of
personalized medicine [33].
Pharmacogenomics, the study of an individual’s response to drugs as a result of
their genetic makeup, has been merged with pharmacology and genomics to produce
safe and effective drugs that are customized to the unique genetic profile of each
individual [30]. The amount of data generated in genomics fits the definition of big
data and needs specific bioinformatics proces sing following standard steps: data
collection, processing, analysis, and interpretation [34].
Genome-wide association studies (GWAS) have proved to be a beneficial method
to identify novel common genetic variations not only for disease susceptibility but
also for drug efficacy and drug-induced toxicity, creating a field of pharmacogenomics studies [35]. The identification of disease-causing biomolecules using
genome sequencing has enabled the development of chemical probes of function,
preclinical lead modalities, and ultimately FDA-approved drugs [36].
In conclusion, genomics and personalized medicine have opened up new opportunities and challenges in drug design. The use of genomic data in drug design has an
immediate impact on structural proteomic/genomic projects, as well as on rational
drug design. Recent technological and analytical advances in genomics have made it
possible to rapidly identify and interpret the genetic variation underlying disease,
leading to the development of personalized medicine. Pharmacogenomics addresses
patient-to-patient variation in drug response and has the potential to produce safe and
effective drugs that are customized to the unique genetic profile of everyone [37, 38].
3 A Brief Introduction to Pharmacogenomics and Personalized Medicine in... 57
4.2 Ethical and Legal Issues in Genomics and Personalized
Medicine for Drug Design
Ethical and legal issues are important considerations in the development and implementation of genomics and person alized medicine for drug design. The emergence
of genetic testing (GT) has raised ethical, legal, and social implications (ELSI)
[39]. The adoption of personalized medicine will require changes in healthcare
infrastructure, diagnostics and therapeutics business models, reimbursement policy
from government and private payers, and a different approach to regulatory oversight [40]. Governance issues arise in the context of an ongoing dispersion of
national regulatory power, and it has become impossible to govern society from a
single center [ 41].
Pharmacogenomics, the study of an individual’s response to drugs as a result of
their genetic makeup, has the potential to produce safe and effective drugs that are
customized to the unique genetic profile of each individual [38]. However,
pharmacogenomics and pharmacogenetics raise ethical problems with specific
nuances and subtleties and high complexity levels [34]. The use of genomic and
molecular data contained in the patients’ genotypes has allowed for the development
of new personalized pharmaceutical products, but it is important to consider the
informed consent of patients and the protection of their privacy [34].
In conclusion, ethical and legal issues are important considerations in the development and implementation of genomics and personalized medicine for drug design.
The emergence of genetic testing has raised ethical, legal, and social implications.
The adoption of personalized medicine will require changes in healthcare infrastructure, diagnostics and therapeutics business models, reimbursement policy from
government and private payers, and a different approach to regulatory oversight.
Governance issues arise in the context of an ongoing dispersion of national regulatory power. Pharmacogenomics and pharmacogenetics raise ethical problems with
specific nuances and subtleties and high complexity levels, and it is important to
consider the informed consent of patients and the protection of their privacy [42].
To guarantee safe society from the ethical and legal standpoint, law and bioethics
should constantly evolve to follow up technological development and make sure that
ethical and legal matters are in line with scientific advancem ents. The delay in
establishing well-delimited ethical and legal criteria for application of advancements
in healthcare sciences may give rise to a bioethical regress, jeopardizing rights
earned throughout the years.
As broadly discussed in this chapter, pharmacogenomics represents an important
advancement in the strategy to treat pathologies, enabling more effective pharmacological targeting and, thus, increasing patients’ quality of life [43].
This marks a noteworthy advancem ent in personalized medicine, in which comprehension of an individual’s genetic sequencing not only offers insights regarding
their health status but also enables the prescription of highly personalized treatments,
which may be safer and more effective. The fundamental purpose is to identify the
58 G. M. Ferreira et al.
suitable drug in the correct dose and at the right time, all based on deep knowledge of
the patient’s genomics.
To reach that goal, the collection of comprehensive patient information, including
general personal data, genetic data regarding DNA sequencing, as well as information in connection with lifestyle and life habits, heredity, medical history, etc., is
required. All such information is characterized by the confidential, intimate, and
private nature thereof, which is essential and intrinsic to human rights. And these are
the data and information that will allow establishment of pharmacokinetic profile of
the patients, enabling individualized treatment [44].
Therefore, the ethical and legally robust application of pharmacogenomics faces
multiple fundamental challenges within the scope of law and bioethics. This includes
considerations regarding social, economic, legal, and ethical factors. Hence, a
detailed analysis of existing ethical and legal precepts is imperatively required,
aiming, if need be, at creating a general regulatory framework that establishes
guidelines to protect genetic data and promote the use thereof in compliance with
universal bioethical principles and specific laws of each nation.
Within the legal context, crucial issues arise mainly regarding the safeguard of
highly sensitive personal data that have already been internationally regulated by
means of the Data Protection Laws. Furthermore, inspection and restriction of use of
such data for purposes that have not been duly consented to by the holders thereof is
of the essence.
In this setting, two essential legal principles come in: (i) Data Protection and
(ii) Free, Prior, and Informed Consent. This takes place because, by collecting
information of such nature, a space is created for filing of highly sensitive data
that may be employed for purposes beyond pharmacogenomics. Such undue use
may, by itself, breach fundamental principles, such as equality and dignity of
individuals.
The discussion about the use of genetic data is controversial and polemical
because it is known that such information has the potential to lead to discrimination
and improper use in selecting characteristics of humans, individuals, and embryos.
Additionally, bioethics concern comes under an even stronger spotlight, considering that countless abuses were committed in the name of science, jeopardizing
human life and dignity, before global bioethical principles went on to guide scientific
conduct. The main underlying mission of all such bioethical principles is, undoubtedly, full safeguard of human beings, their existence, and, above all, their dignity.
In contemporary society, the importance of ethics cannot be overstated, particularly within the realm of healthcare. Ethical consi derations serve as the cornerstone
for establishing guidelines and protocols that govern medical practice, ensuring the
well-being and rights of patients are upheld. [45] eloquently define ethics as the
science of conduct, presenting two fundamental concepts within this discipline.
First, ethics is perceived as guiding human behavior toward predetermined ends,
derived from an understanding of human nature. Second, it is recognized as the study
of the variability of human conduct, aiming to regulate and guide behavior accordingly. This nuanced understanding underscores the complexity of ethical decision-
3 A Brief Introduction to Pharmacogenomics and Personalized Medicine in... 59
making in healthcare, where practitioners must navigate diverse moral frameworks
to provide optimal care while upholding ethical standards.
Ethics thus becomes an instrument to guide human conducts for the purpose of
safeguarding the individual’s dignity, autonomy, life, physical integrity, equality,
and sameness in healthcare services, especially when no other guidelines to follow
exist.
Bioethics, the concept of which is provided in the Encyclopedia of Bioethics as
this conduct is examined in the light of moral values and principles, [46] steers the
decisions affecting life, health, and dignity of human beings.
Although the work Principles of Biomedical Ethics [47] is not the pioneer in
analyzing and establishing bioethical principles, it is deemed to be the “most
influent” and “more widely broadcast” in study [48].
In the dynamic landscape of biomedical ethics, the contributions of [47] stand as a
cornerstone, reshaping the discourse and practice of ethical decision-making in
healthcare. Their seminal work, Principles of Biomedical Ethics, not only
established a set of guiding principles but also offered a comprehensive framework
for their practical application. Beauchamp and Childress recognized the need for
more than theoretical constructs; they sought to provide clinicians and ethicists with
a robust toolkit for navigating the complexities of ethical dilemmas in medical
practice. By elucidating the operational intricacies of bioethical principles, they
empowered stakeholders to engage in informed decision-making processes that
prioritize patient welfare and ethical integrity. Thus, their work remains a foundational resource in shapi ng ethical standards and practices within the biomedical
sciences.
Given the intricate nature of the subject, bioethics may not offer absolute solutions to the conflicts at hand; however, it may provide guidance that establishes
guidelines that are reasonable and prudent [49]. The objective is to guarantee a fair,
equitable, and universal distribution of the benefits from healthcare services, without
discriminating [50].
Within the context of the healthcare area, however, the complexity of the conflicts
at stake often requires making decisions that involve assessment of the associated
costs and benefits. In the work Principles of Biomedical Ethics, the inherent complexity of moral decision-making, particularly within the healthcare domain, is
emphasized. This complexity arises from the multitude of factors that must be
considered when making healthcare-related decisions, which extend beyond purely
medical considerations. Health-related decisions inherently involve the assessment
of values that encompass both medical and nonmedical aspects, such as weighing the
costs and benefits of medical interventions. Physicians routinely base their treatment
judgments on the balance between potential benefits and harm to the patient.
Four fundamental principles of bioethics emerge from this context: autonomy,
nonmaleficence, beneficence, and justice. These principles provide the foundation
for robust bioethical guidelines that can guide the application of pharmacogenomics
with legal rigor and adherence to universal ethics, irrespective of specific regulatory
frameworks.