Pharmacogenetics

Pharmacogenetics is an emerging branch of medicine that deals with the study of inter-individual variations in DNA sequence, called single nucleotide polymorphisms (SNPs), which are responsible for individual responses to drugs, both in terms of efficacy and toxicity as well as drug metabolism.

What is Pharmacogenetics?

Although pharmacokinetic and pharmacodynamic variability was once predominantly related to the influence of non-genetic factors (such as age, sex,
nutritional status, kidney and liver function, alcohol abuse, smoking, concomitant taking of other drugs and the presence of comorbidities), in around the 1950s, the scientific community saw hereditary factors as an important component of the diversity in individual response to drugs, thus attributing to genes the ability to influence the variability in response to a given active ingredient, including the absence of clinical response to a given treatment or the occurrence of adverse drug reactions (ADRs).

Over the years, this has led to the development of studies on pharmacogenetic aspects, understood as allelic variations in genes correlated with absorption, distribution, metabolism, excretion and biological action of the drug that may influence its action. Thanks to the Genome Project, we know that DNA is 99.9% identical in all individuals; the remaining 0.1% makes each of us different (unique and unrepeatable) from the others, with a variability of one base per thousand between different individuals. These single-nucleotide variables are called single-nucleotide polymorphisms (or SNPs) and form the genetic basis of each individual’s uniqueness. More than 2 million of these SNPs are known.
Pharmacogenetics is studying how these differences lead to different responses to drugs and how this information can be exploited to create a therapy that takes into account the uniqueness of the genome, avoiding adverse reactions and ensuring better therapeutic efficacy, thus enabling personalised therapy.
The metabolism of drugs in the human body (pharmacokinetics) and their therapeutic and toxic effects (pharmacodynamics) are regulated by complex biochemical processes in which numerous proteins encoded by different genes participate, and which are not only involved in the transport and metabolism of drugs, but also in their mechanism of action.

Is it an invasive test?

A buccal swab, a simple venous blood sample or histological samples are required.

How are SNPs investigated?

Through molecular biology examinations on the affected gene sequences. Tests are performed on a simple buccal swab or a venous blood draw.

Why is it important to take the test?

The response to drugs can differ from person to person, as can the occurrence of different side effects. Each person is characterised by a unique and personal genetic make-up that influences the effectiveness of the drug but also the safety of its use. In two different persons, a drug, even if administered at the same dosage, may be more or less effective and may be responsible for the appearance of more or fewer side effects. Drugs are metabolised by the body by different enzymes. Innovative drug therapies consist of ensuring that a drug remains active in the body long enough to be effective without causing side effects. The possible presence of gene variants can help identify:
  • subjects who may develop any adverse reactions, on a metabolic basis, to drugs;
  • patients who are ‘responders’ and not ‘responders’ to drugs;
  • the right dosage of a drug for each patient.
This information makes it possible to establish personalised therapies (Genomics and Personalised Medicine).

What variants are being analysed?

Variants are investigated in genes coding for proteins involved in drug absorption, distribution, metabolism and excretion (pharmacokinetics) and in those coding for the primary therapeutic target, such as receptors, ion channels, enzymes, etc. (pharmacodynamics). Pharmacogenetic tests also make it possible to determine whether these variants are present in heterozygosity (present in only one copy of the gene) or in homozygosity (present in both copies of the same gene), a characteristic that is capable of influencing both individual response and reaction to the drug.

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