Drug development: drug discovery and preclinical research

The different drug development phases

Developing a drug is an extremely long and regulated process. It globally includes a drug discovery phase, during which drug candidates are identified, and a preclinical phase where drug candidates have to demonstrate their proof-of-concept.

For this, screening methods in in vitro tests or in vivo studies are commonly used. In the clinical phase, drug candidates that have passed the previous phases are tested on humans. If the drug candidate is judged to be safe and effective, it will have to get market approval.

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In vivo models

In vivo model tests are performed on animals. They may be part of the proof-of-concept validation or may be performed for the regulatory dossier. Typically, in vivo tests will study the physiological and behavioral aspects, as well as the toxicity of the molecules being studied.

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In vitro models

Tests on in vitro models are generally part of the pre-clinical study phase of drug development. They are used to test compounds by studying their effects on defined targets and functions. The robustness of in vitro tests is a determining factor for their use in R&D projects.

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HCS & HTS screening

High throughput screening (HTS) or high content screening (HCS) are techniques that aims at studying and identifying, within chemical and target libraries, molecules with novel and biologically active properties. Screening consists of using a large number of molecules in a biochemical or cellular test, which must be particularly robust, reproducible, and if possible inexpensive.

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Biochemical models

The biochemical model is used in the discovery of candidates. The advantage of this type of model is to limit the number of molecular actors, and thus validate a target or mechanism of action. FRET and HTRF techniques applied to biochemical models are particularly effective in studying the phosphorylation and signalling pathways of molecules.

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In silico studies

In silico studies correspond to the modelling of biological phenomena, such as the interaction between several molecules or a change in the structural conformation of an active domain. This analysis is relevant upstream of more expensive studies, or when classical chemical methods have reached their limits.

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Tools for innovative therapies

ATMPs (Advanced Therapy Medicinal Products) are medicines based on genes, tissues or cells for human use. They offer revolutionary new possibilities for the treatment of diseases and injuries.

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Molecules synthesis and optimization

The development of a "small molecule" drug candidate requires tools directly derived from chemistry. In this case, the de novo synthesis of the molecule, the search for candidates in chemical libraries, and the possibility of modifying these molecules by labelling techniques.

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Formulation and galenic

Formulation is a critical step in drug development and partly determines the success of a drug's market entry. The aim is to propose the solution best suited to the nature of the pharmaceutical ingredient candidates, their therapeutic target and the route of administration envisaged.

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Regulatory studies and assays

Pharmacokinetics studies the fate of an active substance of a drug after its administration in an organism. It consists of four phases: absorption, distribution, metabolism and excretion of the active ingredient (ADME). Different tests, in vitro and in vivo, exist to answer these pharmacokinetic questions.

The different stages of drug development

Each drug development follows a unique process, in terms of drug candidate identification, validation and optimization, pre-clinical and clinical protocols and marketing. There are, however, some broad outlines in the drug development phases, which are described here.

Discovery - 2-4 years

Definition of the target: or target signal path
Setting up a primary test and screening (compounds, antibodies, etc.)
Validation by a secondary test
Preliminary in vitro toxicity tests
Structural optimization and synthesis (chemical or bioproduction)
Validation in small animals

Pre-clinical - 1-2 years


Measurement of ADME(Absorption, Distribution, Metabolism, and Elimination): potency tests, solubility, LogD, Caco-2 permeability, CYP inhibition, etc.
Measurement of pharmacokinetics and pharmacodynamics PK/PD
Structural optimization and synthesis (chemical or bioproduction)
Non-GLP toxicity
Selection of candidates
GLP toxicity

The different types of providers

The different drug development phases involve a large number of actors with different capacities.


Academic structures

Academic structures are involved in the development of drugs, particularly at the level of the in vitro and in vivo studies they can propose.
Some very expensive equipment may also be required (e.g. for mass spectrometry or robots for HTS screening) - in this case, academic platforms may be asked by private companies to support them.


Service companies for experimentation

Many service companies produce tools in drug discovery or development. This concerns in vitro tests for example, or formulation optimization. Other companies are specialized in regulatory testing, such as PK/PD and toxicity experiments.
These companies are often required to work under Good Laboratory Practice (GLP) conditions.


Service companies for production

Anticipating the drug production during its development is an early process: a marketed molecule has to be manufactured in very particular conditions (good manufacturing practice, GMP). The GPM production is not necessary for research use and preclinical studies, but commercial and clinical batches have to meet the GMP conditions.

What defines a cell model?

Cell models, if appropriately designed, can be used to rapidly identify the molecular mechanisms of human diseases and develop new therapies.

The design of a robust, reproducible, relatively easy-to-read test (it should use quantifiable molecular markers) is particularly appropriate when using a molecule library for high-throughput screening.

As soon as the model is designed, the experimenter raises the question of how to quantify the expected effect: either by molecular markers or by phenotypic observation.

A molecular marker that is well identified and characterized in a pathology or cellular process has the great advantage of limiting observations linked to an indirect effect.

The FRET technique typically proves to be relevant when studying conformational changes (e.g. intracellular nuclear receptors), aggregation (especially in neurodegeneration), or measurement of receptor-ligand interactions. FRET is based on the transfer of energy between two fluorophores, possible when the two molecules are physically close. Other methods for measuring molecular markers, such as qPCR or dPCR for modulation of gene expression, ELISA or Western Blot for protein quantification, etc., are also available.

Microscopy and imaging in general are useful in phenotypic studies.

The technologies used in drug development

Cell culture & in vitro tests

Animal facility

Imaging on organisms


HTS and HCS screening

Prediction in silico

Cloning, sequencing, recombinant expression

Estimated rates for this type of services

A few hundred to a few thousand euros for a non-regulatory in vitro test.
An in vivo test can be between € 8,000 and € 100,000.
Outsourced HTS screening can cost between € 50,000 and € 100,000, an HCS screening can cost up to double, depending on the number of molecules tested.
Formulation optimization can cost several tens of thousands of Euros for in silico studies, and several hundreds of thousands of Euros for optimization by synthesis and validation.
Regulatory toxicity studies are very expensive and vary considerably depending on the test required.

Some services

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