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Once the therapeutic
target has been identified, scientists must
then find one or more leads (e.g.,
chemical compounds or molecules) that interact with the therapeutic
target so as to induce the desired
therapeutic effect, e.g., through antiviral or antibacterial activity.
In order to discover the compounds whose pharmacological properties
are likely to have the required therapeutic effects, researchers
must test a large variety of them on one or more targets. The pharmaceutical
companies possess veritable libraries of synthetic or natural compounds,
ready to be tested. To test the chosen compounds in large numbers, scientists use
an entirely automated process known as high density screening.
In general, of the thousands of compounds tested, barely 1% will
qualify for further and more probing analysis.
Duration: from
4 to 6 months
Between 5 and 50 000 compounds are examined in the laboratory,
of which only 100 to 200 are perfected in order to be
tested on systems in vitro and in vivo.
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To allow biologists to complete an exhaustive evaluation of the
selected compounds or molecules, specialists in process
chemistry synthesize them in order to produce quantities sufficient to meet
R&D needs. First of all, biologists ensure that the chosen
compounds have the desired therapeutic or antiviral effect on the
target. Then, they test the compounds’ relative toxicity,
or, in the case of a vaccine, their viral activity, using in vitro
cellular and/or tissue systems. Finally, they check their bio-availability
in vivo on animals. The compounds that demonstrate an ability to act specifically
and selectively on the therapeutic
target, are well absorbed and
show minimum toxic effects, are patented. They become candidates
for subsequent transformation into drugs. The documentation required for patent application
is prepared by the researchers (chemists and biologists)
in collaboration with
the patent agent. A Canadian patent protects the discovery for
the next 20 years. Nonetheless, the stages remaining to be covered
are critical and require an average of ten years before the drug
reaches the sales counter. |
