A new medication is seldom
really new-the search for a new drug usually starts 10 or 15
years before it is ready for patients to use.
For example, scientists at
the Merck Frosst Centre for Therapeutic Research in Montreal
have been working for 13 years on a new way to control
asthma. This chronic disease is caused by inflammation and
constriction of bronchial tubes in the lung, which make it
difficult to breathe. Asthma affects 5 to 10 percent of the
Canadian population.
Some existing asthma
medications have serious side effects, and others work only
after an asthma attack. It would be far better to stop the
asthma reaction from occurring at all, and that may finally
be possible.
In 1979 a group of Swedish
scientists identified the compounds — called
leukotrienes (LT's) —that are responsible for
constricting bronchial tubes. Everyone has LT's, but an
asthma attack involves an unusually high production of them.
Scientists at Merck Frosst
realized that this discovery could lead to a safe way to
prevent asthma attacks,. and they began exploring two
possible approaches.
One involves making
compounds to inhibit the enzymes that produce too many LT's..
That would prevent the LT excess that can trigger an asthma
reaction.
The other approach has been
to make compounds (called LT receptor antagonists) that
attach themselves to the tissue sites that LT's are looking
for. By getting there first, they prevent the LT's from
settling in and constricting the tissues.
Both approaches-as in any
search for a new medication-start with organic chemists who
find or create compounds that might work. They start either
with natural sources, such as plant extracts, or with
synthetic chemical compounds.
Testing and refining the
compounds can be a long process-only I in 10,000 will have
the properties needed.
When a compound has passed a
variety of tests for activity, non- toxicity, solubility, and
so on, then pharmacy researchers take over. These researchers
include analytical chemists to study the compound's purity
and how well it is absorbed by the body, and physical
chemists to study the compound's physical properties and
stability.
Eventually they decide on
the best form for the new medication-pill, capsule, aerosol,
etc. Finally, the drug is ready for testing on human patien
which may take months or years.
The Merck Frosst scientists
have developed compounds both to prevent an excess production
of LTs, and to stop excess LTs from causing an attack.
It is a long process, but a
new asthma -therapy is within sight.
