Note: Descriptions are shown in the official language in which they were submitted.
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TOPICAL USE OF ANTI-MUSCARINIC AGENTS
Field of the Invention
This invention relates to the treatment of topical conditions using anti-
muscarinic
agents.
Background of Invention
Gajewski, Pol. Tyg. Lek. 25(47) 1815-6 ( 1970), discloses that psoriatic skin
rashes
disappeared in the course of atropine therapy.
Various quaternary ammonium atropine-like drugs have been used in the
treatment
of hyperhydrosis, i. e. excessive sweating. They inhibit sweating but
generally do not have
systemic effects.
US-A-5185350 discloses substituted pyridinyl amines that are useful as topical
anti-inflammatory agents for the treatment of various dermatoses.
US-A-5084281 discloses the use of cholinergic agents, in combination with a
solution of sea water or a sea salt solution, for the treatment of persistent,
neuropathic
dermal ulcers.
WO-A-94/15623 discloses pharmaceutical compositions comprising various
components, including urea and hyaurolonic acid, for the treatment of contact
dermatitis
and other topical conditions.
WO-A-98/00119 discloses the use of agents that affect non-neuronal
acetylcholine
functions, for the treatment of skin ailments. It also discloses that
topically effective
antagonists of muscarinic receptors, including ipratropium, are useful for the
treatment of
skin ailments. Various skin ailments that are disclosed include atopic
dermatitis,
neurodermatitis, psoriasis and cholinergic urticaria.
Summary of the Invention
According to the present invention, skin conditions are treated by the topical
application of a quaternary ammonium or other compound having anti-muscarinic
activity,
a high dipole moment (greater than 4D) and high anti-proliferation activity
(at least SO%
inhibition at 10 pM). It may also have high receptor-binding activity (half
life for receptor
dissociation greater than 0.11 h at M1 ). Topical compositions containing such
compounds
may also be new.
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Description of the Invention
This invention is based at least in part on studies, using the assay described
below,
showing the inhibition of keratinocyte proliferation using anti-muscarinic
agents. Such
agents may be defined by their dipole moment. Dipole moment is related to drug
polarity,
which in turn is related to the penetration of a given drug through the upper
layers of skin
tissue. Ando, J. Pharm. Sci. (1984) 73(4):461-467, demonstrated a linear
relationship
between drug flux across the stratum corneum and dipole moment, and that drugs
with a
dipole moment of greater than 4.0 show limited systemic exposure due to poor
passage
across the skin to the circulatory system. The less polar of these agents,
such as atropine
( 1.232D), and homatropine ( 1.066D), may be effective in the given assay, for
the inhibition
of proliferation, but have central nervous activity when applied topically.
While this in
some indications may be an attractive property (e. g. motion sickness), for
local conditions
in which the drug is applied topically, it can give rise to serious side
effects that limit the
use of the drug. Other anti-muscarinic agents also show efficacy in the
proliferation assay.
These agents may be characterised by dipole moments greater than that of
atropine, e.g.
scopolamine (3.946D), revatropate (4.168D), ipratropium (13.45D) and
glycopyrrolate
( 15.1 OD). Agents with a high dipole moment are more suitable for topical
administration
to treat skin conditions. This invention therefore relates to the use of anti-
muscarinic
agents for the treatment of skin conditions, especially psoriasis, in which
there is a low
potential for systemic exposure as defined by a dipole moment greater than
4.0D, and
preferably greater than IOD.
For use in this invention, suitable antiproliferative anti-muscarinic agents
have a
human plasma half life of less than 3 hours. Systemic pharmacological effects
characteristic of anti-muscarinic agents are caused by high sustained levels
of drug in the
plasma. This leads to distribution of the compound to receptors around the
body. For
effective therapy of a topically applied anti-muscarinic agent in
proliferative conditions,
a combination of antiproliferative activity (for efficacy) and low plasma half
life (to limit
side effects) is necessary. Such compounds of short plasma half life include,
but are not
limited to, glycopyrrolate, ipratropium and tiotropium.
Agents for use in this invention preferably also have high receptor-binding
affinity.
A long duration of action is extremely desirable for a topically applied drug
to treat local
conditions. This leads to low reapplication rates of medication, which in turn
ensures
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minimum disturbance to patient lifestyle, and high patient compliance.
Compounds with
high receptor binding afFnity include glycopyrrolate, ipratropium and
tiotropium.
Although ipratropium meets the criteria described above, it is not as
satisfactory
as a treatment of skin conditions when compared to glycopyrrolate and
tiotropium. This
is not due to its receptor affinity (which is similar to that of
glycopyrrolate) but is due to
its high offrate of receptor binding. Both glycopyrrolate and tiotropium have
receptor off
rates that are very attractive for dermal dosing. Barnes, British Journal of
Pharmacology
(1999) 127:413-420, showed a t'/2 off set for glycopyrrolate of 96minutes
compared to
59min for ipratropium in a clinical study of muscarinic activity in human
smooth muscle.
This attractive offrate can be defined using a tritated [N-methyl-3H]-
scopolamine (NMS)
assay; in this experiment, Barnes showed a 60% protection against [3H]-NMS
binding at
30nM) when compared to ipratropium bromide.
At the clinical level, glycopyrrolate is known to have a longer duration of
action
in muscarinic antagonism than ipratropium; see J. Allergy Clin. Immunol.
(1988) 82:115.
In addition, in Frey's syndrome, a two day duration of action from a single
dermal
application appears to be common, in the use of glycopyrrolate.
In addition, Disse et al, Life Sciences (1993) 52/5-6:537-544, compared the
dissociation rates of ipratropium and tiotropium. For muscarinic receptor Ml,
the half lives
were 0.11 h and 14.6 h; for M3, they were 0.26 h and 34.7 h, respectively. The
relatively
low off rate and long half life for tiotropium are responsible for its very
long duration of
action in smooth muscle relaxation involving muscarinic antagonism.
More particularly, suitable agents for use in the invention may initially be
identified
by the Assay Protocol described below. This is a model of psoriasis and thus
of a
proliferative skin condition. An agent for use in the invention preferably has
an ICS° value
below 100 gM, most preferably below 10 ~M, e.g. below 1 pM, and most
preferably
below 100 nM.
Examples of agents that can be used in the invention, provided that they meet
the
essential criteria, include ambutonium, benzilonium, dibutoline, diphemanil,
emepronium,
glycopyrrolate, isopropamide, lachesine, mepenzolate, methantheline,
oxyphenonium,
oxytroprium, penthienate, phenthimentonium, pipenzolate, poldine, tiemonium,
tiotropium,
tricyclamol and tridihexethyl. Glycopyrrolate is preferred.
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These and other compounds for use in the invention may be provided in the form
of a free base or salt. All such forms are within the scope of the invention,
and in
particular salts, organic and inorganic, are included. For example, quaternary
ammonium
compounds may be provided as a halide or other salt.
Many anti-muscarinic agents exhibit isomerism, whether optical or structural
(stereoisomerism/regioisomerism). These include glycopyrrolate and tiotropium.
Application of a single isomer or a non-stoichiometric mixture of isomers,
e.g. non-
racemic mixture, in the case of optical isomers, may optimise the desired
antiproliferative
activity.
Conventional topical formulations and administration techniques may be used.
For
example, suitable compositions include, but are not limited to, creams,
ointments, gels,
shampoos, lotions, ionotophoresis, patches and emollients. This invention also
includes
the use of anti-muscarinic agents to treat skin condition by topical
administration, in which
the drug is placed in a formulation system in which the drug flux across the
skin is
1 S maintained at such a rate that systemic blood levels are retained at a low
level. However,
the drug flux is maintained at a level to effect topical activity in the skin.
In this way, anti-
muscarinic agents may be used that would otherwise be limited by their side-
effects.
Conditions that may be treated include all forms of psoriasis, including
psoriatic
and scalp arthritis, skin cancer, melanoma, pemphigus, atopic dermatitis,
neuro-dermatitis,
eczema, contact dermatitis, acne, leprosy, seborrheic dermatitis, lupus and
urticaria. The
invention is particularly suited to the treatment of topical proliferative
conditions such as
psoriasis. Treatment may be combined with radiological therapy. Alternatively
or in
addition, treatment may be combined with a conventional agent, ofwhich
examples include
steroids, vitamins A, D and their analogues, salicylates, anthralines and coal
tar
preparations.
The amount of the active agent to be used will depend on the usual factors,
such
as the potency of the agent, the nature and state of the condition to be
treated, the state
of the patient, etc. All these factors can be taken into account, and the
relevant dose
determined accordingly, by the skilled man.
Human Keratinocyte Assay Protocol
Neo-natal human epithelial keratinocytes (Biowhittaker) are grown in defined
media (Keratinocyte growth medium KGM-2, Biowhittaker) until confluent.
Passages 2-4
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are preferred. Cells are plated in a 96-well plate at a density of 1 x 104 /
well in 100p.1
KGM-2. Cells are left to settle at 37°C for 48 hours. Medium is removed
and drug is
added. Vitamin D3 is included as a standard, and a dose-response to the drug
is
performed.
5 Cell proliferation is measured 5 days (or 3 days in the case of ipratropium)
after
addition of drug. This is performed using a protein-based colorimetric assay,
SRB
(Sulforhodamine Blue) and read at an absorbency of S l5nm. Results (tabulated
below)
are presented as % inhibition of control growth (no drug); it will be
appreciated that
glycopyrrolate is 3 orders of magnitude more active than other drugs tested,
and
particularly suitable for use as an anti-proliferative agent.
Atropine 30 % ( 10 ~.M)
Scopolamine 20 % ( 10 ~,M)
Propentheline 35 % ( 10 ~.M)
Glycopyrrolate 50 % ( 10 nM)
1 S V itamin D3 40-80 % ( 10 ~M)
Ipratropium 20 % ( 10 ~.M)
