| When Pfizer first
launched Viagra (sildenafil) in the US in April 1998,
a whole new market was created - the oral treatment of male
erectile dysfunction.
Although various creams, injections
and devices had been available to treat impotence before,
Viagra created massive media interest as news spread of
the magical effects of the little blue pill, and it was
one of the first instant pharmaceutical blockbusters.
According to IMS HEALTH's Monthly
MIDAS
sales system, in the
12 months to May 2001, Viagra was the leading product in
the G4B therapy class, which covers "other" urological preparations
(also consisting of treatments for prostate disorders and
urinary incontinence). Viagra had a 27.9% share of the Monthly
MIDAS market, registering 25% growth from the previous year
at constant exchange rates. The universe consists of the
world's 13 leading retail pharmacy markets: US, Canada,
Germany, Italy, France, Spain, UK, Brazil, Mexico, Argentina,
Australia, New Zealand and Japan (hospital sales are also
included for the Japanese market).
*Note: 2001 sales an IMS HEALTH projection based on 1H01
figures
Source: Pfizer annual reports
The only other erectile dysfunction
product to register in the top 20 of the G4B market is Pharmacia
Corporation's Caverject (alprostadil). This, however,
is injected into the side of the penis.
Uprima first to compete
Viagra's first real challenge
will come from Uprima/Ixense (apomorphine), licensed
from Pentech by Takeda and Abbott Laboratories' joint venture
TAP Holdings for the US, Canada and Puerto Rico. Outside
North America, Takeda and Abbott will co-market in 37 countries,
then in the rest of the world, Abbott has exclusive rights.
Apomorphine received EU approval in May 2001, and has since
been launched in several European countries according to
IMS HEALTH's Drug
Launches
service. TAP and Abbott
use the trade name Uprima, and Takeda Ixense.
Uprima works in a different way
to Viagra, stimulating an erection through mechanisms originating
in the brain. It has shown effectiveness in erectile dysfunction
of organic, psychogenic, and mixed etiology. The tablet
dissolves under the tongue and works within 20 minutes
- faster than Viagra. It also has the advantage of not interacting
with some cardiovascular drugs, unlike Viagra.
Apomorphine has had some problems,
mainly due to the incidence of nausea in patients taking
the highest dose, of 4mg. Only the 2mg and 3mg tablets have
been approved in the EU. In June 2000, TAP withdrew its
US NDA for apomorphine in order to conduct further safety
and efficacy studies on the 3mg tablet. The US consumer
group Public Citizen urged the FDA not to approve Uprima
because of the side-effects, which also include fainting
and dizziness. TAP is planning to re-file the NDA in the
future.
Cialis waits in the wings...
Already garnering significant
attention is Cialis, also known as IC 351, developed
through the Lilly ICOS LLC joint venture between Eli Lilly
and ICOS Corp. Like Viagra, this is a phosphodiesterase
5 inhibitor. Cialis, however, is more selective for PDE5,
and as such is not associated with two of Viagra's side-effects:
blue-tinged vision (linked to PDE6) and facial flushing
(PDE1). It is also being tested in women.
Cialis is pending approval in
the US and EU, and head-to-head studies against Viagra are
planned. As well as a flow of positive results from clinical
trials over the second quarter of 2001, in July Lilly ICOS
successfully challenged a Pfizer method of use patent for
PDE inhibitors in the EU. Although Pfizer's compound patent
for sildenafil is unaffected, Pfizer can no longer claim
exclusivity for PDE inhibitors in the treatment of erectile
dysfunction. Pfizer's patent was first ruled
invalid in the UK,
in November 2000.
In one Cialis trial, presented
at the 96th annual meeting of the American Urological Association
in Anaheim, June 2001, Cialis 20mg led to improved erections
in 85% of men, regardless of the severity of their impotence.
Other trials revealed that Cialis improved the ability to
achieve erections up to 24 hours after administration;
it begins working in 30-45 minutes. Cialis has also shown
efficacy in diabetes-related erectile dysfunction, which
has so far proved a therapeutic challenge, leading to a
response in 64% of men. Lilly ICOS says side-effects diminish
with continued treatment, but include back, muscle and head
aches and upset stomach.
..as Bayer prepares vardenafil
Another PDE5 inhibitor, vardenafil,
is in Phase III trials with developer Bayer. A US filing
is planned towards the end of 2001. At the 16th congress
of the European Association of Urology in Geneva, April
2001, Bayer presented Phase III results showing that vardenafil
20mg improves erectile function in up to 80% of patients,
independent of severity, cause and age. It has also shown
efficacy in diabetic men. Side-effects include headaches,
flushing, and indigestion, but are generally mild. Vardenafil
has a half-life of 4-6 hours, which Bayer sees as an advantage.
Bayer is planning to find a partner
to co-market vardenafil. In an interview with IMS HEALTH's
Pharmaceutical
Company Profiles
in May 2001, General Manager
of Pharmaceuticals, David Ebsworth, commented:
"Bayer is looking for either
a global partner, or two partners, one which will be just
for Japan and the other which will be for all other territories.
It depends on whether a Japanese partner is prepared to
pay incrementally more than the global partner would pay
for all the territories and also on the skill sets of that
partner." Others have commented that Bayer would particularly
benefit from extra strength in the US.
According to Ebsworth, Bayer's
ideal partner would "have muscle in that therapeutic area
and a willingness to spend. They also must have a real vision
and understanding of what we can do with the brand. The
icing on the cake would be if they had broad consumer marketing
experience. After that, it is down to the chemistry of how
the companies can work together."
Plenty of room for growth?
Pfizer
is
so far playing it cool about the competition for Viagra,
even though it has been reported that about 50% of users
don't renew their prescriptions. It has conducted numerous
studies with Viagra, and thinks it will take time for its
challengers to build up comparable safety and efficacy data.
In mid-2001, Pfizer presented new data on Viagra's efficacy,
including results from trials in men with diabetes and cardiovascular
disease risk factors.
Erectile dysfunction is also
under-treated, and Pfizer believes that the introduction
of new therapies could expand the market through
increased awareness. Bayer's Ebsworth agrees:
"Everyone knows what Viagra is,
but nevertheless, only one-fifth of men with impotence take
it. I think the market is ripe for expansion – there is
room not only for ourselves and Pfizer, but also for Lilly's
drug Cialis when they launch. The challenge will be to do
in erectile dysfunction what has happened over the past
15 years with depression – depression has come out of the
cupboard during that period and dropped its mask. Maybe
we can achieve the same thing in erectile dysfunction."
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