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Eyes turning to neuropathic
pain market
The European and US
neuropathic pain markets are currently worth $2.5 billion combined. While most
drugs currently used are not primarily indicated for neuropathic pain, the
blockbuster status of Neurontin in this indication has focused the attention of
several pharmaceutical giants on this potentially lucrative market. As such,
Datamonitor expects the market to be worth over $4 billion by 2007.
Neuropathic pain is defined as pain associated with a functional abnormality of
the nervous system. Clinical features can include an abnormal, unpleasant
sensation (dysesthesia) that frequently has a burning or electrical sensation
with occasional brief shooting or stabbing pain. Although the onset of most
neuropathic pain is within days after the precipitating injury, there is no
absolute temporal relationship to the originating neural trauma. In fact, it can
begin weeks, months, or even years later.
Large patient pool
Key sub-types of neuropathic pain include diabetic neuropathic pain (DNP),
post-herpetic neuralgia (PHN) and HIV-associated neuropathic pain (HIVNP). DNP
offers the larger patient population, although estimates of the actual size of
the patient pool vary.
Sometimes it is also difficult to distinguish neuropathic pain from nociceptive
pain. Examples of nociceptive pain include postoperative, cancer and arthritis
pain. It is important to differentiate nociceptive from neuropathic pain because
recommended treatment protocol differs. In general, nociceptive pain responds to
opioids and non steroidal anti-inflammatory drugs (NSAIDs), whereas neuropathic
pain tends to be partially responsive to opioid therapy and can be alleviated
with tricyclic antidepressants (TCAs) and anticonvulsant compounds.
As of June 2005, just five drugs were approved for the treatment of neuropathic
pain syndromes in the US: Cymbalta (Eli Lilly), Lidoderm (Endo), Neurontin
(Pfizer), Lyrica (Pfizer) and carbamazepine, although a variety of agents are
frequently used off-label and an estimate of which is included as the current
market size. Despite the presence of these drugs, there is still a large amount
of unmet need.
The consensus among physicians is that gabapentin (generic Neurontin) is the
gold-standard treatment of neuropathic pain. In a February 2004 study,
Datamonitor found that Neurontin is used in over 50% of cases of
pharmacologically-treated patients with DNP and PHN in the US. However, since
this survey was carried out, Neurontin has lost patent protection in the US and
now a number of generic gabapentin versions are available.
In the US, Pfizer's own generic gabapentin had the second highest sales in 2004,
closely followed by tablet and capsule versions from Teva and Alpharma,
respectively. In the five major EU countries, where Neurontin lost patent
protection in 2000, Teva, Hexal and Merckle have strongly performing generic
versions of gabapentin. However, in the US and the five EU markets, Neurontin
still out-performed generic gabapentin, in terms of sales and volume of product
in 2004.
The Japanese neuropathic pain market differs significantly from both the EU and
US markets: gabapentin and lidocaine patches are not available in Japan, and
physicians will often use nerve blocks and vitamin B - often in combination - to
control patients' pain. Furthermore, despite a lack of clinical data to warrant
their use, physicians in Japan frequently prescribe NSAIDs, such as loxoprofen,
for neuropathic pain.
On the flipside, because the Japanese market is significantly different - based
on NSAIDs and nerve blockers - to the US and Europe, it does present a good
opportunity for new treatments in neuropathic pain.
Packed pipeline
At the time of writing, there were at least 97 compounds in development for the
treatment of neuropathic pain, making it one of the most active pipelines in the
central nervous system area. The rationale for such a big pipeline is simple.
The current neuropathic pain market offers a considerable commercial opportunity
by combining a large patient potential with a huge need for new therapies. The
phase II pipeline is particularly impressive, boasting a whole host of novel
compounds under development by specialist companies as well as top tier players.
To succeed in the current market, new products must be at least equivalent in
terms of the safety and efficacy to gabapentin, although a product with a proven
pain reduction of greater than 50% in a significant majority of patients would
be very successful. However, it should be noted that the achievement of such
efficacy scores can be as much based on the correct choice of pain scale and
trial design as true product efficacy.
Current pipeline products are competing in terms of improved dosing
formulations, a key factor in taking market share if the primary efficacy need
cannot be met. The mode of drug delivery also has important implications on the
ease of drug administration and patient compliance, a key issue in a market
where the gold standard has a dosing profile of up to four tablets per day.
The majority of current treatments are orally available, but a single daily
treatment with similar efficacy to gabapentin would be very well received in the
neuropathic pain market. As many neuropathic pain patients are also being
treated for other conditions such as HIV, MS, and diabetes, medication that can
be easily taken, for example once-daily oral medication, will improve patient
compliance. Drug-drug interactions should also be carefully examined for the
same reason.
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