Parkinson's Disease in Need of Fresh Impetus

February 06, 2009 Therapeutic focus - Parkinson’s disease in need of fresh impetus

Evaluate Vantage

For a disease that was formally classified nearly 200 years ago and affects an estimated four million people worldwide, the fact that one drug, L-dopa, which was introduced over 40 years ago, remains the best treatment option available today to sufferers of Parkinson’s disease must rank as one of the biggest disappointments in the history of clinical research in the pharmaceutical industry.

Whilst the phase III results announced this week for Merck Serono and Newron Pharmaceuticals’ safinamide were encouraging, the fact that most experts believe the drug will at best provide a modest improvement to current treatments highlights the painfully slow progress of current research into Parkinson’s. This lack of breakthrough treatments is causing some experts, such as Peter Jenner, Professor of Pharmacology at King's College London, to warn that Parkinson’s research could go the way of stroke research, which is now almost negligible following a number of massive setbacks which caused big pharma companies to turn their backs on the area.

Shrinking market

According to forecast data from EvaluatePharma, the Parkinson’s disease market, which was worth $3.22bn in 2008, is set to decline 3% per year to $2.74bn by 2014.

Although some revenue growth is expected from some recently launched products, such as UCB’s Neupro and Teva’s Azilect, the cause of the overall decline is clear when considering that all five of the biggest-selling drugs in 2008 will be exposed to generic competition by 2014.

Anti-Parkinson's Disease Market: growth drivers and brakes 2008 - 14 WW annual sales ($m)

Generic Pharmacological Patent Product Company Phase 2008 2014 Name Class Expiry

Growth Drivers

Dopamine D2 Mar 1 Neupro rotigotine UCB Marketed 93 566 & D3 agonist 2021

Teva rasagiline Pharmaceutical Feb 2 Azilect MAOB inhibitor Marketed 134 406 mesylate Industries + 2017 Lundbeck

5HT1A (serotonin) Pardoprunox agonist Dec 3 pardoprunox Solvay Phase III - 129 (SLV 308) & dopamine D2 2019 partial agonist

Dopa carbidopa Jan 4 Duodopa decarboxylase Solvay Marketed 56 145 & levodopa 2014 inhibitor

Adenosine A2A 5 SCH 420814 preladenant receptor Schering-Plough Phase II - - 50 antagonist

Growth Brakes

Dopamine D3 Boehringer Oct 1 Sifrol/Mirapex pramipexole Marketed 1,037 402 agonist Ingelheim 2010

ropinirole Dopamine D2 May 2 Requip GlaxoSmithKline Marketed 493 198 hydrochloride agonist 2008

Novartis + Oct 3 Comtan entacapone COMT inhibitor Marketed 543 288 Orion 2013

levodopa Dopamine 4 Madopar Roche Marketed - 287 81 & benserazide precursor

Dopamine D2 Pfizer + Kissei Dec 5 Cabaser/Dostinex cabergoline Marketed 166 27 antagonist Pharmaceutical 2005

Other products 336 449

Total 3,223 2,741

Parkinson’s, a degenerative disorder that impairs motor skills, speech and multiple other functions such as bladder control, is caused by insufficient formation and action of dopamine in the brain.

L-dopa, or levodopa, which is converted into dopamine by enzymes in the brain, remains the best treatment option and can significantly improve the lives of Parkinson’s patients. However, only 1-5% of L-dopa reaches its target receptors, the remainder of which is metabolised elsewhere in the body, causing serious side-effects. In addition, introducing L-dopa can cause a negative feedback loop on the formation of naturally occurring L- dopa, a process which can eventually become counterproductive.

As a result, the majority of new therapies launched within the last ten years have focused on various other ways of stimulating the production, or preventing the breakdown, of dopamine, such as dopamine agonists which target specific dopamine receptors.

Single or multiple target approach? However, it is this more specific, single target approach, which could be one of the reasons that newer drugs have failed to provide the significant breakthrough that patients have been craving.

Whilst GlaxoSmithKline’s Requip and Boehringer Ingelheim’s Mirapex target the D2 and D3 receptors respectively, L-dopa targets all 1-5 dopamine receptors.

Professor Jenner believes that rather than the single-target screening approach much loved by the majority of pharma companies: “what we actually need is more ‘dirty drugs’, which can hit the most number of targets as possible”.

However, a review of current pipeline candidates for Parkinson’s reveals that a number of research products are still adopting the single-target strategy. Parkinson's disease agents - selected phase III & II pipeline WW annual sales

candidates ($m)

Generic Pharmacological Phase Product Company Launch 2010 2012 2014 Name Class

5HT1A (serotonin) Phase Pardoprunox agonist pardoprunox Solvay 2012 - 74 129 III (SLV 308) & dopamine D2 partial agonist

Dopamine Safinamide safinamide Merck KGaA 2010 - 18 35 reuptake inhibitor

Adenosine A2A Kyowa Hakko KW-6002 istradefylline receptor 2010 - 21 31 Kirin antagonist

Dopa melevodopa V1512 decarboxylase Vernalis 2010 0 1 2 & carbidopa inhibitor

Adenosine A2A Phase SCH 420814 preladenant receptor Schering-Plough 2012 - 17 50 II antagonist

Dopamine D2 Aplindore aplindore Neurogen - - - - agonist

Adenosine A2A BIIB014 - receptor Biogen Idec - - - - antagonist

Dopamine gene Oxford ProSavin - - - - - therapy BioMedica

Neurturin gene CERE-120 - Genzyme - - - - therapy

Alpha 2 receptor Santhera JP-1730 fipamezole - - - - antagonist Pharmaceuticals

Adenosine A2A Synosia SYN-115 - receptor - - - - Therapeutics antagonist

Adenosine A2A V2006 - receptor Vernalis 2011 - - - antagonist

Anti-Parkinson's Osmotica OS - 320 - - - - - agent Pharmaceutical

Anti-Parkinson's Osmotica OS - 352 - - - - - agent Pharmaceutical

Non-dopamine approaches

“I was initially very bullish about non-dopamine approaches to treatment, but have become increasingly jaded by the increasing number of failures in this area”, says Professor Jenner.

The biggest most recent disappointment was the FDA’s rejection a year ago of Kyowa Hakko Kirin’s istradefylline, an Adenosine A2A receptor antagonist, which had been held up as a potential breakthrough treatment.

With another four Adenosine A2A receptor antagonists currently in phase II trials, the hope must be that the failure of istradefylline was more down to poor trial design, as some have argued, than a fundamental lack of activity for this new class of drug.

Hopes and fears

Of the other pipeline candidates, Professor Jenner believes gene therapies, such as Oxford BioMedica’s ProSavin, could ultimately provide a breakthrough treatment, although the recent failure of Genzyme’s neurturin gene therapy candidate, CERE-120, suggests the road to clinical success will be a rocky one.

However, with a number of high profile clinical failures in the sector, Professor Jenner is concerned that research into Parkinson’s could go down the “stroke route”; after pumping billions of dollars into new stroke treatments and producing nothing to show for it, the industry has now largely halted further research.

The ever decreasing number of product deals in the sector in recent years, with just two deals in the entire industry last year, suggests these fears may be materialising already.

Count of anti-Parkinson's product deals per year

Year Count of deals

2008 2

2007 6

2006 6

2005 4

2004 9

2003 5

2002 5

2001 4

2000 5

Total 46