Drug in Focus March 2006: Sumatriptan

'Drug In Focus' is written by Leighton Howard, a patent information expert with extensive generics experience.  He has worked within the professional patent information industry and major generic pharmaceutical firms and now provides consultancy services to the generics industry and government organisations via his company XIP Pty Ltd.  He is also the founder of GenericsWeb and remains instrumental in maintaining the high quality and accuracy of data contained in Pipeline Patent Intelligence.  Please email any comments or queries.

The active ingredient Sumatriptan, a breakthrough pharmaceutical for the treatment of migraine and cluster headaches will lose patent protection in some major territories in the coming months. Based on information contained in the GenericsWeb Pipeline Selector report for Sumatriptan, this month's Drug In Focus analyses the patent landscape surrounding this product with a view to determining the impact of generic launch on GlaxoSmithkline's current monopoly.

The Sumatriptan General Information (Table 1) shows that Sumatriptan is currently available in several dosage forms, oral tablet, nasal spray and injectable. Of these forms, the nasal spray is reported to contain the Sumatriptan base active ingredient (see later comments), whilst the other dosage forms both contain the active in the form of a succinate salt.

The Key Patent Indicator (Table 1) for Sumatriptan confirms that the active ingredient was patented in two consecutive patents, the latter selecting the specific chemical formula of Sumatriptan from the many formulae disclosed in the first patent.

Pharmaceutical patent term extensions were granted on patents in either the first or second of these families, dependent on the country. The active ingredient will ultimately lose protection (from one patent or the other) in Germany and the UK in May 2006, Australia in March 2007, and January 2009 in the USA, due to an additional 6 months paediatric extension.

In addition to the molecule patent families mentioned above, three other constraining patent families has been identified by the Key Patent Indicator, two relating to the nasal spray and one relating to the oral tablets.

Although the active ingredient listed for the nasal formulations is the Sumatriptan base compound, it can be seen from the excipients that sulphuric acid is also added to the solution. The resulting Sumatriptan sulphate salts formed in-situ are the subjects of another patent family identified in the Key Patent Indicator, giving protection until 2011-2013 (Table 2). Further protection of the Innovator nasal dosage form is afforded by additional granted patents claiming aspects of the nasal delivery device.

Film-coated oral Sumatriptan tablets are the subject of granted patents expiring in 2012 and beyond in most major markets, however the direct Pipeline Selector hyperlinks to national patent office registers reveal that the British, German and Australian equivalents from this family ceased in 2005, whilst the maintenance fees for the Canadian equivalent appear to be overdue. This may be an oversight by the patentee (GlaxoSmithKline), but is more likely to be a tactical response to the large amount of patenting activity in relation to formulations of Sumatriptan filed by generic competition, as demonstrated by the Patent Category Distribution graph (Figure 1) in the Patent Risk Analysis section of the Pipeline Selector, based on comprehensive patent data (details of which is accessible in the corresponding Pipeline Developer subscription). Removal of a significant formulation patent barrier by the innovator may hurt larger generics companies who have invested heavily in R&D and subsequent patenting by opening the oral tablet market to much smaller generic competitors, thus eroding the post-generic price. Furthermore, those generics companies who attempted to circumvent the Innovator patents should exercise caution in ensuring that all formulation patents have been considered prior to launch.

The Patent Filing Trends graph for Sumatriptan (Figure 2) shows how well GlaxoSmithKline has managed the lifecycle of this enormously successful drug, with numerous patent filings prior to initial product launch.

Whilst the innovator appears to have accepted the loss of protection of its oral and injectable Sumatriptan dosage forms, the extended patent protection on the nasal dosage form, combined with a push to switch as many patients as possible to this fast-acting product should see continued strong return on their investments in developing this active ingredient, whilst generic competitors will compete heavily for the remaining, less profitable dosage forms.

Comprehensive data for patent families relating to Sumatriptan, based on professional patent searching, may be accessed by subscribing to GenericsWeb Pipeline Developer reports which include twelve monthly updates to keep you abreast of recently published patents and applications. Until April 15th 2006, GenericsWeb are pleased to offer a 10% discount on the standard price of a Pipeline Developer subscription to Sumatriptan. GenericsWeb Pipeline Selector reports are available for any active ingredient upon request.

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