The document you are referring to is a Canadian patent application, which has different rules than the US patent system, so it is somewhat unclear in which context you are asking the question. This answer will be in the context of the US patent system.
In order to get the full story on the inventive step, you need to follow the related documents. The claims in patent applications are often narrowed and revised significantly (through a series of Office Actions) prior to being issued in a grant.
The claims in this application are written broadly in this case, and serve as prior art in that space, to prevent similar applications from being filed in the space. The independent claim in that application states only:
Use of a combination of cannabinoids in the manufacture of a
medicament for use in the treatment of cancer.
where, as specified in the abstract, the cannabinoids include but are not limited to tetrahydrocannabinol (THC) and cannabidiol (CBD).
There is currently only one grant (US 8,632,825) based on that patent application. The sole independent claim is:
A method for treating glioblastoma multiforme in a human in need
thereof consisting essentially of administering to said human
therapeutically effective amounts of cannabidiol (CBD) and
tetrahydrocannabinol (THC) in combination as pure cannabinoids wherein
the cannabinoids are in a ratio of from 1:1 to 1:20 (THC:CBD).
In order to get this patent granted, the inventors needed to narrow their claims to include the specific compounds (tetrahydrocannabinol and cannabidiol) within a defined ratio (between 1:1 and 1:2), as well as the specific disease that is being treated (glioblastoma multiforme).
The independent claim is generically "a [method of administering] [discrete compounds] within [defined ratio] to treat [specific disease] in [target species]".
There is prior art noted for each of the compounds listed in the independent claim:
EP1177790 (Guzman et al.) describes the treatment of cerebral tumours by the administration of a natural or synthetic cannabinoid, specifically THC.
The applicant's earlier patent EP1802274 describes the use of the
cannabinoid CBD to impede the progress of cancer cells migrating from
their primary tumour location to a secondary site.
Now you can see a more complete story developing. Here we see two European patent grants including two enforceable in Germany (DE60020111 D1 and DE60020111 T2) from the same inventors (Guzman et al.), comprising therapeutic methods involving the individual compounds.
The assignee for these patents, GW Pharma Limited is based in the United Kingdom but also operates in the United States. Of particular note is that the previous patents involving the single compounds were applied for but never granted in the United States (US 20080262099 and US 20120225136). If you examine the priority dates (2004) and the publication dates (2012) you could come to the conclusion that there was a great deal of difficulty pursuing such broad claims in the United States patent system.
Therefore, in order to gain some amount of patent coverage in the United States, the company applied for a patent using a combination of the two compounds.
The product that is being covered by this patent is Sativex:
GW’s lead product, Sativex, is an oral spray which consists of a
formulated extract of the cannabis sativa plant that contains the
principal cannabinoids delta-9-tetrahydrocannabinol, or THC, and
cannabidiol, or CBD, as well as other minor cannabinoids and other
active non-cannabinoid plant components. In order to achieve a fully
standardized formulation of these complex extracts, GW employs a range
of advanced analytical technologies to demonstrate batch-to-batch
uniformity. As a result of these technologies, GW is able to
standardize the formulation across the extracts as a whole, not simply
by reference to their key active components.
As noted on their own web site, these compounds do not naturally exist in plants in a uniform ratio necessary for medical applications. By limiting the compounds to a defined set and also limiting to a defined, measurable ratio, this necessitates extracting the compounds out from the plant, performing some purification, and validating the concentrations of each compound on a batch-by-batch basis. This is a different method than the traditional approach. Combining this with a specific medical application, you have a step that is considered inventive within the US patent system.
