Sufficiency of disclosure: How much is enough?
The recent decision of the UK Supreme Court in Warner-Lambert Company LLC (Appellant) v Generics (UK) Ltd t/a Mylan and another  made an important ruling regarding the sufficiency of disclosure in second medical use patents. Second medical use patents relate to a new (previously unknown) medical use of a known pharmaceutical compound, for example, the use of thalidomide (previously used to treat morning sickness) in the treatment of leprosy.
The case revolved around a second medical use of the drug pregabalin for the treatment of inflammatory pain and neuropathic pain. Pregabalin has been previously known to treat seizure disorders under the brand name Lyrica. The legal battle, for a second medical use of pregabalin, started in the UK High Court in 2016 and concluded with the recent UK Supreme Court ruling that certain claims of the patent for a second medical use of pregabalin, were invalid. The Supreme Court ruled that the patent did not sufficiently describe the (new) claimed therapeutic indication of treating neuropathic pain, specifically of treating central neuropathic pain.
As in both Europe and the UK, sufficiency of disclosure is a general requirement of a patent in South Africa. The statutory obligation created by Section 32 (3) (b) of the South African Patents Act 57 of 1978 provides that a complete specification shall “sufficiently describe, ascertain and, where necessary, illustrate or exemplify the invention and the manner in which it is to be performed in order to enable the invention to be performed by a person skilled in the art of such invention” and the function of the complete specification has been held by our courts to be “to instruct the public how to carry out the invention when the field is eventually open”.1
Furthermore section 61(e) of the Act further provides, as a ground of revocation, where “the complete specification concerned does not sufficiently describe, ascertain and, where necessary, illustrate or exemplify the invention and the manner in which it is to be performed in order to enable the invention to be carried out by a person skilled in the art of such invention”.
Furthermore, South African case law has held that “the patentee must make the nature of his invention and how to perform it clear and intelligible...”2 and that sufficiency is found by asking the question “does the specification contain proper instructions for enabling a person skilled in the art to put the invention into use?”.3 However the adequacy of a disclosure that would be regarded as sufficient is difficult to determine when addressing inventions of new uses for known compounds.
The judgement in the Warner-Lambert case has now provided some clarity on the aspect of sufficiency as applied to a “Swiss-form patent”, amongst other things. A “Swiss-form patent” relates to a method of manufacturing a medicament by using the known substance in its manufacture.
The Supreme Court also maintained a threshold plausibility test for sufficiency of disclosure for new therapeutic uses of previously known drugs. The court held that the invention “...is not made plausible by a bare assertion to that effect, and the disclosure of a mere possibility that it will work is no better than a bare assertion” and went further on to say that “...the effect on the disease process need not necessarily be demonstrated by experimental data. It can be demonstrated by a priori reasoning.” It can therefore be summarized that a disclosure of a new use is regarded as sufficient if it renders it plausible that the product has the relevant biological activity, and that there is a “reasonable prospect” that the claimed indication would prove to be true.
Since the invention as claimed is not the compound per se, but rather the use thereof, bare disclosure of the chemical formula is inadequate. The invention is “the new use” and therefore sufficient disclosure of “the new use” must be contained in the specification, a mere disclosure of what the compound could be used for is insufficient.
Thus far, the aspect of sufficiency for the second medical use of a known compound has not been tested in South African courts but it is likely that they would seek direction from the Warner-Lambert case when having to make similar decisions in the future. Given the highly persuasive nature of UK rulings in South Africa, in my opinion it would be folly not to adopt a similar view to that of the UK courts in a matter such as this.
1 Letraset Ltd v Helios Ltd 1972 BP 243 (A)
2 Edison and Swan Electric Light Co v Holland (1896) 6 RPC 243 (CA)
3 Reeves Brothers Incorporated and Spunnyfoam Laminations (Pty) Ltd v Furpile (Pty) Ltd 1971 BP 21 (CP)
This article was first published in Business Day.