Discovery of a New Mechanism of Action is Not an Invention

Alcon Canada Inc v Apotex Inc / olopatadine (NOC) 2012 FC 410 Barnes J
             2,195,094 / olopatadine / PATANOL / T-564-10

“Merely knowing something new about something old is not enough” to support a patent: Genentech Inc.'s Patent [1989] RPC 147, 208 (CA); see also Chamberlain & Hookham v Mayor of Bradford (1903), 20 RPC 673, 687 (HL). In particular, discovering the mechanism of action of a known drug will not support a patent if the use itself is not new: Lundbeck v Ratiopharm 2009 FC 1102 at [ 20], [149], [189-92]; Astrazeneca v Apotex / omeprazole (NOC), 2007 FC 688, [103]. The reason is that the claims define the scope of the invention, so it is the invention as claimed which must be novel. Discovery of a new mechanism of action does not lend novelty to an invention if a patent would prevent the public from doing that which was already known.

Alcon / olopatadine presents a slight variation on this theme. The inventors had discovered that a known compound had a previously unknown mechanism of action. However, no new therapuetic uses were explicitly disclosed, and the claims, on their face, claimed known uses. In this NOC proceeding, Alcon tried to remedy the problem by arguing that the claims should be construed to be limited to treatment of diseases which were dependent on the mechanism of action in question. This strategy failed. Barnes J recognized “purposive construction is capable of expanding or limiting a literal text” [28] but on the facts the interpretation proposed by Alcon could not be supported. A straightforward reading of the claims was clear, as Alcon acknowledged [33], and Barnes J might have decided the case on the principle that the text plays a dominant role, even in purposive interpretation: Canada Trustco 2005 SCC 54, [2005] 2 SCR 601 [10]. However, Barnes J did not decide on so narrow a ground. He recognized that “[e]ven a term that appears to be plain and unambiguous may, when read in the context, reasonably support a different meaning” [27] and he relied primarily on a purposive interpretation of the disclosure. Ultimately, the specification itself did not define a novel use, so the difficult question of whether the claims, properly construed, should be limited by the use disclosed but not explicitly claimed, did not really arise.

Olopatadine was a known compound which was known to be an antihistamine useful in treating allergic eye diseases in humans [20]. Allergic eye diseases arise when allergens bind to mast cells which then degranulate, releasing a variety of chemical mediators including histamines. The mediators cause the allergy symptoms [9]. An antihistamine suppresses the allergic response by blocking histamine receptors. A drawback of antihistamines is that they only block one type of mediator. There was therefore a recognized need for mast cell stabilizers, that would work by preventing degranulation. It was thought that compounds that were effective antihistamines were unlikely to be useful as mast cell stabilizers because they were observed in vitro to rupture mast cells – that is, antihistamines were generally thought to be mast cell destabilizers [14]. Alcon’s technical contribution was the discovery that olopatadine, even though it was known to be an antihistamine, was also a mast cell stabilizer at therapeutic doses [16].

The claims at issue in Alcon / olopatadine, Claim 8 and 20 of the ‘094 patent [20], were to the use of, and a composition of, 0.1% w/v of olopatadine “for treating allergic eye diseases.” The difficulty, as Alcon acknowledged, is that on a plain reading the claims were too broad [33]: “allergic eye diseases” encompasses any eye disease, whether mediated by antihistamines or other mediators, and “treating” encompasses relieving the symptoms by either blocking histamines, or by preventing mast cell degranulation. If so interpreted, the claims would be invalid as encompassing the known use of olopatadine as an antihistamine. Alcon argued that these words should be interpreted in light of the disclosure as meaning that the claimed composition must be a mast cell stabilizer for treatment of “an allergic eye disease wherein mast cell degranulation contributes to the development of the disease state” [23] (and see [33]).

The difficulty is that while the specification of the ‘094 patent discussed at length the novel discovery that olopatadine was a mast cell inhibitor, and it also stated clearly that it could therefore be used for treating allergic eye diseases, even the disclosure did not specify any new use: “While these activity profile features are described in the disclosure and quantified with respect to olopatadine’s mast cell stabilizing property, those references are similarly not tied to any new form of clinical use” [38]. If a new use had been clearly specified in the disclosure, but omitted from the claims, there would still be a difficult question of whether that use should be read as a limitation, on a purposive construction of the claims. But absent any clear limitation on the use somewhere, whether in the disclosure or the claims, there was no new invention disclosed at all, but only a new mechanism of action. As Barnes J put it:

[39] The disclosure passages Alcon relies upon also fail to clearly identify the nature or the scope of the invention. There is nothing in these passages which distinctly and explicitly identifies the subject matter of the invention whether as a new use or otherwise. While there are references to prophylactic use, dosing frequencies and demonstrated stabilization activity at specific concentrations, none of those features are clearly identified as an element of the inventive concept and none of that language is used in a way that would serve to clearly define the words in dispute in Claims 1 and 13.

This seems to me to be a fair reading of the specification. The disclosure does state that “[t]he present invention relates to topical ophthalmic formulations used for treating allergic eye such as allergic conjunctivitis, vernal conjunctivitis, vernal keratoconjunctivitis, and giant papillary conjunctivitis” (p1), and at the claim construction date it was apparently believed that all these were thought to have mast cell degranulation as all or part of the disease state, but the “such as” language is not limiting. In other circumstances one can imagine that Alcon might have objected strenuously to using a “such as” list to implicitly define a limitation on the uses to which the invention might be put.

The expert evidence foundered for the same reason (my emphasis):

[45] Except for a reference to a possible use as a prophylaxis, Dr. Church and the other Alcon witnesses identify no new clinical use for olopatadine that arises out of the discovery of its mast cell stabilizing properties beyond the sophism that if olopatadine was never used before as a mast cell stabilizer it therefore must be a new use. It seems to me that this approach seriously strains the meaning of the word “treating” and the concept of a new use discovery. The information discovered by Alcon may be useful but it does not, by that fact alone, constitute a new use for olopatadine. A clinician treats a patient for an allergic reaction in the eye by suppressing the troubling or damaging signs and symptoms of the disorder. In the absence of a new clinical use for an old drug, new knowledge about how it works is not patentable. Similarly, the discovery that olopatadine was more effective in the treatment of allergic eye diseases than initially understood (see Affidavit of Martin K. Church, Ph.D., D. Sc. (24 January 2011) at paras 42-43, 46-48 [ Affidavit of Dr. Church]) is unpatenable because the improved efficacy of the drug was inherent in its known utility as an antihistamine.