PAB Rejects Patent for Method of Medical Treatment

PAB Rejects Patent for Method of Medical Treatment

Re. Application 2,365,923 CD 1343


The Application is for a patent for the use of a drug to treat patients suffering from a rare genetic disease using an enzyme. Due to genetic abnormality patients are unable to breakdown ceramide trihexoside due to a deficiency of the à-Gal A enzyme. The resulting condition is referred to as Fabry disease. Symptoms include burning pain in the extremities and accumulation of cermide trihexoside in blood vessels, tissues and organs impairing their proper function.

The patent application contained 91 claims. Claims 76 to 91 were voluntarily cancelled in an effort to speed prosecution.

The issue before the board were:

  1. Are the claims anticipated?
  2. Are the claims obvious?
  3. Do the claims fail to comply with section 2 of the Act for being directed at a method of medical treatment?
  4. Are claims 40-47 indefinite?

Claim 1 appears as:

Use of a human à-Galactosidase A (à-Gal A) preparation wherein more than 50% of the total glycans of the preparation are complex glycans, in the treatment of à-Gal A deficiency, wherein the human à-Gal A preparation is for administration in a dose of between about 0.1-0.3 mg of the human à-Gal A preparation per kilogram of body weight of a subject.


The Board begins by construing the claims using principles of purposive construction. At the conclusion of this the Board identifies two categories which the claims fall under: pharmaceutical compositions and methods of medical treatment.


If a single piece of prior art publicly discloses all of the essential elements of the claimed invention in an enabling manner there is anticipation. Prior disclosure and enablement should be considered separately under this system.[46]

A paper authored by Selden disclosed genetic expression constructs identical to the present claims. The Applicant argued that the Selden paper does not teach the specific dosage ranges claimed. Where a narrower dosage range is claimed subsequent to the disclosure of a broader range one might conclude that there is anticipation.[52] The dosage range was not disclosed in the Selden paper and the range in Selden starts at 0.01mg/kg where as the claimed range is 0.1 to 0.3 mg/kg. The Selden range encompasses a 10,000 fold increase from the 0.01mg/kg starting range which the board holds to be not a credible range. The broad medical use claims therefore define novel subject matter.[57]

The composition claims are undoubtedly found within the Selden paper and are therefore anticipated.[61]


The Board adopts and applies the Sanofi approach for obviousness. With respect to the inventive concept of the patent the Board examined the entire specification from the perspective of a person of ordinary skill. The Board concludes that a person of ordinary skill would not understand the description to say that an enzyme replacement therapy had been well established by the relevant date.[71]

The inventive concept of the medical use claims is the use of a human a-Gal A preparation within a specific range. The composition claims are no different in terms of inventive concept than the Selden article discloses.

Finally the Board held that it was self-evident that what was being tried ought to work. As well the Board held that there are a finite number of predictable solutions known to a person of skill in the art.[82] There was no undue experimental burden to reach the solution especially since the prior art established a range that contained the range claimed in the patent application.[88] As well the specific disclosure of additional chemicals different from the Selden paper was not sufficient since the person of skill would be knowledgeable in the preparation of protein pharmaceutical compositions.[86]

A person of ordinary skill would have experience conducting clinical trials and would be directed to well-known, well-established guidelines for determining therapeutic dosing regimens. The person would be familiar with animal models and would understand to conduct preliminary experiments in animals to determine appropriate ranges to experiment in.[92]

The Board then stated that the 10,000 fold range disclosed by the Selden paper is unrealistic as an operating range. The Board states that because the patent ‘selects’ a narrower range than that of the Selden paper it may be viewed as a selection case. The Board points out that the patent does not disclose any unexpected advantages from the range disclosed in the Selden paper.[95]

For the above reasons the Commissioner found that the patent claims obvious subject matter.

Medical Treatment

Some Federal Court cases have held that dosage regimes accompanied by medical use may not be considered methods of medical treatment.[121] In this case an individualized approach is required to tailor the treatment to the patient.[124] This is within the skill of a professional and as such is unpatentable subject matter.[127]


The Commissioner through the Patent Appeal Board indicates that determining satisfactory dosage ranges through clinical trials represents nothing more than “routine testing carried out by a person skilled in the art”[94]. Respectfully clinical trials and determination of effective dosage ranges are typically outside the realm of routine experimentation. As well the Commissioner was presented with several other opportunities to address obviousness. For example the dosage range falls within the range disclosed by the Selden paper. Experimenting within that range may make the end invention obvious to try however this argument was never explicitly raised. Instead the Board indicates that the 10,000 fold range disclosed by the paper is an unrealistic operating range. Their consideration of ‘selection’ patent criteria after this is confounding especially given that the paper is a journal article written to inform the public about an area that merits further investigation.