Prior art squeezes out common general knowledge

Charlotte Jemmet | February 2016

Accord Healthcare Limited v medac Gesellschaft [2016] EWHC 24 (Pat)

This recent decision of Mr Justice Birss not only confirms that in invalidity proceedings there can be a so called “squeeze” between whether or not a patent adequately discloses the invention it claims and whether the invention is obvious, but also warns of the problems associated with arguments for invalidity in view of common general knowledge alone.

The judgement concerns an action brought by Accord Healthcare against a registered patent belonging to medac entitled "Concentrated Methotrexate Solutions" (patent EP (UK) 2 046 332).

The patent protected the use of a formulation of a drug called methotrexate with a concentration of about 50 mg/ml for the treatment of individuals with inflammatory autoimmune diseases, such as rheumatoid arthritis and juvenile chronic arthritis, by subcutaneous injection.  That concentrations up to 25 mg/ml methotrexate could be used for these conditions, and much higher doses (typically, up to several grams diluted in saline) for the treatment of cancer, was known to the medical profession before the patent was filed. 

The court held that the patent was obvious in view of “Russo”, a journal letter published 6 years before the priority date.  Russo reported positive results for children with juvenile chronic arthritis being treated with a 23.25 mg/ml formulation of methotrexate by parenteral administration.  The data showed the higher dose parenteral methotrexate to be safe and to cause a similar frequency of side effects as lower dose oral administration.  However, 20 % of the children on the higher parenteral dosage were said to report “pain at injection site”.  Birss J held that the “problem” to be solved starting from Russo would be producing a formulation of methotrexate that could be administered by a less painful subcutaneous injection.  He concluded that, from the point of view of the skilled formulator, it would be wholly obvious to use a more concentrated formulation of the drug so that the injection volume could be minimised.

Having found the patent invalid, Birss J then commented on Accord’s argument that the invention was obvious over common general knowledge alone.  He warned:

The problem with arguments over common general knowledge alone is that the combination of features relied on is always and necessarily one created with hindsight knowledge of the invention, and worse, is one which the person attacking validity has not been able to find as a pre-existing combination in the concrete prior art.  If they had they would have relied on that concrete prior art.  Either the combination has not been made in the concrete prior art at all or it only appears with additional inconvenient details.  If an invention is not obvious over the concrete prior art which is relied on, the court is entitled to be sceptical that an argument that it is nevertheless obvious over common general knowledge alone is correct.

Birss J also discussed what was referred to as the insufficiency/inventive step “squeeze” argument proposed by Accord.

An argument of this kind is typically constructed on the basis that the critical feature or advantage for establishing that the patent is inventive is not sufficiently disclosed in the patent itself.  Thus, the argument runs that either the patent is insufficient because it is outside the knowledge and/or ability of the skilled person to employ this feature and it is not taught within the patent such that the skilled person can perform the invention, or else the patent is obvious (i.e. not inventive) because the skilled person could and would employ such a feature as part of their common general knowledge and skill in the art.  Hence the patentee is “squeezed” between the patent being insufficient or lacking inventive step.

In this particular case, the patent described how the invention solved the problem of pain on subcutaneous injection caused by a relatively large volume of drug being injected.  Another aspect of the problem advanced by the patentee at trial (albeit not mentioned in the patent) was a concern about possible side effects on using a higher concentration formulation of methotrexate. 

Accord argued that if the claims in the patent were found inventive on the basis that the formulation overcomes concern about side effects, then those claims would be insufficient because the 50 mg/ml methotrexate formulation had not been demonstrated to avoid side effects, i.e. the technical effect that is asserted had not been made plausible.

In agreement with Accord, Birss J took the view that if it was inventive to make a 25 mg dose using a 50 mg/ml concentration in a 0.5 ml volume in order to reduce pain, this would not reveal a sufficiency problem because the patent explains that the reduced volume reduces pain. However the position with side effects is different.  If it was inventive to administer a 25 mg dose using a 50 mg/ml concentration in a 0.5 ml volume subcutaneously because of a concern about the risk of side effects, then the patent does not provide any comfort at all about that risk.  If the skilled person would not administer the formulation to treat rheumatoid arthritis due to the risk of side effects, so that such an administration would be inventive, they would still not do so after reading the patent hence the claim to the use of that formulation would be insufficient.

This decision highlights that attacks on whether a patent is inventive would generally be stronger when based on prior art rather than solely on common general knowledge, and on the other side, suggests that a patentee typically has a better chance of overcoming a “squeeze” attack when there is evidence of the asserted technical advantage within the patent itself.