The (high) value of second medical use patents: legal background

Second medical use claims can be of high value for the patent owner, particularly when defining effectors of a medical target by their functionality.

European patents are not granted for methods of treatment, surgery, therapy or diagnostic methods which are practised on the human or animal body. However, they can be granted for products for use in any of these methods. Known substances or compositions may be patented for use in these methods only if their medical use was not previously disclosed (the first medical use). A typical formulation of a first medical use claim can be seen in the table below. If the known substance or composition was previously disclosed for use in a medical method, a claim can still be directed to a second or further medical use, provided that this use is novel and inventive over any prior art, disclosing the use of the compound as a medicament. The European Patent Office (EPO) allows claims directed to the modulation of a pharmaceutical effect or a mere functional definition of a pathological condition only in certain circumstances. For example, the discovery that a substance selectively binds a receptor does not make a second medical use claim patentable. When the condition to be treated is defined in functional terms (eg, “any condition susceptible of being improved or prevented by inhibition or enhancement of a specific enzyme activity”, the claim is generally allowable only if experimental tests or testable criteria are disclosed in the specification of the patent application.

Description of compound
This report considers the following questions:

• How broadly can or how narrowly must a compound be defined in use claims?
• Is it necessary to define a compound by a chemical structure?
• Alternatively, can a compound also be defined in functional terms?

In general, the scope defined by the claims must be as precise as possible. However, according to the EPO examination guidelines, a claim may broadly define a feature in terms of its function, even where only one example of the feature has been given in the description, if the skilled person would appreciate that other means could be used for the same function and would have no difficulty in providing some means of performing this function without being inventive.

Functionality versus structure
However, functional definitions in the claims often do not fulfil a further patentability criterion – namely, the sufficiency of disclosure. An invention must be disclosed in the specification of a European patent application such that it can be carried out by a person skilled in the art. A detailed description of at least one way of practising the invention must be provided. The number of examples which are necessary to support the invention over the entire claimed scope is case dependent.

Commercial value
Second medical use claims can be of high value for the patent owner, especially when the claims define effectors of a medical target by their functionality rather than by their structure. Consequently, they should be carefully drafted. To support functional terms in the claims, the specification should contain several example compounds that fulfil the claimed function and at least one in vivo example demonstrating the therapeutic efficacy thereof. Since the allowable claim wording may differ from country to country, the specification should support different claim wordings. Finally, some countries (eg, India, Egypt, the Philippines and the Andean Pact countries) do not allow second medical use patents. Thus, expertise is necessary when defining the geographical scope of protection.  

Table 1: General examples of second medical use claims