The COVID-19 pandemic has highlighted the importance of investigating the use of known medications for the treatment of new diseases. Given the long road to clinical approval for new drugs, the repurposing of existing drugs represents a promising avenue, particularly in the face of fast-moving pandemics such as that we are currently experiencing. Patents protecting new uses of known drugs may also provide valuable protection for innovators after expiry of the initial composition-of-matter patent.

At the time of publication, clinical trials are testing the potential use of known antivirals, which are currently used to treat diseases such as HIV and SARS, in the fight against COVID-19. One such example is remdesivir, which was originally developed for the treatment of Ebola. It is now undergoing Phase III clinical trials for the treatment of COVID-19 (more on this, and the worldwide pharma response to the coronavirus, can be found here).

In this article, we consider so-called “second medical use” patents from the perspective of European patent law.

Patenting second and subsequent medical uses

Where a substance or composition is already known for one medical use, it may still be patentable for a second or subsequent medical use, provided that use is novel and inventive (Art. 54(5) EPC).

In the US and other territories, such uses may be protected by way of method of treatment patents. However, in Europe, methods of treatment are excluded from patentability. The new use of a known medication must therefore be patented in a different way, as we discuss below.

A second or subsequent medical use may relate to:

  1. the use of a known drug to treat a new disease (“Known drug/new disease”); or

  2. the use of a known drug to treat a known disease using a new therapeutic method (“Known drug/known disease/new therapeutic use”)

Considering each in turn:

1) Known drug/new disease

In order to claim a second or subsequent medical use at the European Patent Office, the following claim format should be used:

“Product X for use in the treatment of disease Y”

While in most claims the phrase “for use” is interpreted as “suitable for use”, second medical use claims represent an exception and are fully use-limited product claims.

The treatment of more than one disease can be covered by a single claim, provided that the treatment of those diseases forms a single general inventive concept (Art. 82 EPC).

It is possible to define the condition being treated in functional terms, for example “the treatment of any condition susceptible of being improved or prevented by selective occupation of receptor x”. However, it is necessary for the patent application to set out experimental tests or testable criteria to allow the skilled person to recognise conditions that fall within this definition, or that such tests are common general knowledge in the art (T241/95). Furthermore, the patent application should indicate specific examples of such conditions, to ensure that the invention clearly relates to a therapeutic application and not merely the discovery of a pharmacological effect (T241/95).

In Europe, the product in a second medical use claim must be a “substance or composition”. “Substances or compositions” are generally held to relate to “the active agent or ingredient” of a particular medical use. Therefore, a filler that, despite being made up of chemical molecules such as collagen, achieves its role in surgery in view of its macroscopic 3D form, is not considered a “substance or composition” according to Article 54(5) EPC (T1758/15). However, a dye used for selectively staining a component of the eye during surgery is (T826/06).

Second medical use claims cannot be used to protect a new medical use of any other type of product, for example a device (T2003/08, T773/10). However, such claims can specify that a substance or composition (e.g. a drug) is used in conjunction with a device, and its use in conjunction with the device may be the sole novel and inventive feature of this claim.

Language to avoid

Claims in the format “Use of product X in the treatment of disease Y” or “A method of treating a subject afflicted with/suffering from disease Y by administration of product X” are not allowed as they relate to a method of treatment and such methods are excluded from patentability in Europe (Art. 53(c) EPC).

Claims in the format “Product X for use in treating a subject afflicted with/suffering from disease Y” should be avoided as there is a risk that the EPO may consider that such claims are not actually limited to the treatment of disease Y.

So-called “Swiss-style claims” in the format “Use of product X for the manufacture of a medicament for the treatment of disease Y” are no longer valid for applications with a priority date of 29 January 2011 or later.

2) Known drug/known disease/new therapeutic use

G2/08 clarified that a new medical use does not have to be limited to the treatment of a new disease. It can encompass the treatment of the same disease by a new therapeutic method, for example a new dosage regime, administration mode or patient group.

Claims relating to such new therapeutic methods should take the following form:

“Product X for use in the treatment of disease Y, wherein product X is [new feature].”

For a new dosage regime, the above claim could specify that, for example, the product is “administered three times daily”, or in a specific discontinuous administration pattern (T1020/03). If the dosage regime claimed is a selection from a broader known range, the existing case law with respect to selection inventions applies.

For a new mode of administration, the above claim could specify that product X is “administered topically” or “administered subcutaneously”, for example (T51/93).

For a new patient group, the new group must be distinguished from the known group by its physiological or pathological status (T19/86, T233/96). The new group must not overlap with the old group (T233/96). It also must not be arbitrary; a special technical effect within the group claimed must have been observed (T233/96). Examples of new patient groups include an immunologically different population of animals e.g. sero-positive piglets (vs sero-negative piglets, T19/86) or haemophilic patients (vs non-haemophilic patients, T0893/90).

The new patient group can also be established by reference to a diagnostic method in the claim. For example, reciting an active step of determining the presence or absence of a biomarker, or defining a population of patients having said biomarker, may render a claim novel, even if the drug was known for the treatment of the same disease (T734/12).

As with other inventions, these new therapeutic uses must still fulfil the requirements of novelty, inventive step and sufficiency.

Practice points

  • It is possible to patent:

  1. the use of a known drug to treat a new disease; and

  2. the use of a known drug to treat a known disease using a new therapeutic method, e.g. a new dosage regime, administration mode or patient group.

  • The correct claim format must be used:

  1. “Product X for use in the treatment of disease Y” or

  2. “Product X for use in the treatment of disease Y, wherein product X is [new feature].”

  • Method of treatment claims (e.g. “Use of product X in the treatment of disease Y” or “A method of treating a subject afflicted with/suffering from disease Y by administration of product X”) are not patentable in Europe and should be reworded to one of the above formats.

  • The product in a second medical use claim must be a “substance or composition” (usually the active ingredient); it is not possible to patent a new medical use of a known device.