Eisai, second medical indication (EPO, G 5/83, 1984)

Dhenne Avocats · 11 October 2026

Our analysis

Summary

The EPO Enlarged Board of Appeal addressed the protection of the « second medical indication ». A claim directed to the use of a substance or composition for the treatment of the human or animal body by therapy cannot be allowed, since it differs only in form from a method of treatment excluded by Article 52(4) EPC 1973. By contrast, a European patent may be granted with claims directed to the use of a substance or composition for the manufacture of a medicament for a specified new and inventive therapeutic application, novelty being derived from that new use. The decision thus established the « Swiss-type » claim within the EPC system.

Facts and procedure

In seven appeals against refusals of European patent applications, including Eisai’s, Technical Board of Appeal 3.3.1 referred the following question to the Enlarged Board by decision of 20 June 1983 (T 92/82): can a patent with claims directed to the use be granted for the use of a substance or composition for the treatment of the human or animal body by therapy? Invited to comment on the practice of the Swiss Federal Intellectual Property Office, which allowed claims to the use of an active ingredient for the manufacture of a medicament even for a second indication, the appellants stated that they did not wish to be heard if the Enlarged Board allowed that type of claim; the oral proceedings were cancelled (summary of the procedure).

The applicable law

The Enlarged Board interpreted the EPC 1973 in accordance with Articles 31 and 32 of the Vienna Convention on the Law of Treaties, applied by analogy (points 1 to 5), taking account of case law in the Contracting States in the interest of harmonisation (point 6). The provisions at issue were Article 52(4), which excludes methods for treatment of the human or animal body by therapy, Article 54(5), which protects the first medical indication of a known substance, and Article 57 on industrial application.

Question

Can a use claim protect the use of a substance or composition for therapeutic treatment, and in what form may a second medical indication be protected?

Decision

Whether an activity is claimed as a method or as a use is a matter of preference, with no difference of substance for the EPO (point 11). A claim to the use of a substance for therapeutic treatment does not differ in essential content from a method of treatment: it conflicts with Article 52(4), and no patent may be granted with such a claim (points 12 and 13). Article 54(5) gives the inventor of a first medical indication a purpose-limited product claim (point 15). The Enlarged Board declined, for the time being, to follow the Federal Court of Justice (BGH) in Hydropyridine, since the Office could hardly follow the practice of the superior court of a single Contracting State on a controversial matter bearing on infringement (points 17 and 18).

Claims to the use of a substance for the manufacture of a medicament for a specified therapeutic application do not conflict with Article 52(4) or Article 57; the difficulty lies in novelty where the medicament is in no way different from a known one (points 19 and 20). By analogy with Article 54(5), novelty of the claimed process may be derived from the new therapeutic use, whether or not any pharmaceutical use of the medicament was already known, an approach confined to substances for use in a method referred to in Article 52(4) (point 21). Article 52(4) is intended only to free non-commercial and non-industrial medical activities, and neither the text nor the preparatory documents show any intention to exclude second medical indications (point 22). Such claims are therefore allowable in principle, even where the manufacturing process does not differ from known processes (point 23).

Key points for practice

• A claim to the use of a substance for therapeutic treatment is equivalent to an excluded method of treatment and cannot be granted (points 12 and 13).
• A second medical indication may be protected by a claim to the use of a substance for the manufacture of a medicament for a specified new and inventive therapeutic application (point 23).
• Novelty of such a claim is derived from the new therapeutic use, an approach limited to substances for use in a therapeutic method (point 21).
• Practical point: for patents governed by the EPC 1973, protection of a new indication runs through the Swiss-type form, whose novelty rests entirely on the claimed therapeutic application, which therefore has to be defined precisely.

Provisions applied

European Patent Convention (1973 text)

Art. 52 ; Art. 54 ; Art. 57 ; Art. 64 ; Art. 69 ; Art. 84 ; Art. 97 ; Art. 112

Other provisions

Rule 29 of the Implementing Regulations to the EPC 1973; Vienna Convention on the Law of Treaties, Arts 4, 31 and 32; Protocol on the Interpretation of Article 69 EPC

Case law cited

J 8/82; T 128/82; BGH, X ZB 4/83, Hydropyridine; BGH, Benzene sulfonyl urea; BGH, Sitosteryl glycoside; Fothergill v Monarch Airlines (House of Lords, 1981)

Prepared by Dhenne Avocats from the text of the decision (epo.org, decision page and official PDF), consulted on 11 October 2026. Only the official text is authoritative.