In certain technical areas (e.g. biotechnology, pharmacy) cases occur where:

It may happen that such applications contain so-called "reach-through" claims, i.e. claims directed to a chemical compound (or the use of that compound) defined only in functional terms with regard to the technical effect it exerts on one of the above molecules.

Typical examples of such claims would be: "An agonist/antagonist to polypeptide X [optionally as identified by the screening method of claim A]."; "An agonist/antagonist to polypeptide X [optionally as identified by the screening method of claim A], for use in therapy."; "An agonist/antagonist to polypeptide X [optionally as identified by the screening method of claim A], for use in the treatment of disease Y.", where the description indicates that polypeptide X is involved in disease Y.

According to Art. 83 and Rule 42(1)(c), the claim must contain sufficient technical disclosure of the solution to the problem. A functional definition of a chemical compound ("reach-through" claim) covers all compounds possessing the activity or effect specified in the claim. It would be an undue burden to isolate and characterise all potential compounds (e.g. agonists/antagonists), without any effective pointer to their identity (see F‑III, 1), or to test every known compound and every conceivable future compound for this activity to see if it falls within the scope of the claim. In effect, the applicant is attempting to patent what has not yet been invented, and the fact that the applicant can test for the effect used to define the compounds does not necessarily confer sufficiency on the claim; in fact it constitutes an invitation for the skilled person to perform a research programme (see T 435/91 (Reasons 2.2.1), followed by T 1063/06 (Headnote II)).

In general, claims directed to merely functionally defined chemical compounds that are to be found by means of a new kind of research tool (e.g. using a new screening method based on a newly discovered molecule or a new mechanism of action) are directed to future inventions, for which patent protection under the EPC is not designed. In the case of such "reach-through" claims, it is both reasonable and imperative to limit the subject-matter of the claims to the actual contribution to the art (see T 1063/06 (Headnote I)).