"Reach-through" claims are defined as claims attempting to obtain protection for a chemical product (and also uses thereof, compositions thereof, etc.) by defining that product functionally in terms of its action (e.g. agonist, antagonist) on a biological target such as an enzyme or receptor (see F‑III, 9). In many such cases, the applicant functionally defines chemical compounds in this way by reference to a newly identified biological target. However, compounds which bind to and exercise this action on that biological target are not necessarily novel compounds simply because the biological target which they act on is new. Indeed in many cases, the applicants themselves provide test results in the applications, whereby known compounds are shown to exert this action on the new biological target, thus demonstrating that compounds falling within the functional definition of the "reach-through" claim are known in the state of the art and so establishing that a reach-through claim relating to compounds defined in this way lacks novelty.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/g_vi_9.htm
Date retrieved: 17 May 2021