definiens: shall mean one of the following forms of interact ion between a particular Collaboration Compound and its applicable Collabora tion Target : ( a ) such Collaboration Compound activates or agonizes such Collaboration Target whe n tested in an in vitro activity assay expressing such Collaboration Target ( alone or together with its co -receptors, if any ), unless such Collaboration Compound, when tested in an applicable animal model, causes a physiologic outcome that is characteristic, in such animal model, of molecules that antagonize or inhibit such Collaboration Targe t, in which case such Collaboration Compound shall be deemed to be included in clause ( b ) below ; or ( b ) such Collaboration Compound antagonizes or inhi bits such Collaboration Target when tested in an in vitro activity assay expressing such Collaboration Targe t ( alone or together with its co - receptors, if any ) unless such Collaboration Compound, when tested in an app licable animal model, causes a physiologic outcome that is characteristic, in such animal model, of molecules that activate or agoniz e such Collaboration Target, in which case such Colla boration Compound shall be deemed to be included in clause ( a ) above