definiens: means the compound known as GLPG0634 and any metabolite, salt, ester, hydrate, solvate, isomer, enantiomer, free acid form, free base form, crystalline form, co - crystalline form, amorphousform, pro - drug ( including ester pro - drug ) form, racemate, polymorph, chelate, stereoisomer, tautomer, or opticallyactive form of the foregoing . If a Compound Failure occurs with respect to the Lead Compound, the Lead Compoundshall be replaced by a Follow - On Compound, such Follow - On Compound to be determined by [COMPANY] if more than oneFollow - On Compound is in Development, and such Follow - On Compound shall be deemed to be the Lead Compoundeffective from the point in which the Compound Failure determination has been made by the JDC