<p>It is intended to provide a platelet substitute which would not undergo aggregation together with inactive platelets in a blood vessel and thus never induces unnecessary thrombosis or coagulation in the blood vessel. More specifically, it is found out that a conjugate having a dodecapeptide contained in the GPIIb/IIIa recognition site of fibrinogen bonded thereto has a characteristic preferable as a platelet substitute, i.e., specifically binding exclusively to activated GPIIb/IIIa.</p>
