The present invention provides a pharmaceutical composition comprising a binary conjugate, DC009, which is a conjugate of a thrombolytic peptide (Pro-Ala-Lys) and a tetrahydroisoquinoline compound having two C1-4 alkyl groups via a lysine linking arm, and a pharmaceutical acceptable carrier. The composition has a pH less than 6.5, preferably has a pH about pH 2-5.5 The composition may comprise a pharmaceutical acceptable excipient such as mannitol, sorbitol, sucrose, lactose, or trehalose.