Systematic research of peptide spacers controlling drug release from macromolecular prodrug system, carboxymethyldextran polyalcohol-peptide-drug conjugates.

The primary purpose of this study was to comprehensively delineate specificity of the peptide spacer sequence to tumor-expressed proteases for the design of macromolecular carrier−peptide spacer−drug conjugate system. 225 conjugates of carboxymethyldextran polyalcohol (CM-Dex-PA) as water-soluble carrier and a dansyl derivative (N-(4-aminobutyl)-5-(dimethylamino)-1-naphthalenesulfonamide, DNS) as the model drug linked with different tetrapeptide spacers (Gly-Gly-P2−P1, P2, P1: Ala, Asn, Gly, Cit, Gln, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, and Val) were combinatorially synthesized. First, the drug release assay of all of the fluorogenic model conjugates was performed in murine Meth A solid tumor homogenates. The drug release rate was higher with conjugates having hydrophobic amino acids at P2. It was also found that conjugates with Asn release the drug rapidly and, in contrast, those with Pro does not. Second, we selected three peptide spacers (Gly-Gly-Phe-Gly, Gly-Gly-Ile-Gly, Gly-Gly-Pro-Leu), whi...