Chemical modifications for improvement of the pharmacological properties of therapeutic agents.

摘要

N-Formyl-methionyl peptides can specifically bind to surface receptors on phagocytic cells. A single copy of N-formyl-methionine-leucine-phenylalanine (fMLF) covalently linked to a poly(ethylene glycol)-based polymer displayed reduced binding avidity (K_d = 190 nM) for differentiated HL-60 cells relative to free fMLF (K_d = 28 nM). However, increasing the number of fMLF residues (up to eight) attached to a single polymer resulted in enhanced avidity for these cells (K_d = 0.18 nM). However, no conjugates showed enhanced ability to activate phagocytic cells, relative to free peptide (EC₅₀ = 5 nM), as measured by transient stimulation of released calcium ions from intracellular stores into the cytoplasm. A polymer bearing four fMLF and four digoxigenin residues showed specific enhancement in binding to differentiated HL-60 cells and mouse peritoneal macrophages in situ relative to a polymer lacking fMLF. These results suggest that multiple fMLF residues linked to a drug-delivery polymer can be used to target appended drugs to phagocytic cells with relatively low toxicity due to cellular activation.; A unique feature of the HIV-1 replication cycle is its requirement for the virally encoded Tat protein to bind to a region in nascent viral transcripts (TAR) and alleviate a transcriptional blockage. Previously, in our laboratory, a Tat peptide antagonist [N-acetyl-RKKRRQRRRK(biotin)-NH₂] was designed based on the TAR binding domain of Tat peptide (Wang et al., 1995). In this study, this Tat antagonist was synthesized with D-amino acids, assembled in reverse order of that found in parent peptide (commonly referred to as retro-inverso peptide). The retro-inverso antagonist peptide appended to PEG showed an inhibitory effect in HIV-1 replication at 0.01 μM concentration. Also, bioreversible PEG polymers, that could serve as carriers for peptides or proteins, were synthesized and characterized in this study.; A polycation peptide-antisense DNA conjugate was synthesized in order to study the effect of positive charges on the neutralization of negative charges on the oligonucleotide moiety. A competitive gel shift assay was designed to determine the dissociation constant of this oligonucleotide conjugate. This modification resulted in a three-fold increase of binding affinity to the single-stranded DNA or RNA targets.