Abstract: A method of treating a patient for a condition wherein the bioactive agent of choice is DRUG, wherein DRUG is a substrate that is effluxed by the P-gp transporter, is provided, the method comprising administering to the patient an effective amount of a compound of formula (I): DRUG-X—Y(n)-Z(n?)-Z?(n?)-R ??(I) wherein each X, Y, Z, and Z? is independently Met, Val, Thr, Tyr, Trp, Ser, Ala, or Gly; R is H or an amino-protecting group; n is 1, and each n?, or n? is independently 0 or 1; or a pharmaceutically acceptable salt thereof, with the proviso that DRUG is not acyclovir or ganciclovir and that DRUG is non-peptidyl.

Abstract: Dipeptide, and tripeptide and tetrapeptide ester derivatives of bioactive agents are provided wherein the parent agents are substrates effluxed by the P-gp transporter. The derivatives are useful in treating the same condition as the bioactive agent. Also disclosed is a method for preparing a bioactive agent for targeted delivery by nutrient or peptide transporters comprising linking the agent to one or more groups of the formula —X—Y(n)-Z(n?)-Z?(n?)-R; wherein each X, Y, Z, and Z? is independently Met, Val, Thr, Tyr, Trp, Ser, Ala or Gly; R is independently H or an amino-protecting group; n=1, and each, n?, or n? is independently 0 or 1.

Abstract: Amino acid ester, dipeptide, and tripeptide ester derivatives of bioactive agents are provided wherein said parent agents are substrates effluxed by the P-gp transporter. The derivatives are useful in treating the same condition as the bioactve agent. Also disclosed is a method for preparing a bioactive agent for targeted delivery by nutrient or peptide transporters comprising linking the agent to one or more groups of the formula —X—Y(n)-Z(n?)-Z?(n?)-R; wherein each X, Y, Z, and Z? is independently Met, Val, Thr, Tyr, Trp, Ser, Ala or Gly; R is independently H or an amino-protecting group; and each n, n?, or n? is independently 0 or 1.