Half-life extension of the HIV-fusion inhibitor peptide TRI-1144 using a novel linker technology.

We have previously developed a linker technology for half-life extension of peptides, proteins and small molecule drugs (1). The linkers undergo β-elimination reactions with predictable cleavage rates to release the native drug. Here we utilize this technology for half-life extension of the 38 amino acid HIV-1 fusion inhibitor TRI-1144. Conjugation of TRI-1144 to 40kDa PEG by an appropriate β-eliminative linker and i.v. administration of the conjugate increased the in vivo half-life of the released peptide from 4 to 34h in the rat, and the pharmacokinetic parameters were in excellent accord with a one-compartment model. From these data we simulated the pharmacokinetics of the PEG-TRI-1144 conjugate in humans, predicting a t1/2,β of 70h for the released peptide, and that a serum concentration of 25nM could be maintained by weekly doses of 8μmol of the conjugate. Using a non-circulating carrier (2) similar simulations indicated a t1/2,β of 150h for the peptide released from the conjugate and that dosing of only 1.8μmol/week could maintain serum concentrations of TRI-1144 above 25nM. Hence, releasable β-eliminative linkers provide significant half-life extension to TRI-1144 and would be expected to do likewise for related peptides.