Synthesis, drug release and anti-HIV activity of a series of PEGylated zidovudine conjugates

A series of methoxy poly(ethylene glycol)-succinyl-5′-O-zidovudine conjugates (mPEG-succinyl-AZT) with different molecular weight (Mw: 750 Da, 2, 5 or 10 kDa) of mPEG were synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (1H NMR) spectroscopy, and matrix-assisted laser desorption/ionization time of flight mass (MALDI TOF MS) spectrometry analysis. All conjugates showed good stability in vitro release experiments, and good anti-HIV activity and low cytotoxicity in MT-4 cells, in which, mPEG750-succinyl-AZT exhibited good inhibition to wild-type viruses (strains IIIB and ROD) with EC50 values of 0.11 and 0.090 μmol/L, respectively, and it showed no cytotoxicity up to 110 μmol/L. Oral pharmacokinetic study in rats showed the half-life time (T1/2) of all conjugates are prolonged compared to free AZT. Especially, mPEG750-succinyl-AZT displayed a ∼2.3-fold prolonged half-life and approximately 224% increased bioavailability of AZT.