Poster Presentation 10th Australian Peptide Conference 2013

Synthesis and characterization of HIV1-Tat and bovine antimicrobial peptide indolicidin conjugated to levofloxacin (#134)

Khairunnisa Abdul Ghaffar 1 , Mariusz Skwarczynski 1 , Istvan Toth 1 2
  1. SCMB, University of Queensland, Brisbane, Queensland, Australia
  2. Pharmacy Australia Centre of Excellence, University of Queensland, Brisbane, Australia

There is a need for new drug compounds or new ways in delivering a drug to its target due to the rising trend in drug resistance1 . Levofloxacin is a potent broad-range antibiotic belonging to the class of fluoroquinolones currently used as a first-line therapy for community-acquired pneumonia23  . However, levofloxacin resistance occurs worldwide. We developed a new drug delivery method to combat antibiotic resistance by attaching peptides to the antibiotic. The peptides; indolicidin and Tat were chosen for this study as they have been known to assist in drug delivery by increasing membrane permeability. Indolicidin peptide has antimicrobial properties, however; it is also haemolytic4 .
The parent peptides, indolicidin and Tat, were synthesised using Fmoc SPPS. Subsequently, either glycine or glycolic acid linker was attached to the peptides. Conjugation of levofloxacin to the peptide via glycine linker was performed using HBTU/DIPEA. An additional catalyst, DMAP, was used alongside HBTU/DIPEA for the conjugation of levofloxacin to the peptide via ester linker. Conjugates were characterised using ESI-MS and analytical HPLC prior purification by preparative HPLC. Haemolytic assay was carried out following conjugation.
The parent peptides (indolicidin and Tat) and final conjugates (levofloxacin-glycine-indolicidin, levofloxacin-glycolic acid-indolicidin, levofloxacin-glycine-Tat and levoflxacin-glycolic acid-Tat) were successfully synthesised. The conjugation methods were optimised to attain the final compounds with moderate to high yields (44-80%) and excellent purity (≥95%). Haemolytic assay was performed on all the 7 compounds including levofloxacin. Both indolicidin-levofloxacin conjugates were haemolytic (11% ± 0.05 and 13% ± 0.01) at 100µM. However, these conjugates were not haemolytic at lower concentrations while both Tat-levofloxacin conjugates were not haemolytic (≤0.4% ± 0.01) even at high concentrations of 100µM. These new antibiotic derivatives are currently under biological evaluation to determine their antimicrobial activity. The current study has paved a novel method for drug delivery.

  1. Sebbage, V. Bioscience Horizons 2009, 2, 64-72
  2. Hurst, M.; Lamb, H. M; Scott, L. J. & Figgit, D. P. Drugs 2002,62, 2127-2167.
  3. Wimer, S.M.; Schoonover, L. & Garrison, M.W. Clinical Therapeutics 1998, 20: 1049-1070.
  4. Rossi, L. M.; Rangasamy, P.; Zhang, J.; Xiao-Qing, Q. & Wu, G. Y. Journal of Pharmaceutical Sciences2007, 97, 1060-1070.