Assessing aggregation of peptide conjugate of doxorubicin using quasi-elastic light scattering and 600 MHz NMR.
The use of doxorubicin in treating prostate cancer is limited by its systemic toxicities especially cardiotoxicity and immunosuppression. Prodrugs that reduce the systemic exposure of doxorubicin are believed to provide a safety advantage. A prodrug of doxorubicin which contains a peptide sequence that can be recognized by prostate-specific antigen (PSA) and cleaved in the prostate was formulated for clinical use. The i.v. formulation and manufacture of this peptide conjugate posed several challenges. The main issue of the i.v. formulation were chemical and physical stability. The physical stability challenges posed during formulation and manufacture of his peptide conjugate is described herein. A heptapeptide conjugate of doxorubicin was found to aggregate in solution forming large ill defined aggregates (60-1300 nm). In contrast to doxorubicin, the average hydrodynamic diameter measured for this compound by dynamic laser light scattering technique is very large. Increasing concentration of the drug and lowering pH promoted aggregation. We rationalize the difference in the effective hydrodynamic diameter due to hydrogen bonding of the peptide which allows for the formation of large particle sizes relative to doxorubicin. We have also used 600 MHz 1H NMR to assess the aggregation of this compound.
Karki
Shyam B
SB
Pharmaceutical Research and Development, Merck Research Laboratories, Merck & Co., Inc., P.O. Box 4, West Point, PA 19486, USA. shyam_karki@merck.com
Ostovic
Drazen
D
D000903:Antibiotics, Antineoplastic / Q000008:administration & dosage / Q000737:chemistry*; D004317:Doxorubicin / Q000008:administration & dosage / Q000737:chemistry*; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D008027:Light; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010455:Peptides / Q000737:chemistry*; D011355:Prodrugs; D012542:Scattering, Radiation
D000903:Antibiotics, Antineoplastic; D010455:Peptides; D011355:Prodrugs; D004317:Doxorubicin