Preclinical pharmacokinetics, metabolism, and toxicity of azurin-p28 (NSC745104) a peptide inhibitor of p53 ubiquitination

Cancer Chemother Pharmacol. 2011 Aug;68(2):513-24. doi: 10.1007/s00280-010-1518-3. Epub 2010 Nov 18.


Purpose: Characterize the preclinical pharmacokinetics, metabolic profile, multi-species toxicology, and antitumor efficacy of azurin-p28 (NSC 745104), an amphipathic, 28 amino acid fragment (aa 50-77) of the copper containing redox protein azurin that preferentially enters cancer cells and is currently under development for treatment of p53-positive solid tumors.

Methods: An LC/MS/MS assay was developed, validated, and applied to liver microsomes, serum, and tumor cells to assess cellular uptake and metabolic stability. Pharmacokinetics was established after administration of a single intravenous dose of p28 in preclinical species undergoing chronic toxicity testing. Antitumor efficacy was assessed on human tumor xenografts. A human therapeutic dose was predicted based on efficacy and pharmacokinetic parameters.

Results: p28 is stable, showed tumor penetration consistent with selective entry into tumor cells and significantly inhibited p53-positive tumor growth. Renal clearance, volume of distribution, and metabolic profile of p28 was relatively similar among species. p28 was non-immunogenic and non-toxic in mice and non-human primates (NHP). The no observed adverse effect level (NOAEL) was 120 mg/kg iv in female mice. A NOAEL was not established for male mice due to decreased heart and thymus weights that was reversible and did not result in limiting toxicity. In contrast, the NOAEL for p28 in NHP was defined as the highest dose (120 mg/kg/dose; 1,440 mg/m(2)/dose) studied. The maximum-tolerated dose (MTD) for subchronic administration of p28 to mice is >240 mg/kg/dose (720 mg/m(2)/dose), while the MTD for subchronic administration of p28 to Cynomolgous sp. is >120 mg/kg (1,440 mg/m(2)/dose). The efficacious (murine) dose of p28 was 10 mg/kg ip per day.

Conclusions: p28 does not exhibit preclinical immunogenicity or toxicity, has a similar metabolic profile among species, and is therapeutic in xenograft models.

Publication types

  • Research Support, N.I.H., Extramural
  • Validation Study

MeSH terms

  • Animals
  • Antineoplastic Agents / adverse effects*
  • Antineoplastic Agents / metabolism
  • Antineoplastic Agents / pharmacokinetics*
  • Antineoplastic Agents / therapeutic use
  • Azurin / adverse effects*
  • Azurin / metabolism
  • Azurin / pharmacokinetics*
  • Azurin / therapeutic use
  • Biotransformation
  • Cell Line, Tumor
  • Drug Evaluation, Preclinical
  • Female
  • Humans
  • Macaca fascicularis
  • Male
  • Mice
  • Mice, Nude
  • Neoplasms / drug therapy*
  • No-Observed-Adverse-Effect Level
  • Peptide Fragments / adverse effects
  • Peptide Fragments / metabolism
  • Peptide Fragments / pharmacokinetics*
  • Peptide Fragments / therapeutic use
  • Specific Pathogen-Free Organisms
  • Tumor Burden / drug effects
  • Tumor Suppressor Protein p53 / antagonists & inhibitors*
  • Tumor Suppressor Protein p53 / metabolism
  • Ubiquitination / drug effects
  • Xenograft Model Antitumor Assays


  • Antineoplastic Agents
  • Peptide Fragments
  • Tumor Suppressor Protein p53
  • Azurin
  • azurin (50-77)