A phase IB trial of 24-hour intravenous PX-12, a thioredoxin-1 inhibitor, in patients with advanced gastrointestinal cancers

Amanda F Baker, K. N. Adab, N. Raghunand, Hsiao-Hui Chow, Steven P Stratton, S. W. Squire, M. Boice, L. A. Pestano, D. L. Kirkpatrick, T. Dragovich

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27 Scopus citations


We investigated the safety, pharmacokinetics, and pharmacodynamics of PX-12, a thioredoxin-1 (Trx-1) inhibitor, administered as a 24-hour infusion every 7 or 14 days in patients with gastrointestinal malignancies. PX-12 is the first Trx-1 inhibitor to undergo clinical development. The first Phase 1 study of PX-12 demonstrated promising clinical activity, but the 1 and 3 hour-infusion schedules investigated were associated with a strong and irritating odor due to exhalation of one of its metabolites, 2-butanethiol. In an effort to achieve tolerability and achieve a drug exposure level necessary for biological activity, the current study was undertaken. While the maximally tolerated dose was estimated to be 300 mg/m2 /24 h once a week as the 2-butanethiol expirate was tolerable at that dose level, no evidence of clinical activity was observed. Pharmacokinetic studies of the parent compound PX-12 demonstrated rapid, irreversible binding to plasma components, resulting in low (ng/ml) peak plasma concentrations of non-bound PX-12 during infusion. DCE-MRI was performed pre-and post-infusion in three patients. There were no significant trends observed in changes in plasma Trx-1, vascular endothelial growth factor (VEGF), or beta fibroblast growth factor (FGF-2) pre- or post-treatment. However, there was a trend for a decrease in circulating Trx-1 during the first four PX-12 treatment cycles in patients that had a Trx-1 baseline level >18 ng/mL. Aggregate clinical trial results suggest that further clinical development of PX-12, as an intravenous infusion, is not feasible. However, the Trx-1 pathway remains a target of interest in patients with gastrointestinal malignancies.

Original languageEnglish (US)
Pages (from-to)631-641
Number of pages11
JournalInvestigational New Drugs
Issue number3
Publication statusPublished - Jun 2013



  • GI Cancers
  • PX-12
  • Redox
  • Thioredoxin-1

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Oncology

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