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

A. F. Baker, K. N. Adab, N. Raghunand, H. H.S. Chow, S. P. Stratton, S. W. Squire, M. Boice, L. A. Pestano, D. L. Kirkpatrick, T. Dragovich

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40 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
StatePublished - Jun 2013
Externally publishedYes


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

ASJC Scopus subject areas

  • Oncology
  • Pharmacology
  • Pharmacology (medical)


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