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A phase I pharmacokinetic study of the P-glycoprotein inhibitor, ONT-093, in combination with paclitaxel in patients with advanced cancer.

AbstractBACKGROUND:
ONT-093 is an orally bioavailable inhibitor of P-glycoprotein (P-gp). In pre-clinical studies, ONT-093 could inhibit P-gp and reverse multidrug resistance at nM concentrations with no effect on paclitaxel pharmacokinetics. Phase I trials of ONT-093 in normal human volunteers showed no dose-limiting toxicities at serum concentrations associated with biologic activity achieved with doses ranging from 300 to 500 mg.
METHODS:
Phase I pharmacokinetic trial of ONT-093 in doses from 300 to 500 mg administered before and after intravenous paclitaxel doses of 150 to 175 mg/m(2) repeated every 21 days. All patients received paclitaxel alone on cycle 1.
RESULTS:
18 patients were enrolled onto 4 dose levels. Toxicity of the combination included neutropenia, arthralgia, myalgia, and peripheral neuropathy. Four of 6 patients receiving 500 mg doses of ONT-093 and paclitaxel at 175 mg/m(2) (dose level 4) had higher-grade neutropenia with cycle 2, with 1 patient experiencing febrile neutropenia. Plasma pharmacokinetic parameters of paclitaxel were unchanged between cycle 1 and 2 for dose levels 1 to 3, but at dose level 4, 45-65% increases in paclitaxel AUC were observed in 4 of the 6 patients. Mean C(max) of ONT-093 was 9 microM (range 5-15 microM) which were 3- to 5-fold higher than in single agent studies of ONT-093.
CONCLUSIONS:
Doses of ONT-093 achieving serum concentrations associated with biological activity were well tolerated in combination with standard doses of paclitaxel. Toxicities of the combination in this schedule were mainly attributable to paclitaxel and dose-limiting toxicity was limited to febrile neutropenia. There was an apparent pharmacokinetic interaction between paclitaxel and ONT-093, possibly related in part to the excipient, Cremophor, present in the paclitaxel formulation.
AuthorsKim N Chi, Stephen K Chia, Ross Dixon, Michael J Newman, Vince J Wacher, Branimir Sikic, Karen A Gelmon
JournalInvestigational new drugs (Invest New Drugs) Vol. 23 Issue 4 Pg. 311-5 (Aug 2005) ISSN: 0167-6997 [Print] United States
PMID16012790 (Publication Type: Clinical Trial, Clinical Trial, Phase I, Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antineoplastic Agents
  • Antineoplastic Agents, Phytogenic
  • Imidazoles
  • OC 144-093
  • cremophor
  • Polyethylene Glycols
  • Paclitaxel
Topics
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 (antagonists & inhibitors)
  • Adult
  • Aged
  • Alopecia (chemically induced)
  • Antineoplastic Agents (administration & dosage, adverse effects, pharmacokinetics)
  • Antineoplastic Agents, Phytogenic (administration & dosage, adverse effects, pharmacokinetics)
  • Arthralgia (chemically induced)
  • Dose-Response Relationship, Drug
  • Drug Therapy, Combination
  • Female
  • Humans
  • Imidazoles (administration & dosage, pharmacokinetics)
  • Male
  • Middle Aged
  • Neoplasms (drug therapy)
  • Neutropenia (chemically induced)
  • Paclitaxel (administration & dosage, pharmacokinetics)
  • Polyethylene Glycols (administration & dosage, adverse effects)

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