Phase I study of PF-04691502, a small-molecule, oral, dual inhibitor of PI3K and mTOR, in patients with advanced cancer

Invest New Drugs. 2014 Jun;32(3):510-7. doi: 10.1007/s10637-013-0062-5. Epub 2014 Jan 7.


Purpose: To determine the maximum tolerated dose (MTD), safety, pharmacokinetics, pharmacodynamics, and preliminary evidence of antitumor activity of the PI3K/mTOR inhibitor PF-04691502, administered orally once daily.

Methods: Escalating doses of PF-04691502 were administered to 23 patients with advanced solid tumors in sequential cohorts across the following dose levels: 2 mg, 4 mg, 8 mg, and 11 mg. 14 additional patients were enrolled in an expansion cohort at the MTD to ensure at least five matched pre- and post-treatment biopsies for biomarkers of PI3K activity.

Results: The MTD of PF-04691502 was 8 mg orally once daily. There were three dose-limiting toxicities: one grade 3 fatigue at 8 mg, one grade 3 rash at 11 mg, and one intolerable grade 2 fatigue at 11 mg. Among 37 patients enrolled, treatment-related adverse events included fatigue, decreased appetite, nausea, hyperglycemia, rash, and vomiting. Across all dose levels, average steady-state plasma PF-04691502 concentrations approximated or exceeded the target concentration of 16.2 ng/mL required for ≥75 % tumor growth inhibition in preclinical models. PF-04691502 resulted in increased mean fasting serum glucose, insulin, and c-peptide levels, and produced partial blockade of PI3K signalling in five paired tumor biopsies, as demonstrated by reductions in phosphorylated Akt, FKHR/FKHRL1, and STAT3. No objective anti-tumor responses were observed.

Conclusions: Daily oral administration of PF-04691502 was tolerable at 8 mg orally once daily, with a safety profile similar to other PI3K/mTOR inhibitors. PF-04691502 demonstrated PI3K pathway inhibition by changing glucose homeostasis, and by decreasing phosphorylation of downstream molecules in tumor tissue.

Publication types

  • Clinical Trial, Phase I
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Adult
  • Aged
  • Aged, 80 and over
  • Antineoplastic Agents / administration & dosage*
  • Antineoplastic Agents / adverse effects
  • Antineoplastic Agents / pharmacokinetics
  • Female
  • Humans
  • Male
  • Middle Aged
  • Neoplasms / drug therapy*
  • Neoplasms / genetics
  • Neoplasms / metabolism
  • PTEN Phosphohydrolase / metabolism
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors / administration & dosage*
  • Protein Kinase Inhibitors / adverse effects
  • Protein Kinase Inhibitors / pharmacokinetics
  • Pyridones / administration & dosage*
  • Pyridones / adverse effects
  • Pyridones / pharmacokinetics
  • Pyrimidines / administration & dosage*
  • Pyrimidines / adverse effects
  • Pyrimidines / pharmacokinetics
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / metabolism


  • 2-amino-8-(4-(2-hydroxyethoxy)cyclohexyl)-6-(6-methoxypyridin-3-yl)-4-methylpyrido(2,3-d)pyrimidin-7(8H)-one
  • Antineoplastic Agents
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors
  • Pyridones
  • Pyrimidines
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • PTEN Phosphohydrolase
  • PTEN protein, human