Phase II Study of Taselisib (GDC-0032) in Combination with Fulvestrant in Patients with HER2-Negative, Hormone Receptor-Positive Advanced Breast Cancer

Clin Cancer Res. 2018 Sep 15;24(18):4380-4387. doi: 10.1158/1078-0432.CCR-18-0613. Epub 2018 May 23.

Abstract

Purpose: This single-arm, open-label phase II study evaluated the safety and efficacy of taselisib (GDC-0032) plus fulvestrant in postmenopausal women with locally advanced or metastatic HER2-negative, hormone receptor (HR)-positive breast cancer.Patients and Methods: Patients received 6-mg oral taselisib capsules daily plus intramuscular fulvestrant (500 mg) until disease progression or unacceptable toxicity. Tumor tissue (if available) was centrally evaluated for PIK3CA mutations. Adverse events (AE) were recorded using NCI-CTCAE v4.0. Tumor response was investigator-determined using RECIST v1.1.Results: Median treatment duration was 4.6 (range: 0.9-40.5) months. All patients experienced ≥1 AE, 30 (50.0%) had grade ≥3 AEs, and 19 (31.7%) experienced 35 serious AEs. Forty-seven of 60 patients had evaluable tissue for central PIK3CA mutation testing [20 had mutations, 27 had no mutation detected (MND)]. In patients with baseline measurable disease, clinical activity was observed in tumors with PIK3CA mutations [best confirmed response rate: 38.5% (5/13; 95% CI, 13.9-68.4); clinical benefit rate (CBR): 38.5% (5/13; 95% CI, 13.9-68.4)], PIK3CA-MND [best confirmed response rate: 14.3% (3/21; 95% CI, 3.0-36.3); CBR: 23.8% (5/21; 95% CI, 8.2-47.2)], and unknown PIK3CA mutation status [best confirmed response rate: 20.0% (2/10; 95% CI, 2.5-55.6); CBR: 30.0% (3/10; 95% CI, 6.7-65.2)].Conclusions: Taselisib plus fulvestrant had clinical activity irrespective of PIK3CA mutation status, with numerically higher objective response rate and CBR in patients with PIK3CA-mutated (vs. -MND) locally advanced or metastatic HER2-negative, HR-positive breast cancer. No new safety signals were reported. A confirmatory phase III trial is ongoing. Clin Cancer Res; 24(18); 4380-7. ©2018 AACR.

Publication types

  • Clinical Trial, Phase II
  • Multicenter Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Antineoplastic Combined Chemotherapy Protocols / administration & dosage*
  • Antineoplastic Combined Chemotherapy Protocols / adverse effects
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / genetics
  • Breast Neoplasms / pathology
  • Class I Phosphatidylinositol 3-Kinases / genetics*
  • Disease-Free Survival
  • Drug-Related Side Effects and Adverse Reactions / classification
  • Drug-Related Side Effects and Adverse Reactions / pathology
  • Female
  • Fulvestrant / administration & dosage
  • Fulvestrant / adverse effects
  • Humans
  • Imidazoles / administration & dosage*
  • Imidazoles / adverse effects
  • Middle Aged
  • Mutation
  • Oxazepines / administration & dosage*
  • Oxazepines / adverse effects
  • Receptor, ErbB-2 / genetics
  • Receptors, Estrogen / genetics

Substances

  • 2-(3-(2-(1-isopropyl-3-methyl-1H-1,2-4-triazol-5-yl)-5,6-dihydrobenzo(f)imidazo(1,2-d)(1,4)oxazepin-9-yl)-1H-pyrazol-1-yl)-2-methylpropanamide
  • Imidazoles
  • Oxazepines
  • Receptors, Estrogen
  • Fulvestrant
  • Class I Phosphatidylinositol 3-Kinases
  • PIK3CA protein, human
  • ERBB2 protein, human
  • Receptor, ErbB-2