Study to Evaluate Safety and Dosimetry of [18F]GEH121224 in Patients With Locally Advanced or Metastatic Breast Cancer

The study described in this protocol is a Phase 1, single center clinical trial to evaluate the safety and potential of \[18F\]GEH121224 as a PET radiotracer for the diagnostic imaging of HER2 positive breast cancer lesions. A group of 6 patients will be selected to perform a dosimetry study with \[18F\]GEH121224 followed by another group of 6 patients in a test-retest study. The results of this study will provide crucial information to guide the development of \[18F\]GEH121224 for the detection of HER2 status in advanced breast cancer patients. This study will use established methods for characterizing the radiation dosimetry, biodistribution and basic pharmacokinetics of a radiotracer.

Group 1 : Six female patients with locally advanced or metastatic breast cancer and with HER2-positive primary tumor status will be included. These patients will receive a single injection of GEH121224 (18F) Injection and will then undergo a dynamic whole-body PET/CT scan starting at the time of injection (8 sequential scans over 90 minutes anticipated) followed by static whole-body scans starting at 120 minutes and 240 minutes after injection. Blood samples will be collected at specified time points during imaging for pharmacokinetic analysis. Safety and imaging data will be reviewed on an ongoing basis after dosing of each patient in Group 1. The injected activity may be adjusted for subsequent patients in Group 1 based on this review. A complete aggregate review of safety and imaging data will be performed by the Sponsor once all 6 patients in Group 1 have been dosed. If no safety concerns are raised, enrollment into Group 2 will start. The injected radioactivity may also be optimized before enrolling patients in Group 2. Review of safety data is described in the Safety Data Review Plan. Group 2 : Six female patients with locally advanced or metastatic breast cancer and with HER2-positive primary tumor status will be included in Group 2 and will receive a single injection of GEH121224 (18F) Injection on each of 2 separate days. On Imaging Day 1, patients will receive a single injection of GEH121224 (18F) Injection and will then undergo \[18F\]GEH121224 PET imaging at the optimal scan time identified in Group 1. Within 3 weeks (3 to 21 days; Imaging Day 2), patients will receive a second single injection of GEH121224 (18F) Injection and again undergo \[18F\]GEH121224 PET imaging at the optimal scan time identified in Group 1. Patient safety will be monitored throughout the course of the study, including a 24-hour safety follow-up by phone after each dose of \[18F\]GEH121224.