PathHunter® eXpress Receptor Tyrosine Kinase (RTK) Internalization Assay kits provide a robust, highly sensitive and easy-to-use, cell-based assay for monitoring a direct and quantitative measurement of internalized RTKs localized to early endosomes. The eXpress kits contain everything needed for a complete receptor tyrosine kinase internalization experiment including cells, detection reagents, media and plates. The pre-validated, frozen eXpress cells have been manufactured for short term use and are provided in a ready-to-assay format that saves time and adds convenience. Assays have been designed for 96-well plate analyses.