652 NT-I7 (efineptakin alfa), a long-acting IL-7, in combination with pembrolizumab improves T cell fitness in heavily pretreated subjects with gastrointestinal tumors by Cara Haymaker, Aung Naing, Minal Barve, Marya Chaney, Se Hwan Yang, Siyoung Lee, Byung Ha Lee, Sara Ferrando-Martinez, Hirva Mamdani, Richard D Kim, Meredith Pelster, Mohamed Derbala, Jack Goon, Samuel Darko, Julie Murphy, Lauren Gorelik, Allison Bierly