804 Anti-tumor effect of a novel Vβ TCR-targeting bifunctional agent in combination with anti-PD1 in checkpoint refractory murine lung cancer models by Jeffrey Schlom, Jacques Moisan, Claudia Palena, Kristen Fousek, Lucas A Horn, Andrew Bayliffe, Haiyan Qin, Shantel Angstadt, Madan Katragadda