PHASE 2 KEYNOTE-667 STUDY OF PEMBROLIZUMAB (PEMBRO) IN CHILDREN AND YOUNG ADULTS WITH NEWLY DIAGNOSED CLASSICAL HODGKIN LYMPHOMA (Chl) AND SLOW EARLY RESPONSE (SER) TO FRONTLINE CHEMOTHERAPY (CHEMO). (October 2022) - Vinti, L.; Daw, Stephen; Alvarez, C.; Fagioli, F.; Beishuizen, A.; Michel, G.; Moleti, M.; Cepelova, M.; Thorwarth, A.; Rigaud, C.; de Sabando, D.; Parker, J.; et al.