The main aims of this study are to evaluate the safety and tolerability, and to determine the maximum tolerated dose (MTD) or the recommended combination dose of Anvumetostat in combination with IDE397 in adult participants with metastatic or locally advanced MTAP-null solid tumors, and to evaluate the preliminary anti-tumor activity of anvumetostat in combination with IDE397 in adult participants with metastatic or locally advanced MTAP-null Non-Small-Cell Lung Cancer (NSCLC).