The primary objective of Parts 1 and 2 of this study is to evaluate the safety, tolerability, and to determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of Anvumetostat alone and in combination with docetaxel in adult participants with metastatic or locally advanced methylthioadenosine phosphorylase (MTAP)-null solid tumors. The primary objective of Part 3 of this study is to evaluate the efficacy of Anvumetostat in adult participants with metastatic or locally advanced MTAP-null solid tumors.