The purpose of this study is to assess the safety and efficacy of BMS-986504, a selective, MTA-cooperative PRMT5 inhibitor, in combination with Nab-paclitaxel/Gemcitabine (nab-p/gem) versus placebo in combination with nab-p/gem, in participants with untreated metastatic Pancreatic Ductal Adenocarcinoma (PDAC) with homozygous methylthioadenosine phosphorylase (MTAP) deletion.