RecruitingDrug trialStudy of PM54 in Combination With Immunotherapy in Adult Participants With Advanced MalignanciesThe main purpose of the study is to evaluate the safety, tolerability and recommended dose of PM54 in combination with pembrolizumab. To assess the antitumor activity of PM54 in combination with pembrolizumab in terms of clinical benefit rate (CBR) and objective response rate (ORR) based on investigator's assessment in participants in other cohorts.