A Study of Sigvotatug Vedotin in Advanced Solid Tumors

This trial will look at a drug called sigvotatug vedotin (SGN-B6A) alone and with pembrolizumab, with or without chemotherapy, to find out whether it is safe for people who have solid tumors. It will study sigvotatug vedotin to find out what its side effects are. A side effect is anything the drug does besides treating cancer. It will also study whether sigvotatug vedotin works to treat solid tumors. The study will have four parts. * Part A of the study will find out how much sigvotatug vedotin should be given to participants. * Part B will use the dose found in Part A to find out how safe sigvotatug vedotin is and if it works to treat solid tumors. * Part C of the study will find out how safe sigvotatug vedotin is in combination with these other drugs. * Part D will include people who have not received treatment. This part of the study will find out how safe sigvotatug vedotin is in combination with these other drugs and if these combinations work to treat solid tumors. * In Parts C and D, participants will receive sigvotatug vedotin with either: * Pembrolizumab or, * Pembrolizumab and carboplatin, or * Pembrolizumab and cisplatin.