This study is exploring a new medicine, MT-6402, for people with advanced solid cancers that have a specific marker called PD-L1. The study has two parts: finding a safe dose and seeing how well the medicine works. MT-6402 is given through an IV, which is a method of delivering medicine directly into the bloodstream over 30 minutes each week. Participants may remain in the study as long as the treatment is helping them and they wish to continue. To join, participants must be adults with advanced cancer that cannot be treated with standard methods. The study involves several visits over a period of time, including initial screenings and follow-ups after treatment.

• The study lasts up to 24 months with regular weekly treatments and follow-up visits.
• Participants must undergo biopsies to check for specific cancer markers.
• Participants will be monitored closely for safety and effectiveness of the treatment.

Before joining, potential participants should discuss with their doctor to understand eligibility, risks, and benefits.