PLT012

The goal of this clinical trial is to learn about what doses of PLT012 are safe to use in adults with advanced cancers in solid tumors. It will also learn about how effective different doses of PLT012 are in treating cancer. The main questions it aims to answer are: What adverse events and toxicities (harmful side effects) are associated with different doses of PLT012? What are the blood levels of PLT012 in your body at different timepoints? What effect does PLT012 have on reducing tumor size and/or preventing the worsening of cancer? All participants will receive PLT012 and none will receive placebo (a look-alike substance that contains no drug). Participants will receive PLT012 by intravenous infusion once every 3 weeks. Treatment with PLT012 can continue until the participant's disease worsens or they cannot tolerate treatment. For the first 12 weeks, visits to the clinic will be more frequent (from 1 to 5 times over a 3-week period). After the first 12 weeks, visits will be reduced to once every 3 weeks.