The purpose of this study is to see if investigational study cells, called CAR T cells, are safe and tolerable for participants with multiple myeloma that has returned after previous treatment (relapsed) or did not respond to previous treatment (refractory). The investigational study cells are made from participant's own immune cells (called T-cells) that are genetically modified by the study funder. The study will also see if the investigational CAR T cells kill tumor cells.

The purpose of this research study is to test whether LYL797, an investigational cell product, is safe at different doses. The study will try to find the optimal dose of LYL797 for further research. Another goal is to see if the study cells are able to kill cancer cells in participants who have non-small cell lung cancer or breast cancer that has come back after previous treatment (relapsed), or did not respond to previous treatment (refractory). To be eligible, participants cancer must have a protein in the cancer cells called ROR1. LYL797 is made up of immune cells collected from the participant and then are genetically engineered.