The purpose of this study is to test the safety of NXC-201 at different doses in participants with relapsed/refractory AL amyloidosis, and to confirm the best dose for further testing. In addition, the study will evaluate the effectiveness of NXC-201 in treating relapsed/refractory AL amyloidosis.

AL amyloidosis is a rare systemic disorder caused by an abnormality of plasma cells (a type of white blood cell that is part of the immune system) in the bone marrow. Misfolded proteins produced by these cells can build up in and around tissues, nerves and organs, gradually affecting their function. This can cause progressive and widespread organ damage.

NXC-201 is made using a person's own T Cells (immune system cells that protect the body from infections, cancer, and other possible harms). The T cells are collected then genetically modified (changes are made to the DNA or genes) outside of the body in a laboratory. A virus is used to introduce a gene that creates a protein (called a chimeric antigen receptor or CAR) on the surface of T cells. The virus then becomes inactive. The changes are designed to help the NXC-201 cells find and destroy plasma cells that have a protein on their surface called B-cell maturation antigen (BCMA). T-cell therapies like NXC-201 are called CAR T-cell therapies. After being reinjected, the CAR-T cells multiply and spread throughout the body.

NXC-201 is an investigational "treatment", which means it has not been approved by the US Food and Drug Administration (FDA) for the treatment of AL Amyloidosis or any other disease.

Calling the study drug a "treatment" in this consent form does not indicate that it will be effective in treating your AL Amyloidosis.

Before receiving NXC-201, participants will receive lymphodepleting chemotherapy (or lymphodepletion) with cyclophosphamide and fludarabine to briefly weaken (suppress) your immune system. The lymphodepletion will help prepare the body for receiving NXC-201. Cyclophosphamide and fludarabine are FDA-approved for use as lymphodepleting chemotherapy.

This study is sponsored by Nexcella, Inc., which is responsible for funding and organizing the study.