The invention provides novel cytotoxic compounds and cytotoxic conjugates comprising these cytotoxic compounds and cell-binding agents. More specifically, this invention relates to novel thailanstatin A analogs, useful as cytotoxic small molecule toxins in antibody-drug conjugates (ADCs). The present invention further relates to compositions including these cytotoxic compounds and ADCs, and methods for using these toxins and ADCs to treat pathological conditions including cancer.
