Abstract: Provided herein is the conjugation of an amanita toxin compound to a cell-binding molecule with branched linkers for having better targeted treatment of abnormal cells. It also relates to a branched-linkage method of conjugation of an amanita molecule to a cell-binding ligand, as well as methods of using the conjugate in targets treatment of cancer, infection and autoimmune disease.

Abstract: The present invention relates to the conjugates of Tubulysin derivatives (anologs) and cell-binding molecules using branched (side-chain) linkers, and the resulting conjugates have better pharmacokinetic properties, and thus can more accurately target and kill abnormal cells. The invention also relates to the conjugation methods of the Tubulysin derivatives (anologs) to cell-binding molecules, and methods for synthesizing the small molecules, and methods of using the conjugates for targeted therapy for cancers, infections and autoimmune diseases. The conjugates of Tubulysin derivatives with long branched linkers demonstrated increased half-life, minimal exposure to non-targeted cells, tissues or organs in system circulation, leading to reduced off-target toxicity.