The invention provides polypeptides comprising a complement factor B analog. The invention also provides various complement factor B analogs including complement factor B analogs comprising a mutation of a free cysteine amino acid and related methods, nucleic acids and vectors. These complement factor B analogs and related methods, nucleic acids and vectors can be used to modulate a complement pathway or for the study and/or treatment of various conditions or diseases related to a complement pathway.La presente invención se refiere a un polipéptido, que comprende un análogo de proteína del factor B del complemento, caracterizado porque el análogo del facto B del complemento comprende una sustitución de un aminoácido de cisteína libre； y en donde la cisteína libre corresponde al aminoácido 292 de la SEQ ID NO: 1.
