The present invention relates to a multi-domain polypeptide comprising (i) a first complement control protein repeat (CCP)-comprising domain being a convertase decay accelerating domain for convertases of the classical and alternative pathways of complement activation, (ii) a host cell recognition domain, and (iii) a second CCP-comprising domains with cofactor activity. The present invention further relates to a polynucleotide encoding said multi-domain polypeptide, to a vector comprising said polynucleotide, and to a host cell comprising said polynucleotide and/or said vector. Further, the present invention relates to the multi-domain polypeptide, the polypeptide, and the vector for use in medicine and for treating and/or preventing inappropriate complement activation and/or a disease having inappropriate complement activation as a symptom. Moreover, the present invention relates to methods and uses related to multi-domain polypeptide, the polypeptide, and the vector.