Discloses the use of a complement factor B protein sequence, comprising a mutational change at position 279 or 280 of the protein sequence, for manufacture of a medicament for treating a complement mediated diseases. The medicament further comprises a viral vector encoding the complement factor B protein sequence, or analog, adapted for administration to a subject by a pharmaceutically acceptable carrier. Further disclosed are complement factor B protein sequence variants that are designed to have increased native complement factor B binding affinity. Such variants are directed towards the manufacture of a medicament for treating diseases or conditions related to the eyes.
