The present disclosure provides, among other aspects, codon-altered polynucleotides encoding Factor VIII variants for expression in mammalian cells. In some embodiments, the disclosure also provides mammalian gene therapy vectors and methods for treating hemophilia A.本發明尤其提供編碼因子VIII變異體之密碼子經改變聚核苷酸以在哺乳動物細胞中表現。在一些實施例中,本發明亦提供用於治療A型血友病之哺乳動物基因治療載體及方法。