The present invention provides stabilized activin IIB receptor polypeptides and proteins capable of binding and inhibiting the activities of activin A, myostatin、 or GDF-11. The present invention also provides polynucleotides, vectors and host cells capable of producing the stabilized polypeptides and proteins. Compositions and methods for treating muscle-wasting diseases and disorders are also provided.本發明提供穩定化的激活素(activin)IIB受體多肽以及能結合與抑制激活素A、肌肉生長抑制素(myostatin)或GF-11之活性的蛋白質。本發明亦提供多肽、載體以及能產生穩定化的多肽與蛋白質的宿主細胞。亦提供用於治療肌肉瘦弱疾病與疾患之組成物與方法。