Baxter International Inc., of Deerfield, Ill., said it acquired Aesrx LLC, of Newton, Mass., gaining rights to Aes-103, developed in collaboration with researchers at the NIH's National Center for Advancing Translational Sciences, for treating the underlying mechanism of sickle cell disease. The drug is designed to bind directly to hemoglobin and to change its structure, thereby reducing the sickling of red blood cells. Under the terms, Baxter made an initial payment to acquire the company and may make additional future payments based on specified development, regulatory and commercial milestones. The specific terms of the agreement were not disclosed.