Phase 1 KLH Challenge

The ability of AT-1501 to block immunoglobulin class switching in healthy subjects who have received a Keyhole Limpet Hemocyanin (“KLH”) challenge was explored in a subset of the 8 mg/kg cohort of the Phase 1 safety study where KLH, a shellfish protein, was injected subcutaneously in four subjects. In the control subject that did not receive AT-1501, there was a robust antibody response to the foreign KLH protein which peaked at 15 days. AT-1501, however, successfully completely abrogated an immune response to KLH in two of the three treated subjects and reduced the immune response in the third treated subject.