All other aesthetic neurotoxins are a 'Type A' protein. Myobloc is a unique 'Type B' protein. While both types work by relaxing muscles, your body can sometimes develop antibodies to the Type A protein, making it less effective over time.
Because Myobloc has a different molecular structure, these antibodies don't recognize it. It effectively bypasses the resistance, allowing you to achieve the beautiful, smooth results you thought were gone for good.