Structure−Activity and Protraction Relationship of Long-Acting Glucagon-like Peptide-1 Derivatives:  Importance of Fatty Acid Length, Polarity, and Bulkiness

We here report a series of derivatives describing the structure-activity relationship around liraglutide, a once-daily human glucagon-like peptide-1 fatty acid derivative, with respect to potency as well as protraction in vivo. The spacer region between the fatty acid and the peptide is mostly important for potency, whereas the fatty acid or fatty acid mimetic is important for both potency and protraction. The length of the fatty acid is the most important parameter for protraction.