GLP-1 (TRZ)

GLP-1 (TRZ) is a synthetic 39-residue polypeptide designed by merging elements of the native GIP and GLP-1 sequences with structural modifications intended to improve stability. Alanines at positions 2 and 13 are replaced with α-aminoisobutyric acid (Aib), a non-proteinogenic residue that resists cleavage by DPP-4. The lysine at position 20 is modified with a γ-glutamyl-(AEEA)₂ linker bearing a C20 fatty diacid (icosanedioyl). Biophysical studies and in silico modeling have characterized how the diacid moiety drives association with serum albumin, while the Aib substitutions reduce proteolytic susceptibility. Chemical synthesis efforts have confirmed molecular identity and purity via mass spectrometry and amino acid analysis.

Cell-based assays using heterologous cells expressing human GIPR or GLP-1R have characterized GLP-1 (TRZ)'s engagement at each receptor. At GIPR, the peptide activates cAMP accumulation and β-arrestin recruitment with potency and efficacy comparable to native GIP. At GLP-1R, it shows reduced potency and partial agonism relative to native GLP-1, with minimal β-arrestin translocation — indicating a biased signaling profile that favors the G-protein (cAMP) pathway at that receptor. Willard et al. (2020) characterized these biased-signaling properties across low-density Gαs-coupled and β-arrestin recruitment assays, establishing distinct intracellular signaling patterns at the two receptors. Binding kinetics and affinity assays have further mapped differential receptor engagement between the two targets.

Single-particle cryo-EM has been applied to examine how GLP-1 (TRZ) binds its target receptors at near-atomic resolution. Sun et al. (2022, PNAS) solved structures of GLP-1R and GIPR complexes with GLP-1 (TRZ), revealing that the peptide's N-terminal residues form hydrogen bonds and ionic interactions with conserved residues at each receptor in patterns that parallel the binding modes of the respective native incretins. In the GLP-1R complex, the α-carbon backbone closely mimics GLP-1 contacts, but shifts associated with the Aib substitutions and the fatty-diacid tail alter receptor conformation relative to native-peptide-bound structures. In the GIPR complex, the peptide more closely mirrors native GIP's binding mode, forming a network of polar contacts at the receptor interface. The C-terminal region — including the fatty-acid chain — was not resolved, consistent with conformational flexibility. Structural comparisons and molecular-dynamics analyses from that study examined the basis for dual-receptor engagement with distinct pharmacological profiles at each target.

Pharmacokinetic studies have focused on the contribution of GLP-1 (TRZ)'s modified structure to circulating exposure. In vitro assays demonstrate that the C20 fatty-diacid side chain drives substantial association with human serum albumin (HSA): in the presence of HSA, the peptide's apparent receptor potency is shifted, consistent with a large fraction remaining albumin-bound under physiological conditions. Combined with resistance to proteolysis conferred by Aib substitutions, this albumin association extends the plasma half-life of the parent peptide substantially relative to native incretins. Sun et al. (2022, Nat Rev Drug Discov) examined pharmacokinetics and receptor-occupancy modeling in preclinical and clinical research contexts. Metabolic studies indicate the peptide undergoes both backbone proteolysis and fatty-chain β-oxidation, with the parent peptide remaining detectable over extended periods.

GLP-1 (TRZ) has been examined in registered clinical studies within metabolic-research contexts; those records are listed in the references for study-design context only, and no efficacy claims or clinical verdicts are drawn from them. The remainder of the characterization rests on in vitro and structural work: translational studies in rodent models have examined receptor engagement and downstream signaling in GLP-1R/GIPR systems, complementing the in vitro mechanistic and cryo-EM structural characterization summarized above.