Researchers writing in the British Journal of Pharmacology report that LVV-haemorphin 7, a peptide fragment derived from hemoglobin, acted as a positive modulator of the GLP-1 receptor, the same receptor targeted by semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound).

The work was done entirely in cells: human embryonic kidney (HEK293) cells and a rat insulinoma line (INS-1 832/3), plus computational docking. No animals were dosed and no human trial is reported. Haemorphins are short peptides released from hemoglobin that act on G protein-coupled receptors, and the authors note that reduced serum haemorphin levels have been associated with diabetes and obesity.

Key results

LVV-H7 shifted GLP-1's dose response to the left, meaning less GLP-1 was needed for the same receptor signal. The effect appeared with GLP-1 itself but not with orforglipron (LY3502970), the small-molecule oral candidate, which the authors read as evidence of a peptide-peptide interaction rather than a general receptor effect.

In the insulinoma cells, LVV-H7 potentiated GLP-1-induced insulin expression and its protective effect against glucose-induced cytotoxicity. It slightly reduced GLP-1's association kinetics without changing its binding properties.

The allosteric site

Docking pointed to a putative allosteric binding pocket at the junction between the helical and extracellular domains of the receptor, with Trp6 of LVV-H7 and a specific set of receptor residues flagged as critical. Importantly, the active GLP-1 and receptor complex had to already be formed for LVV-H7 to do anything, which makes this a modulator rather than an agonist in its own right.

That selectivity is the genuinely interesting part. A molecule that only amplifies an existing signal behaves very differently from one that switches a receptor on, and the field has spent years looking for exactly that profile on this receptor.

Limitations

This is cell-based and computational work. There is no in vivo model, no dosing, and no measurement of glucose or weight in a living animal, let alone a person. The association between low serum haemorphin levels and diabetes or obesity is cited as background, not demonstrated here, and association is not causation.

A first for haemorphins

The authors describe this as the first Class B GPCR shown to be modulated by haemorphins, which is a real addition to how this receptor family is understood. Whether any of it survives contact with a whole organism is the open question.