This Week in Peptide Research: Repurposed GLP-1 Drugs, an Engineered LL-37 Carrier, and Bone-Building Peptides in Kidney and Transplant Patients

Peptide Science Daily reviewed new PubMed listings for its tracked compounds from August 31 through September 6, 2026. It was a moderate week for new literature, with no new phase 3 trial readout, but five threads stood out: GLP-1 drugs studied or used off-label for surgical and bariatric complications, an engineered delivery system for the antimicrobial peptide LL-37, a newly reported brain mechanism for thymosin alpha-1, two papers on bone-building peptides in patients with kidney disease or organ transplants, and a small human study of afamelanotide's acute skin effects.

Two papers this week involved liraglutide, an approved GLP-1 receptor agonist marketed as Victoza and Saxenda, used or manufactured outside its core diabetes and weight-management role. A systematic review and meta-analysis in Cardiology in Review searched for randomized trials of perioperative subcutaneous liraglutide against placebo or usual insulin-based care in adults undergoing cardiac surgery. Across seven reports covering four trials and 446 randomized patients, the authors found no significant difference between liraglutide and comparators in 30-day mortality (1 of 161 patients versus 3 of 160), a composite of any postoperative complication, cardiac adverse events, hypoglycemia, or postoperative nausea and vomiting. The authors framed GLP-1 drugs as a theoretically attractive option for perioperative glucose control because they lower glucose only when it is elevated, but said the pooled trial data so far show no clear benefit or harm. Separately, in Pharmaceutical Research, a team primarily employed by the pharmaceutical company developing the product compared a chemically synthesized liraglutide against the original recombinant-origin reference drug, using structural, biophysical, NMR-based, and functional assays. They reported highly comparable secondary structure, assembly behavior, and GLP-1 receptor activity between the two products, with no evidence of abnormal aggregation, and concluded the approach offers a workable framework for evaluating synthetic peptide products referencing recombinant reference drugs.

A related case series in JCEM Case Reports described three patients with postbariatric hypoglycemia, a complication of Roux-en-Y gastric bypass surgery, who were treated off-label with tirzepatide, the approved dual GLP-1/GIP receptor agonist marketed as Mounjaro and Zepbound. All three had failed or only partially responded to conventional measures such as dietary changes and acarbose. After starting tirzepatide, the authors reported increased time in target glucose range, fewer and less severe hypoglycemic episodes, and reduced glucose variability. They described the finding as suggestive rather than conclusive and said larger studies are needed to confirm the effect and establish dosing.

Two papers concerned LL-37, an investigational human antimicrobial peptide with no FDA, EMA, or TGA approval. A team in China engineered a fusion protein linking LL-37 to ferritin light chain, designed to improve the peptide's poor natural stability and add targeting to inflammatory tissue through a receptor expressed on macrophages. In a murine sepsis model, the fusion protein retained LL-37's antimicrobial activity, showed added anti-inflammatory effects, reduced organ damage more than free LL-37, and showed no significant hemolytic activity, immunogenicity, or tissue toxicity in the reported safety evaluations. Separately, a Japanese observational study measured plasma LL-37 in 58 people with obstructive sleep apnea and 20 healthy controls. Plasma LL-37 was lower in participants with more severe apnea (mean 47.1 nanograms per liter in those with an apnea-hypopnea index of 15 or higher, versus 75.3 in those below that threshold) and correlated with several sleep and oxygenation measures. The authors proposed plasma LL-37 as a possible biomarker of sleep quality and oxygenation severity in obstructive sleep apnea, noting implications for infection risk given the peptide's role in host defense, though the study was observational and does not establish causation.

In neuroscience, a study published in Advanced Science reported a previously undescribed mechanism for thymosin alpha-1, a synthetic thymic peptide with unclear regulatory status: it is marketed as thymalfasin (Zadaxin) and approved in China and a number of other countries for chronic viral hepatitis and as an immune adjuvant, but has no FDA, EMA, or TGA approval. The researchers found that thymosin alpha-1 can bind a neuronal receptor called HCRTR1, normally associated with the orexin signaling system, and that this engagement suppresses a cell-death pathway called necroptosis in neurons. In mouse models of ischemic stroke, circulating thymosin alpha-1 levels were reduced and correlated with stroke severity, a pattern the authors said they also observed in stroke patients; deleting the gene that encodes the peptide worsened stroke injury in mice, while administering thymosin alpha-1 after stroke improved outcomes. The authors described the peptide as a candidate for further study as a neuroprotective agent, based on this preclinical and correlational human data rather than a clinical trial.

Two papers addressed bone-building peptides in patients with reduced kidney function. A retrospective single-center cohort in Archives of Osteoporosis followed 39 kidney, lung, and liver transplant recipients with severe post-transplant osteoporosis who were treated with teriparatide, an approved parathyroid hormone analog, for a median of about 22 months. Bone mineral density increased significantly at the lumbar spine, femoral neck, and total hip, and no episodes of graft rejection were observed; six patients had fractures after starting treatment, two of them during active therapy and four after it was stopped, and one patient developed hypercalcemia that led to discontinuation. The authors called the safety profile acceptable in this small, real-world cohort and said prospective studies are needed to define optimal use. A separate narrative review in the American Journal of Nephrology examined adynamic bone disease, a low-turnover bone disorder common in advanced chronic kidney disease that the authors attributed largely to sustained suppression of parathyroid hormone. The review concluded that intermittent PTH-analog therapy, particularly teriparatide, may improve bone formation markers and density in selected patients with this condition, while abaloparatide, a related approved osteoporosis drug, was described as mechanistically promising but not yet clinically validated in this setting.

Finally, a small exploratory study in Photochemical and Photobiological Sciences examined afamelanotide, an approved melanocortin-1 receptor agonist marketed as Scenesse for the light-sensitivity disorder erythropoietic protoporphyria. In nine healthy volunteers, researchers measured skin responses to a UVB dose series before and six days after a single 16-milligram afamelanotide implant. After treatment, the UV-induced erythema response was reduced and reflectance-based melanin density increased modestly, though visible melanin staining on biopsy was unchanged and the minimal erythema dose increase did not reach statistical significance. The study's authors disclosed research collaborations with Clinuvel Ltd, the company that markets afamelanotide, and described the findings as an early signal that its anti-inflammatory, photoprotective effects seen in laboratory studies may also occur in humans shortly after dosing, warranting further study in acute UV-related skin conditions.

This week's items span two systematic reviews or meta-analyses, two narrative reviews, two observational or case-series studies, two preclinical or comparability studies, and one small human physiology study. Liraglutide, tirzepatide, teriparatide, abaloparatide, and afamelanotide are approved drugs, but several uses described here, perioperative liraglutide, tirzepatide for postbariatric hypoglycemia, teriparatide in transplant recipients or chronic kidney disease, and afamelanotide in healthy volunteers, fall outside or beyond their approved indications. LL-37 remains investigational with no FDA, EMA, or TGA approval, and thymosin alpha-1's regulatory status is unclear, approved in China and other markets as thymalfasin but not by the FDA, EMA, or TGA. As with all research covered here, these are findings a given study reported, not established clinical fact or treatment guidance.