Treatment with the dual-incretin agonist DA-CH5 demonstrates potent therapeutic effect in a rat model of Wolfram Syndrome

**Background:** Wolfram Syndrome (WS) is a rare, progressive neurodegenerative disorder caused by mutations in the WFS1 gene, characterized by diabetes mellitus, optic nerve atrophy, deafness, and a median lifespan of 30-40 years. No cure exists. Incretin mimetics, particularly GLP-1 receptor agonists like liraglutide, have shown disease-modifying potential in preclinical and clinical WS studies. Dual agonists targeting both GLP-1 and GIP receptors are reportedly more efficacious and better tolerated. This study evaluated the therapeutic potential of the dual agonist DA-CH5 in a Wfs1 knock-out (KO) rat model.

**Methods:** Eight-month-old male Wfs1 KO rats and wild-type (WT) controls were continuously treated with DA-CH5 (25 nmol/kg, s.c., daily) or saline for 4 months (n=8-10/group). An acute 7-day screening paradigm in 5-month-old rats compared DA-CH5, DA-JC4 (another dual agonist, 25 nmol/kg), liraglutide (25 nmol/kg), and saline. Glycemic profile (intraperitoneal glucose tolerance test, IPGTT; area under the curve, AUC; serum insulin and C-peptide), visual acuity (optomotor task), and hearing sensitivity (distortion product otoacoustic emissions, DPOAEs) were monitored longitudinally at 8 (pre-treatment), 10.5, and 12 months. Pancreata and retinas were harvested at 12 months for immunohistological analysis of endocrine islet composition (insulin+, glucagon+, somatostatin+ cells) and retinal ganglion cell (RGC) density (Brn3a+ cells). Supportive insulin was given to hyperglycemic KO rats (basal glucose ≥10 mmol/l).

**Key Results:** - **Acute treatment:** In 5-month-old symptomatic KO rats, 7-day DA-CH5 and DA-JC4 normalized glucose intolerance (AUC not significantly different from WT), while equimolar liraglutide did not. DA-CH5 significantly improved glucose-stimulated serum insulin and C-peptide secretion in KO rats (p<0.05). - **Long-term glycemic control:** At 8 months, KO rats were severely glucose intolerant (mean AUC 3198 vs. WT). DA-CH5 treatment reversed this: at 10.5 months, DA-CH5-treated KO rats had significantly lower AUC than saline-treated KO rats (p<0.01) and were not different from WT. This effect was maintained at 12 months (p<0.05). No significant differences in serum insulin or C-peptide were observed between DA-CH5 and saline KO groups at 10.5 or 12 months, but C-peptide index improved. - **Pancreatic histology:** Saline-treated KO rats had enlarged pancreata (p<0.05), reduced endocrine islet area (p<0.01), and disrupted islet architecture with a ~61% reduction in beta-cell density and a ~4-fold increase in delta-cell density. DA-CH5 treatment normalized pancreatic mass, increased islet area (p<0.05), partially restored beta-cell density (~32% reduction vs. WT, not significant), and normalized alpha- and delta-cell densities. - **Visual function:** At 8 months, KO rats had impaired visual acuity (p<0.01). At 10.5 months, DA-CH5-treated KO rats showed significantly better acuity than saline-treated KO rats (p<0.05) and were not different from WT. At 12 months, acuity remained better preserved in DA-CH5-treated KO rats. Cataract severity did not differ between groups. - **Retinal ganglion cells:** Brn3a+ RGC density was significantly lower in saline-treated KO rats vs. WT (p<0.01). DA-CH5-treated KO rats had no significant difference in RGC density compared to WT, indicating neuroprotection. - **Hearing:** Hearing sensitivity was impaired in KO rats at 8 months and remained stable; DA-CH5 did not rescue hearing loss.

**Clinical Implications:** This study provides the first preclinical evidence that long-term dual incretin agonist therapy (DA-CH5) can reverse established glucose intolerance and preserve vision in a rat model of WS, even when treatment begins after symptom onset. The superior efficacy over mono-agonists (liraglutide) at equimolar doses suggests dual agonists may offer a more potent therapeutic option with potentially fewer gastrointestinal side effects. The findings support further investigation of dual incretin agonists, such as tirzepatide, in clinical trials for WS patients, emphasizing the need for early diagnosis to maximize therapeutic benefit.