Following 12 weeks of treatment in a biopsy-confirmed, diet-induced obese mouse model of NASH, ALT-801, a GLP-1R/GCGR dual agonist, was shown to significantly lower body weight, plasma cholesterol and liver enzymes, liver weight, liver steatosis, histological markers of inflammation and fibrosis and, importantly, composite NAS, compared to vehicle-treated control. Remarkably, most of these parameters improved to the normal lean (not shown) range while the fibrosis improvement was comparable to semaglutide and elafibranor treatments. In addition, the study revealed that PK properties of ALT-801 were comparable to those of semaglutide and therefore consistent with a weekly dosing schedule and similar exposure for patients, but with a delayed Tmax and lowered Cmax, which may provide reduced peak to trough ratios during treatment.
Treatment of DIO-NASH mice with ALT-801 resulted in greater reductions in most measures of NASH compared to either semaglutide or elafibranor, and ALT-801 administration significantly reduced the inflammatory marker Gal-3 and fibrosis marker Col1A1, with Gal-3 reduction at a greater degree than either comparator drug. All DIO-NASH animals treated with ALT-801 improved composite NAS to ≤ 3, which was driven by reductions in steatosis, lobular inflammation, and hepatocellular ballooning scores. The extent of clearance of hepatic steatosis with ALT-801 is particularly striking in comparison to the GLP-1R only agonist, semaglutide (Fig. 3).
Equivalent doses of ALT-801 and semaglutide were used throughout this study. While an approximately seven-fold higher dose of semaglutide (based on allometric scaling) was recently approved for weight loss in overweight and obese individuals, the 12% weight loss effected by semaglutide in this study is similar to that observed clinically with high dose semaglutide7 supporting the dose used in this study. Elafibranor has been employed here as a positive control at the dose used in other rodent models of NASH42,43.
While previous studies with investigational NASH agents that have reached clinical testing have reported body weight, liver weight, plasma lipids, AST, ALT, or histological findings27,28,29,30, only GLP-1 based approaches have been associated with significant weight loss in published trials to date. Significant improvement of NASH has been associated with greater than 5% weight loss, but resolution of fibrosis appears to require > 10% body weight loss for optimal effects9,11,31,32,33. In this context the pronounced weight loss effects observed with ALT-801, together with the demonstrated effects on the other NASH indices reported here, whether directly or indirectly resulting from weight loss, is especially important. It is worth noting that while GCGR are present in livers of rodents and primates, GLP-1R are not34,35.
The chemical structure of ALT-801 utilizes a stabilized peptide structure including sequence elements of both GLP-1 and glucagon, coupled with EuPort™ modification, a proprietary glycolipid moiety designed to achieve a prolonged duration of action consistent with weekly dosing20. The glycolipid surfactant, which provides near quantitative but transient binding to serum albumin (estimated as > 99%), helps prevent proteolysis and clearance by glomerular filtration. In addition, the surfactant-like features of the EuPort™ domain lead to formation of micelles, which, upon s.c. administration, slow the release of the drug substance into the blood stream, as evidenced by the reduced Tmax and Cmax and prolonged AUC. While glycolipid surfactant conjugation has not been used previously in peptide design, injection site depot formation and serum albumin binding are recognized design approaches and have similarities to earlier drug designs36,37,38,39.
Pharmacokinetic assessment of ALT-801 in mice demonstrated reduced Cmax but with similar AUC0–inf values (50% and > 86%, respectively) compared to the semaglutide parameter values. These parameters are potentially attractive in that there is potential for lowered peak to trough ratio during dosing40 and therefore potential for a decreased gastrointestinal side effect profile for ALT-801 compared to those typically seen with GLP-1 agonists41.
Results of this study indicate that a GLP-1R/GCGR dual agonist (ALT-801) performed better than GLP-1R and PPAR-α/δ agonists in treating most NASH parameters. Seminal studies in DIO mice demonstrated that GLP-1R/GCGR dual agonists had improved effects on weight loss compared to GLP-1R agonists, while maintaining glucoregulatory action12,13,18. Moreover, ALT-801 is a balanced dual receptor agonist19,20 with closely matched potencies at the GLP-1R and GCGR (39 pM and 42 pM, respectively20), as distinguished from the dual agonists cotadutide42 and BI45690643, which appear to be biased 5:1 and 7.5:1, respectively, toward GLP-1R activation. A study that evaluated GLP-1R/GCGR dual agonists of varying ratios of potency at the GLP-1R and GCGR, in essence evaluating the pharmacodynamic effects of dual agonists that were either balanced in their receptor activation potencies or biased toward one receptor or the other, indicated that a dual agonist with near balanced activity at GLP-1R and GCGR was associated with the greatest weight loss and with glycemic control18. The potency and efficacy of ALT-801 is further demonstrated by the remarkable weight loss effected by a single dose of 10 nmol/kg to the vehicle group on day 63 (Fig. 2). Given this background and the fact that the apparent potency of ALT-801 for the GLP-1R is comparable to that of semaglutide (EC50 of 39 pM and 15 pM, respectively20) it is reasonable to conclude that GCGR activation is responsible for the improved activity of ALT-801 over semaglutide in this NASH model.
Similarly, another study compared body weight, food consumption, and total energy expenditure outcomes for GLP-1R/GCGR dual agonist and a GLP-1R agonist in DIO mice and DIO monkeys16. Results of this study indicated that both agonists improved glycemic control; however, the dual agonist elicited a greater reduction in body weight in both species relative to the GLP-1R agonist alone. Notably, the dual agonist was able to elicit greater body weight loss in DIO monkeys at a tenfold lower dose than the GLP-1R agonist, demonstrating greater efficacy. That study also demonstrated that a GLP-1R/GCGR dual agonist induced body weight loss across species, which is promising for ALT-801 development to treat NASH and the accompanying liver fibrosis. ALT-801 (denoted as Compound 17) has also been shown to reduce blood glucose in the diabetic db/db mouse model at least as well as an equivalent dose of semaglutide20, suggesting that the glucoregulatory effects of the GLP-1R activation by ALT-801 were not disrupted by simultaneous agonism of the GCGR. While previous studies have compared GLP-1R/GCGR and GLP-1R agonists, the current study appears to be the first to directly compare a GLP-1R/GCGR and a PPAR-α/δ agonist, demonstrating statistically improved activity of ALT-801 over elafibranor in most NASH measures.
Overall, the potential for lower side effects related to lower Cmax values, coupled with improvements of body weight, liver pathology, and metabolic parameters in this DIO-NASH mouse model, highlight ALT-801 as an attractive new drug candidate for the treatment of NASH and human clinical studies are underway.