Ascletis' announces promising results for ASC47 adipose-targeted THRβ

Ascletis Pharma has announced that results of its Phase I single ascending dose (SAD) study in Australia in subjects with elevated low-density lipoprotein cholesterol (LDL-C) (NCT06427590) for its first-in-class, muscle-preserving weight loss drug candidate - ASC47 for the treatment of obesity - demonstrated a half-life of 21 days in subjects with elevated LDL-C >110 mg/dL (2.8mmol/L) who received ultra-long acting, subcutaneously injected ASC47, supporting once-monthly administration in patients with obesity. Furthermore, ASC47 demonstrated target engagement with significant reductions of lipid biomarkers at day 29 after single subcutaneous (SQ) injections.

The SAD study of ASC47 monotherapy in subjects with elevated LDL-C has five cohorts with subjects receiving 10mg, 30mg, 90mg, 180mg, 360mg ASC47 or placebo via SQ injections. The subjects have multiple outpatient visits over eight weeks after the single SQ injections of ASC47 or placebo. Dosing of the first three cohorts (10mg, 30mg and 90mg) has been completed where a total of 20 subjects with elevated LDL-C have received ASC47 or placebo.

ASC47 demonstrated a favourable tolerability profile with no serious adverse events (SAEs) and no discontinuations due to adverse events (AEs). The majority of AEs were mild (grade 1). Only two subjects (2/20) reported mild injection site reactions (grade 1 only). No gastrointestinal and cardiac AEs were reported. No abnormal liver enzymes were reported. No clinically meaningful findings in laboratory tests, electrocardiograms, vital signs, or physical examinations were observed.

Based on safety, pharmacokinetic and target engagement data of the SAD study of ASC47 monotherapy in subjects with elevated LDL-C, the second Phase I study (SAD study of ASC47 monotherapy in patients with obesity) has been initiated in Australia. Topline data are expected in the first quarter of 2025.

ASC47 has two additional Phase I studies in Australia: multiple ascending dose (MAD) study of ASC47 monotherapy in patients with obesity, and MAD study of ASC47 in combination with tirzepatide or semaglutide in patients with obesity. Detailed clinical data from these trials are expected to be presented at medical conferences in 2025.

ASC47 monotherapy demonstrated dose-dependent healthy weight loss (muscle-preserving weight loss) in two head-to-head diet-induced obese (DIO) mouse studies compared to semaglutide and tirzepatide. In both studies, ASC47 demonstrated clinically meaningful weight loss at low doses of 15mg/kg and 45mg/kg (once every two weeks or once weekly) via SQ injections. These doses in mice are predicted to translate into clinically applicable doses in humans.

Compared to semaglutide (30nmol/kg, once daily, SQ), a clinically relevant dose of ASC47 (45 mg/kg, once every two weeks, SQ) reduced total fat mass (-63.5%, p=0.007 vs semaglutide), statistically and significantly more than semaglutide (-39.6%) in a DIO mouse study (Table 1). ASC47 increased total muscle mass (+5.8%, p<0.0001 vs semaglutide) compared to a decline in total muscle mass of semaglutide (-9.3%) (Table 1). Total body weight reduction was similar between ASC47 (-24.6%) and semaglutide (-23.1%) (Table 1), even though caloric intake reduction in ASC47-treated DIO mice was significantly less than semaglutide-treated DIO mice.

Table 1: ASC47 reduced more fat and increased muscle in a dose-dependent manner compared to semaglutide in a head-to-head DIO mouse study. Note: Q2W: once every two weeks; SQ: subcutaneous; QD: once daily

Compared to tirzepatide (3 nmol/kg, once daily, SQ), a clinically relevant dose of ASC47 (45 mg/kg, once weekly, SQ) reduced total fat mass (-68.0%, p=0.01 vs tirzepatide), statistically and significantly more than tirzepatide (-50.4%) in a DIO mouse study (Table 2). ASC47 increased total muscle mass (+8.1%, p=0.004 vs tirzepatide) compared to a decline in total muscle mass of tirzepatide (-3.8%) (Table 2). Total body weight reduction was similar between ASC47 (-23.6%) and tirzepatide (-22.4%) (Table 2), even though caloric intake reduction in ASC47-treated DIO mice was significantly less than tirzepatide-treated DIO mice.

Table 2: ASC47 reduced more fat and increased muscle in a dose-dependent manner compared to tirzepatide in a head-to-head DIO mouse study. Note: QW: once weekly; SQ: subcutaneous; QD: once daily

As a potential first-in-class muscle-preserving weight loss drug candidate, ASC47 is an adipose-targeted thyroid hormone receptor beta (THRβ) selective small molecule agonist. ASC47 is a new molecular entity (NME) discovered and developed in-house at Ascletis.

ASC47 possesses unique and differentiated properties to enable adipose targeting, resulting in dose-dependent high drug concentrations in the adipose tissue. Adipose-targeted delivery of ASC47 differentiates ASC47 from other THRβ selective agonists, which are primarily liver-targeted.

Expression of THRβ is high in adipose tissue as well as in liver tissue. As such, clinically meaningful weight loss requires high concentrations of THRβ selective agonists in adipose tissue. In recent years, a number of THRβ selective agonists showed success for treatment of metabolic dysfunction-associated steatohepatitis (MASH, a liver disease) through liver-targeted delivery. However, these THRβ agonists lack adipose-targeting properties. For example, there is significant high concentration of resmitirom in liver tissue but little or no resmitirom in adipose tissue. ASC47 possesses both THRβ selectivity and adipose-targeted delivery. Targeted delivery of ASC47 to the adipose tissue enables the use of low and clinically applicable doses of ASC47 for the treatment of obesity.