CT-388vsL-Carnitine

CT-388 is a once-weekly subcutaneous dual GLP-1/GIP receptor agonist, mechanistically similar to tirzepatide but with a distinct molecular structure designed for differentiated pharmacology. Activation of both receptors produces complementary metabolic effects: GLP-1 receptor agonism centrally suppresses appetite through hypothalamic and brainstem signalling, slows gastric emptying, and stimulates glucose-dependent insulin secretion from pancreatic beta cells, while GIP receptor agonism enhances beta-cell insulin response, modulates lipid handling in adipose tissue, and amplifies the central anorectic effect of GLP-1 through distinct hypothalamic neuronal circuits.

The molecule was engineered with a balanced potency profile across the two receptors and incorporates fatty acid acylation that enables strong albumin binding, extending half-life to approximately one week. This pharmacokinetic profile supports once-weekly subcutaneous dosing with stable plasma exposure across the dosing interval, which is associated with better gastrointestinal tolerability than less stable formulations that produce sharp peaks and troughs.

In the Phase 2 obesity trial of 469 participants, CT-388 produced up to 22.5% placebo-adjusted body weight reduction at 48 weeks at the highest dose. The weight-loss curve had not yet plateaued at the end of the trial, suggesting further reductions might be achievable with longer dosing. Roche acquired Carmot Therapeutics in late 2024 specifically to obtain CT-388, positioning it as their lead anti-obesity asset competing directly against tirzepatide and the next-generation Lilly and Novo Nordisk pipeline.

L-Carnitine plays an indispensable role in cellular energy metabolism as the sole carrier molecule for transporting long-chain fatty acids (14+ carbons) across the inner mitochondrial membrane, which is otherwise impermeable to them. This transport system, known as the carnitine shuttle, is the rate-limiting step for fatty acid beta-oxidation — without carnitine, long-chain fats simply cannot be burned for energy.

The shuttle operates through a three-enzyme system. First, carnitine palmitoyltransferase I (CPT-I), located on the outer mitochondrial membrane, conjugates carnitine to a fatty acyl-CoA molecule, forming acylcarnitine. This acylcarnitine crosses the inner membrane via the carnitine-acylcarnitine translocase (CACT). Inside the mitochondrial matrix, carnitine palmitoyltransferase II (CPT-II) releases the fatty acid (as acyl-CoA) for beta-oxidation while regenerating free carnitine, which shuttles back out. Each cycle of beta-oxidation cleaves two carbons from the fatty acid chain, producing acetyl-CoA (which enters the citric acid cycle), FADH2, and NADH — generating substantial ATP.

Beyond fat transport, L-carnitine serves additional metabolic functions. It buffers the acyl-CoA/CoA ratio in cells, preventing toxic accumulation of acyl-CoA intermediates. It supports branched-chain amino acid metabolism and may improve mitochondrial function in aging tissues. In people with genuine carnitine deficiency (genetic or dialysis-related), supplementation produces dramatic improvements in energy and fat metabolism. However, in individuals with normal carnitine levels, supplementation has shown more modest effects, as the carnitine shuttle is rarely the limiting factor when carnitine is already adequate.