What Is TG103? Definition and What Research Reports

Definition

TG103 is the development code for an investigational long-acting GLP-1/Fc fusion protein — a molecule in which a glucagon-like peptide-1 (GLP-1) analogue is genetically fused to the Fc (crystallisable fragment) portion of an immunoglobulin, a design intended to extend circulating half-life so that dosing can be infrequent. Researchers evaluated TG103 in a single ascending dose study in Chinese healthy subjects that characterised its safety, pharmacokinetics and pharmacodynamics (PMID 37062422), and in a randomized, double-blind, placebo-controlled, multiple-dose phase 1b study in participants who were overweight or obese (PMID 38807146). In the literature the term "TG103" refers to that specific clinical-stage biologic candidate, not to a generic research peptide sold for laboratory work. This page is for educational purposes only and is not medical advice; consult a licensed physician about any medical question.

What Class of Molecule Is TG103?

TG103 belongs to the incretin mimetic class. Incretins are gut hormones released after eating; GLP-1 is the best characterised of them, and drugs that activate the GLP-1 receptor are grouped together as GLP-1 receptor agonists. Where native GLP-1 is degraded within minutes, pharmaceutical developers extend the peptide's duration of action using several engineering strategies — amino-acid substitutions, fatty-acid acylation, or, as in TG103, fusion to an antibody Fc domain. The Fc fragment engages the neonatal Fc receptor recycling pathway, which is the standard rationale for turning a short-lived peptide into a long-acting biologic.

That construction places TG103 in a different practical category from the small synthetic peptides that dominate informal peptide discussions. It is a recombinant fusion protein produced for clinical development and studied under a formal trial framework, as the published phase 1 and phase 1b reports describe (PMID 37062422, PMID 38807146).

Terms that appear alongside TG103

• GLP-1 receptor agonist — the pharmacological class TG103 was designed to fall into.
• Fc fusion protein — the structural format used to prolong exposure.
• Single ascending dose (SAD) — the phase 1 design used in healthy volunteers (PMID 37062422).
• Multiple-dose phase 1b — the follow-on design used in participants who were overweight or obese (PMID 38807146).
• Incretin co-agonist — a related but distinct group of molecules that hit two or more receptors, reviewed separately in the cardiometabolic literature (PMID 40949933).

How the Term Is Used in Peptide Research

Within published research, TG103 appears in three recurring contexts. First, as the subject of its own early-phase clinical pharmacology reports, where the endpoints are tolerability, exposure over time, and pharmacodynamic markers rather than long-term outcomes (PMID 37062422). Second, as a named entry in pipeline reviews: a 2025 systematic review of emerging pharmacotherapies for obesity catalogued candidate agents at various stages of development, of which long-acting GLP-1 receptor agonists form one branch (PMID 39952695). Third, as a comparator or contextual example in discussions of how incretin-based drugs are evolving from single-receptor agonists toward co-agonists, a trajectory summarised in a 2025 review of incretin co-agonists in cardiometabolic care (PMID 40949933).

Because TG103 is an investigational biologic rather than an approved medicine, the literature about it is narrower than for marketed GLP-1 drugs. The published record is dominated by early clinical pharmacology, not by large outcome trials.

What the Published Literature Reports

The first-in-human work was a single ascending dose study in Chinese healthy subjects, in which researchers reported on the safety, pharmacokinetics and pharmacodynamics of TG103 after one subcutaneous administration (PMID 37062422). The design — escalating single doses in healthy volunteers with safety monitoring and serial blood sampling — is the standard route by which a long-acting fusion protein's exposure profile is first mapped, and the study's stated purpose was to establish that profile for a novel GLP-1/Fc construct (PMID 37062422).

The subsequent step was a randomized, double-blind, placebo-controlled, multiple-dose phase 1b study in participants who were overweight or obese, in which researchers again assessed safety, tolerability, pharmacokinetics and pharmacodynamics, this time with repeated administration in the population of interest rather than in healthy volunteers (PMID 38807146). Placebo control and blinding matter here: they are what allow investigators to separate drug-attributable changes from expectation and background variation in an early study.

At the review level, the 2025 systematic review of emerging obesity pharmacotherapies placed candidates such as long-acting GLP-1 receptor agonists within a crowded development landscape, noting that many agents remain in early or mid-stage evaluation (PMID 39952695). A parallel 2025 review of incretin co-agonists described the broader shift in cardiometabolic pharmacology toward multi-receptor molecules and discussed the efficacy and safety evidence base accumulating for that class (PMID 40949933).

Reported Adverse Events: What Studies Report

Early-phase reports are the primary source of safety information for TG103. The single ascending dose study in healthy Chinese subjects was designed with safety as a co-primary focus and reported on tolerability across escalating single administrations (PMID 37062422). The multiple-dose phase 1b study in participants who were overweight or obese likewise reported safety and tolerability alongside pharmacokinetic and pharmacodynamic endpoints under placebo-controlled conditions (PMID 38807146).

More broadly, the review literature notes that gastrointestinal effects are the characteristic tolerability issue for incretin-based agents as a class, and the 2025 incretin co-agonist review examined efficacy and safety across that class rather than for any single molecule (PMID 40949933). The 2025 systematic review of emerging obesity pharmacotherapies similarly framed safety as an open question for agents still moving through development (PMID 39952695). Phase 1 sample sizes are small and durations short by design, so they cannot characterise uncommon or delayed events.

Published Studies at a Glance

What the Literature Does Not Establish

The published record for TG103 is early-phase. Studies of this type are built to describe exposure and short-term tolerability, not to demonstrate long-term efficacy, cardiovascular outcomes, or comparative advantage over approved GLP-1 receptor agonists. The 2025 systematic review of emerging obesity pharmacotherapies underscored that a large number of candidates are still working through clinical development, with evidence maturity varying widely between them (PMID 39952695). Readers encountering the term should therefore treat it as a development code attached to a specific investigational biologic with a limited published evidence base — not as an established therapy, and not as something with a defined role outside clinical research.

Nothing on this page describes how any substance should be used. It summarises what the cited publications reported about study design, population and endpoints. This page is for educational purposes only and is not medical advice; consult a licensed physician for individual guidance.

References

• Safety, pharmacokinetics, and pharmacodynamics of TG103, a novel long-acting GLP-1/Fc fusion protein after a single ascending dose in Chinese healthy subjects (European Journal of Pharmaceutical Sciences, 2023)
• Safety, tolerability, pharmacokinetics, and pharmacodynamics of TG103 injection in participants who are overweight or obese: a randomized, double-blind, placebo-controlled, multiple-dose phase 1b study (BMC Medicine, 2024)
• Emerging pharmacotherapies for obesity: A systematic review (Pharmacological Reviews, 2025)
• Efficacy and safety of incretin co-agonists: Transformative advances in cardiometabolic healthcare (World Journal of Cardiology, 2025)