Semaglutide Testing
GLP-1 receptor agonist with extended half-life via a C18 diacid albumin-binding chain. The branded versions are Ozempic and Wegovy.
Mechanism of action
Semaglutide is a GLP-1 receptor agonist with an Aib substitution at position 2 (DPP-4 resistance) and a C18 fatty-diacid side chain at Lys26 that drives reversible albumin binding. Albumin reservoir behavior — not slow clearance per se — extends pharmacokinetics to a once-weekly dosing window. Receptor binding triggers glucose-dependent insulin secretion, glucagon suppression, slowed gastric emptying, and hypothalamic satiety signaling.
Sequence & structure
31-residue peptide with two non-natural modifications. The γGlu-γGlu spacer between Lys26 and the C18 diacid is critical — incorrect spacer length is a frequently observed synthesis defect.
Research areas
- ●Type 2 diabetes (FDA-approved as Ozempic)
- ●Chronic weight management (Wegovy)
- ●Cardiovascular risk reduction (SELECT trial)
- ●MASH / NASH
- ●Addiction and reward research
Dosing in the literature
Clinical: titrated from 0.25 mg weekly up to 2.4 mg (Wegovy) or 2.0 mg (Ozempic). Research compounding is often supplied at 5–10 mg/vial. Under-fill of 10–30% vs. label is the single most common QC failure we see across compounded vials.
For research/informational purposes only — not medical advice.
What we test on Semaglutide
Apollo runs a 60-minute shallow RP-HPLC gradient (0.1% TFA / acetonitrile, C18, 214 nm) capable of resolving des-Aib2 from main peak. Identity by LC-MS/MS on Orbitrap; we report intact mass (±5 ppm), top-down sequence confirmation, and free C18 diacid quantitation. Counter-ion by ion chromatography; water by Karl Fischer; endotoxin by kinetic chromogenic LAL.
- ✓RP-HPLC purity (UV 214 nm)
- ✓LC-MS/MS identity (Orbitrap)
- ✓Counter-ion / residual TFA
- ✓Water content (KF)
- ✓Endotoxin (LAL, USP <85>)
Common impurities & failure modes
- Des-Aib2 truncation
Loss of Aib at position 2 destroys DPP-4 resistance — even 1–2% of this impurity meaningfully changes pharmacokinetics. Co-elutes near the main peak on standard methods; requires shallow gradient or LC-MS to resolve.
- Free C18 diacid
Unconjugated fatty diacid from incomplete Lys26 acylation. Visible as a late-eluting hydrophobic peak; quantified separately.
- Deamidation isomers (Asn → Asp / iso-Asp)
Forms during storage in solution; the iso-Asp variant is biologically inert and is a primary stability indicator.
- Oxidation at Trp/Met
Trp25 oxidation shows +16 Da mass shift; accelerated by light and trace metals.
- TFA counter-ion residue
TFA at the gram scale is cytotoxic; injectable-grade material should be confirmed as acetate or HCl salt.
Storage & stability
2–8 °C lyophilized; reconstituted vials stable ~28 days refrigerated, away from light.
Regulatory status
FDA-approved (Ozempic 2017, Wegovy 2021, Rybelsus oral 2019).
Frequently asked questions
How long does semaglutide testing take?+
Standard 5 business days or less for most tests for purity + identity + impurity profile. Rush 2–3 day available.
Can you tell counterfeit semaglutide from real?+
Yes — intact-mass LC-MS immediately reveals substituted peptides (we have seen 'semaglutide' vials test as liraglutide or as plain mannitol). Truncated synthesis products are also resolved.
What purity should genuine semaglutide hit?+
Reference standard (Novo Nordisk) is ≥99% by HPLC. Well-made research material typically lands 95–98%. Anything below 90% should be considered substandard.