This gets cited here weekly, usually second-hand, so it is worth setting out what it does and does not establish.
The pharmacokinetics explain nearly every practical question asked here. Albumin binding above 99% slows clearance enough to make weekly dosing possible; a terminal half-life near a week means four to five weeks to steady state and therefore a four-week titration interval; subcutaneous bioavailability around 89% means injection site barely matters. Those three facts answer most timing questions before they are asked.
Where I think it is weakest: the follow-up is short relative to how long people actually take these drugs, so durability is an assumption here rather than a finding.
What would genuinely help is knowing which effects tachyphylax and which persist, because the answer explains why tolerability improves while the appetite effect keeps working. If the honest answer is that nobody knows, that is a useful answer and I would rather have it.
Figures above are from the primary publication rather than the press summary. If a number here disagrees with one you have, post yours and we will work out which of us is reading a secondary source.
NeuroNate said:The pharmacokinetics explain nearly every practical question asked here.
Semaglutide structural biology relevant to the pharmacology: semaglutide is a 31-amino acid peptide with 94% homology to native GLP-1(7-36). Three key modifications enable its pharmacokinetic profile:
- Aib8 substitution: DPP-4 resistance (prevents enzymatic degradation)
- Arg34 substitution: improved chemical stability
- C18 fatty diacid at Lys26: albumin binding → long half-life
These three modifications transform a peptide with a 2-minute half-life (native GLP-1) into one with a 168-hour half-life (semaglutide). A masterclass in peptide engineering.
NeuroNate said:The pharmacokinetics explain nearly every practical question asked here.
I read this differently from NeuroNate, on substance rather than tone. The mechanism is more central than most summaries suggest. Receptor agonism in the arcuate nucleus activates POMC neurons and inhibits AgRP/NPY signalling, and the downstream MC4R pathway is the same one disrupted in monogenic obesity — convergent genetic evidence that the target is the right one. Peripherally there is glucose-dependent insulin secretion, glucagon suppression and delayed gastric emptying, but the gastric component largely adapts over months while the central effect persists, which is why the durable effect is appetite rather than fullness.
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Browse GL BiochemPeptideChemSF said:The mechanism is more central than most summaries suggest.
Amycretin (AMY/GLP-1 dual agonist) emerging data relevant to the pharmacology: Phase 1 showed -13.1% body weight at only 12 weeks, the fastest trajectory ever seen for an anti-obesity agent[1].
Amylin receptor agonism enhances satiety signaling through the area postrema and reduces glucagon secretion. Combined with GLP-1R agonism, this dual mechanism may produce even greater efficacy than current agents.
Early-stage data — interpret with caution. But the trajectory is extraordinary.
[1] Novo Nordisk investor presentation, September 2023.
PharmacoVig_BOS said:Semaglutide structural biology relevant to the pharmacology: semaglutide is a 31-amino acid peptide with 94% homology to native GLP-1(7-36).
Same pattern here, and in the same order.