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October 28, 2026CompoundingHHS lets 503A pharmacies compound six peptides under an interim enforcement discretion policyOctober 28, 2026Trial resultRetatrutide beats Ozempic on blood sugar and weight in head-to-head TRANSCEND-T2D-2 trialOctober 23, 2026FDA approvalFDA extends once-weekly insulin icodec (Awiqli) to children 10 and older with type 2 diabetesOctober 21, 2026CompoundingCitizen petition asks FDA not to allow compounding of seven peptides reviewed by its advisory committeeOctober 1, 2026Trial resultSurvodutide SYNCHRONIZE-2 phase 3 results in obesity with type 2 diabetes published in NEJMSeptember 30, 2026Trial resultEloraTZP (eloralintide plus tirzepatide) phase 2 results presented at EASD 2026September 30, 2026Trial resultOrforglipron ACHIEVE-4 cardiovascular safety trial published in The LancetSeptember 29, 2026Trial resultFull TRIUMPH-2 retatrutide results published in The LancetSeptember 24, 2026FDA approvalFDA approves insulin efsitora alfa (Onswik), a once-weekly basal insulin for type 2 diabetesSeptember 21, 2026WADAWADA publishes 2027 Prohibited List, naming peptides as examples of non-approved substances

October 28, 2026CompoundingHHS lets 503A pharmacies compound six peptides under an interim enforcement discretion policyOctober 28, 2026Trial resultRetatrutide beats Ozempic on blood sugar and weight in head-to-head TRANSCEND-T2D-2 trialOctober 23, 2026FDA approvalFDA extends once-weekly insulin icodec (Awiqli) to children 10 and older with type 2 diabetesOctober 21, 2026CompoundingCitizen petition asks FDA not to allow compounding of seven peptides reviewed by its advisory committeeOctober 1, 2026Trial resultSurvodutide SYNCHRONIZE-2 phase 3 results in obesity with type 2 diabetes published in NEJMSeptember 30, 2026Trial resultEloraTZP (eloralintide plus tirzepatide) phase 2 results presented at EASD 2026September 30, 2026Trial resultOrforglipron ACHIEVE-4 cardiovascular safety trial published in The LancetSeptember 29, 2026Trial resultFull TRIUMPH-2 retatrutide results published in The LancetSeptember 24, 2026FDA approvalFDA approves insulin efsitora alfa (Onswik), a once-weekly basal insulin for type 2 diabetesSeptember 21, 2026WADAWADA publishes 2027 Prohibited List, naming peptides as examples of non-approved substances

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What peptides are · Part 4: How to read a peptide

Formula and molecular weight

Lesson 1.4.2 · 6 min read · Professional plan

What you'll learn

A molecular formula counts each type of atom in one molecule.
Sulfur in a formula usually points to cysteine or methionine.
Small differences in molecular weight between databases are common because of different calculation methods.
Labels often give the weight of the free peptide, while the product itself is a salt such as an acetate.

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