AOD-9604: 16-Residue Sequence, Disulfide Bridge, CAS 221231-10-3 and Registry Records

No: AOD-9604 is not the same as tesamorelin. AOD-9604 is a synthetic 16-residue peptide acid, YLRIVQCRSVEGSCGF, with one Cys7-Cys14 disulfide bridge, formula C78H123N23O23S2, molecular weight 1815.10 Da and CAS 221231-10-3. Tesamorelin is a synthetic 44-residue peptide amide, formula C221H366N72O67S, molecular weight 5135.86 Da and CAS 218949-48-5. The two sequences share no run of two consecutive residues; aligned from the N-terminus, they match only at Tyr1, Ser9 and Gly15. This page sets out the sequence, the disulfide bridge, the registry records and the 2026 US list status of AOD-9604, so that a label, a certificate or a registry entry can be matched to the right molecule.

Is AOD-9604 the same as tesamorelin?

No. AOD-9604 is a 16-residue peptide acid, C78H123N23O23S2, 1815.10 Da, CAS 221231-10-3, and tesamorelin is a 44-residue peptide amide, C221H366N72O67S, 5135.86 Da, CAS 218949-48-5, so they are two different peptides with different sequences, lengths, termini, formulas and CAS numbers. AOD-9604 has 16 residues and tesamorelin has 44; tesamorelin is about 2.8 times heavier (5135.86 Da against 1815.10 Da, a gap of 3320.76 Da). The names are often grouped under one catalog heading, which is where the confusion starts, but the sequences, termini, formulas and CAS numbers are all different.

Aligned residue by residue from the N-terminus, the two sequences match at only three of AOD-9604's 16 positions (Tyr1, Ser9 and Gly15) and have no two consecutive residues in common; in tesamorelin the Tyr1 also carries the hexenoyl group. On a mass-spectrometry report the two cannot be confused, because their masses differ by more than 3,300 Da. The sequence family that tesamorelin belongs to, with sermorelin and CJC-1295 no DAC aligned beside it, is set out in Mod GRF 1-29, CJC-1295, sermorelin and tesamorelin.

Is AOD-9604 the same as hGH Fragment 176-191?

AOD-9604 is not identical to hGH Fragment 176-191. The native fragment is the 16-residue sequence that begins with Phe176; AOD-9604 has tyrosine in that position, which is why it is written Tyr-hGH(177-191) or [Tyr176]-hGH(176-191). Tyrosine is phenylalanine plus one oxygen atom, so the native fragment in the same disulfide-closed form works out to C78H123N23O22S2 (calculated), with a calculated average mass of 1799.08 Da, about 16 Da lighter than AOD-9604. The native fragment does not carry CAS 221231-10-3.

What are the AOD-9604 sequence, CAS number and registry records?

The AOD-9604 sequence is Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe-OH (one-letter code YLRIVQCRSVEGSCGF), with a disulfide bridge between Cys7 and Cys14. In hGH numbering the two cysteines are Cys182 and Cys189. The table lists every identifier that a label, certificate or database entry for AOD-9604 should match.

The formula can be checked from the sequence: the sixteen residues joined by fifteen peptide bonds, with the two cysteine thiols closed into one disulfide (minus two hydrogen atoms), give C78H123N23O23S2. Registry numbers sometimes drift between listings; the CAS numbers and molecular weights reference collects the same identifiers for every listed compound, and the overview of research peptides places AOD-9604 among the other listed compound families.

Why does the AOD-9604 formula contain two sulfur atoms?

The two sulfur atoms in C78H123N23O23S2 come from the two cysteine residues at positions 7 and 14, whose side-chain thiols are joined into a single S-S disulfide bridge. The formula and the 1815.10 Da molecular weight describe that oxidized, bridged form. Closing the bridge is usually a separate oxidation step after the linear chain is assembled; the synthesis stages for disulfide-bridged sequences are covered in how research peptides are made.

The bridge gives three mass checks that are specific to AOD-9604. The masses below are calculated from the formulas with standard monoisotopic atomic masses and a proton mass of 1.00728; the ion values are m/z.

• Reduced form, +2.02 Da. A deconvoluted mass about 2 Da above the expected value points to the open chain with two free thiols rather than the bridged peptide.
• Native fragment, -15.99 Da. A mass about 16 Da below the expected value points to the Phe176 sequence rather than AOD-9604.
• Dimer, exactly twice the formula. The dimer's [M+2H]2+ ion falls at the same m/z as the monomer's [M+H]+ (1814.87), so the isotope spacing decides: peaks 1 unit apart belong to the singly charged monomer, peaks 0.5 apart to the doubly charged dimer.

The catalog molecular weight of 1815.10 Da and the calculated average of 1815.08 Da differ only because atomic-weight tables differ in the last decimal. The same calculated columns for every listed compound are in the expected mass table for peptide mass spec.

What is the US legal status of AOD-9604 in 2026?

On the FDA compounding page whose content is current as of April 22, 2026, AOD-9604 appears in the table of bulk drug substances nominated but withdrawn, which covers substances previously in Category 2 of the interim policies whose nominations were withdrawn by the nominators. It is not in the current Category 2 table on that page, and it is not on the 503A category list dated May 14, 2026 or the 503B category list dated March 21, 2025. Tesamorelin is not named in either table of the April 22, 2026 page. These lists concern compounding by pharmacies, physicians and registered outsourcing facilities under sections 503A and 503B; the full table and its dates are at FDA Category 2 peptides 2026, and the labeling facts for research-use-only sale are at peptide legal status 2026.

Pepta Labs lists AOD-9604 as a supplier-stated 5 mg of lyophilized powder in a sealed glass vial. The product page shows the reported RP-HPLC purity. The documented testing is independent third-party HPLC purity analysis and mass-spectrometry identity confirmation, commissioned through the purchasing group on a sampled production run from the source; Pepta Labs does not test in-house. Vial labels identify the compound, quantity and research-use designation and do not carry lot or batch numbers. Sterility, endotoxin or LAL, potency, pharmaceutical-grade, cGMP, contaminant-panel and vial fill-quantity testing are not claimed.

The report is sent by email on request, before ordering if wanted, through the report request form or at support@peptalabs.com. How to read its two sections is covered in the COA verification guide and HPLC vs mass spectrometry; the counter-ion question is covered in TFA vs acetate and net peptide content; sealed-vial handling (2-8 C on arrival, -20 C for long-term storage, away from light and moisture) is covered in the peptide storage guide. The full documentation policy is on the quality page.

Frequently asked questions

Is AOD-9604 the same as tesamorelin?

No. AOD-9604 is a 16-residue peptide acid with one Cys7-Cys14 disulfide (C78H123N23O23S2, 1815.10 Da, CAS 221231-10-3). Tesamorelin is a 44-residue peptide amide with an N-terminal trans-3-hexenoyl group (C221H366N72O67S, 5135.86 Da, CAS 218949-48-5). The two sequences share no run of two consecutive residues; aligned from the N-terminus, they match only at Tyr1, Ser9 and Gly15.

Which registry records and research codes belong to AOD-9604?

AOD-9604 is CAS 221231-10-3, PubChem CID 71300630 and FDA UNII 7UP768IP4M. Its research code is written AOD-9604, AOD9604 or AOD 9604, and its descriptive names are Tyr-hGH(177-191), [Tyr176]-hGH(176-191) and hGH Fragment 176-191 analogue. The FDA compounding page of April 22, 2026 lists it under the name AOD-9604.

Why does the AOD-9604 formula contain two sulfur atoms?

The peptide has two cysteine residues, at positions 7 and 14, joined by an intramolecular disulfide bridge. Both sulfur atoms in C78H123N23O23S2 come from those cysteines, and the formula describes the oxidized, bridged form; the reduced, open-chain form is C78H125N23O23S2, about 2 Da heavier.

What does CAS 221231-10-3 identify?

CAS 221231-10-3 is the Chemical Abstracts Service registry number for the free AOD-9604 peptide, Tyr-hGH(177-191) with the Cys7-Cys14 disulfide. It does not identify the native hGH Fragment 176-191 or tesamorelin, and the salt actually supplied is stated on the analytical report.

How many residues does AOD-9604 have?

AOD-9604 has 16 residues: Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe, one-letter code YLRIVQCRSVEGSCGF. Fifteen correspond to hGH residues 177-191, and the N-terminal tyrosine takes the place of Phe176 in the native fragment.

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