VIP (Vasoactive Intestinal Peptide)

1 Identity

Base synthetic peptide, 28 residues, C-terminally amidated — a synthetic replicate of a native human sequence rather than an analog. All-L proteinogenic residues, no cysteine, no disulfide, no acylation, no cyclization, no metal, no non-proteinogenic residue. The single post-translational feature is the C-terminal primary amide at Asn28 in place of a free acid, and it is an identity attribute rather than a detail. Basic overall — three lysines and two arginines against three acidic residues — and freely water-soluble. Two tyrosines and one phenylalanine give a genuine 280 nm chromophore, which most of the short-peptide records in this catalog do not have. One methionine at position 17 and four Asn/Asp residues make oxidation and deamidation release attributes rather than storage curiosities. Supplied as the lyophilized acetate salt. and the name under which the cheapest institutional listings are found. and aviptadil — the INN of the synthetic article. CAS 40077-57-4.

Sequence

H-His-Ser-Asp-Ala-Val-Phe-Thr-Asp-Asn-Tyr-Thr-Arg-Leu-Arg-Lys-Gln-Met-Ala-Val-Lys-Lys-Tyr-Leu-Asn-Ser-Ile-Leu-Asn-NH2. One-letter: H-HSDAVFTDNYTRLRKQMAVKKYLNSILN-NH2. Twenty-eight residues, all L, no disulfide, no acylation, free N-terminal histidine, and the modification that defines the article — a C-terminal primary amide at ASN28, not A free acid. The amide is annotated on UniProt P01282 as a modified residue ("Asparagine amide") on the mature chain, so it is a database-annotated feature rather than a synthesis assumption, and a non-amidated preparation is a different chemical entity that must not be shipped under this name. Met17 is oxidation-labile; Asn9, Asn24, Asn28 and the two aspartates are deamidation- and isoaspartate-prone. Supplied as the lyophilized acetate salt.

Molecular formula

C147H238N44O42S (free base, C-terminally amidated). Salt forms carried as separate formula units: mono-acetate C149H242N44O44S; mono-trifluoroacetate C149H239F3N44O44S. The free acid (des-amido) form is a different formula and a different article: C147H237N43O43S.

Average mass

3325.847 Da (C147H238N44O42S), computed from the formula and independently reconstructed residue-by-residue from the 28-residue sequence with a C-terminal amide; the two routes return the same formula and the same number. Published supplier figures for the same formula are 3325.83 and 3325.80, which agree with the computed value within the atomic-weight table each was calculated on. Salt forms: mono-acetate 3385.899; mono-trifluoroacetate 3439.869. Des-amido free acid 3326.831 — one dalton, and a different article.

Monoisotopic mass

3323.75610 Da neutral (C147H238N44O42S). Working ions: [M+2H]2+ m/z 1662.88533, [M+3H]3+ m/z 1108.92597, [M+4H]4+ m/z 831.94629. A plus or minus 5 ppm window on the neutral is plus or minus 0.0166 Da. The number this panel is built around: des-amido (free acid) C147H237N43O43S, 3324.74011 monoisotopic, exactly plus 0.98401 Da — which at 3+ is 0.33 m/z and at 4+ is 0.25 m/z, well inside an unresolved isotope envelope on a mid-range instrument, so the charge state at which the limit was demonstrated is printed on the certificate. Met17 sulfoxide C147H238N44O43S, 3339.75101, plus 15.995. Sermorelin, the closest confusable, is 3355.81870 — 32.06 Da away, about 1 percent.

Salt / variant note

Des-amido VIP, the free acid at Asn28, C147H237N43O43S, 3326.831 average / 3324.74011 monoisotopic — plus 0.98401 Da. It is what an incorrect resin choice or incomplete amidation produces, it is substantially the wrong molecule, and an ordinary purity method does not see it; at 3+ and 4+ the gap is 0.33 and 0.25 m/z. Deamidation and isoaspartate formation at Asn9, Asn24, Asn28, Asp3 or Asp8 each add the same plus 0.98 Da and are mass-degenerate with it, so the two are separated chromatographically or not at all. Met17 sulfoxide C147H238N44O43S, 3341.846 / 3339.75101, plus 15.995, which forms in the vial from headspace oxygen. Label and salt variants sold as separate SKUs over the same 28-mer: free base, acetate salt, the INN "aviptadil" and the clinical code RLF-100 are four labels for one molecule, and one vendor lists "Aviptadil" and "Aviptadil Acetate" as two distinct catalog items; a single acetate counterion adds 60.05 Da to the labeled mass basis. Human, porcine and bovine VIP are the identical sequence. Genuine confusables, each computed from its own sequence rather than transcribed: sermorelin, GRF(1-29) amide, C149H246N44O42S, 3357.933 / 3355.81870 — only 32.06 Da from this article, about 1 percent, both C-terminally amidated peptides of 28 to 29 residues carrying a single methionine, sold by the same catalogs at the same sizes, and not cleanly distinguished on A low-resolution MALDI trace where the parent peak is broad. PACAP-27, C142H224N40O39S, 3147.655 / 3145.64951, same superfamily, shares the His-Ser-Asp N-terminus, 178.19 Da lighter. Secretin, C130H220N44O40, 3039.458 / 3037.65335, same superfamily, also C-terminally amidated. PHM-27, from the same precursor. Truncations from an incomplete synthesis are the routine internal risk on a 28-mer and are limited as a class rather than named individually.

2 Class & testing panel

Form

Single article

Testing panel

P1 — panel definition

3 Primary sources & evidence

The index reports the design and provenance of the literature, not a conclusion about effect.

Literature exists in volume and is recorded here by study type, design, size and identifier, with no outcome and no effect stated. Mechanistic and physiological reviews: PMID 31559013, F1000Research 2019, review. Animal work: PMID 32050257, Nature 2020, mouse; PMID 36910129, Gastro Hep Adv 2022, mouse. Mixed animal and human-cell work: PMID 41478571, J Biol Chem 2026, mouse and human T cells. Randomized controlled trials of the synthetic article under its INN: PMID 37348524, Lancet Respir Med 2023, multicenter randomized placebo-controlled trial across 28 United States sites with 461 participants in the relevant comparison (231 and 230); PMID 36044317, Crit Care Med 2022, randomized trial; PMID 39870064, Med Princ Pract 2025, multicenter prospective double-blind placebo-controlled trial, n=80 across 9 centers. Published methodological correspondence attaching to that last trial: PMID 40928995, letter; PMID 40652932, author response; PMID 40982414 and PMID 40675136, further correspondence. Human retrospective and review literature on a fixed combination containing the same molecule: PMID 40192471, J Sex Med 2025, retrospective series of 308 men; PMID 18485029, BJU Int 2008, review; PMID 30895359, World J Urol 2019, systematic review. Commentary on the conduct of the pandemic-era program: PMID 36227034, Crit Care Med 2022; PMID 11566015 and PMID 21050351, drug-development commentary and retrospective. None of these results is restated, no indication or population is named as a use, and the research page presents counts by study type with identifiers rather than claims. Several claims circulating in the trade under this name are contradicted or unsupported by the trials listed above, and the site therefore carries no claim in either direction.

4 Storage & specification

Storage

Lyophilized white to off-white powder in the sealed original vial under nitrogen backfill, with in-pack desiccant, protected from light. Labeled storage -20 degrees C plus or minus 5 degrees C, desiccated; -80 degrees C for the retained reference portion. Met17 oxidizes from headspace oxygen inside a closed vial, the sulfoxide carries a numeric release limit, and a vial filled in air is a stability excursion that no thermometer records, so the fill atmosphere is a specification item and not a packaging preference. Vials are equilibrated to room temperature sealed before opening. Reconstituted solutions are refrigerated, used promptly and not refrozen; repeated freeze-thaw is recorded on the in-use protocol as a named handling failure for a 3.3 kDa amidated peptide. Shipped frozen with a validated shipper and a temperature logger, and the logger record is filed against the order number.

Shelf life

Provisional retest interval 24 months at -20 degrees C plus or minus 5 degrees C in the sealed original container under nitrogen, provisional pending this company's own ICH Q1A-format study on three production lots, with the retained reference portion held at -80 degrees C. The three stability-indicating attributes are named in advance and each is quantified at every time point: Met17 sulfoxide at plus 15.995 Da; the des-amido free acid at plus 0.98401 Da; and deamidation and isoaspartate species at the four Asn/Asp positions, which are mass-degenerate with the des-amido species and therefore have to be resolved chromatographically before the first lot goes on stability. An area-percent purity figure alone does not date this molecule. The rule is fixed before testing starts: if any of the three exceeds half its release limit at the month-12 point, the interval drops to 12 months and the lot is re-tested annually thereafter. Shortened on data, never extended without a completed dataset.