Reference

KPV molecular data

KPV structure, sequence, formula C16H30N4O4, 342.43 g/mol, CAS 67727-97-3, PubChem CID 125672, and how the free acid, amide and acetate differ.

By the KPV Peptide editorial team · Last reviewed November 11, 2026 · Editorial review: approved by Ryan DeLauz (bulk sign-off in chat, 2026-11-11)

Short answer

KPV is L-lysyl-L-prolyl-L-valine: formula C₁₆H₃₀N₄O₄, molecular weight 342.43 g/mol, monoisotopic mass 342.2267 Da, PubChem CID 125672, CAS 67727-97-3 [PubChem][FDA briefing 2026]. The amide (–NH₂) and acetate salt are distinct substances with different formulas.

Interactive molecular viewer

2D layout from PubChem CID 125672. Choose a residue to highlight it, or switch the C-terminus.

Wedges show the three L-stereocentres. Depiction coordinates: PubChem.

Residues

Form: KPV (free acid / "free base"), H-Lys-Pro-Val-OH
Formula: C16H30N4O4
Mol. weight: 342.43 g/mol
Monoisotopic: 342.22670545 Da
InChIKey: YSPZCHGIWAQVKQ-AVGNSLFASA-N
PubChem: CID 125672

Three forms, three identities

Free acid, amide and acetate forms of KPV
Form	Formula	MW (g/mol)	Identifier	Note
KPV (free acid / "free base"), H-Lys-Pro-Val-OH	C16H30N4O4	342.43	PubChem CID 125672	The form FDA calls "KPV (free base)". A free C-terminal carboxylic acid. [PubChem]
KPV amide, H-Lys-Pro-Val-NH2	C16H31N5O3	341.45	PubChem CID 7019758	Residues 11–13 of native α-MSH end in an amidated valine, so several studies used capped or amidated forms. [PubChem]
KPV acetate (1:1 salt)	C16H30N4O4 · C2H4O2	402.5	UNII 7V6LGD8S5R	FDA treats the acetate salt as a separate bulk drug substance. GSRS lists UNII 7V6LGD8S5R for this salt. [FDA briefing 2026]

FDA evaluates the free base and the acetate as different bulk drug substances, because salts can differ in solubility, stability and behaviour[FDA briefing 2026]. A certificate of analysis should therefore state which form a material is, and its formula should match that form.

Identity and physicochemical properties

Identity and physicochemical properties of KPV with sources
Property	Value	Source
Sequence	Lys-Pro-Val (KPV)	[PubChem]
Origin	C-terminal residues 11–13 of α-melanocyte-stimulating hormone (α-MSH)	[PubChem]
IUPAC name (free acid)	(2S)-2-[[(2S)-1-[(2S)-2,6-diaminohexanoyl]pyrrolidine-2-carbonyl]amino]-3-methylbutanoic acid	[PubChem]
CAS number	67727-97-3 (also used for the acetate in most public references)	[FDA briefing 2026]
PubChem CID	125672 (free acid); 7019758 (amide)	[PubChem]
UNII	7V6LGD8S5R (acetate 1:1 salt)	[FDA GSRS]
XLogP3	−3.5 (computed)	[PubChem]
Topological polar surface area	139 Å² (computed)	[PubChem]
H-bond donors / acceptors	4 / 6 (computed)	[PubChem]
Rotatable bonds	9 (computed)	[PubChem]
Water solubility	0.7 mg/mL (free base, as cited by FDA)	[FDA briefing 2026]
Reported stability	Up to 3 years at −20 °C (free base); acetate at 2–8 °C, as reported in the literature FDA reviewed	[FDA briefing 2026]
Main stress degradant	Lys-Pro diketopiperazine under acid, alkali and peroxide stress (HPLC study)	[Pawar 2015]
Pharmacopoeial monograph	None in USP–NF, Ph. Eur. 11.8 or JP 18	[FDA briefing 2026]

Analysis and stability

A validated reversed-phase HPLC method separates KPV from its degradation products, with a quantitation limit of 0.25 µg/mL. Under acid, alkali and peroxide stress the main degradant was a lysine–proline diketopiperazine [Pawar 2015]. There is no USP–NF, European or Japanese pharmacopoeial monograph for KPV[FDA briefing 2026]. Related reading: how we verify identity data.

Frequently asked questions

What is the molecular weight of KPV?

342.43 g/mol for the free acid (C16H30N4O4), 341.45 g/mol for the C-terminal amide (C16H31N5O3), and about 402.5 g/mol for the 1:1 acetate salt.

What is the CAS number of KPV?

67727-97-3. FDA notes that most public references use the same CAS number for the acetate salt as for the free base.

Is “KPV” on PubChem the right compound?

Not necessarily. A PubChem name search for “KPV” returns an unrelated small molecule (2-oxo-5-phenylpentanoic acid). Use CID 125672 or the sequence Lys-Pro-Val.

References

Pawar KR, Mulabagal V, Smith F et al. (2015). Stability-indicating HPLC assay for lysine-proline-valine (KPV) in aqueous solutions and skin homogenates. Biomed Chromatogr. PubMed 25298219 · doi:10.1002/bmc.3347[Analytical, grade D]
PubChem, National Library of Medicine. Lys-Pro-Val (CID 125672). Source[retrieved 2026-11-11]
PubChem, National Library of Medicine. Lys-Pro-Val-NH2 (CID 7019758). Source[retrieved 2026-11-11]
FDA Global Substance Registration System. L-Valine, L-lysyl-L-prolyl-, acetate (1:1); UNII 7V6LGD8S5R. Source[retrieved 2026-11-11]
U.S. Food and Drug Administration, Pharmacy Compounding Advisory Committee (2026-07-23). FDA Briefing Document: KPV-Related Bulk Drug Substances (KPV (free base) and KPV acetate). Source[retrieved 2026-11-11]