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[D-Arg1,D-Trp7,9,Leu11]-Substance P, commonly known as Spantide I, is a classical peptide Substance P antagonist developed through D-amino-acid and C-terminal substitutions.
Spantide I became an important early pharmacological tool for studying Substance P and tachykinin-dependent responses before highly selective non-peptide NK1 antagonists became widely available.
Product Information
| Product Name | [D-Arg1,D-Trp7,9,Leu11]-Substance P |
| Catalog No. | AS2542 |
| CAS No. | 91224-37-2 |
| Synonym | Spantide I; Spantide |
| Sequence | D-Arg-Pro-Lys-Pro-Gln-Gln-D-Trp-Phe-D-Trp-Leu-Leu-NH2 |
| Peptide Length | 11 residues |
| Molecular Formula | C75H108N20O13 |
| Molecular Weight | Approximately 1497.8 Da |
| Key Modifications | D-Arg1; D-Trp7; D-Trp9; Met11 → Leu |
| Pharmacological Profile | Classical Substance P / tachykinin antagonist |
Why Spantide Became a Reference Peptide Antagonist
Early comparative studies identified Spantide among the most active Substance P antagonists of its generation. Reported pA2 values were approximately 7.1–7.2 in classical smooth-muscle assays.
The peptide was also notable for combining antagonist potency with relatively weak spasmogenic and histamine-releasing activity compared with several related early analogs.
We recommend keeping these historical potency values associated with their original tissue assays. Spantide I should not be treated as equivalent to a modern receptor-selective NK1 antagonist in recombinant human systems.
D-Amino Acids and the Leu11 Substitution
D-Trp7 and D-Trp9 strongly alter the stereochemical presentation of the C-terminal receptor-interaction region. Replacement of Met11 by Leu also removes the methionine oxidation site.
This combination makes Spantide useful for studying both antagonist pharmacology and how stereochemistry converts an agonist peptide framework into an inhibitory ligand.
Research Applications
Spantide I can support classical Substance P antagonist studies, tachykinin pharmacology, smooth-muscle research, neural signaling experiments and historical peptide antagonist comparisons.
Frequently Asked Questions
Is [D-Arg1,D-Trp7,9,Leu11]-Substance P the same as Spantide?
Yes. It is commonly known as Spantide or Spantide I.
Is Spantide I a highly selective modern NK1 antagonist?
No. It is best considered a classical peptide Substance P/tachykinin antagonist whose observed potency can depend on the biological preparation.
Does Spantide contain methionine?
No. Met11 is replaced with Leu.