SP5 (SIRPa inhibitor) peptide

• Handling and Storage of Synthetic Peptides
• Material Safety Data Sheets (MSDS)

Batch to batch variation of the purity

SP5 is a short macrocyclic-like peptide with the sequence CTQDAWHIC that binds to SIRPα and blocks its interaction with CD47. It was identified among a series of SIRPα-binding peptides (SP1–SP6) developed by Xu and colleagues in 2020. SP5 displays relatively high affinity for SIRPα, with a dissociation constant (Kd) of approximately 0.38 μM, and interferes with the SIRPα/CD47 interaction in a dose-dependent manner in CHO-K1 cells expressing human SIRPα.

Functionally, SP5 promotes macrophage-mediated phagocytosis of HT29 human colon tumor cells at concentrations around 200 μM and reduces tumor growth in mouse tumor models. Like other CD47/SIRPα-blocking peptides such as D4-2, SP5 appears to act by engaging SIRPα and occupying regions that overlap with the CD47 binding interface, thereby disrupting the inhibitory signal that SIRPα transmits upon CD47 engagement.

• Hazama D, Yin Y, Murata Y, et al. Macrocyclic Peptide-Mediated Blockade of the CD47-SIRPα Interaction as a Potential Cancer Immunotherapy. Cell Chem Biol. 2020;27(9):1181-1191.e7. doi:10.1016/j.chembiol.2020.06.008

Trifluoroacetic acid (TFA) is a common counterion from the purification process using High-Performance Liquid Chromatography (HPLC). The presence of TFA can affect the peptide's net weight, appearance, and solubility.

Impact on Net Weight: The TFA salt contributes to the total mass of the product. In most cases, the peptide content constitutes >80% of the total weight, with TFA accounting for the remainder.

Solubility: TFA salts generally enhance the solubility of peptides in aqueous solutions.

In Biological Assays: For most standard in vitro assays, the residual TFA levels do not cause interference. However, for highly sensitive cellular or biochemical studies, please be aware of its presence.