VGSC blocker-1 is a powerful small molecule that serves as a blocker for the neonatal isoform of the VGSC subtype known as Nav1.5 (nNav1.5). It effectively blocks INa peak currents by 34.9% at a concentration of 1 μM, and demonstrates a 0.3% inhibition of cell invasion at the same concentration in the MDA-MB-231 human breast cancer cell line, without compromising cell viability.