Purpose The next-generation anti-tumor drug peptide CIGB-300, developed by the Center for Genetic Engineering and Biotechnology (CIGB), targets casein kinase 2 (CK2) and its substrates, implicating significant therapeutic potential in cancer treatment. A key focus of this study was to compare CIGB-300 and a primary synthetic byproduct, CIGB-300iso, which shares the amino acid sequence with CIGB-300 but was proposed to differ d...