A pH-responsive, endosomal membrane disruptive, metabolite-derived polyamide PP-75 is developed to deliver the MBP-Apoptin fusion protein, which induces tumor-specific apoptosis into human osteogenic sarcoma Saos-2 cells. The intracellular distribution and colocalization of MBP-Apoptin-AF647 (MA-AF649) and PP-75-FITC provide strong evidence that PP-75 both enhances uptake and facilitates cytoplasmic release of MBP-Apoptin.