A class of antisense agents having a distributed guanidinium peptide nucleic acids (GPNA) backbone which has excellent uptake into mammalian cells, can bind to the target DNA or RNA in a highly sequence specific manner and can resist nucleases and proteases both outside and inside the cell(s) of interest. In one embodiment, either systemic or intratumoral administration of antisense Epidermal Growth Factor Receptor (“EGFR”) GPNA oligonucleotides is believed to downmodulate EGFR levels, thus in turn to reduce head and neck squamous cell carcinoma tumor growth, which has been confirmed to date both in vitro and in vivo.