In this work, we have studied both in vitro and in vivo therapeutic potential of the newly developed peptide–drug conjugate P6-SN38, comprised of the cyclic peptide carrier P6 and the potent Topo I isomerase inhibitor SN38, the active metabolite of Irinotecan [27,28], on the EGFR+ NSCLC model. Here, EGFR is linked to non-small cell lung carcinoma.