Synthesis and biological evaluation of a peptide-paclitaxel conjugate which targets the integrin αvβ6

The integrin αvβ6 is an emergent biomarker for non-small cell lung cancer (NSCLC) as well as other carcinomas. We previously developed a tetrameric peptide, referred to as H2009.1, which binds αvβ6 and displays minimal affinity for other RGD-binding integrins. Here we report the use of this peptide to actively deliver paclitaxel to αvβ6-positive cells. We synthesized a water soluble paclitaxel-H2009.1 peptide conjugate in which the 2′-position of paclitaxel is attached to the tetrameric peptide via an ester linkage. The conjugate maintains its specificity for αvβ6-expressing NSCLC cells, resulting in selective cytotoxicity. Treatment of αvβ6-positive cells with the conjugate results in cell cycle arrest followed by induction of apoptosis in the same manner as free paclitaxel. However, initiation of apoptosis and the resultant cell death is delayed compared to free drug. The conjugate demonstrates anti-tumor activity in a H2009 xenograft model of NSCLC with efficacy comparable to treatment with free paclitaxel.