Tumor Specific Radiosensitization Through Drug Conjugated Activatable Cell Penetrating Peptides Sunil J Advani Session title: (DPD 04) Biology 1 - GI, GU, and Breast Cancers Session date: :45 Location: Room D-2 Monitor number: 2

Activatable Cell Penetrating Peptides to Preferentially Deliver Tumor Radiosensitizing Monomethyl Auristatin E Take Home Points  MMAE is a potent tumoricidal and radiosensitizing drug  ACPP-cRGD-MMAE can be targeted to irradiated tumors with improved tumor regression compared to non-targeted MMAE delivery  IR induced alterations in tumor microenvironment protease activity can be non- invasively imaged using ratiometric ACPP molecules

PANC1 cells were treated with vehicle (open bar) or MMAE (filled bar) and IR. A) Neutral Comet Assay. comets images and mean B)  H2Ax foci formation. C) SF2 clonogenic survival. *p<0.01, **p< MMAE is a Potent Radiosensitizer

Ratiometric ACPP Accumulation in Irradiated and Non-Irradiated Tumor Xenografts Tumor xenografts were grown in both hindlimbs. The right tumor was irradiated and the left tumor shielded. Ratiometric ACPP was IV injected. Ratiometric ACPP has Cy5 on polycationic cell penetrating peptide and Cy7 on autoinhibitory polyanionic peptide portion. Upon linker peptide cleavage by MMPs, Cy5:Cy7 emission ratio increases. Cy5:Cy7 emission ratio measured (pseudocolor scale at far right) of tumors in situ and excised.

Targeted MMAE in Combination with Irradiation Produces Sustained Tumor Xenograft Regression PANC-1 tumor xenografts were grown to 200 mm 3. 6 nmoles of MMAE was given on days 0, 1 either as free drug or conjugated as ACPP-cRGD-MMAE. 3 Gy was given on days 1 and 2. Tumors were measured biweekly. Chart on right shows % of mice whose tumors at day 25 were smaller than their initial tumor volume on day 0.