Cell Penetrating Peptides Conjugated to Anti-Carcinoembryonic Antigen “Catch-and-Release” Monoclonal Antibodies Alter Plasma and Tissue Pharmacokinetics in Colorectal Cancer Xenograft Mice

Cell penetrating peptides conjugated to delivery vehicles, such as nanoparticles or antibodies, can enhance the cytosolic delivery of macromolecules. The present study examines the effects of conjugation to cell penetrating and endosomal escape peptides (i.e., TAT, GALA, and H6CM18) on the pharmacokinetics and distribution of an anti-carcinoembryonic antigen "catch-and-release" monoclonal antibody, 10H6, in a murine model of colorectal cancer. GALA and TAT were conjugated to 10H6 using SoluLINK technology that allowed the evaluation of peptide-to-antibody ratio by ultraviolet spectroscopy. H6CM18 was conjugated to either NHS or maleimide-modified 10H6 using an azide-modified valine-citrulline linker and copper-free click chemistry. Unmodified and peptide-conjugated 10H6 preparations were administered intravenously at 6.67 nmol/kg to mice-bearing MC38CEA+ tumors. Unconjugated 10H6 demonstrated a clearance of 19.9 ± 1.36 mL/day/kg, with an apparent volume of distribution of 62.4 ± 7.78 mL/kg. All antibody-peptide conjugates exhibited significantly decreased plasma and tissue exposure, increased plasma clearance, and increased distribution volume. Examination of tissue-to-plasma exposure ratios showed an enhanced selectivity of 10H6-TAT for the GI tract (+25%), kidney (+24%), liver (+38%), muscle (+3%), and spleen (+33%). 10H6-GALA and 10H6-H6CM18 conjugates demonstrated decreased exposure in all tissues, relative to unmodified 10H6. All conjugates demonstrated decreased tumor exposure and selectivity; however, differences in tumor selectivity between 10H6 and 10H6-H6CM18 (maleimide) were not statistically significant. Relationships between the predicted peptide conjugate isoelectric point (pI) and pharmacokinetic parameters were bell-shaped, where pI values around 6.8-7 exhibit the slowest plasma clearance and smallest distribution volume. The data and analyses presented in this work may guide future efforts to develop immunoconjugates with cell penetrating and endosomal escape peptides.