A Polymer-Based Antibody-Vinca Drug Conjugate Platform: Characterization and Preclinical Efficacy.

Antibody-drug conjugates (ADC) are an emerging drug class that uses antibodies to improve cytotoxic drug targeting for cancer treatment. ADCs in current clinical trials achieve a compromise between potency and physicochemical/pharmacokinetic properties by conjugating potent cytotoxins directly to an antibody at a 4:1 or less stoichiometric ratio. Herein, we report a novel, polyacetal polymer-based platform for creating ADC that use poly-1-hydroxymethylethylene hydroxymethyl-formal (PHF), also known as Fleximer. The high hydrophilicity and polyvalency properties of the Fleximer polymer can be used to produce ADC with high drug loading without compromising physicochemical and pharmacokinetic properties. Using trastuzumab and a vinca drug derivative to demonstrate the utility of this platform, a novel Fleximer-based ADC was prepared and characterized in vivo. The ADC prepared had a vinca-antibody ratio of 20:1. It exhibited a high antigen-binding affinity, an excellent pharmacokinetic profile and antigen-dependent efficacy, and tumor accumulation in multiple tumor xenograft models. Our findings illustrate the robust utility of the Fleximer platform as a highly differentiated alternative to the conjugation platforms used to create ADC currently in clinical development. ©2015 American Association for Cancer Research.