Targeted prodrug treatment of HER‐2‐positive breast tumor cells using trastuzumab and paclitaxel linked by A‐Z‐CINNTM Linker

Abstract
Targeting drugs for delivery and release has the potential to increase the efficacy of treatment. A bifunctional linker, A-Z-CINN Linker was used to create a targeted prodrug, A-Z-CINN 310. A-Z-CINN Linker links to a potent chemotherapeutic agent, paclitaxel, via an energy-reversible ester bond and also binds a targeting agent, the monoclonal antibody trastuzumab (Herceptin). This study demonstrates the effectiveness of a single-treatment use of A-Z-CINN 310 in decreasing tumor volume and tumor cell density of human HER-2-positive BT-474 mammary tumor cells implanted in scid mice, compared to treatment with simultaneously administered trastuzumab and paclitaxel and with saline control. After treatment with A-Z-CINN 310, some mice received light exposure at 6 h for 5 min adjacent to the tumor to cause light-accelerated release of paclitaxel. Changes in tumor volume were measured for 28 days following treatment; changes in histology were measured at 31 days. Animals treated with A-Z-CINN 310, then light, showed dose-dependent decreases in tumor volume and tumor cell density which were more rapid and extensive than those seen with A-Z-CINN 310 without light or a 10-fold higher concentration of co-administered trastuzumab plus paclitaxel. This suggests that targeted delivery of paclitaxel using A-Z-CINN 310 kills tumor cells by localized release of paclitaxel at the tumor site, which can be accelerated by light treatment. These results indicate that a targeted prodrug therapy containing trastuzumab as the targeting agent and A-Z-CINN-paclitaxel as the prodrug results in a conjugate that is more effective in killing tumor cells than equivalent concentrations of co-administered trastuzumab and paclitaxel. Targeting of a drug can reduce the dose needed for effective therapy and can increase local bioavailability. This makes targeted therapy using an A-Z-CINN prodrug delivery system feasible for treating both primary and metastatic tumors.

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