Replenishable drug depot to combat post-resection cancer recurrence.

Local drug presentation made possible by drug-eluting depots has demonstrated benefits in a vast array of diseases, including in cancer, microbial infection and in wound healing. However, locally-eluting depots are single-use systems that cannot be refilled or reused after implantation at inaccessible sites, limiting their clinical utility. New strategies to noninvasively refill drug-eluting depots could dramatically enhance their clinical use. In this report we present a refillable hydrogel depot system based on bioorthogonal click chemistry. The click-modified hydrogel depots capture prodrug refills from the blood and subsequently release active drugs locally in a sustained manner. Capture of the systemically-administered refills serves as an efficient and non-toxic method to repeatedly refill depots. Refillable depots in combination with prodrug refills achieve sustained release at precancerous tumor sites to improve cancer therapy while eliminating systemic side effects. The ability to target tissues without enhanced permeability could allow the use of refillable depots in cancer and many other medical applications.