Figure 4.

Intratumoral drug distribution following systemic and intratumoral drug delivery. A) Systemic drug delivery is limited by poor penetration of the tumor interstitium resulting in insufficient treatment of cells distant from blood vessels. B) Intratumoral injections of free drug are prone to leakage, rapid clearance, and intravasation leading to incomplete and heterogenous tumor drug coverage. C) In contrast, intratumoral injections using in situ-forming hydrogels can improve on-target drug delivery and retention resulting in prolonged tumor drug exposure [59].