Drug formulation augments the therapeutic response of carboplatin administered through a lymphatic drug delivery system

Treatment of metastatic lymph nodes (LNs) is challenging due to their unique architecture and biophysical traits. Systemic chemotherapy fails to impede tumor progression in LNs due to poor drug uptake and retention by LNs, resulting in fatal systemic metastasis. To effectively treat LN metastasis, achieving specific and prolonged retention of chemotherapy drugs in the tumor‐draining LNs is essential. The lymphatic drug‐delivery system (LDDS) is an ultrasound‐guided drug‐delivery methodology for administration of drugs to LNs that addresses these requirements. However, early‐stage metastatic LNs have an additional set of drug transport barriers, such as elevated intranodal pressure and viscosity, that negatively impact drug diffusion. In the present study, using formulations of elevated osmotic pressure and viscosity relative to saline, we sought to favorably alter the LN's physical environment and study its impact on pharmacokinetics and consequently the therapeutic efficacy of carboplatin delivered using the LDDS. Our study confirmed the capability of a drug formulation with elevated osmotic pressure and viscosity to alter the architecture of LNs, as it caused notable expansion of the lymphatic sinus. Additionally, the study delineated an optimal range of osmotic pressure and viscosity, centered around 1897 kPa and 11.5 mPa·s, above and below which therapeutic efficacy was found to decline markedly. These findings suggest that formulation osmotic pressure and viscosity are parameters that require critical consideration as they can both hinder and promote tumorigenesis. The facile formulation reported here has wide‐ranging applicability across cancer spectrums and is thus anticipated to be of great clinical benefit. A simple modification to a drug formulation, resulting in the elevation of the formulation's osmotic pressure and viscosity, enhances the administered drug's therapeutic response by improving its pharmacokinetic profile. In particular, administration of a drug formulation of 1897 kPa and 11.5 mPa·s (CP II[L]) using the lymphatic drug delivery system effectively inhibits lymph node metastasis, thereby preventing the onset of fatal systemic metastasis.