Augmented therapeutic efficacy of irinotecan is associated with enhanced drug accumulation

The goal of this study is to determine whether treatment with methylselenocysteine (MSC) results in differential uptake of irinotecan and its active metabolite (SN-38) between tumors of head and neck squamous cell carcinomas and normal tissue. The in vivo synergy between MSC and irinotecan is influenced by treatment schedule and associated with enhancement of tumor vessel maturation, intra-tumor concentration of SN-38 and apoptotic death of tumor cells. Normal tissue drug concentrations were not impacted by selenium treatment. The finding is of clinical relevance for enabling the delivery of higher doses of irinotecan to reverse tumor resistance, recurrence and ultimately enhancing cure rates.

► The in vivo synergy between MSC and irinotecan is influenced by treatment schedule.
► Sequential combination has superior antitumor effect to concurrent combination.
► Intra-tumor highest drug concentration is at d14 post sequential combination; no impact on normal tissue concentrations.
► Intra-tumor microvessel maturation is enhanced at d14 after sequential combination.
► Sequential combination enhances apoptosis of tumor cells at d14 after treatment.