Efficacy of nanoparticles containing irinotecan prepared using poly(DL-lactic acid) and poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) against M5076 tumor in the early liver metastatic stage

Nanoparticles containing irinotecan (NP) were prepared by the co-precipitation method with an addition of water to the acetone solution: poly(DL-lactic acid), poly(ethylene glycol)-poly(propylene glycol) -poly(ethylene glycol) and irinotecan. NP showed a drug content of 5% (w/w) and a mean particle diameter of 231 nm with a narrow size distribution. The antitumor effect was measured using M5076-bearing mice in the early liver metastatic stage. With a single administration, NP and irinotecan aqueous solution were significantly effective at a high dose only (90 mg irinotecan eq./kg). With repeated administrations, only NP were significantly effective for middle and high doses (22.5 × 2, 45 × 2 and 30 × 3 mg irinotecan eq./kg). At each administration schedule, NP showed a higher survival effect than the irinotecan aqueous solution and the decrease in body weight was not marked. NP is suggested to be a possibly useful dosage form against M5076 tumor in the early liver metastatic stage.