Pharmacokinetics and dosimetry of (111)In/(188)Re-labeled PEGylated liposomal drugs in two colon carcinoma-bearing mouse models

PEGylated liposomes are important drug carriers for nanomedicine cancer therapy. PEGylated liposomes can encapsulate radio- and chemo-drugs and passively target tumor sites via enhanced permeability and retention effect. This study estimated the pharmacokinetics and dosimetry after administration of radio-chemotherapeutics ((111)In-labeled vinorelbine [VNB]-encapsulated liposomes, InVNBL, and (188)Re-labeled doxorubicin [DXR]-encapsulated liposomes, ReDXRL) for radionuclide therapy in two colon carcinoma-bearing mouse models. A C26 colon carcinoma tumor/ascites mouse model and a subcutaneous solid tumor-bearing mouse model were employed. Biodistribution studies of InVNBL and ReDXRL after intraperitoneal administration in tumor/ascites-bearing mice (protocol A) and intravenous administration in subcutaneous solid tumor-bearing mice (protocol B) were performed. The radiation dose to normal tissues and tumors were calculated based on the results of distribution studies in mice, using the OLINDA/EXM program. The cumulated activities in most organs after administration of InVNBL in either the tumor/ascites-bearing mice (protocol A) or the subcutaneous solid tumor-bearing mice (protocol B) were higher than those of ReDXRL. Higher tumor-to-normal-tissues absorption dose ratios (T/NTs) were observed after administration of InVNBL than those of ReDXRL for protocol A. The T/NTs for the liver, spleen, and red marrow after injection of InVNBL for protocol B were similar to those of ReDXRL. The critical organ was found to be red marrow, and thus the red marrow absorption dose defined the recommended maximum administration activity of these liposomal drugs. Characterization of pharmacokinetics and dosimetry is needed to select the appropriate radiotherapeutics for specific tumor treatment applications. The results suggest that InVNBL is a promising therapeutic agent, which is as good as ReDXRL, in two mouse tumor models.

Comparative dosimetric evaluation of nanotargeted (188)Re-(DXR)-liposome for internal radiotherapy

A dosimetric analysis was performed to evaluate nanoliposomes as carriers of radionuclides ((188)Re-liposomes) and radiochemotherapeutic drugs [(188)Re-doxorubicin (DXR)-liposomes] in internal radiotherapy for colon carcinoma, as evaluated in mice.

METHODS

Pharmacokinetic data for (188)Re-N, N-bis (2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA), (188)Re-liposome, and (188)Re-DXR-liposome were obtained for the estimation of absorbed doses in tumors and normal organs. Two colon carcinoma mouse models were employed: subcutaneous growing solid tumor and malignant ascites pervading tumor models. Radiation-dose estimates for normal tissues and tumors were calculated by using the OLINDA/EXM program. An evaluation of a recommended maximum administered activity (MAA) for the nanotargeted drugs was also made.

RESULTS

Mean absorbed doses derived from (188)Re-liposome and (188)Re-DXR-liposome in normal tissues were generally similar to those from (188)Re-BMEDA in intraperitoneal and intravenous administration. Tissue-absorbed dose in the liver was 0.24-0.40 and 0.17-0.26 (mGy/MBq) and in red marrow was 0.033-0.050 and 0.038-0.046 (mGy/MBq), respectively, for (188)Re-liposome and (188)Re-DXR-liposome. Tumor-absorbed doses for the nanotargeted (188)Re-liposome and (188)Re-DXR-liposome were higher than those of (188)Re-BMEDA for both routes of administration (4-26-fold). Dose to red marrow defined the recommended MAA.

CONCLUSIONS

Our results suggest that radionuclide and chemoradiotherapeutic passive targeting delivery, using nanoliposomes as the carrier, is feasible and promising in systemic-targeted radionuclide therapy.