Phase II trial of irinotecan (CPT-11) in relapsed or refractory non-Hodgkin's lymphomas

Nonclinical pharmacokinetics and activity of etirinotecan pegol (NKTR-102), a long-acting topoisomerase 1 inhibitor, in multiple cancer models

Purpose

The aim of the study was to demonstrate the activity of etirinotecan pegol, a polymer conjugate of irinotecan, in multiple human tumor models and to establish both the pharmacokinetic/pharmacodynamics (PK/PD) relationship and clinical relevance of the findings.

Experimental design

Anti-tumor activity was evaluated in mouse models of human lung, colorectal, breast, ovarian, and gastric cancers. Etirinotecan pegol was administered intravenously (once or every 3–7 days) to animals with established tumors. Activity was assessed by tumor growth delay (TGD) and regression. Mice bearing established colorectal and lung tumors were treated with etirinotecan pegol or irinotecan, and serial blood and tumor samples were collected at planned times between 0 and 60 days post-treatment for quantitation of etirinotecan pegol and SN38. For PK analysis, analyte concentration–time data were fit with compartmental models; PK/PD analysis was based on an inhibitory E_max response model.

Results

Etirinotecan pegol was active in all tumor models. TGD was sustained for 2–10 weeks after last dose, while conventional irinotecan resulted in little suppression of tumor growth. Etirinotecan pegol was eliminated very slowly from the tumor (t_1/2 = 17 days), achieving higher and more sustained tumor exposure when compared with conventional irinotecan. The increased tumor exposure following etirinotecan pegol correlated with strong and prolonged suppression of tumor growth. Sustained plasma exposure to active SN38 was consistently observed across nonclinical species (including mouse, rat, and dog) and translated to cancer patients.

Conclusions

Etirinotecan pegol is the first long-acting topoisomerase 1 inhibitor that provides sustained exposure, which results in prolonged anti-tumor activity in a wide variety of cancer models.

Electronic supplementary material

The online version of this article (doi:10.1007/s00280-014-2577-7) contains supplementary material, which is available to authorized users.

The effect of Saccharomyces boulardii on reducing irinotecan-induced intestinal mucositis and diarrhea

To investigate the efficiency of Saccharomyces boulardii on irinotecan-induced mucosal damage and diarrhea in rats, fifty rats were randomized into three groups with 20 rats in two study groups and 10 rats in the control group. Control group did not receive any treatment. Irinotecan (60 mg/kg) alone was administered intravenously once a day for four consecutive days to the rats of Group A. Throughout the experiment, Group B rats were additionally given Saccharomyces boulardii (800 mg/kg) for 3 days before administration of irinotecan and 7 days throughout the experiment. Delayed diarrhea was more severe in Group A than Group B (P = 0.009). The weight loss was 34.7 +/- 3.8 mg for Group A, while it was 17.4 +/- 1.7 mg for Group B (P < 0.001). Findings of mucositis most clearly appeared in the jejunum. Regarding edema (P = 0.003), leukocyte migration (P = 0.038), and inflammation (P = 0.006) significant recovery was detected in the mucosa of rats receiving Saccharomyces boulardii. Villous thickness was significantly greater in Group A than Group B (P < 0.001). The results indicate that Saccharomyces boulardii provided significant improvement in irinotecan-induced diarrhea and mucositis.