A study of pipeline drugs in neuroendocrine tumors.

PURPOSE: Inhibition of neovessel development can stabilize tumor growth. A rapid in vitro method that can evaluate the effectiveness of anti-angiogenic drugs would aid in drug development. We tested a series of investigational agents to determine their ability to inhibit angiogenesis in our in vitro human angiogenesis model.
METHODS: A total of 74 neuroendocrine tumors were tested with five therapeutic agents for anti-angiogenic activity. Angiogenic responses were assessed visually and the percent of tumor explants that developed an angiogenic response was determined. The extent of neovessel growth was rated using a validated semi-quantitative visual scale. Analysis of variance was used to compare treatment outcome results to control values for these angiogenic parameters.
RESULTS: Vatalanib (2 × 10(-5) M) and patupilone (1 × 10(-8) M) were highly effective inhibitors of human tumor angiogenesis (mean overall angiogenic response for drug versus control 1.3 vs. 5.9 and 0.2 vs. 5.2, respectively) and were statistically significant at p <0.0001. Imatinib (2.5 × 10(-6) M) and everolimus (1 × 10(-8) M) were also effective (mean overall angiogenic response for drug versus control 2.2 vs. 5.9 and 4.5 vs. 5.9, respectively), and these were also statistically significant at p <0.0001. Pasireotide (1 × 10(-8) M) had no effect on angiogenesis (mean overall angiogenic response for drug vs. control 5.5 vs. 5.2).
CONCLUSIONS: Significant differences in angiogenic response to test drugs were noted in this neuroendocrine patient population. In vitro screening of a large series of fresh human tumors may be a cost-effective way to select drugs for continued clinical development.