Spectrum Pharmaceuticals Presents Data on SPI-1620

Spectrum Pharmaceuticals has presented positive data on SPI-1620, the company's endothelinB agonist.

SPI-1620 stimulates receptors on endothelial cells, the innermost layer of cells lining the blood vessels, to selectively dilate blood vessels in the tumor, resulting in transient increase in blood flow and a consequent increase in the delivery of anticancer drugs, such as paclitaxel, to the tumor, as shown in animal studies to date.

Administration of SPI-1620 resulted in a 150 percent and 318 percent increase in tumor perfusion in breast and melanoma tumor bearing animals, respectively. SPI-1620 increased the tumor concentration of paclitaxel by 730 percent compared to controls, without significantly enhancing paclitaxel concentration in other organs.

Although SPI-1620 increased the blood perfusion and enhanced the delivery of paclitaxel to tumors, it did not produce any differences in plasma pharmacokinetics, supporting the lack of effect on normal organs.

Efficacy studies using breast tumor bearing rats revealed that administration of SPI-1620 followed by paclitaxel significantly reduced the tumor volume compared to paclitaxel alone and complete remission of the tumor was observed in 15 percent of rats, while no complete remissions were observed in the control group.

These studies indicate that SPI-1620 could be used to selectively increase the delivery of chemotherapy drugs to tumors and to enhance the efficacy of chemotherapeutic agents.