PRECLINICAL DEVELOPMENT OF A RECOMBINANT TOXIN CONTAINING CIRCULARLY PERMUTED INTERLEUKIN-4 AND TRUNCATED PSEUDOMONAS EXOTOXIN FOR THERAPY OF MALIGNANT ASTROCYTOMA

Effective treatment is lacking for malignant glioblastoma/astrocytoma. We have identified interleukin-4 receptors (IL-4R) on human malignant astrocytoma. We demonstrate that 16 of 21 surgical samples of high-gr ade astrocytoma and glioblastoma but not normal brain tissues expresse d IL-4R as assessed by reverse transcriptase PCR. We further demonstra te that human malignant astrocytoma cell lines express high-affinity I L-4R. Using a chimeric protein composed of circularly permuted IL-4 an d a truncated form of Pseudomonas exotoxin A, we observed that this to xin (IL4(38-37)-PE38KDEL) is highly cytotoxic to IL-4R-bearing gliobla stoma cells. Compared with a previously reported IL4-PE chimeric prote in (IL-PE4E), IL4(38-37)-PE38KDEL bound with higher affinity and was 3 -30-fold more cytotoxic to glioblastoma cell lines, Upon intrathecal a dministration in monkeys, high cerebrospinal fluid IL4(38-37)-PE38KDEL levels mere achieved using 2- and 6-mu g/kg doses without any central nervous system or other abnormalities. IL4(38-37)-PE38KDEL levels wer e not detectable in the serum of any monkey studied. When IL4(38-37)-P E38KDEL was injected into the right frontal cortex of rats, localized necrosis was observed at 1000-ng/ml doses but not at less than or equa l to 100-ng/ml doses. We conclude that by localized administration, no ntoxic levels of IL4(38-37)-PE38KDEL can be achieved, which may have s ignificant cytotoxic activity against malignant astrocytoma.