Seragen Inc. announced Wednesday that clinical trial results oftwo different Phase I/II trials in cancer patients, usingSeragen's (NASDAQ:SRGN) first interleukin-2 (IL-2) receptor-targeted fusion toxin, are reported in the Journal of ClinicalOncology and Cancer Research.
The fusion toxin, DAB486IL-2, was tested in severely ill,chemotherapy-resistant cancer patients.
Investigators have found evidence that one way to selectlymphoma patients most likely to benefit from IL-2 fusiontoxin is by screening for the presence of the p55 chain of theIL-2 receptor in patients' tumor tissue. Two of three cutaneousT cell lymphoma (CTCL) patients in each study who testedpositive for p55 demonstrated tumor regression after receivingDAB486IL-2.
"Testing for the p55 chain of the IL-2 receptor can be donesimply with an existing, commercially available antibody," saidJean Nichols, Seragen's senior vice president. "Predicting whichpatients are most likely to benefit from IL-2 fusion toxin willbe helpful in expediting our clinical trial process."
"Three of the five CTCL patients achieved significant tumorresponses," Paul Hesketh, clinical director of the Section ofMedical Oncology and Associate Professor of Medicine at BostonUniversity Medical Center, wrote in the Journal of ClinicalOncology. "One patient attained a complete clinical andpathologic response, which has been sustained without anyinterval treatment for more than 33 months," Hesketh said."Two other patients achieved partial responses of 17-plus andfour months' duration," he added. Two of these patientsexhibited IL-2 receptors on their malignant tissue; IL-2receptor expression could not be determined for the otherpatient.
"The results suggest that CTCL may be particularly sensitive tothis novel biologic agent," Hesketh concluded. "DAB486IL-2demonstrated significant clinical activity with acceptabletoxicity in a group of heavily pretreated patients with CTCL."
C. Frederick LeMaistre, director of the Section of Bone MarrowTransplants at the University of Texas Health Science Center atSan Antonio, reported on another Phase I/II study in thejournal Cancer Research. He administered DAB486IL-2 to 23patients with various hematologic malignancies.
In this varied group, LeMaistre found that in four patients whotested negative for the presence of p55, there were noindications of response. This observation supports thehypothesis that the presence of p55 is necessary for IL-2fusion toxin to work.
IL-2 receptor expression was undetermined in eight patients.Of 11 patients testing positive for p55, four exhibited sometumor reduction. Two of these four were CTCL patients.
Seragen of Hopkinton, Mass., said its fusion toxins havepotential applications in a wide range of diseases, many ofwhich are incurable or inadequately served by existingtherapies, including certain cancers and such autoimmunedisorders as rheumatoid arthritis and type 1 diabetes.
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