Seragen Inc. said Tuesday that it filed an investigational newdrug (IND) application for a new version of its interleukin-2fusion toxin, which the company hopes will replace itspredecessor.

The new fusion toxin, called DAB389IL-2, has demonstrated inpreclinical studies 10 times the potency against target diseasedcells and far less misdirected toxicity than Seragen's first drug,DAB486IL-2, according to the company.

"These properties may enable the DAB389Il-2 Fusion Toxin tohave increased efficacy and be associated with even fewer andmilder side effects than those produced by the DAB486IL-2molecule," Seragen said.

If the 389 compound demonstrates as much improvement over486 in humans as it has in animal studies, the company plansto halt clinical development of 486 and turn its attention to itsreplacement.

Seragen's stock (NASDAQ:SRGN) closed unchanged Tuesday at$8.75 a share. The company went public in April at $12 ashare.

Seragen is exploring a broad range of potential therapeutic usesfor its fusion toxins, including cancers, autoimmune diseasessuch as rheumatoid arthritis and recent onset type-1 diabetes,and to aid acceptance of organ transplants.

Fusion toxins are composed of fragments of toxin fused toligands that target specific surface receptors of diseased ordisease-causing cells. The fusion toxins are designed topenetrate the cell and destroy its ability to manufactureproteins, killing the cell.

Among the potential initial targets for DAB389IL-2 trials arecancers and severe rheumatoid arthritis, two therapeutictargets where its predecessor, 486, has demonstrated positiveresults.

The DAB486IL-2 compound showed in a Phase I trial an abilityto shrink cancerous tumors in four of 18 patients withleukemia or lymphomas without the side effects common tochemotherapy. The data were reported in the May edition ofBlood, the Journal of the American Society of Hematology.

Results from a Phase I/II study to treat severe rheumatoidarthritis, reported to a scientific conference last May, showedfavorable responses in 14 of 19 patients treated withDAB486IL-2. Results from an ongoing Phase II double-blindclinical study of the compound for treating severe rheumatoidarthritis are expected in early 1993, said Helen Maslocka,Seragen's director of investor relations.

Seragen has rights to patents and applications related toDAB389IL-2, in addition to having exclusive rights to thebroader underlying fusion toxin technology, which it licensed in1983 from Harvard College, Maslocka said.

The company, which claims to be alone in the commercialdevelopment of most fusion toxins, is also working on fusiontoxins involving IL-4, IL-6, CD4, EGF (epidermal growth factor)and MSH (melanocyte stimulating hormone).

-- Ray Potter Senior Editor

(c) 1997 American Health Consultants. All rights reserved.