Seragen Inc. on Saturday reported results of its interleukin-2(IL-2) receptor-targeted fusion toxin, DAB486IL-2 in twoapplications, severe rheumatoid arthritis and type 1 diabetes,at the Seventh Annual Conference of the Clinical ImmunologySociety in Philadelphia.
According to Seragen spokeswoman Helen Maslocka, data fromthe severe rheumatoid arthritis trial, which were retreatmentdata from ongoing Phase I safety studies, demonstrated thatthe duration of response to the IL-2 fusion toxin went up withthe second treatment without a lessened effect and with nosignificant safety problems.
Seragen of Hopkinton, Mass., has begun a double-blind,placebo-controlled Phase II clinical trial of the compound forthis application.
Results from an ongoing 33-patient study of DAB486IL-2 fortype 1 diabetes demonstrated reduced insulin requirements inapproximately 55 percent of patients and preserved pancreaticislet cell function, which may allow the preserved islet cells toproduce insulin, according to Maslocka.
Industry analysts said Seragen will soon drop its DAB486IL-2(486) for DAB389IL (389)-2, the company's latest version of itsIL-2 receptor-targeted fusion toxin.
According to Maslocka, Seragen discovered 389 after itperformed a series of deletion experiments consisting of threeamino acids each to determine the most efficient amino acidlinks or where the specific activity was lost.
The company found that the 389 molecule is 15 percentsmaller in molecular weight and more agile than the 489molecule. It is able to bind approximately five times better tothe IL-2 receptor than 486; is 10 times more potent, thusenabling it to inhibit the protein synthesis of target cells; andhas shown to be three times less toxic than 486, which alreadyhad demonstrated low toxicity.
"They'll end up going with 389," said Mary Anne Gray of KidderPeabody in New York. "All the preliminary data seem tosuggest this version is more potent, so a lot less can beadministered without changing the toxicity, yet increasing thetherapeutic index."
Calvert Crary, an analyst with Martin Simpson & Co. in NewYork, said that 389 will "most definitely" replace 486. "They're(Seragen) curing people," Calvert said. "It's a solid product."
Maslocka said the decision will be made following completionof Phase I/II studies of 389 in both lymphoma and severeprogressive rheumatoid arthritis, which is expected by mid-1993.
Seragen's IL-2 receptor-targeted fusion toxins treat not thesymptoms, but the destructive behavior of T cells. Seragen'sapproach targets only the small percentage of damaging T cells,leaving the rest of the immune system intact, explained Crary.
Crary predicted that Seragen will have a product for severerheumatoid arthritis on the market by 1996, with first-yearU.S. revenues of about $30 million and second-year earnings of$130 million.
The company's stock (NASDAQ:SRGN) was up $1.25 a share onMonday to $11.50.
-- Michelle Slade Associate Editor
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