Isis Pharmaceuticals Inc. believes it has found at least part of the answer to why it saw different results in the first and second halves of a Phase II/III trial of its ISIS 2302 antisense compound to treat Crohn's disease. The new analysis, which showed the compound to be effective in women and heavier patients, has given rise to the company's hypothesis that a higher dose will be more effective. But the company still isn't sure why results were better in these two groups.

Last December, ISIP announced data from a 300-patient Phase II/III trial demonstrating a 20 percent rate of complete remission plus complete steroid withdrawal (the combined primary end point) in all