Patients are randomized to receive P3C541b or placebo within each of two study groups. Enrollment in the first group will be independent of HLA type, whereas all but two of the patients enrolled in group 2 must have one or more HLA types A33, B8, B27, or Bw62. Treatment in group 2 will not begin until those in group 1 have reached day 14 without serious toxicity.