Recent advances in our understanding of the immune response are allowing for the logical design of new approaches to cancer immunization. Bacterial DNA is capable of inducing activation of B cells, NK cells, and monocytes (1-5). In addition, bacterial DNA can induce production in vitro and in vivo of a variety of proinflammatory cytokines (6-8). In contrast, vertebrate DNA does not induce lymphocyte activation. Bacterial DNA contains a much higher frequency of unmethylated CpG dinucleotides than does vertebrate DNA due to (i) CpG suppression (the under representation of CpG in vertebrate genomes) and (ii) methylation of 80% of the CpG in vertebrates. It is possible that lymphocyte activation by the CpG motif in bacterial DNA represents an immune defense mechanism that can distinguish bacterial from host DNA (1). Select synthetic oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODN) have immunologic effects similar to those seen with bacterial DNA. CpG ODN can stimulate monocytes, macrophages, and dendritic cells that then produce several cytokines, including the TH1 cytokine interleukin 12. This effect synergizes with CpG ODN to induce NK cell production of interferon ␥ (6). Both human and murine leukocytes respond to this novel pathway of immune activation, although individual CpG ODN differ somewhat in their ability to activate various immune cell populations and induce cytokine production in human and murine systems.The molecular mechanisms responsible for CpG ODNinduced immune cell activation are still under investigation. We have recently reported that CpG ODN trigger the production of reactive oxygen species that activate NF-B (9). This activation, in turn, leads to cellular activation. Irrespective of the mechanism involved, it is clear that select CpG ODN can have powerful immunologic effects and might be useful therapeutic agents in a number of circumstances, including cancer immunotherapy. For example, we have demonstrated that CpG ODN can enhance antibody-dependent cellular cytotoxicity and improve the in vivo efficacy of monoclonal antibody therapy in a syngeneic murine lymphoma model (10).CpG ODN can induce activation of antigen-presenting cells and enhance production of cytokines known to participate in the development of an active immune response. They also enhance B cell activation, particularly when the B cell receptor is cross-linked (1). These effects are likely to promote antigenspecific responses. Indeed, Branda et al. (11) demonstrated that an anti-sense ODN, which in retrospect is noted to contain the CpG motif, enhances antibody response to antigen. We therefore used a well-established animal model to assess whether CpG ODN can function as an immune adjuvant in antitumor immunization.

Safety and efficacy of the fully human anti-CD20 monoclonal antibody, ofatumumab, was analyzed in a multicenter dose-escalating study including 33 patients with relapsed or refractory chronic lymphocytic leukemia. Three cohorts of 3 (A), 3 (B), and 27 (C) patients received 4, once weekly, infusions of ofatumumab at the following doses: (A) one 100 mg and three 500 mg; (B) one 300 mg and three 1000 mg; (C) one 500 mg and three 2000 mg. Sixty-seven percent of the patients were Binet stage B, and the median number of previous treatments was 3. The maximum tolerated dose was not reached. The majority of related adverse events occurred at first infusion, and the number of adverse events decreased at each subsequent infusion. Seventeen (51%) of 33 patients experienced infections, 88% of them of grade 1-2. One event of interstitial pneumonia was fatal; all other cases resolved within one month. The response rate of cohort C was 50% (13/26), one patient having a nodular partial remission and 12 patients partial remission. In conclusion, ofatumumab was found to be well tolerated in patients with chronic lymphocytic leukemia (CLL) in doses up to 2000 mg. Preliminary data on safety and objective response are encouraging and support further studies on the role of ofatumumab in CLL patients. This trial was registered at www.clinicaltrials.gov as no.

Compared with IWC, the IWC+PET-based assessment provides a more accurate response classification in patients with aggressive NHL.