CpG Oligonucleotide (1018 ISS) May Overcome Rituximab (R) Resistance in Follicular Lymphoma (FL) through Enhanced ADCC, T Cell Expansion, and Alteration of Tumor Microenvironment.

Immunostimulatory oligonucleotides containing nonmethylated CpG motifs (ISS) have multiple actions on adaptive and innate immune responses, including enhanced antigen presentation and costimulatory molecule expression, stimulation of dendritic cell maturation, and induction of cytokines that result in enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) and Th1 immune responses. Through these mechanisms, we hypothesized ISS might be able to overcome R resistance. Our completed phase I study combining an ISS (1018 ISS, Dynavax Technologies) with R in patients (pts) with relapsed or refractory, advanced stage NHL, demonstrated that the combination is safe, and causes a dose-related increase in the expression of several interferon (IFN)-inducible genes.(Blood 105:489). We have subsequently enrolled 16 pts (median age 60; 9 female) with R-naïve or sensitive FL in a phase II trial to further investigate the efficacy and biological activity of this rational combination. Pts received 4 injections of 1018 ISS (0.2 mg/kg sc) at weekly intervals, beginning at the time of the second of 4 weekly standard R infusions. No grade III/IV toxicities occurred. Genotyping of 13 evaluable pts for the FcγRIII-A 158 polymorphism revealed VF (n=6) and FF (n=7). Flow cytometry of peripheral blood demonstrated a significant expansion of CD3+ cells in 9 pts following 4 weeks of 1018 ISS. When tested with allogeneic stimulation using an EBV transformed B cell line (Mann) in ELISPOT assay, T cell secretion of IFN-γ was increased following 1018 ISS (mean count pre 1018 ISS: 362; mean count post 1018 ISS: 565; p = 0.05), whereas T cell secretion of IL-2 did not change, both consistent with an emerging Th1 immune response. Using a standard chromium release assay, 7/13 pts (54%) demonstrated increases in ADCC of peripheral blood mononuclear cells following ISS compared to baseline (effector:target ratio of 25:1); including 5 pts with FCγRIIIA genotype 158 FF. Skin biopsies were obtained in all patients at baseline, and following ISS therapy at the injection site and a distant site. Following 1018 ISS, 5 pts (42%) had significant skin infiltration with CD8+ lymphocytes; and 5 pts had increased numbers of CD68+ cells at injection sites. Biopsies of tumor were obtained at baseline, and post 1018 ISS treatment when possible, and evidence of CD8+ T cell infiltration within residual FL nodules was observed following R and 1018 ISS therapy. As of 08/05, at a median follow-up of 9 months, only 3 pts have experienced disease progression, one of whom subsequently converted to CRu without further therapeutic intervention. We conclude that the combination of 1018 ISS and rituximab is safe, and demonstrates significant local and systemic biological activity. Moreover, the demonstration of enhanced ADCC in pts with an FCγRIIIA 158 FF genotype (expected poor prognosis following R in pts with FL), the associated development of a Th1 response, and measurable alteration of the tumor microenvironment all suggest ISS could overcome both innate and acquired R resistance mechanisms in pts with FL.