Rogers, Laura M.

Abstract CMP-001 is a virus-like particle containing a TLR9 agonist (class A CpG ODN) encapsulated by the Qβ capsid. Preclinical studies and early phase clinical trials of intralesional injection with CMP-001, combined with anti-PD1 antibody, demonstrate promising results. Prior work by our group has demonstrated that the immunostimulatory effects of CMP-001 are dependent on generation of an anti-Qβ antibody response which results in opsonization of CMP-001 by plasmacytoid dendritic cells (pDCs) and production of IFNα. While a variety of cell types including monocytes and B cells can take up CMP-001, the immune response to CMP-001 is based in large part on rapid induction of IFNα production by pDCs. The current studies were designed to assess the downstream effects of CMP-001 and anti-Qβ antibody on various arms of the immune response using normal donor human peripheral blood mononuclear cells (PBMCs) as a model. Stimulation of PBMCs with CMP-001 and anti-Qβ antibody induced production of IFNα from pDCs as previously observed. This IFNα production occurred very rapidly (within 2 hours) and was short lived, but had long term secondary effects, including induction of CXCL10 production by monocytes. Single cell RNA sequencing done 24 hours after stimulation demonstrated additional downstream changes including the following: Upregulation of CXCL10, MIP1-α, IL1-RA and IDO by monocytes. Downregulation of CD14 by monocytes. Upregulation of a broad variety of interferon response genes in various cell types including NK cells and T cells. We conclude the primary effect of in situ immunization with CMP-001 is to induce rapid production of IFNα production by pDCs. This results in significant downstream effects on various cell populations that contribute to the anti-tumor immune response. Understanding these pathways could help identify the most promising combination immunotherapies involving CMP-001. Ongoing studies are exploring the kinetics of these responses and whether similar changes are observed in the tumor microenvironment. Citation Format: Shakoora Sabree, Andrew Voigt, Laura Rogers, Sue Blackwell, Caitlin Lemke-Miltner, George J. Weiner. Evaluation of the complexity of the immune response to CMP-001, a TLR9 agonist [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6666.

Abstract The anti-CD20 monoclonal antibody rituximab (R) is widely used to treat B-cell malignancies including follicular lymphoma (FL). A better understanding of activity and resistance mechanisms is necessary for improving treatment outcomes. We previously reported that genetic variants in the complement pathway are associated with event-free survival of FL patients following R therapy. This correlation was particularly high for SNP rs3766404, located in intron 6 of Complement Factor H (CFH). Subjects with the minor allele of this SNP experienced inferior event-free survival. Five CFH related proteins (CFHR1-5) share a similar and sometimes overlapping function with CFH, including suppression of complement activation. Genetic variations within the CFH family locus are linked to a variety of complement-mediated disorders such as age-related macular degeneration (AMD) and atypical hemolytic uremic syndrome. Interestingly, AMD patients with the minor allele of rs3766404 frequently have deletion of CFHR3 and CFHR1, suggesting that loss of these proteins functionally impacts complement regulation. The current studies were designed to better understand the relationship between R therapy of FL and CFH family proteins. CFH and CFHR1 protein levels were quantified in serum samples from both normal subjects (n=59) and FL (n=108) subjects from the Iowa/Mayo Lymphoma SPORE Molecular Epidemiology Resource. No correlation was observed between the quantity of CFH in serum and SNP genotype in either cohort. However, in both cohorts, individuals homozygous for the minor allele in SNP rs3766404 lacked detectable expression of CFHR1. Homozygotes for the major allele expressed the highest levels of CFHR1, and heterozygotes expressed intermediate levels. Among FL subjects treated with R as a component of initial therapy, increased levels of CFHR1 were associated with improved event-free survival (hazard ratio 0.48, 95% confidence interval 0.28-0.82, p=0.0051). In contrast, CFHR1 levels had no impact on outcome among the FL subjects who did not receive R as a component of initial therapy. This subset of FL subjects included those observed off therapy. The effect of CFHR1 levels on outcome for those subjects treated with R versus those not treated with R was statistically different (p=0.0023 based on a Cox proportional hazard model). There was no correlation between CFH levels and outcome in any population. CFHR1 binds the complement component C3b, inhibiting downstream complement activation. We previously demonstrated that complement can inhibit R activity in vitro. Specifically, C3b deposition can have a negative impact on antibody–mediated tumor cell killing by interfering with R-induced NK cell activation and antibody dependent cellular cytotoxicity. Our current finding that higher CFHR1 correlates with improved outcome following R therapy provides further evidence that the effect of complement on therapeutic monoclonal antibodies is complex. These findings may have implications for predicting response to, and optimization of, anti-CD20 and other antibody therapies. Ongoing studies are exploring this possibility in additional patient cohorts, the potential role of other CFH family members, and the underlying biology associated with these observations. Disclosures: Link: Genentech: Consultancy; Millenium: Consultancy; Pharmacyclics: Consultancy; Spectrum: Consultancy; Genentech: Research Funding; Millenium: Research Funding; Pharacyclics: Research Funding.