Mobilization of innate and adaptive antitumor immune responses by the RNP-targeting antibody ATRC-101.

Immunotherapy approaches focusing on T cells have provided breakthroughs in treating solid tumors. However, there remains an opportunity to drive anticancer immune responses via other cell types, particularly myeloid cells. ATRC-101 was identified via a target-agnostic process evaluating antibodies produced by the plasmablast population of B cells in a patient with non-small cell lung cancer experiencing an antitumor immune response during treatment with checkpoint inhibitor therapy. Here, we describe the target, antitumor activity in preclinical models, and data supporting a mechanism of action of ATRC-101. Immunohistochemistry studies demonstrated tumor-selective binding of ATRC-101 to multiple nonautologous tumor tissues. In biochemical analyses, ATRC-101 appears to target an extracellular, tumor-specific ribonucleoprotein (RNP) complex. In syngeneic murine models, ATRC-101 demonstrated robust antitumor activity and evidence of immune memory following rechallenge of cured mice with fresh tumor cells. ATRC-101 increased the relative abundance of conventional dendritic cell (cDC) type 1 cells in the blood within 24 h of dosing, increased CD8+ T cells and natural killer cells in blood and tumor over time, decreased cDC type 2 cells in the blood, and decreased monocytic myeloid-derived suppressor cells in the tumor. Cellular stress, including that induced by chemotherapy, increased the amount of ATRC-101 target in tumor cells, and ATRC-101 combined with doxorubicin enhanced efficacy compared with either agent alone. Taken together, these data demonstrate that ATRC-101 drives tumor destruction in preclinical models by targeting a tumor-specific RNP complex leading to activation of innate and adaptive immune responses.

Pan-Filovirus Serum Neutralizing Antibodies in a Subset of Congolese Ebolavirus Infection Survivors.

One year after a Zaire ebolavirus (EBOV) outbreak occurred in the Boende Health Zone of the Democratic Republic of the Congo during 2014, we sought to determine the breadth of immune response against diverse filoviruses including EBOV, Bundibugyo (BDBV), Sudan (SUDV), and Marburg (MARV) viruses. After assessing the 15 survivors, 5 individuals demonstrated some degree of reactivity to multiple ebolavirus species and, in some instances, Marburg virus. All 5 of these survivors had immunoreactivity to EBOV glycoprotein (GP) and EBOV VP40, and 4 had reactivity to EBOV nucleoprotein (NP). Three of these survivors showed serologic responses to the 3 species of ebolavirus GPs tested (EBOV, BDBV, SUDV). All 5 samples also exhibited ability to neutralize EBOV using live virus, in a plaque reduction neutralization test. Remarkably, 3 of these EBOV survivors had plasma antibody responses to MARV GP. In pseudovirus neutralization assays, serum antibodies from a subset of these survivors also neutralized EBOV, BDBV, SUDV, and Taï Forest virus as well as MARV. Collectively, these findings suggest that some survivors of naturally acquired ebolavirus infection mount not only a pan-ebolavirus response, but also in less frequent cases, a pan-filovirus neutralizing response.

Non-progressing cancer patients have persistent B cell responses expressing shared antibody paratopes that target public tumor antigens.

There is significant debate regarding whether B cells and their antibodies contribute to effective anti-cancer immune responses. Here we show that patients with metastatic but non-progressing melanoma, lung adenocarcinoma, or renal cell carcinoma exhibited increased levels of blood plasmablasts. We used a cell-barcoding technology to sequence their plasmablast antibody repertoires, revealing clonal families of affinity matured B cells that exhibit progressive class switching and persistence over time. Anti-CTLA4 and other treatments were associated with further increases in somatic hypermutation and clonal family size. Recombinant antibodies from clonal families bound non-autologous tumor tissue and cell lines, and families possessing immunoglobulin paratope sequence motifs shared across patients exhibited increased rates of binding. We identified antibodies that caused regression of, and durable immunity toward, heterologous syngeneic tumors in mice. Our findings demonstrate convergent functional anti-tumor antibody responses targeting public tumor antigens, and provide an approach to identify antibodies with diagnostic or therapeutic utility.

Molecular analysis of gene expression in the developing pontocerebellar projection system.

As an approach toward understanding the molecular mechanisms of neuronal differentiation, we utilized DNA microarrays to elucidate global patterns of gene expression during pontocerebellar development. Through this analysis, we identified groups of genes specific to neuronal precursor cells, associated with axon outgrowth, and regulated in response to contact with synaptic target cells. In the cerebellum, we identified a phase of granule cell differentiation that is independent of interactions with other cerebellar cell types. Analysis of pontine gene expression revealed that distinct programs of gene expression, correlated with axon outgrowth and synapse formation, can be decoupled and are likely influenced by different cells in the cerebellar target environment. Our approach provides insight into the genetic programs underlying the differentiation of specific cell types in the pontocerebellar projection system.

Immunodynamics: a cancer immunotherapy trials network review of immune monitoring in immuno-oncology clinical trials.

The efficacy of PD-1/PD-L1 targeted therapies in addition to anti-CTLA-4 solidifies immunotherapy as a modality to add to the anticancer arsenal. Despite raising the bar of clinical efficacy, immunologically targeted agents raise new challenges to conventional drug development paradigms by highlighting the limited relevance of assessing standard pharmacokinetics (PK) and pharmacodynamics (PD). Specifically, systemic and intratumoral immune effects have not consistently correlated with standard relationships between systemic dose, toxicity, and efficacy for cytotoxic therapies. Hence, PK and PD paradigms remain inadequate to guide the selection of doses and schedules, both starting and recommended Phase 2 for immunotherapies. The promise of harnessing the immune response against cancer must also be considered in light of unique and potentially serious toxicities. Refining immune endpoints to better inform clinical trial design represents a high priority challenge. The Cancer Immunotherapy Trials Network investigators review the immunodynamic effects of specific classes of immunotherapeutic agents to focus immune assessment modalities and sites, both systemic and importantly intratumoral, which are critical to the success of the rapidly growing field of immuno-oncology.

Regulation of pontine neurite morphology by target-derived signals.

The molecular cues that regulate neurite morphology within the target environment are key to the formation of complex neural circuitry. During development of the ponto-cerebellar projection, pontine fibers sprout and form elaborate arbors within the inner cerebellar layer prior to arrival of their target cells, the cerebellar granule neurons. Here, we describe the biochemical fractionation of two granule neuron-derived factors that stimulate elaboration of pontine neurites. These factors were identified using a dissociated pontine bioassay and biochemically fractionated from granule cell (GC) conditioned medium (GCCM). One of the factors, STIM1, is a protein with a molecular weight greater than 30 kDa that is distinct from known neurotrophins. The other, STIM2, is a small, protease-resistant molecule with an estimated molecular weight below 1 kDa. We show that these factors stimulate pontine neurite elongation both independently and cooperatively and thus may contribute to the formation of elaborate pontine arbors within the cerebellar cortex.

Suppression of human CD4+ T cell activation by 3,4-dimethoxycinnamonyl-anthranilic acid (tranilast) is mediated by CXCL9 and CXCL10.

3,4-dimethoxycinnamonyl-anthranilic acid (tranilast) is an orally available anti-allergic drug with structural and functional homologies to immunosuppressive catabolites of the essential amino acid tryptophan and broad anti-inflammatory properties. It has recently been shown to be effective in animal models of multiple sclerosis and rheumatoid arthritis, two autoimmune diseases that are mediated by auto-aggressive Th1-polarized CD4+ T lymphocytes. Here we demonstrate potent suppressive effects of tranilast on the function of naïve human CD4+ T cells. Tranilast inhibited inhibits activation and proliferation of purified CD4+ T cells stimulated through the T cell receptor with an EC50 of less than 10 µM, a concentration that is well below plasma levels achieved after oral administration of approved doses of 200-600 mg in humans. The antiproliferative effects were less potent on naïve CD8+ T cells. Suppression of CD4+ and CD8+ T cell proliferation was associated with an inhibition of T cell activation. Cytokine analyses of naïve CD4+ T cells revealed that tranilast interferes with the production of cyto- and chemokines driven by signal transducer and activator of transcription 1 (STAT1), notably chemokine (C-X-C motif) ligands (CXCL) 9 and 10. Tranilast limited STAT1 phosphorylation in activated T cells and supplementation of CXCL9 or CXCL10 reversed the anti-proliferative effects of tranilast. These data imply CXCL9 and CXCL10 as novel therapeutic targets of tranilast in Th1-mediated autoimmune diseases and identify phospho-STAT1 and its target chemokines CXCL9 and CXCL10 as potential markers for monitoring the bioactivity of tranilast in humans.