Dysregulated fibroblast growth factor (FGF) signaling has been implicated in the pathogenesis of human cancers. Aberrant activation of FGF receptor 2 (FGFR2) signaling, through overexpression of FGFR2 and/or its ligands, mutations, and receptor amplification, has been found in a variety of human tumors. We generated monoclonal antibodies against the extracellular ligand-binding domain of FGFR2 to address the role of FGFR2 in tumorigenesis and to explore the potential of FGFR2 as a novel therapeutic target. We surveyed a broad panel of human cancer cell lines for the dysregulation of FGFR2 signaling and discovered that breast and gastric cancer cell lines harboring FGFR2 amplification predominantly express the IIIb isoform of the receptor. Therefore, we used an FGFR2-IIIb-specific antibody, GP369, to investigate the importance of FGFR2 signaling in vitro and in vivo. GP369 specifically and potently suppressed ligand-induced phosphorylation of FGFR2-IIIb and downstream signaling, as well as FGFR2-driven proliferation in vitro. The administration of GP369 in mice significantly inhibited the growth of human cancer xenografts harboring activated FGFR2 signaling. Our findings support the hypothesis that dysregulated FGFR2 signaling is one of the critical oncogenic pathways involved in the initiation and/or maintenance of tumors. Cancer patients with aberrantly activated/amplified FGFR2 signaling could potentially benefit from therapeutic intervention with FGFR2-targeting antibodies.

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The c-fos gene was one of the earliest vertebrate genes shown to be transcriptionally induced by growth factors. Intensive study of the promoter of c-fos (؊325 to ؊80) by transient or permanent transfections of synthetic DNA constructs has repeatedly shown the importance of several sequence elements and the resident nuclear proteins that bind them (e.g. ternary complex factor/ELK1; serum response factor, cAMP response element-binding protein/amino-terminal fragment/AP-1). However these studies have left unanswered numerous questions about the role of these proteins in the regulation of the native chromosomal gene. In particular, the role of a site in this enhancer that binds STATs has been controversial. We present evidence here that STAT3 and not STAT1 accumulates on the chromosomal c-fos promoter and provides a boost to transcription without the activation of resident nuclear proteins through serine kinases. Also, when resident nuclear proteins such as ELK1 are activated to varying extents by mitogen-activated protein kinase pathways, STAT3 activation provides a 2-fold boost regardless of the final level of activated transcription. Thus the several proteins that interact with the c-fos enhancer apparently can act either in a cooperative or independent manner to achieve very different levels of transcription.

ONCR-177 is an engineered recombinant oncolytic herpes simplex virus (HSV) with complementary safety mechanisms, including tissue-specific miRNA attenuation and mutant UL37 to inhibit replication, neuropathic activity, and latency in normal cells. ONCR-177 is armed with five transgenes for IL12, FLT3LG (extracellular domain), CCL4, and antagonists to immune checkpoints PD-1 and CTLA-4. In vitro assays demonstrated that targeted miRNAs could efficiently suppress ONCR-177 replication and transgene expression, as could the HSV-1 standard-of-care therapy acyclovir. Although ONCR-177 was oncolytic across a panel of human cancer cell lines, including in the presence of type I IFN, replication was suppressed in human pluripotent stem cell–derived neurons, cardiomyocytes, and hepatocytes. Dendritic cells activated with ONCR-177 tumor lysates efficiently stimulated tumor antigen–specific CD8+ T-cell responses. In vivo, biodistribution analyses suggested that viral copy number and transgene expression peaked approximately 24 to 72 hours after injection and remained primarily within the injected tumor. Intratumoral administration of ONCR-177 mouse surrogate virus, mONCR-171, was efficacious across a panel of syngeneic bilateral mouse tumor models, resulting in partial or complete tumor regressions that translated into significant survival benefits and to the elicitation of a protective memory response. Antitumor effects correlated with local and distant intratumoral infiltration of several immune effector cell types, consistent with the proposed functions of the transgenes. The addition of systemic anti–PD-1 augmented the efficacy of mONCR-171, particularly for abscopal tumors. Based in part upon these preclinical results, ONCR-177 is being evaluated in patients with metastatic cancer (ONCR-177-101, NCT04348916).

Development of next-generation oncolytic viruses requires the design of vectors that are potently oncolytic, immunogenic in human tumors, and well tolerated in patients. Starting with a joint-region deleted herpes simplex virus 1 (HSV-1) to create large transgene capability, we retained a single copy of the ICP34.5 gene, introduced mutations in UL37 to inhibit retrograde axonal transport, and inserted cell-type-specific microRNA (miRNA) target cassettes in HSV-1 genes essential for replication or neurovirulence. Ten miRNA candidates highly expressed in normal tissues and with low or absent expression in malignancies were selected from a comprehensive profile of 800 miRNAs with an emphasis on protection of the nervous system. Among the genes essential for viral replication identified using a small interfering RNA (siRNA) screen, we selected ICP4, ICP27, and UL8 for miRNA attenuation where a single miRNA is sufficient to potently attenuate viral replication. Additionally, a neuron-specific miRNA target cassette was introduced to control ICP34.5 expression. This vector is resistant to type I interferon compared to ICP34.5-deleted oncolytic HSVs, and in cancer cell lines, the oncolytic activity of the modified vector is equivalent to its parental virus. In vivo , this vector potently inhibits tumor growth while being well tolerated, even at high intravenous doses, compared to parental wild-type HSV-1.

The therapeutic effectiveness of oncolytic viruses (OVs) delivered intravenously is limited by the development of neutralizing antibody responses against the virus. To circumvent this limitation and to enable repeated systemic administration of OVs, here we develop Synthetic RNA viruses consisting of a viral RNA genome (vRNA) formulated within lipid nanoparticles. For two Synthetic RNA virus drug candidates, Seneca Valley virus (SVV) and Coxsackievirus A21, we demonstrate vRNA delivery and replication, virus assembly, spread and lysis of tumor cells leading to potent anti-tumor efficacy, even in the presence of OV neutralizing antibodies in the bloodstream. Synthetic-SVV replication in tumors promotes immune cell infiltration, remodeling of the tumor microenvironment, and enhances the activity of anti-PD-1 checkpoint inhibitor. In mouse and non-human primates, Synthetic-SVV is well tolerated reaching exposure well above the requirement for anti-tumor activity. Altogether, the Synthetic RNA virus platform provides an approach that enables repeat intravenous administration of viral immunotherapy.

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Although oncolytic viruses have shown clinical efficacy for local treatment of cancerous tumors, the ability to induce immune-mediated regression to visceral lesions is not robust. Immune checkpoint modulation has been efficacious in a fraction of cancers associated with an inflamed microenvironment but is associated with toxicity due to nonspecific T-cell activation. Therefore, combining these two strategies has the exciting potential to be an effective cancer therapy. Oncolytic virus can be genetically modified to decrease pathogenicity to normal cells and to increase their lytic potential and ability to stimulate antitumor immunity, thus improving the risk-benefit ratio for cancer patients. Oncorus oHSV (ONCR) are novel oncolytic herpes simplex virus type-1 vectors developed for the treatment of solid tumors. ONCR utilizes a unique conditional-lethal strategy in which tissue-specific miRs binding sites are inserted into early genes essential for viral replication and in the neurovirulence gene ICP34.5. This strategy curtails viral replication in normal cells, including neurons, and limits the expression of g34.5 to tumor cells, thus promoting potent viral replication in presence of type I interferon. Fifteen immunostimulatory transgenes and combination thereof were systematically evaluated in dual flank syngeneic mouse tumor models to test both for oncolysis and abscopal efficacy on the contralateral noninjected tumor. Among the selected transgenes, IL-12 was found to elicit the most potent efficacy on the ipsilateral and contralateral tumors. We demonstrated that the replication of ONCR and the expression of IL-12 was limited to the injected tumors. By contrast, induction of systemic immunity as assessed by IFNg production in contralateral tumors and in plasma was observed. ONCR expressing IL-12 elicited efficacy in multiple subcutaneous and metastatic models. Additional payloads designed to stimulate antigen presentation, recruitment of immune cells and inhibition of tumor immune suppression were identified as further enhancing IL-12 activity. Data supporting the selection of a suite of payloads cloned into a single ONCR vector will be presented. ONCR represents a new class of oncolytic virus that promote antitumor responses through a multiprong mechanism of action dependent on selective tumor cell killing, the induction of systemic antitumor immunity and reversion of immune suppression. Citation Format: Lorena Lerner, Edward M. Kennedy, Terry Farkaly, Allison Colthart, Caity Montagna, Prajna Behera, Judith Jacques, Peter Grzesik, Jennifer Lee, Agnieszka Denslow, Jacqueline Gursha, Brian Haines, Michael Ball, Daniel Wambua, Cecilia Kwong, Lingxin Kong, Michael Paglia, Laura Viggiano Salta, Lorenz Ponce, Caroline Webb, Mitchell Finer, Christophe Quéva. microRNA attenuated oHSV-1 armed with multiple immunomodulatory payloads mediates robust and selective antitumor immune response in preclinical tumor models [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B23.