A Phase Ib Open-Label, Multicenter Study of Inhaled DV281, a TLR9 Agonist, in Combination with Nivolumab in Patients with Advanced or Metastatic Non-small Cell Lung Cancer.

PURPOSE: Although PD-(L)1 inhibitors have shown efficacy in advanced/metastatic non-small cell lung cancer (NSCLC), many patients do not respond to this treatment and more effective combinations with acceptable toxicities are needed. To assess the potential benefit of combining localized innate immune stimulation with checkpoint blockade, the TLR9 agonist DV281 was combined with nivolumab in a phase Ib study. PATIENTS AND METHODS: Patients after one or two prior lines of systemic therapy were enrolled in a dose-escalation study with a 3+3 design. DV281 was administered via inhalation in five dose cohorts at 1 to 25 mg; nivolumab 240 mg was administered intravenously every 2 weeks. Safety, tolerability, pharmacodynamics, and response to treatment were assessed. RESULTS: Twenty-six patients with advanced NSCLC enrolled. Baseline programmed death ligand 1 (PD-L1) expression was present in 16 patients (61.5%); 21 (80.7%) had received previous anti-PD-1/PD-L1. Thirteen patients (50%) had stable disease, nine (34.6%) had progressive disease, and four (15.4%) were not evaluable. Median duration of disease control was 124 days. Adverse events were seen in 16 patients (61.5%), mostly grade 1/2 chills, fatigue, flu-like symptoms, diarrhea, and rash; there was only one grade 3 adverse event (dyspnea). Pharmacodynamic assessment, measured by IFN- inducible gene expression, showed target engagement in all dose cohorts. Systemic pharmacodynamic responses plateaued in the 2 highest dose cohorts. CONCLUSIONS: DV281 with nivolumab was well tolerated with target engagement observed at every dose. Pharmacodynamic advantages at doses above 10 mg were unclear. The long duration of disease control in 50% of patients suggests clinically relevant activity in this population of heavily pretreated patients.

Small-Molecule TLR8 Antagonists via Structure-Based Rational Design.

Rational design of drug-like small-molecule ligands based on structural information of proteins remains a significant challenge in chemical biology. In particular, designs targeting protein-protein interfaces have met little success given the dynamic nature of the protein surfaces. Herein, we utilized the structure of a small-molecule ligand in complex with Toll-like receptor 8 (TLR8) as a model system due to TLR8's clinical relevance. Overactivation of TLR8 has been suggested to play a prominent role in the pathogenesis of various autoimmune diseases; however, there are still few small-molecule antagonists available, and our rational designs led to the discovery of six exceptionally potent compounds with ∼picomolar IC50 values. Two X-ray crystallographic structures validated the contacts within the binding pocket. A variety of biological evaluations in cultured cell lines, human peripheral blood mononuclear cells, and splenocytes from human TLR8-transgenic mice further demonstrated these TLR8 inhibitors' high efficacy, suggesting strong therapeutic potential against autoimmune disorders.

In Situ Vaccination with a TLR9 Agonist and Local Low-Dose Radiation Induces Systemic Responses in Untreated Indolent Lymphoma.

This multicenter phase I/II clinical trial evaluated intratumoral SD-101, a TLR9 agonist, and low-dose radiation in patients with untreated indolent lymphoma. Twenty-nine enrolled patients received 4 Gy of radiation followed by 5 weekly intratumoral injections of SD-101 at a single tumor site. No treatment-related grade 4 or serious adverse events occurred. Nearly all patients had tumor reduction at their treated site. More importantly, 24 patients had tumor reduction at their nontreated sites, with 5 patients achieving a partial response and one achieving a complete response. Treatment-related increases of CD8+ and CD4+ effector T cells and decreases of T follicular helper and T regulatory cells (Treg) were observed in the tumor microenvironment. Low pretreatment levels of CD4+ Tregs, proliferating CD8+ T cells, and Granzyme B+ CD8+ T cells were associated with favorable outcomes. Intratumoral SD-101 in combination with low-dose radiation is well tolerated and results in regression of both treated and untreated sites of disease.Significance: In situ vaccination with the TLR9 agonist SD-101, along with low-dose radiation, was safe and induced systemic responses in patients with indolent lymphoma. Low levels of CD4+ Tregs, proliferating CD8+ T cells, and Granzyme B+ CD8+ T cells in the tumor microenvironment predicted favorable response to treatment. Cancer Discov; 8(10); 1258-69. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1195.

SD-101 in Combination with Pembrolizumab in Advanced Melanoma: Results of a Phase Ib, Multicenter Study.

PD-1 inhibitors are approved for treating advanced melanoma, but resistance has been observed. This phase Ib trial evaluated intratumoral SD-101, a synthetic CpG oligonucleotide that stimulates Toll-like receptor 9 (TLR9), in combination with pembrolizumab in patients with unresectable or metastatic malignant melanoma. The most common adverse events related to SD-101 were injection-site reactions and transient, mild-to-moderate "flu-like" symptoms. Among the 9 patients naïve to anti-PD-1 therapy, the overall response rate (ORR) was 78%. The estimated 12-month progression-free survival rate was 88%, and the overall survival rate was 89%. Among 13 patients having prior anti-PD-1 therapy, the ORR was 15%. RNA profiling of tumor biopsies demonstrated increased CD8+ T cells, natural killer cells, cytotoxic cells, dendritic cells, and B cells. The combination of intratumoral SD-101 and pembrolizumab was well tolerated and induced broad immune activation in the tumor microenvironment with durable tumor responses in both peripheral and visceral lesions.Significance: These early data demonstrate that the combination of pembrolizumab with intratumoral SD-101 is well tolerated and can induce immune activation at the tumor site. Combining an intratumoral TLR9 innate immune stimulant with PD-1 blockade can potentially increase clinical efficacy with minimal additional toxicity relative to PD-1 blockade alone. Cancer Discov; 8(10); 1250-7. ©2018 AACR. This article is highlighted in the In This Issue feature, p. 1195.

First-in-Human Study With the Inhaled TLR9 Oligonucleotide Agonist AZD1419 Results in Interferon Responses in the Lung, and Is Safe and Well-Tolerated.

Current asthma treatments address symptoms rather than the underlying disease pathophysiology, a better understanding of which has led to the identification of the Th2 high endotype. The activation of Toll-like receptors to induce Type I interferons directly in the lungs represents a novel therapeutic approach to reset this underlying Th2 pathophysiology with the potential to provide long-term disease modification. We present the nonclinical data and phase I clinical profile of an inhaled TLR9 agonist, AZD1419, a C-type CpG designed to induce interferon in the lung. In healthy volunteers, AZD1419 was found to be safe and well-tolerated. Target engagement in the lung was demonstrated at all dose levels tested. No evidence of tolerization or amplification of responses was evident on repeated dosing and 15.4 mg was defined as the maximum tolerated dose. AZD1419 clinical data supports its continued development as a potentially disease-modifying therapeutic in asthma.

Hepatocyte mitochondrial DNA drives nonalcoholic steatohepatitis by activation of TLR9.

Nonalcoholic steatohepatitis (NASH) is the most common liver disease in industrialized countries. NASH is a progressive disease that can lead to cirrhosis, cancer, and death, and there are currently no approved therapies. The development of NASH in animal models requires intact TLR9, but how the TLR9 pathway is activated in NASH is not clear. Our objectives in this study were to identify NASH-associated ligands for TLR9, establish the cellular requirement for TLR9, and evaluate the role of obesity-induced changes in TLR9 pathway activation. We demonstrated that plasma from mice and patients with NASH contains high levels of mitochondrial DNA (mtDNA) and intact mitochondria and has the ability to activate TLR9. Most of the plasma mtDNA was contained in microparticles (MPs) of hepatocyte origin, and removal of these MPs from plasma resulted in a substantial decrease in TLR9 activation capacity. In mice, NASH development in response to a high-fat diet required TLR9 on lysozyme-expressing cells, and a clinically applicable TLR9 antagonist blocked the development of NASH when given prophylactically and therapeutically. These data demonstrate that activation of the TLR9 pathway provides a link between the key metabolic and inflammatory phenotypes in NASH.

Pleiotrophin induces formation of functional neovasculature in vivo.

Pleiotrophin (PTN) is a heparin-binding growth/differentiation inducing cytokine that shares 50% amino acid sequence identity and striking domain homology with Midkine (MK), the only other member of the Ptn/Mk developmental gene family. The Ptn gene is expressed in sites of early vascular development in embryos and in healing wounds and its constitutive expression in many human tumors is associated with an angiogenic phenotype, suggesting that PTN has an important role in angiogenesis during development and in wound repair and advanced malignancies. To directly test whether PTN is angiogenic in vivo, we injected a plasmid to express PTN into ischemic myocardium in rats. Pleiotrophin stimulated statistically significant increases in both normal appearing new capillaries and arterioles each of which had readily detectable levels of the arteriole marker, smooth muscle cell alpha-actin. Furthermore, the newly formed blood vessels were shown to interconnect with the existent coronary vascular system. The results of these studies demonstrate directly that PTN is an effective angiogenic agent in vivo able to initiate new vessel formation that is both normal in appearance and function. The data suggest that PTN signals the more "complete" new blood vessel formation through its ability to stimulate different functions in different cell types not limited to the endothelial cell.