Reprogramming tumor-associated immune cells with Z-007, a first-in-class systemic TLR7/8/9 agonist.

Abstract

e14565 Background: Overcoming tumor-mediated immune suppression is a critical barrier in cancer immunotherapy. Anti-tumor immunity depends on IFN-a, which can be induced using separate mimics of viral GU-rich RNA (TLR7/8 agonist) or CpG DNA (TLR9). We developed Z-007, a first-in-class combined GU-rich RNA/CpG-A DNA hybrid TLR7/8/9 agonist in a non-inflammatory lipid nanoparticle (LNP) for systemic (IV) delivery. Methods: Z-007 activity was evaluated in four species: 1) Ex vivo normal human PBMC (N = 10) and human tumor-associated immune cells from gastrointestinal cancer ascites (N = 5); 2) murine tumor models including i) IV delivery in orthotopic organoid MSS CRC liver metastasis (AKPS) resistant to anti-PD-1; ii) intratumoral (IT) delivery in syngeneic subcutaneous prostate cancer (TRAMPC1-GP); iii) IV in B16 melanoma lung metastasis; and iv) intraperitoneal (IP) delivery in IP MC38 CRC; 3) cynomolgus monkeys 4 week IV safety/PD study (N = 2 Z-007, N = 4 control LNPs) ; and 4) pet dogs with spontaneous tumors (N = 7). Results: Z-007 induced human GI tumor-associated ascites cells to secrete high IFN-α without IL-6 or TNF-α; RNA-seq showed increased IFN-a and IFN-g signatures observed in patients who responded to immune checkpoint blockade in published studies, and reduced immune suppressive and MDSC signatures. R848 (TLR7/8 agonist) induced immune suppressive and MDSC signatures with high IL-6 and TNF-α secretion but minimal IFN-α. CpG-A DNA 2216 induced minimal IFN-a or cytokines. In all murine models, Z-007 demonstrated monotherapy efficacy, driving tumor regression and expanding antigen-experienced CD8+ T cells in the tumor microenvironment. In monkeys, IV Z-007 was well-tolerated up to 100x the projected human equivalent dose without cytokine release syndrome (CRS), but with a "pulse" induction of serum IFN-α (1400 pg/mL) and CXCL10 (40,000 pg/mL) by 6 hr that returned toward baseline by 24 hours, avoiding the sustained signaling associated with T-cell exhaustion. In 3/7 pet dogs, IV or IT Z-007 induced > 30% tumor regression, including a dog with a metastatic hemangiosarcoma who had complete resolution of 13 lung and multiple skin metastases, and 87% regression of a cardiac metastasis during 6 months of weekly IV Z-007 monotherapy with no adverse events or lab changes. Conclusions: Z-007 represents a novel class of innate immune activator that successfully decouples high IFN-a induction from pro-tumorigenic inflammation. Its ability to reprogram human MDSCs and induce tumor regression in multiple murine models and in spontaneous canine tumors without evidence of CRS, fever, or altered liver, kidney, or other organ function, supports its clinical development. Based on the propensity of LNPs to be taken up in the liver, IV Z-007 may reprogram tumor-associated immune cells in patients with liver metastases from a wound healing to antiviral response, inducing systemic anti-tumor CD8+ T cell responses.