Low-dose metronomic cyclophosphamide complements the actions of an intratumoral C-class CpG TLR9 agonist to potentiate innate immunity and drive potent T cell-mediated anti-tumor responses
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Weng In Leong1,*, Rachel Y. Ames1,*, Jessica M. Haverkamp1, Laura Torres1, Janine Kline1, Ashil Bans1, Lauren Rocha1, Marilena Gallotta1, Cristiana Guiducci1, Robert L. Coffman1 and Mary J. Janatpour1
1 Dynavax Technologies, Inc., Emeryville, CA 94608, USA
* These authors contribute equally
|Mary J. Janatpour,||email:||[email protected]|
Keywords: TLR9; SD-101; cyclophosphamide; immune therapy; innate immunity
Received: August 16, 2019 Accepted: October 19, 2019 Published: December 31, 2019
The synthetic oligonucleotide SD-101 is a potent and specific agonist for toll-like receptor 9. Intratumoral injection of SD-101 induces significant anti-tumor immunity in preclinical and clinical studies, especially when combined with PD-1 blockade. To build upon this strategy, we studied the enhancement of SD-101 activities by combination with low-dose cyclophosphamide, a well-characterized agent with potentially complementary activities. In multiple mouse tumor models, we demonstrate substantial anti-tumor activity of the combination, compared to each single agent. Combination therapy generated CD8+ T cell dependent immunity leading to rejection of both non-injected and injected tumors and long-term survival, even in very large tumors. Mechanistic studies encompassing global gene expression changes and characterization of immune cell infiltrates show the rapid, sequential induction of innate and adaptive responses and identify discrete contributions of SD-101 and cyclophosphamide. Importantly, these changes were prominent in tumors not injected directly with SD-101. Combination treatment resulted in creation of a permissive environment for a systemic anti-tumor immune response, including a reduction of intratumoral regulatory T cells (Tregs) and an increase in “M1” versus “M2” tumor-associated macrophage (TAM) phenotypes. Additionally, we observed increased immunogenic cell death as well as antigen processing in response to combination treatment.
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