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Published on: December 15, 2017
Imidazoloquinoline optical isomers as TLR7 selective agonists promote macrophage activation for cancer immunotherapy
Yue Pan1, Qiuyue Fu1, Mingze Yang1
1Guangdong Provincial Key Laboratory of New Drug Screening, NMPA Key Laboratory for Research and Evaluation of Drug Metabolism and Guangdong-Hong Kong-Macao Joint Laboratory for New Drug Screening, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, China.
Abstract:
The chirality of drugs profoundly influences their efficacy, safety, and biological functions, particularly in single-enantiomer structures. Toll-like receptor 7 (TLR7) activation represents a promising tumor immunotherapy strategy by bridging innate and adaptive immunity. Herein, we design a chiral TLR7 agonist SMU-L11-R based on an imidazoquinoline scaffold. Compared to its enantiomer, it exhibits nearly 10-fold enhanced excitatory activity in HEK Blue hTLR7 cells (EC₅₀ = 0.012 ± 0.003 μM). Mechanistic studies reveal SMU-L11-R specifically activates TLR7, recruits MyD88, and triggers MAPK/NF-κB pathways, eliciting TNF-α/IL-1β/IL-6 secretion in both mouse and human peripheral blood mononuclear cells. The macrophage polarization experiments revealed SMU-L11-R remarkably upregulated the M1-like macrophage, accounting for 61.1 %, compared to 26.3 % in the control group. In the MC38 mouse model, SMU-L11-R can significantly inhibit tumor growth and exhibit excellent synergistic anti-tumor effects with PD-L1 inhibitors by upregulating CD8+T cells. Taken together, the optical isomer SMU-L11-R exhibits a superior TLR7 activation effect compared to its enantiomer, and demonstrates excellent tumor immune efficacy as a single drug or in combination with PD-L1 inhibitors.
Insights
Chiral Toll-like receptor 7 (TLR7) agonist SMU-L11-R shows enhanced tumor immunotherapy. This single-enantiomer drug activates TLR7, boosts anti-tumor immunity, and synergizes with PD-L1 inhibitors.
Area of Science:
- Immunology
- Pharmacology
- Medicinal Chemistry
Background:
- Chirality is crucial for drug efficacy and safety, especially for single-enantiomer drugs.
- Toll-like receptor 7 (TLR7) activation is a key strategy in tumor immunotherapy, linking innate and adaptive immunity.
- Imidazoquinoline scaffolds are recognized for their potential in developing immunomodulatory agents.
Purpose of the Study:
- To design and evaluate a novel chiral Toll-like receptor 7 (TLR7) agonist, SMU-L11-R, for tumor immunotherapy.
- To compare the efficacy of SMU-L11-R with its enantiomer in TLR7 activation and downstream signaling.
- To investigate the anti-tumor effects of SMU-L11-R in preclinical models, both as a monotherapy and in combination therapy.
Main Methods:
- Synthesis of a chiral imidazoquinoline-based TLR7 agonist (SMU-L11-R) and its enantiomer.
- In vitro assessment of TLR7 activation using HEK Blue hTLR7 cells and measurement of EC50 values.
- Mechanistic studies involving MyD88 recruitment, MAPK/NF-κB pathway activation, and cytokine secretion (TNF-α, IL-1β, IL-6) in human and mouse cells.
- Macrophage polarization analysis to determine M1-like macrophage upregulation.
- In vivo efficacy studies in the MC38 mouse tumor model, evaluating tumor growth inhibition and combination effects with PD-L1 inhibitors, including assessment of CD8+ T cell infiltration.
Main Results:
- SMU-L11-R demonstrated significantly higher TLR7 excitatory activity (nearly 10-fold) compared to its enantiomer, with an EC50 of 0.012 ± 0.003 μM.
- SMU-L11-R specifically activated TLR7, recruited MyD88, and activated MAPK/NF-κB pathways, leading to increased pro-inflammatory cytokine secretion.
- The compound effectively induced M1-like macrophage polarization (61.1% vs. 26.3% in control).
- In the MC38 model, SMU-L11-R significantly inhibited tumor growth and showed synergistic anti-tumor effects with PD-L1 inhibitors by enhancing CD8+ T cell responses.
Conclusions:
- The chiral TLR7 agonist SMU-L11-R exhibits superior TLR7 activation and immune-stimulatory properties compared to its enantiomer.
- SMU-L11-R demonstrates potent anti-tumor efficacy as a single agent and enhances the effects of PD-L1 inhibitors through immune modulation.
- This study highlights the therapeutic potential of enantiomerically pure TLR7 agonists in cancer immunotherapy.
