DSR-6434 is a potent and selective Toll-like receptor 7 (TLR7) agonist, with EC50s of 7.2 nM and 4.6 nM for human and mice TLR7, respectively. DSR-6434 has a strong antitumor effect[1][2].

To assess the specificity of DSR-6434 toward TLR7, an NF-κB-driven reporter assay is performed in HEK293 cells engineered to express either hTLR7, TLR8 or TLR9. In this assay, successful binding of DSR-6434 to the specific receptor leads to NF-κB activation. DSR-6434 is capable of stimulating reporter gene activity only in HEK293 cells expressing hTLR7 and not in HEK293 cells expressing the structurally similar hTLR8 or hTLR9[2].

DSR-6434 treatment (Compound 20; 0.1-1 mg/kg; intravenous injection; biweekly; for 4 weeks; B6C3F1 mice) suppresses the lung metastasis significantly, 78% inhibition at 0.1 mg/kg dosing (with no tumor metastasis at the 1 mg/kg group)[1]. Animal Model: B6C3F1 mice injected with HM-1 ovarian cancer cells[1]

[1]. Nakamura T, et al. Synthesis and evaluation of 8-oxoadenine derivatives as potent Toll-like receptor 7 agonists with high water solubility. Bioorg Med Chem Lett. 2013 Feb 1;23(3):669-72. [2]. Adlard AL, et al. A novel systemically administered Toll-like receptor 7 agonist potentiates the effect of ionizing radiation in murine solid tumor models. Int J Cancer. 2014 Aug 15;135(4):820-9.