Toll-like receptors (TLRs) are an important group of receptors that play a critical role in the
innate and adaptive immune system. TLRs are promising targets for the treatment of infections,
autoimmune diseases, and cancer. To date, 10 members of TLRs have been identified in humans.
In this thesis, we focused on TLR7, an endosomal receptor that recognizes single-stranded RNA.
Enhanced activation of the immune system by TLR7 leads to anti-inflammatory, antiviral, and
antitumor activity. Therefore, TLR7 is a potential target for the treatment of viral infections,
allergic asthma, and cancer.
Based on the chemical structure of the known TLR7 agonist 3-(4-fluorophenyl)-4-(3-methyl
piperidine-1-il)-6-(trifluoromethyl)isoxazolo[5,4-d]pirimidine, we designed and synthesized 11
new potential TLR7 agonists. A six-step synthetic pathway was used to synthesize the 6-
(trifluoromethyl)isoxazolo[5,4-d]pirimidine analogs with different substitutions on the
isoxazole ring. The final compounds were tested on the human HEK293 cell line. The solubility
of the synthesized compounds in DMSO and cell media, cytotoxicity, and potential TLR7
agonist activity were determined.
We found that all synthesized compounds dissolved poorly in cell media due to their high
lipophilicity. For this reason, preliminary tests for agonism were performed at low
concentrations, which affected the potency of TLR7 agonist activity. Compounds 37, 38, 40,
and 41, all with an isobutylamine fragment on the pyrimidine ring, are cytotoxic. Of all the
synthesized compounds, only 3-(4-chlorophenyl)-4-(3-methylpiperidine-1-il)-6-
(trifluoromethyl)isoxazolo[5,4-d]pyrimidine (35) shows TLR7 agonist activity with an EC50
value of 21,4 μM. Compound 35 represent a good starting point for further optimization,
especially in terms of improving physicochemical properties.
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