title: Structure-activity relationships in human Toll-like receptor 8-active 2,3-diamino-furo[2,3-c]pyridines.
abstract: In our ongoing search toward identifying novel and synthetically simpler candidate vaccine adjuvants, we hypothesized that the imidazo[1,2-a]pyrazines, readily accessible via the Groebke-Blackburn-Bienaymé multicomponent reaction, would possess sufficient structural similarity with TLR7/8-agonistic imidazoquinolines. With pyridoxal as the aldehyde component, furo[2,3-c]pyridines, rather than the expected imidazo[1,2-a]pyridines, were obtained, which were characterized by NMR spectroscopy and crystallography. Several analogues were found to activate TLR8-dependent NF-κB signaling. In a focused library of furo[2,3-c]pyridines, a distinct SAR was observed with varying substituents at C2. In human PBMCs, none of the furo[2,3-c]pyridines showed any proinflammatory cytokine induction but upregulated several chemokine ligand genes. In immunization studies in rabbits, the most active compound showed prominent adjuvantic effects. The complete lack of proinflammatory cytokine induction coupled with strong adjuvantic activity of the novel furo[2,3-c]pyridines render this hitherto unknown chemotype an attractive class of compounds which are expected to be devoid of local or systemic reactogenicity.
authors.affiliation: Department of Medicinal Chemistry, University of Kansas, Multidisciplinary Research Building, Room 320D, 2030 Becker Drive, Lawrence, Kansas 66047, USA.
authors.forename: Deepak B
authors.initials: DB
authors.lastname: Salunke
authors.forename: Euna
authors.initials: E
authors.lastname: Yoo
authors.forename: Nikunj M
authors.initials: NM
authors.lastname: Shukla
authors.forename: Rajalakshmi
authors.initials: R
authors.lastname: Balakrishna
authors.forename: Subbalakshmi S
authors.initials: SS
authors.lastname: Malladi
authors.forename: Katelyn J
authors.initials: KJ
authors.lastname: Serafin
authors.forename: Victor W
authors.initials: VW
authors.lastname: Day
authors.forename: Xinkun
authors.initials: X
authors.lastname: Wang
authors.forename: Sunil A
authors.initials: SA
authors.lastname: David
mesh_terms: D000276:Adjuvants, Immunologic / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology; D011725:Pyridines / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D011817:Rabbits; D013329:Structure-Activity Relationship; D051200:Toll-Like Receptor 8 / Q000819:agonists*
chemical_list: D000276:Adjuvants, Immunologic; D011725:Pyridines; D051200:Toll-Like Receptor 8