Screening and Reverse-Engineering of Estrogen Receptor Ligands as Potent Pan-Filovirus Inhibitors

Abstract

Filoviridae, including Ebola (EBOV) and Marburg (MARV) viruses, are emerging pathogens that pose a serious threat to public health. No agents have been approved to treat filovirus infections, representing a major unmet medical need. The selective estrogen receptor modulator (SERM) toremifene was previously identified from a screen of FDA-approved drugs as a potent EBOV viral entry inhibitor, via binding to EBOV glycoprotein (GP). A focused screen of ER ligands identified ridaifen-B as a potent dual inhibitor of EBOV and MARV. Optimization and reverseengineering to remove ER activity led to a novel compound 30 showing potent inhibition against infectious EBOV Zaire (0.09 μM) and MARV (0.64 μM). Mutagenesis studies confirmed that inhibition of EBOV viral entry is mediated by direct interaction with GP. Importantly, compound 30 (XL-147) displayed broad-spectrum anti-filovirus activity against Bundibugyo, Tai Forest, Reston, and Měnglà viruses, and is the first sub-micromolar antiviral agent reported for some of these strains, therefore warranting further development as a pan-filovirus inhibitor.

Comparative analyses of small molecule and antibody inhibition on glycoprotein‐mediated entry of Měnglà virus with other filoviruses

“…In addition to the eight compounds tested here, we showed in 20 Toremifene, sertraline, paroxetine, benztropine, bepridil, and imipramine have all been cocrystalized with the EBOV-GP and shown to bind directly to the EBOV fusion-loop-associated cavity. 11,21 In Schafer et al, we confirmed that these compounds, in addition to dibucaine and orphenadrine, interact with the EBOV fusion-loop-associated cavity via mutational analysis of key residues in that binding pocket.…”

Formulation, Stability, Pharmacokinetic, and Modeling Studies for Tests of Synergistic Combinations of Orally Available Approved Drugs Against Ebola Virus In Vivo

“…In addition, if approved, several investigational drugs may warrant testing in combinations. These include novel selective estrogen receptor modulators [73] and amodiaquine analogues [74], agents that target the HR2 region of EBOV GP2 [75,76], potentially broad-spectrum drugs that target the viral polymerase [77], or drugs that target other EBOV or host cell proteins or their interactions [78][79][80]. Moreover, the possibility exists of adding a third drug as supported by current therapeutic strategies against HIV [19,20] and HCV [21].…”

Estrogen Receptor Modulators in Viral Infections Such as SARS−CoV−2: Therapeutic Consequences

“…These mechanisms were also dependent on the interaction of hormones with their receptors. The inhibitory effect of estrogens on replication was documented [ 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ]. in a panel of viruses (for particulars see Table 1 ).…”

“…Unfortunately, the precise molecular mechanisms of action were deciphered only in a few cases and are usually independent of the interaction with the receptor. Clomifene, raloxifene, ridaifene (+XL-147) and toremifene act via attenuation of the interaction of SARS−CoV−2 or EBOLA with their target cells [ 37 , 40 , 41 , 42 , 43 , 44 ], where some role of the inhibition of SARS−CoV−2 spike protein interaction with receptor ACE2 may be expected [ 36 , 37 , 39 , 44 , 45 , 67 ]. ERMs seem to inhibit the glycan–glycan interaction between the spike protein and ACE2 and so reduces the virus entry to permissive cells [ 43 , 68 ].…”