Development of posaconazole-based analogues as hedgehog signaling pathway inhibitors

Abstract

Inhibition of the hedgehog (Hh) signaling pathway has been validated as a therapeutic strategy to treat basal cell carcinoma and holds potential for several other forms of human cancer. Itraconazole and posaconazole are clinically useful triazole anti-fungals that are being repurposed as anti-cancer agents based on their ability to inhibit the Hh pathway. We have previously demonstrated that removal of the triazole from itraconazole does not affect its ability to inhibit the Hh pathway while abolishing its primary side effect, potent inhibition of Cyp3A4. To develop structure-activity relationships for the related posaconazole scaffold, we synthesized and evaluated a series of des-triazole analogues designed through both ligand-and structure-based methods. These compounds demonstrated improved anti-Hh properties compared to posaconazole and enhanced stability without inhibiting Cyp3A4. In addition, we utilized a series of molecular dynamics and binding energy studies to probe specific interactions between the compounds and their proposed binding site on Smoothened. These studies strongly suggest that the tetrahydrofuran region of the scaffold projects out of the binding site and that π-π interactions between the compound and Smoothened play a key role in stabilizing the bound analogues.

Kinetic Resolution of Tertiary Allylic Alcohols: Highly Enantioselective Access to Cyclic Ethers Bearing an α-Tetrasubstituted Stereocenter

“…The iodination of 13 and subsequent nucleophilic substitution of a sodium triazole salt provided 14, which is one of the core structures of the antifungal drug posaconazole (Scheme 5c). 26 A Hammett analysis with a series of tertiary α-aryl alcohols bearing para or meta substituents was carried out to experimentally evaluate the mechanism. Substrates with electron-donating substituents reacted at faster rates, possibly providing enhanced stabilization for the resulting tertiary allylic carbocationic intermediate (Scheme 6).…”

“…Primary alcohol 13 was readily obtained from the reaction of ( S )- 4d with potassium osmate followed by NaBH 4 reduction. The iodination of 13 and subsequent nucleophilic substitution of a sodium triazole salt provided 14 , which is one of the core structures of the antifungal drug posaconazole (Scheme c) …”

Structure–Activity Relationships for Itraconazole-Based Triazolone Analogues as Hedgehog Pathway Inhibitors

“…Previous studies suggest that ITZ inhibits Hh signaling through direct binding interactions with Smoothened (Smo), a key regulatory protein within the Hh pathway. These studies also suggest that ITZ binds Smo in a distinct manner from other Hh pathway inhibitors that function through Smo antagonism. ,− A common pitfall for Smo antagonists has been the emergence of resistance due to mutations in the binding site on Smo; , however, ITZ maintains potent Hh pathway inhibition in the presence of both wild type and mutant forms of Smo, presumably through its distinct binding interactions.…”

Truncated Itraconazole Analogues Exhibiting Potent Anti-Hedgehog Activity and Improved Drug-like Properties

“…To continue our SAR exploration of this region of the scaffold, we sought to synthesize and evaluate analogues that continue the scaffold truncation that we previously probed by removing the phenyl ring on the “right side” of the scaffold and directly appending the 3-phenolic carboxylic acid of 2 to the piperazine amine to provide analogue 3 . We evaluated this analogue for its ability to decrease Gli1 mRNA expression in the Hh-dependent murine BCC cell line ASZ001. − Analogue 3 demonstrated comparable anti-Hh activity compared to 2 (IC 50 values = 0.26 μM and 0.16 μM, respectively), verifying that this series of compounds retains potent Hh inhibition and encouraging us to synthesize additional analogues that incorporate the 4-phenylpiperazinyl amide.…”