Description
Ciliobrevin A is a hedgehog pathway inhibitor that blocks sonic hedgehog (Shh)-induced hedgehog pathway activation (IC
50 = 7 μM). It disrupts primary cilia formation and inhibits the dynein-dependent microtubial gliding and ATPase activities of the cytoplasmic ATPases associated with various cellular activities (AAA+) family. Ciliobrevin A also inhibits mammalian target of rapamycin complex 1 (mTORC1) activity in uninfected and human cytomegalovirus (HCMV)-infected cells, suggesting that mTORC1 activation requires dynein-dependent transport for cellular activation.
Biochem/physiol Actions
HPI-4 is a Hedgehog pathway inhibitor; ciliogenesis inhibitor. The Hedgehog (HH) signaling pathway is targeted for anti-cancer therapeutics. A key signaling molecule in HH pathway, Smoothened (Smo), has been the target of pharmacological intervention, which has resulted in multiple Smo antagonists including Cyclopamine. However, the oncogenic form of Smo is resistant to Cyclopamine, so the identification of inhibitors of downstream effectors, such as the transcription factors Gli1 and Gli2, is important. Four small molecules were identified to inhibit HH downstream of Smo, HPI-1, HPI-2, HPI-3, and HPI-4. HPI-4 blocked HH pathway activation by SAG, decreased Smo ciliary accumulation, decreased HH activity in a consitutively active HH cell line, and decreased Gli1 and Gli2, processing, and stability. HPI-4 inhibited proliferation of cerebellar granula neuron precursor cells, an important model of HH signaling. Cilia in HPI-4-treated cells were either truncated or absent. The mechanism of action of HPI-4 is hypothesized to be directly through perturbation of ciliogenesis, leading to disruption of Gli1/Gli2 activity, which is distinctly different from that of Cyclopamine.
Synthesis
Example 1: Synthesis of 3-(2,4-dichlorophenyl)-3-oxo-2-(4-oxo-3,4-dihydroquinazolin-2(1H)-ylidene)propanenitrile ['ciliobrevin A']
[0048] 2-(4-oxo-1,4-dihydroquinazolin-2-yl)acetonitrile (202 mg, 1.09 mmol) and triethylamine (167 μL, 1.20 mmol) were dissolved in dioxane (8 mL), and 2,4-dichlorobenzoyl chloride (152 μL, 1.09 mmol) was slowly added. The reaction mixture was refluxed overnight with stirring. After cooling, the solid precipitate formed was collected by vacuum filtration and washed sequentially with methanol, water, methanol and dichloromethane. Drying gave the target product ciliobrevin A (1) (213 mg, 53%).
1H NMR (400 MHz, DMSO-d6) δ ppm: 7.46-7.50 (m, 1H), 7.52 (d, J = 8.2 Hz, 1H), 7.56 (dd, J1 = 8.2 Hz, J2 = 1.9 Hz, 1H), 7.77 (d, J = 2.0 Hz, 1H), 7.83-7.88 (m, 2H), 8.07 (d, J = 8.1 Hz, 1H).
13C NMR (500 MHz, DMSO-d6) δ ppm: 71.74, 117.43, 117.54, 118.71, 125.92, 126.68, 127.66, 129.21, 129.66, 130.49, 134.85, 135.85, 138.15, 139.25, 155.01 , 158.3, 118.75.
HRMS (m/z): [M + Na]+ calc. for C17H9N3O2Cl2Na, 379.9970; found, 379.9967.
