Dose- and Route-Dependent Teratogenicity, Toxicity, and Pharmacokinetic Profiles of the Hedgehog Signaling Antagonist Cyclopamine in the Mouse

Abstract

The Hedgehog (Hh) signaling pathway is an essential regulator of embryonic development and appears to play important roles in postnatal repair and cancer progression and metastasis. The teratogenic Veratrum alkaloid cyclopamine is a potent Hh antagonist and is used experimentally both in vitro and in vivo to investigate the role of Hh signaling in diverse biological processes. Here, we set out to establish an administration regimen for cyclopamine-induced teratogenicity in the mouse. The dysmorphogenic concentration of cyclopamine was determined in vitro via mouse whole-embryo culture assays to be 2.0 microM. We administered cyclopamine to female C57BL/6J mice at varied doses by oral gavage, ip injection, or osmotic pump infusion and assessed toxicity and pharmacokinetic (PK) models. Bolus administration was limited by toxicity and rapid clearance. In vivo cyclopamine infusion at 160 mg/kg/day yielded a dam serum steady-state concentration of approximately 2 microM with a corresponding amniotic fluid concentration of approximately 1.5 microM. Gross facial defects were induced in 30% of cyclopamine-exposed litters, with affected embryos exhibiting cleft lip and palate. This is the first report describing the PKs and teratogenic potential of cyclopamine in the mouse and demonstrates that transient Hh signaling inhibition induces facial clefting anomalies in the mouse that mimic common human birth defects.

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“…However, it does not affect upstream Shh ligand expression. The shortcomings of CPN are its short half-life and off-target effects at higher doses (Lipinski et al, 2008; Zhao et al, 2009). Therefore, a more soluble and potent CPN derivative, IPI-926 (Saridegib), has been explored in clinical trials for basal cell carcinoma (BCC) and metastatic pancreatic cancer.…”

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“…It has been shown that cyclopamine in high concentrations can induce apoptosis by increasing N-SMase2/ ceramide and via generation of nitric oxide [49]. Moreover, it is difficult to reach systemic levels of cyclopamine in vivo because of its toxicity and relatively short elimination half-life [51]. The preclinical studies are further limited by the fact that there is no agreed-upon standard method to measure the Hh pathway activity and none of commercial antibodies against PTCH, SMO, or GLI have ever been shown to work specifically on fixed tissues [52].…”

Selective Release of a Cyclopamine Glucuronide Prodrug toward Stem-like Cancer Cell Inhibition in Glioblastoma

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