PF-04449913 is a potent and selective inhibitor of the Hh signaling pathway through binding to the target, smoothened. PF-04449913 inhibits Hh signaling in vitro and has demonstrated significant antitumor activity in vivo. In the clinic, PF-04449913 is being evaluated both in hematological and solid malignancies, with a phase II trial currently underway in both fit and unfit patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS). Treatment-related adverse-events were nausea, dizziness, somnolence, QT prolongation and pruritus. Based on pre-clinical assessments, CYP3A4 is believed to be primarily involved in the metabolism of PF-04449913 that is why PF-04449913 plasma exposures and peak concentrations were increased following concurrent administration of ketoconazole (CYP3A4 inhibitor).

Sonidegib, also known as LDE225 and marketed as Odomzo, is a Hedgehog signaling pathway inhibitor (via smoothened antagonism) developed as an anticancer agent by Novartis. It was approved by the FDA for treating basal cell carcinoma in July 2015 and is awaiting approval in the EU. The hedgehog pathway is involved in many human cancers. Sonidegib effectively inhibits the regulator called smoothened (Smo), preventing the hedgehog pathway from functioning. As a result, tumours that depend on the hedgehog pathway are unable to grow. Sonidegib is approved for use in the US and EU for treatment of adults with locally advanced basal cell carcinoma (BCC) that has recurred post surgery or radiation therapy. It is also approved for adult patients with BCC who are not eligible for surgery or radiation therapy.

Vismodegib (trade name Erivedge) is a drug for the treatment of basal-cell carcinoma (BCC). It was approved by FDA on January 30, 2012 and by the European Commission on 12 July 2013, for the treatment of adult patients with symptomatic metastatic BCC, or locally advanced BCC inappropriate for surgery or radiotherapy. The drug is also undergoing clinical trials for metastatic colorectal cancer, small-cell lung cancer, advanced stomach cancer, pancreatic cancer, medulloblastoma and chondrosarcoma as of June 2011. The substance acts as a cyclopamine-competitive antagonist of the smoothened receptor (SMO) which is part of the hedgehog signaling pathway. The Hedgehog signaling pathway plays an important role in tissue growth and repair; aberrant constitutive activation of Hedgehog pathway signaling and uncontrolled cellular proliferation may be associated with mutations in the Hedgehog-ligand cell surface receptors PTCH and SMO. SMO inhibition causes the transcription factors GLI1 and GLI2 to remain inactive, which prevents the expression of tumor mediating genes within the hedgehog pathway. This pathway is pathogenetically relevant in more than 90% of basal-cell carcinomas.

FIN-6 (PATIDEGIB, IPI-926), a semisynthetic derivative of alkaloid cyclopamine, is a G protein-coupled receptor Smoothened (Smo) inhibitor with antineoplastic activity. Smo is a key signaling transmembrane protein in the Hedgehog signaling pathway which plays an important role in the proliferation of neuronal precursor cells in the developing cerebellum and other tissues. FIN-6 (PATIDEGIB, IPI-926) is under development for Gorlin syndrome, basal cell carcinomas, and other potential indications.

Taladegib (LY2940680) is an orally bioavailable small molecule antagonist of the Hedgehog (Hh)-ligand cell surface receptor smoothened (Smo) with potential antineoplastic activity. Taladegib inhibits signaling that is mediated by the Hh pathway protein Smo, which may result in a suppression of the Hh signaling pathway and may lead to the inhibition of the proliferation of tumor cells in which this pathway is abnormally activated. The Hh signaling pathway plays an important role in cellular growth, differentiation and repair; constitutive activation of this pathway is associated with uncontrolled cellular proliferation and has been observed in a variety of cancers. Taladegib has excellent pharmacokinetic properties in rodent and non-rodent species. Taladegib administrated orally treats Ptch+/- p53-/- transgenic mice which spontaneously develop medulloblastoma, produces remarkable efficacy and significantly improves their survival. Taladegib reveals rapid kinetics of anti-tumor activity through magnetic resonance imaging of these mice, and Taladegib induces Caspase-3 activity and reduces proliferation by immunohistochemistry analysis of medulloblastoma tumors. Taladegib inhibits Hh regulated gene expression in the subcutaneous xenograft tumor stroma and produces significant anti-tumor activity. Taladegib is currently in phase I clinical trials for ovarian cancer and solid tumours and in phase I/II for esophageal cancer. Ignyta exclusively licensed Taladegib from Eli Lilly and Company in November 2015.

BMS-833923 was discovered by Exelixis and was out-licensed to Bristol-Myers Squibb. BMS-833923 is an orally bioavailable Smoothened antagonist. BMS-833923 reduces hedgehog pathway activity, decreases cell proliferation and induces apoptosis via the intrinsic pathway in esophageal adenocarcinoma (EAC) cell lines. BMS-833923 dose-dependently affects canonical and prostate hedgehog signature gene transcription in vitro. BMS-833923 is in phase II clinical trials for the treatment of chronic myeloid leukaemia.

NPV-LEQ506 is an orally bioavailable small-molecule Smoothened (Smo) antagonist with potential antineoplastic activity. NPV-LEQ506 selectively binds to the Hedgehog (Hh)-ligand cell surface receptor Smo, which may result in the suppression of the Hh signaling pathway, thereby inhibiting tumor cell growth. NPV-LEQ506 is a second-generation inhibitor of smoothened (Smo) with IC50s of 2 and 4 nM in human and mouse, respectively. NPV-LEQ506 has been in clinical trials with Novartis studying the treatment of advanced solid tumors, recurrent or refractory medulloblastoma, and locally advanced or metastatic basal cell carcinoma.

SANT-1 is antagonist of Smoothened (Smo), a distant relative of G protein-coupled receptors, mediates Hedgehog (Hh) signaling during embryonic development and can initiate or transmit ligand-independent pathway activation in tumorigenesis. It suppressed cancer cell viability, proliferation and colony formation.

Smoothened agonist (SAG), a chlorobenzothiophene-containing Hh pathway agonist, was shown to be able to bind directly to Smo and activate Shh-dependent pathway. SAG and similar compounds represent attractive molecules to be developed for treatment of disorders where stimulation of the generation and survival of new neural cells would be beneficial. Thus, it was demonstrated that small-molecule agonist of Smo has potential as a neuroprotective agent in neonates at risk for glucocorticoid-induced neonatal cerebellar injury. Moreover, hedgehog agonist therapy corrects structural and cognitive deficits in a Down syndrome mouse model.