Topical application of the Hedgehog inhibitor patidegib in patients with Gorlin syndrome: a phase II trial

Abstract

BACKGROUND: Patients with Gorlin (basal cell naevus) syndrome (GS) have numerous phenotypic abnormalities due to overactivity of the hedgehog (HH) signalling pathway, most commonly caused by a heritable mutation in PTCH1, which encodes a major inhibitor of this pathway. Oral HH inhibitors (HHi) can reverse some of the manifestations, most prominent of which is the development of numerous cutaneous basal cell carcinomas (BCCs). In order to improve the benefit-risk ratio, we developed a gel containing a small cyclopamine-derived molecule that can be applied topically in expectation that this mode of delivery can reduce the burden of BCCs without producing the systemic adverse effects that cause patients to stop oral HHi treatment. OBJECTIVES: To determine whether or not patidegib topical gel 2% or 4% can accumulate in high enough concentrations to have local anti-BCC efficacy but not so high that systemic drug levels produce the adverse effects typical of oral HHi treatment. METHODS: We conducted a small randomized double-blinded phase IIA trial at two sites in the UK, to assess the clinical and molecular efficacy and adverse effects of 6 months of twice-daily application of patidegib topical gel to the entire face, as well as to treatment-targeted surgically eligible BCCs at other anatomical sites. RESULTS: Post hoc analyses suggested that patidegib topical gel reduced the number of new, surgically eligible BCCs and the level of HH signalling, with minimal adverse effects. CONCLUSIONS: Patidegib topical gel warrants further clinical development.; Gorlin syndrome is a rare genetic condition where people develop a type of skin cancer called ‘basal cell carcinoma’ (or ‘BCC’ for short), as well as other symptoms. People with Gorlin syndrome have mutations in a key regulator of what is known as ‘the Hedgehog signalling pathway’. This can lead to BCC. A drug called ‘patidegib’ inhibits this pathway. Patidegib taken orally has been shown to reduce the size of BCC tumours. In this clinical trial, patidegib was provided as a gel to be applied on the face of people with Gorlin syndrome. We did this to see whether the gel could reduce the number of new skin tumours. We aimed to find out whether applying the gel twice a day could prevent new BCC tumours on the face without causing high levels of the drug in the patient’s blood. High levels of patidegib in the blood could lead to side effects like muscle cramps and hair loss. We found that by applying patidegib as a gel, concentrations of the drug in patients’ blood were very low. Patients had minimal or no major side effects. The findings from this study suggest that patidegib gel applied to the skin could reduce the number of new BCC tumours. More studies with more patients are needed to better assess patidegib gel in treating and preventing BCC tumours in people with Gorlin syndrome.