The aim of this clinical study is to find out how well Patidegib Gel 2% works in preventing new basal cell carcinomas (BCCs) developing on the face of adults with Gorlin syndrome, and how safe Patidegib Gel 2% is to use.

People who take part will apply either Patidegib Gel 2% or a Vehicle Gel (with no active drug substance) to their face twice a day for a year (12 months). The number of new BCCs on the face will be compared between those who used Patidegib Gel 2% or Vehicle Gel after 12 months.

This is a global, multicenter, randomized, double-blind, stratified, vehicle-controlled study of the efficacy and safety of Patidegib Gel 2%, applied topically twice daily to the face of adult subjects with Gorlin syndrome.

Subjects will be randomized (1:1) to receive either Patidegib Gel 2% or Vehicle Gel for 12 months.

The assignment of subjects to the 2 groups will be stratified by sex assigned at birth, age (≥60 or <60 years), and number of BCC lesions at the treatment area (face) (10-15, 16-30 or >30) at Baseline.

All suspicious lesions will be imaged and tracked consistently throughout the study so that new BCCs that arise can be readily identified. New BCCs will be confirmed by dermoscopic analysis through the study. The BCC images will be reviewed and assessed by a Central Photo Review Board (CPRB).

Key Inclusion Criteria:

1. The subject must be at least 18 years old at the Screening Visit.
2. The subject must be confirmed to have a PTCH1 mutation.
3. The subject must have at least 10 BCCs on the face at Randomization (Baseline/Day 1).
4. The subject must be willing to abstain from application of any non-study topical medication (prescription or over the counter) to their facial skin for the duration of the trial, except as prescribed by the investigator.

Key Exclusion Criteria:

1. The subject has used topical treatment to the face or systemic therapies that might interfere with the evaluation of the study Investigational Product (IP).
2. The subject is known to have hypersensitivity to any of the ingredients in the IP formulation.
3. The subject has uncontrolled systemic disease.
4. The subject has been treated for invasive cancer within the past 5 years excluding chronic lymphocytic leukemia Stage 0, non-melanoma skin cancer, successfully treated melanoma in situ and Stage I melanoma, Stage I cervical cancer, or ductal carcinoma in situ of the breast.
5. Inefficacy of previous Hedgehog inhibitor therapy.