Stargardt disease 1 (STGD1) is the most prevalent form of juvenile macular degeneration. It is caused by a rare, inherited autosomal recessive trait, leading to severe and irreversible blindness by the first or second decade of life. Earlier onset of the disease is related to a rapid vision loss, while patients with a later onset tend to have a better prognosis. This study will enrol subjects aged 12-18 years old with a confirmed clinical diagnosis of Stargardt disease type 1 (STGD1). This study will include 2 phases, the phase 1b portion is to determine the optimal dose for phase 2 based on the extent of retinol binding protein 4 (RBP4) reduction after 2 cycles of tinlarebant treatment. The phase 2 portion will evaluate the safety and efficacy of a single daily dose of tinlarebant over a 24-month treatment period.