OBJECTIVES: The aim of this analysis was to characterise the trends in studies aiming to assess gene therapies (GTs) for various designations.

METHODS: The databases of ClinicalTrials.gov have been downloaded on June 2019 and underwent automatized analysis using R algorithms for data mining. The databases were searched for records related to GTs using key words related to gene therapy, gene transfer and adeno-associated vectors. Relevant records were transferred to Excel-based data-extraction table. Trends over time in study phase, design and population were analysed considering 5 years periods from 1990 to 2019.

RESULTS: The number of emerging clinical trials for GTs grow exponentially with 301 studies registered between 2015 and 2019. Between 1990 and 2019 the contribution of respective study phases to overall number of emerging records decreased for phase 1 studies (from 86% to 34%), increased for phase 1/2 (from 14% to 39%) and phase 3 (from 3% to 11%) studies, and remained stable for phase 2 (~14%) and 2/3 trials (2%). The proportion of ongoing trials was 48% and 86% for all studies and studies registered since 2015, respectively. The overall proportions of completed and terminated studies were 32% and 11%, respectively. A total of 68% of the late-phase studies were designed as randomised controlled trials. Overall, studies targeted primarily oncological indications (41%), however the proportion of studies targeting malignant diseases decreased over time (-2% annually), while growing contributions of non-cancer haematological designations (0.7% annually), metabolic and ophthalmological diseases (both 0.5% annually), and muscular dystrophies (0.3% annually) were observed.

CONCLUSIONS: Only few gene therapies have received market authorisation so far, and their availability is limited due to high costs, safety concerns and uncertain efficacy. The raising number of advanced clinical trials give hope that new therapies will be made available to treat patients in the coming years.