Adherence to cysteamine in nephropathic cystinosis: A unique electronic monitoring experience for a better understanding. A prospective cohort study: CrYSTobs.

Introduction: In nephropathic cystinosis (NC), adherence to cysteamine remains challenging; poor adherence is worsening the disease progression with a decline of kidney function and increase of extrarenal morbidities. Our objective was to describe adherence to cysteamine in NC patients, using electronic monitoring systems.

Methods: Patients with confirmed NC, aged > 4 years and receiving oral cysteamine (short acting or delayed release formulation as standard of care) from 3 French reference centers, were included. Adherence to treatment was primarily assessed as the percentage of days with a good adherence score, adherence score rating from 0 (poor) to 2 (good). A descriptive analysis was performed after 1-year follow-up.

Results: Seventeen patients (10 girls, median age: 13.9 (5.4-33.0) years) were included. Median age at diagnosis was 17.0 (3.0-76.9) months and age at start of cysteamine was 21.0 (15.5-116.3) months. Median daily dose of cysteamine was 1.05 (0.55-1.63) g/m/day. Over the year, the median percentage of days with a good adherence score was 80 (1-99)% decreasing to 68 (1-99)% in patients > 11 years old. The median of average number of hours covered by treatment in a day was 22.5 (6.1-23.9) versus 14.9 (9.2-20.5) hours for delayed release versus short acting cysteamine.

Conclusion: Our data are the first describing a rather good adherence to cysteamine, decreasing in adolescents and adults. We described a potential interest of the delayed release formulation. Our data highlight the need for a multidisciplinary approach including therapeutic education and individualized approaches in NC patients transitioning to adulthood. Graphical abstract.