Olanzapine for young PEople with aNorexia nervosa: An open-label feasibility study to test recruitment, treatment acceptance, adherence, safety, outcome measures and patients' experience to prepare for a randomised placebo-controlled trial (OPEN)

Research Question: For young people with anorexia nervosa (AN), is it feasible to conduct a trial to examine the benefits and harms of prescribing olanzapine to those who have not responded to first-line treatments?

Design: Feasibility study; open treatment of 70 patients (55 in the UK, 15 in Australia) with olanzapine for 12 months. Participants will be examined at baseline, and at 8 weeks, 16 weeks, 6 months and 12 months after start of treatment. The Australian arm of the study is funded by the National Health and Medical Research Council (NHMRC).

Setting: Specialist eating disorder services for adolescents and adults. Team: • Eating disorder specialists for adults and adolescents • Researchers • People with lived experience of AN Aims: • To assess the proportion of patients in different treatment settings who: - agree to take olanzapine unblinded and under real-life conditions

- adhere to olanzapine - complete all study assessments and questionnaires at the five assessment points • To examine different methods to measure adherence • To study patients’ experience of recruitment and treatment, reasons for adherence and non-adherence • To examine and document what treatment as usual (TAU) means in practice

• To examine adverse effects and safety • To assess willingness to participate in a randomised-controlled trial (RCT; blinded, placebo-controlled) Study sample: • 70 patients (55 UK, 15 Australia, 12–24-years, males and females) with the inclusion criteria: - Adolescent or young adult inpatients, day-care or outpatients with AN

- Inadequate response to first-line treatments, defined by