Rituximab for Obsessive-compulsive Disorder. (RITS-PO-2019)

This study evaluates the addition of rituximab to 12 patients diagnosed with treatment resistant obsessive-compulsive disorder in an open trial.

Immunological factors may be determinants for some psychiatric disorders, thus immunomodulation may be helpful. Rituximab (antibodies against CD20, cluster of differentiation), a standard treatment for multiple sclerosis, is an anti-inflammatory drug, hitherto not tested for psychiatric disorders.

The aim of this study is to investigate whether the psychiatric symptoms of treatment-resistant adult psychiatric patients, diagnosed with obsessive-compulsive disorder (OCD), are significantly improved after treatment with rituximab. The investigator's purpose is to implement recent insights from "Immunopsychiatry" to find efficacious, but still tolerable treatment for these patients.

This is a single-site, 20-week, open pilot, add-on treatment as usual, trial, where the patients will be followed for 1 year.

Rituximab will be administered with one single dose of 1000 mg. Investigators will analyse inflammatory and metabolic biomarkers in relation to the primary outcome, treatment response (defined as clinically relevant reduction in the validated measure Y-BOCS). Other outcomes are "much" or "very much improved" on Clinical Global Impression - Improvement scale (CGI-I) and change in Personal and Social Performance Scale measuring overall disability.

Eligibility Criteria:
Inclusion Criteria (Swedish citizens):

1. patient ages 18 to 40 years.
2. a duration of illness exceeding 2 years.
3. correspond to "Markedly ill", "Severely ill" or "Among the most extremely ill patients" on the Clinical Global Impression - Severity scale (CGI-S).
4. Global Assessment of Functioning (GAF) below 50.
5. obsessive-compulsive disorder according to The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).
6. treatment resistance, i.e. failing to remit despite adequate treatments.
7. if female and with any risk for pregnancy, willing to use contraceptives.
8. if psychotropic treatment is prescribed the plasma concentrations of the drug must be tested and shown to be within therapeutic interval.
9. subjects should be judged by the investigator to be lucid and oriented to person, place, time, and situation when giving the informed consent.
10. immunoglobulin levels within the normal range.

Exclusion Criteria:

1. on-going immunomodulatory treatment.
2. pregnancy or breast-feeding.
3. weight below 40 kg.
4. clinically relevant on-going infection.
5. chronic infections .
6. positive screening test for hepatitis B, C, HIV or tuberculosis
7. any change of psychotropic medication within the previous 4 weeks
8. "much" or "very much" improved already at baseline according to CGI-I.
9. severe heart failure (NYHA grade IV) or other severe heart disease or history of cardiac arrhythmia or myocardial infarction.
10. unable to make an informed decision to consent to the trial.
11. in compulsory treatment.
12. treatment with clozapine within the last 2 months.
13. previous treatments with immunosuppressive agents.
14. malignancy currently or within 2 years prior to inclusion.