Therapeutic Drug Monitoring of Ixekizumab in Psoriasis Patients

Study Overview
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Brief Summary
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Biologics, such as ixekizumab, are currently the most effective treatment option for patients with moderate-to-severe psoriasis. But they are costly for health care systems and prescribed according to a 'one dose fits all' dosing regimen, leading to potential over- and undertreatment. Within this study the investigators aim to investigate the predictive value of early serum trough levels of ixekizumab and determine the therapeutic window of ixekizumab in psoriasis patients.

Detailed Description
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Patients will be included after siging informed consent. After inclusion, patients will continue on standard dosing schedule of ixekizumab (i.e. one loading dose of 2 subcutaneous injections (160 mg) at week 0, followed by one subcutaneous injection (80 mg) every 2 weeks for 12 weeks, and then one subcutaneous injections (80 mg) every 4 weeks). During each study visit, blood will be taken in order to quantify Ctroughs and/or anti-drug antibodies towards ixekizumab. In addition, the Psoriasis Severity and Area Index (PASI) and the Investigator's Global Assessment (IGA) score will be evaluated by a physician. Patients complete the Dermatology Life Quality Index (DLQI) and European quality of life EQ-5D instrument at each visit.

Official Title
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Evaluation of the Predictive Value of Early Serum Trough Concentrations and Anti-drug Antibodies of Ixekizumab and the Development of Concentration-response Curve of Ixekizumab for Psoriasis Patients

Conditions
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Psoriasis Vulgaris

Intervention / Treatment
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* Procedure: Venapuncture
* Other: Patient questionnaires


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Participants must have a clinical or histological diagnosis of chronic plaque-type psoriasis Participants must sign an ICF indicating that he or she understands the purpose of, and procedures required for, the study and is willing to participate in the study Exclusion Criteria: Participants who have currently a predominant nonplaque form of psoriasis Participants who are pregnant, nursing or planning a pregnancy Participants who are unable or unwilling to undergo multiple venapunctures Participants who are treated according to a different dosing schedule than standard dosing of ixekizumab

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Interventional Model Description: A prospective, open label, non-randomized study
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Standard of care - ixekizumab<br>Patient will continue to receive ixekizumab according to standard of care dosing regimen, i.e. loading dose first (160 mg) at week 0; 80 mg every 2 weeks until week 12, then 80 mg every 4 weeks | Procedure: Venapuncture<br>* Blood samples will be collected to determine the serum trough levels and anti-drug antibodies of ixekizumab<br>Other: Patient questionnaires<br>* The study participant will complete the Dermatology Quality of Life Index (DLQI) and EQ5D5L questionnaires at each study visit.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Predictive value of early serum trough concentrations of ixekizumab | Prediction of the clinical response (PASI) at week 12 and/or week 24 based on serum trough concentrations measurements taken from week 0, 1, 2, 3 and/or 4. | Week 0 until week 24 of treatment | 
| Predictive value of early anti-drug antibodies of ixekizumab | Prediction of the clinical response (PASI) at week 12 and/or week 24 based on anti-drug antibodies measurements taken from week 0, 1, 2, 3 and/or 4. | Week 0 until week 24 of treatment | 
| The development of a therapeutic window of ixekizumab in psoriasis | Defining a therapeutic window for ixekizumab based on serum trough levels corresponding with adequate clinical response. | Week 0 until week 52 of treatment | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| DLQI | The DLQI (Dermatology Life Quality Index) (range 0-30) is a dermatology specific quality of life (QoL) instrument designed to assess the impact of the disease on participant's QoL. It is a ten item questionnaire that, in addition to evaluated overall QoL, can be used to assess six different aspects that may affect QoL: 1) symptoms and feelings, 2) daily activities, 3) leasure, 4) work or school performances, 5) personal relationships, and 6) treatment. The scoring of each question is as follows: Very much - scored 3; A lot - scored 2; A little - scored 1; Not at all - scored 0; Not relevant - scored 0; Question 7, 'prevented work or studying' - scored 3. The DLQI is calculated by summing the score of each question resulting in a maximum of 30 and a minimum of 0. The higher the score, the more quality of life is impaired. | Week 0 until week 52 of treatment | 
| EQ5D5L | The 5-level EQ-5D version (EQ-5D-5L) was introduced by the EuroQol Group in 2009 to improve the instrument's sensitivity and to reduce ceiling effects. The descriptive system comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each dimension has 5 levels: no problems (level 1), slight problems (level 2), moderate problems (level 3), severe problems (level 4) and extreme problems (level 5). The patient is asked to indicate his/her health state by ticking the box next to the most appropriate statement in each of the five dimensions. This decision results in a 1-digit number that expresses the level selected for that dimension. The digits for the five dimensions can be combined into a 5-digit number that describes the patient's health state, which is the outcome result. There is no minimum or maximum score since the the 5 digit-number is a non-numeric variable. | Week 0 until week 52 of treatment | 
| EQ VAS | The EQ VAS (Visual Analogue Scale) (range 0-10) records the patient's self-rated health on a vertical visual analogue scale, where the endpoints are labelled 'The best health you can imagine' and 'The worst health you can imagine'. The VAS can be used as a quantitative measure of health outcome that reflect the patient's own judgement. Minimum score is 0%, max. score is 100%. Lower values mean 'worse health the patient can imagine', higher values mean 'better health the patient can imagine'. | Week 0 until week 52 of treatment | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Psoriasis, Therapeutic drug monitoring, Ixekizumab