A Pharmacokinetic Study of Paliperidone ER

A. Background Schizophrenia is a heterogeneous disorder whose pathophysiology is not yet understood clearly. The treatment of schizophrenia remains suboptimal. Take risperidone for example, response rate of a patient is around only 60% to 80%. The second-generation or atypical antipsychotics are widely used. Apart from dopamine D2 receptor, they also target on 5-HT2 receptors and receptors of other neurotransmission systems. However, these second-generation antipsychotics still result in other common side effects. Therefore, finding predictors for clinical efficacy and side effect profile is a necessary task. Up to date, several genetic and non-genetic factors have been suggested related to the efficacy and side effects of antipsychotics. Noteworthy, pharmacokinetics as indicated by the temporal change of antipsychotics blood levels is usually overlooked. It might be a contributing factor why results from pharmacogenetic studies were usually difficult to be replicated.

Paliperidone (9-hydroxy-risperidone) is an active metabolite of the second-generation antipsychotics risperidone. Pharmacogenetic studies have found polymorphisms of some genes to be related to blood risperidone concentration, side effects and treatment response. Comparing to risperidone, paliperidone has less metabolic side effects, probable faster occurrence of efficacy, and better tolerance for subjects with hepatic insufficiency. Further, paliperidone is more sensitive to P-glycoprotein. There are just a few pharmacogenetic studies on paliperidone and P-glycoprotein. Therefore, one aim of this proposed study is to examine the pharmacogenetic effects on paliperidone extended release (paliperidone ER) for acute treatment of schizophrenia and schizoaffective disorder. The electrophysiological abnormalities as measured by event-related potentials (ERP) are characteristics features of several neuropsychological disorders. For schizophrenia, deficits in mismatch negativity, P50, and auditory steady state response have been frequently reported. Therefore, besides from clinical improvements, the investigators are also interested whether paliperidone treatment can alter the deficits in mismatch negativity, P50, and ASSR.

B. Study aims

1. To study the association of candidate genes, which are related to pharmacodynamics and pharmacokinetics of risperidone, with paliperidone pharmacokinetics and clinical response
2. To evaluate the impact of pharmacodynamics on the efficacy (including ERP change and cognitive function) and side effects of paliperidone ER for acute treatment of schizophrenia
3. To evaluate whether the paliperidone pharmacodynamics is related to the metabolic, hormonal, and bone turnover profiles
4. To evaluate whether paliperidone ER treatment will influence epigenetic markers
5. To evaluate whether paliperidone ER treatment will influence event-related potentials and performance in neurocognitive tests

C. Study design It is a 6-week, prospective, open-label, uncontrolled and non-randomized trial of paliperidone ER for patients with schizophrenia or schizoaffective disorder in an acute episode. A total of 40 subjects will be recruited.

D. Protocol overview:

For at least the first three weeks, participants should receive inpatient treatment in the acute psychiatry ward (03W2) in National Taiwan University Hospital. Medication compliance, efficacy of treatment and side effects will be monitored and evaluated by the psychiatrists who are the principle investigator or sub-investigators of this study.

1. Dosage of titration of paliperidone ER:

   Fixed dose (9 mg/day) of paliperidone ER will be given in the first two weeks of trial (from day 1 to day 14). Since the third week (day 15), the dosage can be adjusted in the range of 6 to 12 mg per day.

2. Medication regulation:

   1. Antipsychotics other than paliperidone ER are not allowed.
   2. For benzodiazepines and sedatives/hypnotics: only lorazepam up to 4 mg per day is allowed to management medication withdrawal, side effects or symptoms.
   3. Anticholinergic agents: for management of extrapyramidal symptoms only biperiden up to 6 mg/day or trihexyphenidyl up to 15 mg/day is allowed.

3. Measurements 3-1. Clinical evaluation on day 0, day 4, day 7, day14, day 28, and day 42:

   1. Efficacy evaluation: positive and Negative Syndrome Scale (PANSS), Personal and Social Performance Scale (PSP), Clinical Global Impression-Severity (CGI-S)
   2. Side effect evaluation: Drug-Induced Extrapyramidal Symptom Scale (DIEPSS), and Udvalg for Kliniske Undersogelser (UKU) Side Effect Rating Scale; any new-onset adverse conditions or worsening of the original conditions will be recorded as side effects and be managed promptly.
   3. Body weight. 3-2. Blood sampling on day 0 (40 ml), day 14 (15 ml) and day 42 (40 ml):
   1. Blood paliperidone concentration and pharmacodynamics of risperidone and paliperidone on day 0, day 14, and day 42.
   2. Blood biochemistry study (AC sugar, uric acid, cholesterol, triglyceride, HDL-cholesterol, leptin, adiponectin, prolactin) on day 0, day 14, and day 42.
   3. Bone turnover markers (serum alkaline phosphatase, calcium, phosphate bone-specific alkaline phosphatase, intact osteocalcin), and hormonal markers (oestradiol, progesterone, LH, FSH and testosterone) on day 0 and day 42.
   4. DNA sample for genetic markers on day 0: 1236C/T of the ABCB1 gene, Ser9Gly of the DRD3 gene, Ser311Cys of the DRD2 gene, 267T/C of the 5HTR6 gene, 102T/C of the 5HTR2A gene, 995G/A of the 5HTR2C gene, dinucleotide repeat (GT)n of the BDNF gene, val108/158Met of the COMT gene, and polymorphisms of the RGS4 gene.
   5. Epigenetic markers on day 0 and day 42. 3-3. Urinary examination for bone turnover markers on day 0 and day 42: urinary deoxypyridinoline cross-links and urinary C-terminal telopeptide fragment of type I collagen 3-4. Electrocardiogram on day 0 and day 42. 3-5. Event-related potential experiments on day 0 and day 42: Participants will receive experiments of mismatch negativity, P50 and auditory steady state response 3-6. Neurocognitive tests on day 0 and day 42: Participants will receive Continuous Performance Test (CPT), Wisconsin Card Sorting Test (WCST), Trail-A test, Trail-B test, verbal fluency test, and selected subtests from Wechsler Adult Intelligence Test-III (Digit Span and Arithmetic).

D. Conditions when a subject drop-out from the trial

1. Whenever a subject withdraws the informed consent.
2. Whenever a serious treatment-emergent adverse event happens.
3. Whenever the treating psychiatrists or the principle investigator judge early dropout necessary for a subject, considering the risks and benefits clinically.
4. Whenever a subject violates the trial protocol to a significant degree, as judged by the treating psychiatrists or the principle investigator.

E. Conditions when the trial will be stopped Since paliperidone ER has been approved for the treatment of schizophrenia by the Food and Drug Administration and the daily dose is within the recommended range, this trial will be terminated or suspended under the following situations: (a) order from the Research Ethics Committee to terminate or suspend the clinical trial; (b) order from the Central Competent Health Authority to terminate or suspend the clinical trial; (c) when paliperidone ER becoming unavailable in the National Taiwan University Hospital.

F. Trial medications Paliperidone Extended-Release Tablets (Invega): 9 mg/tab, 3 mg/tab

G. Data collection and statistical analysis

Since the current study is an open-labeled and single-arm trial, it is not aimed to prove the efficacy of paliperidone for treatment of schizophrenia. Instead, it is aimed to evaluate whether pharmacodynamics factors are related to the clinical response of paliperidone treatment. The variables of clinical response are defined as:

1. Primary efficacy variable: response rate (the ratio of subjects who respond to paliperidone treatment).

   Response to paliperidone treatment is calculated as [(PANSSevaluation - PANSSbaseline)/ (PANSSbaseline -30)]*100%

2. Secondary efficacy variables: PSP, CGI-S, ERPs and neurocognitive tests
3. Side effect variables: DIEPSS, UKU side effect scales, body weight, blood chemistry markers, metabolic markers, hormonal markers, and bone turnover markers

Response rate and other efficacy variables were analyzed with last observation carried forward and intention-to-treat principles. Response rate will be calculated on day 4, 7, 14, 28 and 42, and the impact of pharmacodynamics and genetic effects will be analyzed accordingly. Demographic data, blood paliperidone concentration, and the aforementioned variables will be compared between responder group and non-responder group on last visit (Pearson χ2 test or Fisher exact test will be used to compare categorical variables; independent t test will be used for continuous variables). The secondary efficacy and side effect variables on day 0 (before treatment) and day 42 (after treatment) will be compared with paired t-test. Relationship of the change of the aforementioned variables with blood paliperidone concentration will be examined by Pearson's correlation coefficient test or Spearman's correlation coefficient test. Multiple linear regression analysis will be applied for adjustments of covariates.

The genotyping quality will be checked by Hardy-Weinberg equilibrium tests. Association of the allelic effects of the genetic markers with clinical response and other outcome variables will be analyzed by using PLINK version 1.07 19. Other statistical analyses will be performed by using SAS®9.4 Software (SAS Institute Inc., USA). A p-value of less than 0.05 was considered statistically significant.