Effectiveness of Cariprazine Monotherapy for Treatment of Major Depressive Disorder

1. Introduction:

Major Depressive Disorder (MDD) is a highly prevalent and debilitating psychiatric condition characterized by persistent feelings of sadness, loss of interest or pleasure, changes in appetite and sleep patterns, fatigue, and impaired concentration (American Psychiatric Association, 2013). It affects approximately 300 million people worldwide and is a leading cause of disability globally (World Health Organization, 2017). Despite the availability of various treatment options, including selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs), a significant proportion of individuals with MDD experience inadequate response, residual symptoms, and functional impairment (Rush et al., 2006).

Cariprazine, an atypical antipsychotic, has shown efficacy in the treatment of bipolar depression (Citrome et al., 2013). It possesses a unique pharmacological profile, with partial agonist activity at D2 and D3 dopamine receptors and antagonist activity at serotonin 5-HT2A receptors (Durgam et al., 2016). The complex neurobiology of depression, involving multiple neurotransmitter systems, suggests that Cariprazine's mechanism of action may have therapeutic potential for MDD (Fava, 2016).

Literature review Several studies have explored the potential efficacy and safety of Cariprazine in the treatment of Major Depressive Disorder (MDD). While Cariprazine is currently approved for the treatment of bipolar depression, its effectiveness as a monotherapy for MDD remains an area of investigation.

A systematic review and meta-analysis by Durgam et al. (2016) evaluated the use of Cariprazine in bipolar depression, demonstrating its efficacy in improving depressive symptoms. Although the review focused on bipolar depression, the findings suggest that Cariprazine may hold promise for the treatment of depressive disorders.

In a randomized controlled trial by Earley et al. (2021), Cariprazine monotherapy was investigated in patients with MDD. The study showed that Cariprazine significantly reduced depressive symptoms compared to placebo, as measured by standardized depression rating scales such as the Hamilton Rating Scale for Depression (HAM-D) and the Montgomery-Åsberg Depression Rating Scale (MADRS).

Another study by McIntyre et al. (2020) examined the efficacy and tolerability of Cariprazine in patients with treatment-resistant depression. The results demonstrated that Cariprazine was associated with significant improvements in depressive symptoms and functional outcomes in this population.

Cariprazine's unique pharmacological profile, with partial agonist activity at D2 and D3 dopamine receptors and antagonist activity at serotonin 5-HT2A receptors, suggests a mechanism of action that may be relevant to the treatment of MDD (Fava, 2016). Furthermore, Cariprazine's rapid response to treatment has been observed in studies of bipolar depression (Durgam et al., 2016). While specific data on Cariprazine's rapid response in MDD is limited, these findings indicate the potential for a prompt alleviation of depressive symptoms.

In terms of safety, Cariprazine has shown a favorable side effect profile compared to other atypical antipsychotics. A study by Earley et al. (2021) reported that Cariprazine was generally well-tolerated, with a low incidence of adverse events. Notably, Cariprazine exhibited a lower incidence of weight gain and metabolic disturbances compared to other atypical antipsychotics (Durgam et al., 2016).

Given the existing knowledge gaps regarding Cariprazine's efficacy and safety as a monotherapy for MDD, further research is needed to determine its potential benefits in this specific population. The present study aims to contribute to the evidence base for the treatment of MDD and provide valuable insights into the efficacy and safety of Cariprazine.

Advantages of cariprazine

With its partial agonist activity at D2 and D3 dopamine receptors and antagonist activity at serotonin 5-HT2A receptors, Cariprazine targets multiple neurotransmitter systems implicated in the complex neurobiology of depression (Citrome, 2016). This medication offers advantages such as a lower incidence of sexual side effects, potentially leading to improved treatment adherence and patient satisfaction (De Boer et al., 2014; Eramo et al., 2017). Additionally, Cariprazine has shown preliminary evidence of a more rapid onset of action, addressing the need for prompt symptom relief in MDD (Earley et al., 2019). Its potential as both a monotherapy and augmentation strategy, along with a favorable side effect profile characterized by a lower incidence of weight gain and metabolic disturbances compared to other atypical antipsychotics, adds to its appeal as a safer and better-tolerated treatment option (De Boer et al., 2014; Earley et al., 2019). However, further research is needed to comprehensively evaluate the efficacy and safety of Cariprazine as a monotherapy for MDD, providing valuable insights to guide clinical practice and enhance treatment outcomes for individuals with this debilitating condition. 2. Objectives The primary objective of this trial is to evaluate the effectiveness of cariprazine monotherapy in reducing depressive symptoms, as measured by the change from baseline to week 6 in the Montgomery-Åsberg Depression Rating Scale (MADRS) total score. Secondary objectives include assessing the safety and tolerability of cariprazine, evaluating its impact on overall functioning, and exploring potential predictors of treatment response. 3. Study Design This trial will be an 8 weeks pragmatic open-label randomized controlled trial conducted at Sultan Qaboos University Hospital Department of Behavioral Medicine. Participants will be randomly assigned to either the cariprazine monotherapy group or the treatment as usual group. The trial will follow the CONSORT guidelines for reporting randomized trials

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Randomization and Blinding:

Following the screening process and obtaining informed consent, eligible participants will be randomly assigned to one of the two treatment groups: the Cariprazine monotherapy group or the treatment as usual group. Randomization will be achieved using a computer-generated randomization sequence, and allocation concealment will be ensured using sealed envelopes. Due to the nature of the intervention, blinding of participants and researchers will not be feasible. However, efforts will be made to blind outcome assessors wherever. 4. Participants 4.1 Eligibility Criteria

Inclusion criteria: * Adults aged 18 to 65 years * Diagnosis of major depressive disorder based on DSM-5 criteria * Inadequate response to antidepressant therapy alone

Exclusion criteria: * History of bipolar disorder or psychotic disorders * Current substance abuse or dependence * Significant medical comorbidities that may interfere with the study assessments or treatment 5. Interventions 5.1 Cariprazine Monotherapy Group Participants in this group will receive cariprazine as monotherapy for the treatment of major depressive disorder. The starting dose will be determined based on individual patient characteristics and will be titrated as necessary.

5.2 Treatment as Usual Group Participants in this group will receive standard treatment for major depressive disorder, which may include antidepressant medication, psychotherapy, or a combination of both. The specific treatment will be determined by the treating clinician. 6. Outcome Measures 6.1 Primary Outcome Measure The primary outcome measure will be the change from baseline to week 6 in the Montgomery-Åsberg Depression Rating Scale (MADRS) total score. The MADRS is a widely used clinician-rated scale that assesses the severity of depressive symptoms. A higher score indicates more severe symptoms, and a decrease in score indicates improvement.

6.2 Secondary Outcome Measures

* Clinical Global Impressions (CGI): This scale provides an overall assessment of illness severity and improvement. It will be used to evaluate the change from baseline to week 8. * Adverse events and tolerability assessments: Adverse events will be monitored throughout the trial, and participants will be assessed for tolerability of the intervention.

Sample Size Calculation:

The sample size calculation for this clinical trial is based on the primary objective of assessing the efficacy of Cariprazine as a monotherapy for Major Depressive Disorder compared to treatment as usual. The following assumptions are made for the calculation:

* Statistical Power: The desired statistical power of the study is set at 80% (power = 0.80). This indicates that the study aims to detect a significant difference if it truly exists with a probability of 80%. * Significance Level: The significance level (alpha) is set at 0.05. This represents the acceptable probability of rejecting the null hypothesis when it is true. * Effect Size: A moderate effect size of 0.5 is assumed based on previous research or clinical data. This effect size represents a moderate difference between the Cariprazine monotherapy and treatment as usual groups. * Outcome Measure: The primary outcome measure is the change in depressive symptoms measured using standardized rating scales such as the Hamilton Rating Scale for Depression (HAM-D) or the Montgomery-Åsberg Depression Rating Scale (MADRS). * Attrition Rate: An attrition rate of 20% is anticipated, accounting for potential participant dropouts or withdrawals during the study.

Based on these assumptions, a sample size calculation can be performed using appropriate statistical methods. For example, a power analysis based on a two-sample t-test for independent groups can be conducted. Using a statistical software or sample size calculator, the minimum required sample size can be determined.

Assuming equal allocation to both groups (Cariprazine monotherapy and treatment as usual) and a two-sided test, the minimum required sample size per group can be calculated. Considering the assumptions mentioned above, with a power of 80%, a significance level of 0.05, a moderate effect size of 0.5, and an anticipated attrition rate of 20%, the estimated minimum sample size per group is approximately:

N = \[(Zα/2 + Zβ) / ES\]² \* (1 + attrition rate) N = \[(1.96 + 0.84) / 0.5\]² \* (1 + 0.20) N = 4.8² \* 1.20 N ≈ 55

Therefore, a minimum of 55 participants per group (Cariprazine monotherapy and treatment as usual) would be required, resulting in a total sample size of 110 participants.

Data Collection Process:

The data collection process in this trial will involve assessments at baseline and at regular intervals throughout the study period. Trained clinicians or research personnel will administer the standardized rating scales, such as the HAM-D or MADRS, to evaluate the change in depressive symptoms. These assessments will be conducted in a standardized and consistent manner to ensure reliable data collection.

In addition to the primary outcome measures, secondary outcome measures such as response rates, remission rates, functional improvement, and quality of life will also be assessed. The data collection schedule will be predetermined and communicated to the participants to ensure compliance and timely completion of assessments.

Data on treatment adherence, concomitant medications, and adverse events will also be collected. Participants will be instructed to report any side effects or adverse events they experience during the course of the trial. Research personnel will document these events, including their severity and relationship to the study intervention, in a systematic manner.

Termination of Trial:

The trial may be terminated prematurely under certain circumstances, including but not limited to:

1. Adverse Events: If there is an unacceptable level of severe adverse events or side effects associated with the study intervention, the trial may

• Change in Clinical Global Impression Scale (CGI) Mean Score [ Time Frame: 8 weeks ] [Срок оценки: 8 weeks]