Real-world outcomes post-transition to once-every-3-months paliperidone palmitate in patients with schizophrenia within US commercial plans

Relapse Rates With Paliperidone Palmitate in Adult Patients With Schizophrenia: Results for the 6-Month Formulation From an Open-label Extension Study Compared to Real-World Data for the 1-Month and 3-Month Formulations

BACKGROUND

The 3 paliperidone palmitate (PP) long-acting injectable antipsychotic formulations, PP 1-month (PP1M), PP 3-month (PP3M), and PP 6-month (PP6M), have shown to reduce the risk of relapse in schizophrenia. The current phase-4 study constructed external comparator arms (ECAs) using real-world data for PP3M and PP1M and compared relapse prevention rates with PP6M from an open-label extension (OLE) study in adult patients with schizophrenia.

METHODS

PP6M data were derived from a single-arm, 24-month, OLE study (NCT04072575), which included patients with schizophrenia who completed a 12-month randomized, double-blind, noninferiority, phase-3 study (NCT03345342) without relapse. Patients in the PP3M and PP1M ECAs were identified from the IBM® MarketScan® Multistate Medicaid Database based on similar eligibility criteria as the PP6M cohort.

RESULTS

A total of 178 patients were included in each cohort following propensity score matching. Most patients were men (>70%; mean age: 39-41 years). Time to relapse (primary analysis based on Kaplan-Meier estimates) was significantly delayed in the PP6M cohort (P < .001, log-rank test). The relapse rate was lower in the PP6M cohort (3.9%) vs PP3M (20.2%) and PP1M (29.8%) cohorts. Risk of relapse decreased significantly (P < .001) by 82% for PP6M vs PP3M (HR = 0.18 [95% CI = 0.08 to 0.40]), 89% for PP6M vs PP1M (HR = 0.11 [0.05 to 0.25]), and 35% for PP3M vs PP1M (HR = 0.65 [0.42 to 0.99]; P = .043). Sensitivity analysis confirmed findings from the primary analysis. Although the ECAs were matched to mimic the characteristics of the PP6M cohort, heterogeneity between the groups could exist due to factors including prior study participation, unmeasured confounders, variations in data capture and quality, and completeness of clinical information.

CONCLUSIONS

In a clinical trial setting, PP6M significantly delayed time to relapse and demonstrated lower relapse rates compared with PP3M and PP1M treatments in real-world settings among adult patients with schizophrenia.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04072575; EudraCT number: 2018-004532-30.

Cost-effectiveness analysis of monthly, 3-monthly, and 6-monthly long-acting injectable and oral paliperidone in adults with schizophrenia

BACKGROUND: Paliperidone is among the most cost-effective antipsychotics in adults with schizophrenia, and it has different formulations, including oral paliperidone extended-release (ER) and long-acting injectable (LAI) paliperidone formulations administered every month (PP1M), 3 months (PP3M), or 6 months (PP6M). However, cost-effectiveness analyses comparing different paliperidone formulations were limited. OBJECTIVE: To compare the cost-effectiveness across different paliperidone formulations. METHODS: A Markov model was developed to simulate 1,000 adults aged 40 years with stable schizophrenia transitioning among stable disease-medication adherent, stable disease-medication nonadherent, relapse with hospitalization, relapse with ambulatory care, and death states every 3 months for 5 years. Drug costs were estimated using the prices listed in the Veterans Affairs Federal Supply Schedule, and costs for treating complications were estimated from published studies. All costs were estimated from the US health care system perspective and standardized to 2022 US dollars using the Consumer Price Index Inflation Calculator. Quality-adjusted life-years (QALYs) were estimated using relapse rates from randomized clinical trials and health-related quality of life scores from observational studies. The estimated future costs and QALYs were discounted at 3%. We reported incremental net monetary benefits between alternative formulations at the $50,000 willingness-to-pay (WTP) threshold with a positive value indicating cost-effectiveness. The impact of parameter uncertainty on study outcomes was assessed using 1-way deterministic and probabilistic sensitivity analyses. RESULTS: In adults with schizophrenia stabilized with paliperidone ER, switching to LAI formulations was associated with increased QALY (PP1M = 0.05, PP3M = 0.14, PP6M = 0.15) and increased cost (PP1M = 49,433, PP3M = 26,698, PP6M = 26,147), leading to a negative incremental net monetary benefit (PP1M = -$46,804, PP3M = -$19,508, PP6M = -$18,886) compared with continuing ER. Among LAI formulations, PP6M was cost-saving with the most QALYs gained (cost = $63,277, QALY = 3.731), followed by PP3M (cost = $63,828, QALY = 3.729) and PP1M (cost = $86,563, QALY = 3.638). At the $50,000 WTP threshold, the probabilities for PP1M, PP3M, and PP6M being cost-effective compared with paliperidone ER were 0.4%, 10.2%, and 9.8%, respectively. The probability of PP6M being cost-effective was 92.6% for the PP6M-PP1M pair and 55.2% for the PP6M-PP3M pair, and 91.1% of PP3M use was cost-effective in the PP3M-PP1M pair. The results were generally robust in the sensitivity analyses, even at the $190,000 WTP threshold. CONCLUSIONS: For patients with schizophrenia stabilized with paliperidone ER, switching to LAI formulations was not cost-effective, suggesting the high drug costs for LAI may not justify the improved quality of life within 5 years. Among LAI formulations, PP6M was cost-effective over PP1M and PP3M.

The Effect of Longer Dosing Intervals for Long-Acting Injectable Antipsychotics on Outcomes in Schizophrenia

Medication nonadherence in schizophrenia can have serious implications including relapses and hospitalization. Long-acting injectable (LAI) antipsychotics require fewer administrations, while ensuring sustained medication coverage. In this review, we summarize the expected real-world benefits of longer dosing intervals in the management of schizophrenia. LAIs are associated with improved clinical outcomes of less frequent relapses and reduced functional impairment, encouraging patients to regain control of their lives. Aripiprazole lauroxil and paliperidone palmitate three-monthly (PP3M) LAIs have longer dosing intervals of 2-3 months and provide improved outcomes in patients with schizophrenia. Paliperidone palmitate six-monthly (PP6M) LAI provides the longest dosing interval, twice-yearly dosing, among existing LAIs. Decreasing the frequency of LAI administrations has the potential to reduce occurrence of serious outcomes associated with poor medication adherence. By eliminating the need for daily oral antipsychotic dosing, LAIs could increase the likelihood of patient acceptance, decrease stigma, and promote self-esteem. Longer intervals of medication coverage may be desirable for patients with higher risk of relapse including adults with recent-onset schizophrenia, those living in circumstances that may deprive them of regular access (eg, homeless), those that are in transitions between care settings or to reduce interpersonal contact during public health emergencies (eg, COVID-19 pandemic).

Effectiveness and Quality of Life with Paliperidone Palmitate 3-Monthly in Comparison with Other Long-Acting Drugs

PURPOSE

Antipsychotic long-acting injections (AP-LAIs) are indicated for patients affected by schizophrenia especially those with poor treatment adherence.

PATIENTS AND METHODS

To compare paliperidone palmitate 3-monthly (PP3M), paliperidone palmitate one-monthly (PP1M) and haloperidol decanoate (HAL-D) treatment, we enrolled 90 patients with schizophrenia treated in Mental Health Center with one of the three AP-LAIs for at least six months and followed them for another 6 months. At 6 and 12 months of treatment we administered Clinical Global Impression-Severity, Global Assessment of Functioning and World Health Organization Quality of Life-26 items (WHOQOL-BREF). At 1-year treatment, we evaluated relapses (psychiatric hospitalizations and urgent consultations), side effects and drop-outs.

RESULTS

We did not highlight any statistically significant difference among the three treatments in relapses and scale scores. Weight increase was significantly higher in PP1M and PP3M groups. Twelve patients (13.3%) discontinued AP-LAI. At 1-year AP-LAI treatment, 69% of patients rated quality of life as "good" or "very good" and 71% declared themselves to be "satisfied" or "very satisfied".

CONCLUSION

HAL-D, PP1M and PP3M 1-year treatments were similarly effective in preventing relapses and improving quality of life and health satisfaction. All discontinuations in the new 3-monthly antipsychotic treatment were caused by patient refusal to continue it.

Relapse and Treatment Adherence in Patients with Schizophrenia Switching from Paliperidone Palmitate Once-Monthly to Three-Monthly Formulation: A Retrospective Health Claims Database Analysis

PURPOSE

Relapse and treatment adherence to paliperidone palmitate once-monthly (PP1M) and three-monthly (PP3M) formulations in patients with schizophrenia were evaluated and compared using health claims data.

PATIENTS AND METHODS

Data (June 2015─June 2018) obtained from the MarketScan® Multi-State Medicaid Database were retrospectively analyzed. Patients aged ≥18 years with ≥1 claim for schizophrenia diagnosis prior to and/or at index date (i.e., date of first PP3M prescription record for PP3M patients and same month/year as the matched PP3M patients for PP1M patients) and continuous enrollment in the insurance plan for ≥12 months prior to index date (baseline) were included. PP1M cohort included patients who received ≥4 PP1M doses. PP3M patients were matched with PP1M patients (1:3) using propensity score matching and prevalent new user design. Outcome measures were relapse rate, time to relapse, proportion of days covered (PDC), and level of treatment adherence defined by PDC in five levels. Time to relapse was compared by Kaplan-Meier survival curves and log-rank test with the hazard ratio calculated using Cox proportion hazards model; PDC by t-test, and relapse rate and PDC categories by chi-square test.

RESULTS

A total of 1564 patients (428 PP3M and 1136 PP1M) were included. Relapse rate was lower in PP3M cohort (10.5%) compared with PP1M cohort (15.7%). Incidence rate of relapse was 8.98/100 person-years (PY) in PP3M cohort and 13.81/100 PY in PP1M cohort. After a mean (SD) follow-up of 456.1 (240.28) days in PP3M cohort and 465.4 (237.95) days in PP1M cohort, PP3M patients had a significantly lower relapse risk (hazard ratio: 0.65, 95% CI: 0.47, 0.90) than PP1M patients. Treatment adherence was significantly (p<0.0001) higher in PP3M versus PP1M cohort.

CONCLUSION

Risk of relapse was significantly lower, and treatment adherence was significantly higher in PP3M cohort compared with PP1M cohort. Higher treatment adherence was associated with lower relapse rate.

Long-acting second-generation and oral antipsychotics for substance use disorders and psychotic symptoms: Prescribing attitudes among Italian psychiatrists

PURPOSE

To explore Italian psychiatrists' attitudes toward the off-label use of second generation antipsychotics (SGAs) in patients with substance use disorder and psychotic symptoms.

DESIGN AND METHODS

A sample of 300 Italian psychiatrists associated with the Italian Society of Neuropsychopharmacology was randomly selected to complete a survey about the off-label prescription of SGAs.

FINDINGS

Oral aripiprazole (32.7%), olanzapine (30.2%), and quetiapine (25.2%) were considered "appropriate." Long-acting antipsychoticss were generally considered "inappropriate."

PRACTICE IMPLICATIONS

Our findings reflect a substantial level of uncertainty and a lack of coherent clinical guidance within the realm of dual diagnosis treatment. Therefore, they emphasize the need to develop specific guidelines to improve the management of pharmacotherapy among this population.

Patients' perspectives on three-monthly administration of antipsychotic treatment with paliperidone palmitate - a qualitative interview study

INTRODUCTION

Three-monthly dosage of paliperidone palmitate entails longer time to relapse after discontinuation, is similarly tolerable and safe compared to monthly injections of paliperidone palmitate and is beneficial for the caregivers. However, few studies have so far explored in depth the patients' experiences with paliperidone palmitate medication every three months, or with switching from monthly to three-monthly injections of paliperidone palmitate.

MATERIAL AND METHODS

A qualitative study based on individual interviews with persons with schizophrenia who receive three-monthly paliperidone palmitate in Norway, Sweden and Denmark. Data was analysed according to qualitative content analysis.

RESULTS

Twenty-four patients, 16 men and 8 women, took part in individual interviews. The patients' mental health care professionals mainly recommended the switch to three-monthly paliperidone palmitate, and few or no disadvantages were described. According to the patients, three-monthly paliperidone palmitate had several advantages, such as less frequent injections, less administration and planning and less focus on the illness. In addition, the participants described feeling more stability, being more physically and socially active, and that improvement processes were supported. For some, the use involved practical and economic challenges, and some worried whether the medicine 'wore off' before the next injection. According to the patients, switching to three-monthly paliperidone palmitate did not influence the frequency or content of patients' interaction with health care professionals.

CONCLUSION

Switching from monthly to three-monthly injections with paliperidone palmitate seems to be experienced as advantageous for patients with schizophrenia.

Paliperidone Palmitate Every Three Months (PP3M) 2-Year Treatment Compliance, Effectiveness and Satisfaction Compared with Paliperidone Palmitate-Monthly (PP1M) in People with Severe Schizophrenia

Paliperidone palmitate every three months (PP3M) is expected to facilitate patient's treatment compliance and satisfaction. The objective here was to compare PP3M treatment compliance and satisfaction, effectiveness and tolerability, with paliperidone palmitate-monthly (PP1M) in patients with severe schizophrenia. A 24-month prospective, open-label study of patients with severe schizophrenia treated with PP3M after at least 2 years of stabilization with PP1M (n = 84) was carried out. Treatment satisfaction was assessed with the Treatment Satisfaction Questionnaire for Medication (TSQM) and with a Visual Analogue Scale (VAS). Effectiveness was measured with psychiatric hospital admissions and the Clinical Global Impression-Severity (CGI-S) scale. Tolerability assessments included laboratory tests, weight and adverse effects. Reasons for treatment discontinuation were recorded. CGI-S significantly improved after 24 months. Three patients changed back to PP1M due to adverse effects, and four were hospitalized. There were neither abandoning nor significant changes in weight or biological parameters, and lower incidence of side effects, with PP3M treatment. TSQM and VAS scales increased. No differences were found related to doses. Apart from somewhat improvement in treatment adherence, effectiveness, and tolerability, patients with severe schizophrenia lengthy treated with PP1M showed more satisfaction with PP3M, even those who needed high doses to get clinical stabilization.

Medication adherence, healthcare resource utilization, and costs among Medicaid beneficiaries with schizophrenia treated with once-monthly paliperidone palmitate or once-every-three-months paliperidone palmitate

OBJECTIVE

Antipsychotics with reduced dosing frequency may improve adherence and clinical outcomes for patients with schizophrenia. This study compared treatment patterns, healthcare resource utilization (HRU), and costs between Medicaid beneficiaries with schizophrenia treated with once-monthly paliperidone palmitate (PP1M) and those who transitioned to once-every-three-months paliperidone palmitate (PP3M).

METHODS

Adults with schizophrenia were identified in a four-state Medicaid database (18 May 2014 to 31 March 2019). The index date was the first PP3M claim (PP3M cohort), or a random PP1M claim (PP1M cohort), following ≥4 months of continuous PP1M treatment among patients with ≥12 months of continuous Medicaid enrollment pre- and post-index. Adherence (proportion of days covered by the index treatment ≥80%), persistence (no gap >90/30 days in the PP3M/PP1M supply), HRU, and costs were compared during the 12-month post-index period between cohorts matched 1:1.

RESULTS

Among 2374 patients identified, 374 remained in each cohort after matching (mean age 42 years; 30.5% female). Compared to the PP1M cohort, the PP3M cohort was 2.39 times more likely to be adherent (p < .001), 4.63 times more likely to be persistent (p < .001), 33% less likely to have ≥1 hospitalization (p = .011), and 32% less likely to have ≥1 day with home care services (p = .012). Mean annual medical costs were similar between cohorts ($24,970 in the PP3M cohort and $25,736 in the PP1M cohort; p = .854).

CONCLUSIONS

Medicaid beneficiaries who transitioned to PP3M had higher adherence and persistence, and a reduced likelihood of hospitalization relative to those who continued treatment with PP1M. The results suggest potential clinical value to transitioning eligible patients to PP3M.

Fatal and life-threatening ADRs associated with paliperidone palmitate: an observational study in the French pharmacovigilance database

INTRODUCTION

Paliperidone palmitate (PP), a long-acting intramuscular formulation of paliperidone, has been marketed in Europe within the last 10 years and provides an important treatment option for patients with schizophrenia.Our aim was to describe PP-related adverse drug reactions (ADRs) leading to death or life-threatening events, specifying their main clinical and pharmacological characteristics.

METHODS

This observational study was a retrospective review of PP-related ADRs in the French pharmacovigilance database between January 1, 2013, and December 31, 2019.

RESULTS

Out of 473 PP-related ADRs, we identified 13 deaths and 14 life-threatening events. ADRs were primarily cardiorespiratory (n = 17; 63%). Other symptoms observed were mainly metabolic (n = 4), digestive (n = 4), and neurological (n = 4). Cardiorespiratory symptoms were generally observed within first 6 months after initiation of treatment (11 out of 17 cases), unlike metabolic disorders (all 4 cases 12-21 months after initiation). Cardiac arrests and sudden unexpected deaths occurred 10-14 days after the last PP once-monthly injection (23 cases) or 11-24 days after the last PP three-monthly injection (remaining 4 cases). No PP blood concentration assays were performed for these patients.

DISCUSSION

In this study, PP-related ADRs leading to death or life-threatening events mainly presented with cardiorespiratory symptoms and tended to occur in the first 6 months after the initiation of treatment and within postadministration periods aligned with peak plasma PP concentrations. The hypothesis of supratherapeutic drug concentrations following intramuscular PP injection must be raised.

CONCLUSION

PP-related ADRs leading to death or life-threatening events mainly presented with cardiorespiratory symptoms. Cardiac arrests and sudden unexpected deaths following initiation of PP treatment could be due to supratherapeutic drug concentrations. This study highlights the need to monitor blood concentrations of PP.Key pointsAdverse reactions to paliperidone palmitate can lead to death or life-threatening events.It is hypothesized that cardiac arrests and sudden unexpected deaths following initiation of paliperidone palmitate treatment could be due to supratherapeutic drug concentrations.This paper proposes the need to monitor blood concentrations of paliperidone palmitate in future studies.

Real-World Outcomes and Costs Following 6 Months of Treatment with the Long-Acting Injectable (LAI) Aripiprazole Lauroxil for the Treatment of Schizophrenia

BACKGROUND

Continuous antipsychotic therapy is recommended as part of long-term maintenance treatment of schizophrenia, and gaps in antipsychotic treatment have been associated with increased risks of relapse and rehospitalization. Because the use of long-acting injectable (LAI) antipsychotics may reduce the likelihood of undetected medication gaps, initiating an LAI medication may affect resource utilization and costs. The LAI aripiprazole lauroxil (AL) was approved in the United States (US) in 2015 for the treatment of schizophrenia in adults.

OBJECTIVE

The objective of this retrospective observational cohort study was to examine treatment patterns, resource utilization, and costs following initiation of AL for the treatment of schizophrenia in adults.

METHODS

A retrospective analysis of Medicaid claims data identified a cohort of patients (N = 485) starting AL shortly after Food and Drug Administration approval in October 2015. Treatment patterns, resource utilization, and costs were compared 6 months before and after treatment initiation. Subgroup analyses were conducted based on the type of antipsychotic (LAI, oral, or none) received before initiation of AL.

RESULTS

Over 6 months of follow-up, patients received an average of 4.6 injections out of a maximum of six (77%). After initiating AL, all-cause inpatient admissions decreased by 22.4%; other significant reductions were observed in mental health-related admissions and emergency room (ER) visits. All-cause inpatient costs decreased by an average of US$2836 per patient (p < 0.05) in the 6-month post-AL period, whereas outpatient pharmacy costs increased by US$4121 (p < 0.05), resulting in no significant difference in overall costs between the pre- and post-AL periods. The subgroup of patients who had been prescribed an oral antipsychotic before starting AL had significant reductions in proportion of patients with inpatient and ER visits and costs, but also reported a significant increase in pharmacy costs.

CONCLUSIONS

AL was associated with a significant reduction in inpatient costs and an increase in outpatient pharmacy costs, resulting in no changes in total healthcare costs over 6 months. The adherence rate and reductions in inpatient use may indicate the potential for greater clinical stability among patients initiated on AL compared with their previous treatment.

Transitioning from Once-Monthly to Once-Every-3-Months Paliperidone Palmitate Among Veterans with Schizophrenia

PURPOSE

Compared to once-monthly paliperidone palmitate (PP1M), once-every-3-months paliperidone palmitate (PP3M) reportedly increases treatment adherence. The objective of this study was to compare treatment patterns, utilization, and costs among Veterans Health Administration (VHA) patients with schizophrenia who transitioned to PP3M versus those remaining on PP1M.

PATIENTS AND METHODS

Adult VHA patients with ≥2 health care encounters (inpatient or outpatient) that included a schizophrenia diagnosis who initiated PP1M between January 1, 2015, and March 31, 2018 (identification period) were included in this exploratory retrospective cohort study. Propensity scores were used to match cases (PP1M users who transitioned to PP3M during the identification period) with controls (any patient initiating PP1M during the identification period). Data were assessed until death, health plan disenrollment, or study end. Outcomes were compared using chi-square and t-tests.

RESULTS

A total of 257 eligible PP3M and 2973 eligible PP1M patients were identified among adult VHA patients; mean ages were 53.1 and 53.7 years, respectively. After propensity score matching, the PP3M and PP1M cohorts each held 111 patients. Comorbidities of patients treated with PP3M versus PP1M, respectively, included anxiety (12.5% vs 20%; standardized difference [STD] = 20.6), tobacco use (28.4% vs 43.2%; STD = 31.2), depressive disorder (26.5% vs 36.2%; STD = 21.1), and substance abuse (37.4% vs 44.2%; STD = 13.9). For the PP3M cohort, adherence (proportion of days covered ≥80%) to any antipsychotic agent was higher (78.4% vs 57.7%, P = 0.0009), and all-cause inpatient lengths of stay (LOS) were shorter (3.0 vs 8.3 days, P = 0.0354). Increased all-cause pharmacy costs with PP3M were offset by reduced all-cause medical costs, resulting in overall health care cost-neutrality.

CONCLUSION

Relative to those remaining on PP1M, VHA patients with schizophrenia who transitioned to PP3M experienced improved antipsychotic medication adherence and significantly shorter all-cause inpatient LOS; costs remained neutral.

Switching from clozapine to paliperidone palmitate-3-monthly improved obesity, hyperglycemia and dyslipidemia lowering antipsychotic dose equivalents in a treatment-resistant schizophrenia cohort

Clozapine, an antipsychotic developed in 1958, is considered the gold standard and the treatment of choice in treatment-resistant schizophrenia despite its side effects and despite 40-70% of these patients not responding to clozapine. In the last decade, new antipsychotics, such as paliperidone palmitate (PP), have emerged as well as its long acting-injectable (LAI) formulations, available as PP-1-monthly (PP1M) and the newest PP-3-montlhy (PP3M). Despite paliperidone having shown a similar efficacy as others antipsychotics for the treatment of schizophrenia, and that PP3M has been shown to reduce relapses compared to oral formulations, no study has been carried out in treatment-resistant schizophrenia. The aim of our study was to carry out an exploratory evaluation of endocrine and hepatic profiles as well as the concomitant treatments associated to PP3M vs. clozapine, the gold standard, in patients with treatment-resistant schizophrenia. We designed a retrospective study. A total number of 33 patients previously diagnosed as schizophrenics treatment-resistant, who were prescribed clozapine followed by PP1M and PP3M when available, were selected. Demographic data, BMI, hepatic enzymes (glutamic oxaloacetic transaminase, glutamate-pyruvate transaminase and gamma-glutamyl transferase (GGT)], thyroid function (thyroid stimulating hormone), blood platelets and both white and red blood cells as well as the use of concomitant antipsychotics, benzodiazepines and biperiden were compared under treatment with clozapine and PP3M. Antipsychotics and benzodiazepines dosages were compared using by the defined daily dose (DDD) method and haloperidol or diazepam dose equivalents. All statistical analyses were performed using the paired Student t-test for repeated measures. Our data showed that patients under treatment with PP3M showed a significant decrease in BMI (P < 0.01), glucose (P < 0.01), cholesterol (P < 0.05) and triglycerides (P < 0.01) when compared with basal values under treatment with clozapine. Hepatic cholestasis enzyme, GGT, were significantly elevated (P < 0.05) under treatment with clozapine when compared to PP3M. Switching clozapine to PP3M led to a significant lower pharmacological exposure to antipsychotics, by both the DDD (P < 0.05) and haloperidol dose equivalents (P < 0.001) methods without increasing the dose of benzodiazepines while biperiden was more used under PP3M. Finally, antipsychotic monotherapy was higher and less polypharmacy was used with PP3M. In conclusion, our findings suggest that switching clozapine to PP3M improved endocrine and hepatic profile with a lower total exposure to antipsychotics. More studies are needed to truly establish the role of PP3M in treatment-resistant schizophrenia and should be compared against clozapine by using clinical trials.