: Mechanism of Action
: Paliperidone palmitate is hydrolysed to paliperidone (see Pharmacokinetics as follows). Paliperidone is the major active metabolite of risperidone. The mechanism of action of paliperidone, as with other drugs having efficacy in schizophrenia, is unknown, but it has been proposed that the drug's therapeutic activity in schizophrenia is mediated through a combination of central dopamine Type 2 (D2
) and serotonin Type 2 (5HT2A
) receptor antagonism.
Paliperidone is a centrally active dopamine Type 2 (D2
) receptor antagonist and a serotonin Type 2 (5HT2A
) receptor antagonist. Paliperidone is also active as an antagonist at α1
adrenergic receptors and H1
histaminergic receptors, which may explain some of the other effects of the drug. Paliperidone has no affinity for cholinergic muscarinic or β1
- and β2
-adrenergic receptors. The pharmacological activity of the (+)- and (-)- paliperidone enantiomers is qualitatively and quantitatively similar in vitro
: The efficacy of INVEGA TRINZA for the treatment of schizophrenia in subjects who have been adequately treated for at least 4 months with the 1-month paliperidone palmitate injectable product was evaluated in a long-term double-blind, placebo-controlled relapse prevention randomised withdrawal study and in a long-term double-blind, active-controlled noninferiority study.
Relapse prevention/randomised withdrawal study: Adult subjects who met DSM-IV-TR criteria for schizophrenia could enter the study with acute symptoms (if previously treated with oral antipsychotics) or be clinically stable (if treated with long-acting injectable antipsychotics [LAI]). All subjects who previously received oral antipsychotics received the paliperidone palmitate 1-month initiation regimen (deltoid injections of 150 mg and 100 mg one week apart), while those subjects switching from LAI medication were treated with the 1-month paliperidone palmitate injectable product in place of the next scheduled injection. Specifically: For subjects entering the study who were already being treated with the 1-month paliperidone palmitate injectable product, their dosing remained unchanged.
Subjects entering the study who were being treated with 25 mg, 37.5 mg, or 50 mg of RISPERDAL CONSTA (risperidone long-acting injection) were switched to 50-100 mg of the 1-month paliperidone palmitate administered in the deltoid muscle.
Subjects entering the study who were being treated with any other LAI product were switched to 150 mg initially then 50-150 mg of the 1-month paliperidone palmitate administered in the deltoid muscle.
This study consisted of the following three treatment periods: A 17-week flexible-dose open-label period with the 1-month paliperidone palmitate (first part of a 29-week open-label stabilisation phase). A total of 506 subjects entered this phase of the study. Dosing of the 1-month paliperidone palmitate was individualised based on symptom response, tolerability, and previous medication history. Specifically, the dose could be adjusted at the week 5 and 9 injections and the injection site could be deltoid or gluteal. The week 13 dose had to be the same as the week 9 dose. Subjects had to be clinically stable at the end of this period before receiving INVEGA TRINZA at the week 17 visit. Clinical stability was defined as achieving a PANSS total score <70 at week 17.
A 12-week open-label treatment period with INVEGA TRINZA (second part of a 29-week open-label stabilisation phase). A total of 379 subjects received a single-dose of INVEGA TRINZA which was a 3.5 multiple of the last dose of the 1-month paliperidone palmitate. Subjects had to remain clinically stable before entry into the next period (double-blind). Clinical stability was defined as achieving a PANSS total score <70 and scores of <=4 for PANSS items P1, P2, P3, P6, P7, G8, and G14 at the end of this 12-week period (week 29 of the study).
A variable length double-blind treatment period. In this period, 305 stabilised subjects were randomised 1:1 to continue treatment with INVEGA TRINZA or placebo until relapse, early withdrawal, or the end of study. Subjects were randomised to the same dose of INVEGA TRINZA they received during the open-label phase (i.e., 273 mg, 410 mg, 546 mg, or 819 mg [175, 263, 350 or 525 mg]) or to placebo administered every 12 weeks. The numbers (%) of subjects entering double-blind on each of the dose levels were 6 (4%) for 175 mg, 15 (9%) for 263 mg, 78 (49%) for 350 mg, and 61 (38%) for 525 mg.
The primary efficacy variable was time to first relapse. Relapse was pre-defined as emergence of one or more of the following: psychiatric hospitalisation, ≥ 25% increase (if the baseline score was > 40) or a 10-point increase (if the baseline score was ≤ 40) in total PANSS score on two consecutive assessments, deliberate self-injury, violent behaviour, suicidal/homicidal ideation, or a score of ≥ 5 (if the maximum baseline score was ≤ 3) or ≥ 6 (if the maximum baseline score was 4) on two consecutive assessments of the individual PANSS items P1 (Delusions), P2 (Conceptual disorganisation), P3 (Hallucinatory behaviour), P6 (Suspiciousness/persecution), P7 (Hostility), or G8 (Uncooperativeness).
A pre-planned interim analysis showed a statistically significantly (p-value <0.001) longer time to relapse in subjects treated with INVEGA TRINZA compared to placebo, and the study was stopped early. The hazard ratio for relapse (placebo/INVEGA TRINZA) was 3.45 (95% CI: 1.73, 6.88) indicating a 71% decrease in relapse risk with INVEGA TRINZA. The most common reason for relapse observed across both treatment groups was increase in the PANSS total score value, followed by psychiatric hospitalisation.
The mean (SD) duration of exposure during the double-blind phase was 150 (79) days in the placebo group and 175 (90) days in the INVEGA TRINZA group. Twenty-three percent (23%) of subjects in the placebo group and 7.4% of subjects in the INVEGA TRINZA group experienced a relapse event. The hazard ratio for relapse (placebo/INVEGA TRINZA) was 3.45 (95% CI: 1.73, 6.88) indicating a 71% decrease in relapse risk with INVEGA TRINZA. A Kaplan-Meier plot of time to relapse by treatment group is shown in Figure 1. The median time to relapse (the time at which the cumulative survival function equals 0.5, or 50%) for subjects in the placebo group was 274 days.
An examination of population subgroups did not reveal any clinically significant differences in responsiveness on the basis of gender, age, or race. (See Figure 1.)
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Non‐inferiority study: This study was a randomised, double‐blind, parallel group, multicentre non‐inferiority study to determine if the efficacy of INVEGA TRINZA was non‐inferior to the efficacy of the 1-month paliperidone palmitate injectable product for the treatment of adults with schizophrenia.
The primary efficacy endpoint was the percentage of subjects (per protocol analysis) who had not relapsed at the end of the 48‐week Double‐blind Phase. This was determined based on the Kaplan‐Meier 48‐week cumulative estimate of survival (i.e., percentage of subjects remaining relapse free). The predefined noninferiority margin was 15%.
Eligible subjects were adult men and women who had a DSM-IV-TR diagnosis of schizophrenia for at least 1 year before screening. Subjects were required to have a PANSS total score between 70 and 120 at screening and to have worsening symptoms, in the opinion of the investigator. All subjects must have had a valid reason to discontinue current antipsychotic therapy (including insufficient efficacy with current therapy, safety or tolerability issues, or subject preference for injectable medications). Subjects may not have received a long-acting injectable (LAI) antipsychotic within 4 weeks before screening.
Relapse was defined as one or more of the following (identical to the relapse criteria used in the placebo-controlled relapse prevention/randomised withdrawal study described previously): psychiatric hospitalisation, ≥ 25% increase (if the baseline score was > 40) or a 10-point increase (if the baseline score was ≤ 40) in total PANSS score on two consecutive assessments, deliberate self-injury, violent behaviour, suicidal/homicidal ideation, or a score of ≥ 5 (if the maximum baseline score was ≤ 3) or ≥ 6 (if the maximum baseline score was 4) on two consecutive assessments of the individual PANSS items P1 (Delusions), P2 (Conceptual disorganisation), P3 (Hallucinatory behaviour), P6 (Suspiciousness/persecution), P7 (Hostility), or G8 (Uncooperativeness).
A total of 1,429 subjects with worsening of symptoms (baseline mean PANSS total score: 85.7) were enrolled into the open-label phase and treated with the 1-month paliperidone palmitate injectable product for 17 weeks. The dose could be adjusted (i.e., 50 mg, 75 mg, 100 mg, or 150 mg) at the week 5 and 9 injections and the injection site could be deltoid or gluteal. For subjects that met randomisation criteria at weeks 14 and 17, 1,016 were randomised in a 1:1 ratio to continue on monthly injections of the 1-month paliperidone palmitate injectable product or to switch to INVEGA TRINZA with a 3.5 multiple of the week 9 and 13 dose of the 1-month paliperidone palmitate injectable product for 48 weeks. Subjects received INVEGA TRINZA once every 3 months and received placebo-injectable medication for the other months to maintain the blind.
The primary efficacy endpoint of the study was the percentage of subjects who had not relapsed at the end of the 48-week double-blind phase based on the Kaplan-Meier 48-week estimate (INVEGA TRINZA: 91.2%, 1-month paliperidone palmitate injectable product: 90.0%). The difference (95% CI) between the treatment groups was 1.2% (-2.7%, 5.1%), meeting the pre-specified non-inferiority criterion based on a margin of -15%. Thus, the INVEGA TRINZA treatment group was non-inferior to the 1-month paliperidone palmitate injectable product. (See Figure 2.)
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The efficacy results were consistent across population subgroups (gender, age, and race) in both studies.
: Absorption and Distribution
: Due to its extremely low water solubility, the 3-month formulation of paliperidone palmitate dissolves slowly after intramuscular injection before being hydrolysed to paliperidone and absorbed into the systemic circulation.
The data presented in this paragraph are based on a population pharmacokinetic analysis. Following a single intramuscular dose of INVEGA TRINZA, the plasma concentrations of paliperidone gradually rise to reach maximum plasma concentrations at a median Tmax
of 30-33 days. Following intramuscular injection of INVEGA TRINZA at doses of 175-525 mg in the deltoid muscle, on average, an 11-12% higher Cmax
was observed compared with injection in the gluteal muscle. The release profile and dosing regimen of INVEGA TRINZA results in sustained therapeutic concentrations. The total exposure (AUC) of paliperidone following INVEGA TRINZA administration was dose-proportional over a 175-525 mg dose range, and approximately dose-proportional for Cmax
. The median steady-state peak:trough ratio for a INVEGA TRINZA dose was 1.6 to 1.7 following gluteal and deltoid administration. Following administration of INVEGA TRINZA, the apparent volume of distribution of paliperidone is 1960 L.
In the single dose study of 75 to 525 mg 1 subject on 525 mg clearly had a rapid absorption event with a Cmax
on Day 2 of 416 ng/mL (median for subjects on that dose was 57.9 ng/mL) with no adverse events.
The plasma protein binding of racemic paliperidone is 74%. Following administration of INVEGA TRINZA, the (+) and (-) enantiomers of paliperidone interconvert, reaching an AUC (+) to (-) ratio of approximately 1.7-1.8.
Metabolism and Excretion
: In a study with oral immediate-release 14
C-paliperidone, one week following administration of a single oral dose of 1 mg immediate-release 14
C-paliperidone, 59% of the dose was excreted unchanged into urine, indicating that paliperidone is not extensively metabolised in the liver. Approximately 80% of the administered radioactivity was recovered in urine and 11% in the faeces. Four metabolic pathways have been identified in vivo
, none of which accounted for more than 10% of the dose: dealkylation, hydroxylation, dehydrogenation, and benzisoxazole scission. Although in vitro
studies suggested a role for CYP2D6 and CYP3A4 in the metabolism of paliperidone, there is no evidence in vivo
that these isozymes play a significant role in the metabolism of paliperidone. Population pharmacokinetics analyses indicated no discernible difference on the apparent clearance of paliperidone after administration of oral paliperidone between extensive metabolisers and poor metabolisers of CYP2D6 substrates. In vitro
studies in human liver microsomes showed that paliperidone does not substantially inhibit the metabolism of medicines metabolised by cytochrome P450 isozymes, including CYP1A2, CYP2A6, CYP2C8/9/10, CYP2D6, CYP2E1, CYP3A4, and CYP3A5.
studies have shown that paliperidone is a P-gp substrate and a weak inhibitor of P-gp at high concentrations. No in vivo
data are available and the clinical relevance is unknown.
Based on population pharmacokinetic analysis, the median apparent half-life of paliperidone following INVEGA TRINZA administration over the dose range of 175-525 mg ranged from 84-95 days following deltoid injections and 118-139 days following gluteal injections.
Long-acting 3-month paliperidone palmitate injection versus other paliperidone formulations: The concentration of paliperidone remaining in the circulation 18 months after dosing of 525 mg INVEGA TRINZA is stopped is estimated to be 3% (following deltoid injection) or 7% (following gluteal injection) of the average steady‐state levels.
INVEGA TRINZA is designed to deliver paliperidone over a 3-month period, while 1-month paliperidone palmitate injection is administered on a monthly basis. Simulations show that INVEGA TRINZA, when administered at doses that are 3.5-fold higher than the corresponding dose of 1-month paliperidone palmitate injection, produces paliperidone exposures similar to those obtained with corresponding monthly doses of 1-month paliperidone palmitate injection and corresponding once daily doses of paliperidone extended-release tablets; and that exposure range for INVEGA TRINZA is encompassed within the exposure range for the approved dose strengths of paliperidone extended-release tablets.
The between‐subject variability for paliperidone pharmacokinetics following delivery from INVEGA TRINZA is similar to the variability for paliperidone extended‐release tablets. Because of the difference in median pharmacokinetic profiles among the three paliperidone formulations, caution should be exercised when making a direct comparison of their pharmacokinetic behaviour in a given patient.
: Renal Impairment: INVEGA TRINZA has not been systematically studied in patients with renal impairment. The disposition of a single oral dose of a paliperidone 3 mg extended-release tablet was studied in subjects with varying degrees of renal function. Elimination of paliperidone decreased with decreasing estimated creatinine clearance. Total clearance of paliperidone was reduced in subjects with impaired renal function by 32% on average in mild (CrCl = 50 to < 80 mL/min), 64% in moderate (CrCl = 30 to < 50 mL/min), and 71% in severe (CrCl = 10 to < 30 mL/min) renal impairment, corresponding to an average increase in exposure (AUCinf
) of 1.5, 2.6, and 4.8-fold, respectively, compared to healthy subjects. Based on a limited number of observations with INVEGA TRINZA in subjects with mild renal impairment and pharmacokinetic simulations, the initiation and maintenance dose of 1-month paliperidone palmitate injection should be reduced in patients with mild renal impairment. Subjects can be transitioned over to INVEGA TRINZA using the corresponding 3.5-multiple dose for mild renal impaired subjects. No additional dose reduction upon starting INVEGA TRINZA is necessary (see Dosage & Administration).
INVEGA TRINZA is not recommended for patients with moderate or severe renal impairment (see Dosage & Administration).
Hepatic Impairment: INVEGA TRINZA has not been studied in patients with hepatic impairment. Based on a study with oral paliperidone in subjects with moderate hepatic impairment (Child-Pugh Class B), no dose adjustment is required in patients with mild or moderate hepatic impairment (see Dosage & Administration). In the study with oral paliperidone in subjects with moderate hepatic impairment (Child-Pugh class B), the plasma concentrations of free paliperidone were similar to those of healthy subjects, although total paliperidone exposure decreased because of a decrease in protein binding. Paliperidone has not been studied in patients with severe hepatic impairment.
Elderly (65 years of age and older): No dosage adjustment is recommended based on age alone. However, dose adjustment may be required because of age-related decreases in creatinine clearance (see Dosage & Administration).
Race: No dosage adjustment is recommended based on race. In the Pop-PK analysis of INVEGA TRINZA no influence of race on pharmacokinetics was shown.
Gender: No dosage adjustment is recommended based on gender, although slower absorption was observed in females in a population pharmacokinetic analysis.
Smoking: No dosage adjustment is recommended based on smoking status. Based on in vitro studies utilising human liver enzymes, paliperidone is not a substrate for CYP1A2; smoking should, therefore, not have an effect on the pharmacokinetics of paliperidone.
Body Mass Index (BMI)/Body Weight: No dose adjustment is needed based on BMI. Lower Cmax was observed in overweight and obese subjects. At apparent steady-state with INVEGA TRINZA, the trough concentrations were similar among normal, overweight, and obese subjects.
: Preclinical Safety Data
: Genotoxicity: Paliperidone palmitate was not genotoxic in in vitro tests for bacterial reverse gene mutation and forward mutation in mammalian cells (mouse lymphoma). Paliperidone was also not genotoxic in these tests, or in an in vivo test for clastogenicity (rat micronucleus assay).
Carcinogenicity: No carcinogenicity studies have been conducted with the 3-month paliperidone palmitate extended-release injection. The carcinogenic potential of the 1-month intramuscular paliperidone palmitate injection was assessed in a long-term study in rats. There was an increase in mammary gland adenocarcinomas in female rats at 10, 30 and 60 mg/kg/month, associated with respective exposures (plasma AUC) of 0.4, 1.6 and 3 times clinical exposure at the maximum recommended 150 mg dose of the 1-month paliperidone palmitate injectable product. A no-effect dose was not established. Male rats showed an increase in total mammary gland tumours at 30 and 60 mg/kg/month, associated with respective exposures (plasma AUC) of 1 and 2 times clinical exposure. These rat doses of 10, 30 and 60 mg/kg/month are 0.5, 1.5 and 3 times the maximal recommended clinical dose of INVEGA TRINZA (525 mg/3 months), on a mg/m2 basis. A carcinogenicity study in mice has not been conducted with paliperidone palmitate.
Carcinogenicity studies of risperidone, which is extensively converted to paliperidone in rats, mice and humans, were conducted in Swiss albino mice and Wistar rats. Risperidone was administered in the diet at daily doses of 0.63, 2.5, and 10 mg/kg for 18 months to mice and for 25 months to rats, equivalent to 0.3, 1.3 and 5 times (mice) and 0.6, 2.5 and 10 times (rats) the maximum human dose on a mg/m2 basis. There were statistically significant increases in pituitary gland adenomas in female mice and endocrine pancreas adenomas in male rats at the two highest dose levels, and in mammary gland adenocarcinomas at all dose levels in female mice and female rats and at the highest dose in male rats. An increase in mammary, pituitary, and endocrine pancreas neoplasms has been found in rodents after chronic administration of other antipsychotic drugs and is considered to be mediated by prolonged dopamine D2-receptor antagonism and hyperprolactinaemia. The relevance of these tumour findings in rodents in terms of human risk is unknown (see Precautions).