Pharmacology: Pharmacodynamics: It has been suggested that the efficacy of lurasidone in schizophrenia is mediated through a combination of central dopamine Type 2 (D
2) and serotonin Type 2 (5-HT
2A) receptor antagonism.
In vitro receptor binding studies revealed that lurasidone is an antagonist with high affinity at dopamine D
2 receptors (K
i=0.994 nM) and the 5-hydroxytryptamine (5-HT, serotonin) receptors 5-HT
2A (K
i=0.470 nM) and 5-HT
7 (K
i=0.495 nM), is an antagonist with moderate affinity for α
2C adrenergic receptors (K
i=10.8 nM), is a partial agonist at serotonin 5-HT
1A (K
i=6.38 nM) receptors, an antagonist at α
2C (K
i=40.7 nM) and α
1 (K
i=47.9 nM) adrenergic receptors. Lurasidone exhibits little or no affinity for histamine H
1 and muscarinic M
1 receptors (IC
50>1,000 nM).
The addition of serotonin antagonism to dopamine antagonism (classic neuroleptic mechanism) is thought to improve negative symptoms of psychoses and reduce the incidence of extrapyramidal side effects as compared to typical antipsychotics.
Schizophrenia: Adults: Short-term studies: The efficacy of lurasidone in the treatment of schizophrenia was established in five short-term (6-week), placebo-controlled, studies in adult patients who met DSM-IV criteria for schizophrenia. An active control arm (olanzapine or quetiapine XR) was included in two studies to assess assay sensitivity.
Several instruments were used for assessing psychiatric signs and symptoms in these studies: Positive and Negative Syndrome Scale (PANSS), is a multi-item inventory of general psychopathology used to evaluate the effects of drug treatment in schizophrenia. PANSS total scores may range from 30 to 210.
Brief Psychiatric Rating Scale derived (BPRSd), derived from the PANSS, is a multi-item inventory primarily focusing on positive symptoms of schizophrenia, whereas the PANSS includes a wider range of positive, negative and other symptoms of schizophrenia. BPRSd scores may range from 18 to 126.
The Clinical Global Impression severity scale (CGI-S) is a validated clinician-rated scale that measures the subject's current illness state on a 1 to 7-point scale.
The endpoint associated with each instrument is change from baseline in the total score to the end of Week 6. These changes are then compared to placebo changes for the drug and control groups.
The results of the studies follow (Table 1): In a 6-week, placebo-controlled trial (N=145) involving two fixed doses of lurasidone (40 or 120 mg/day), both doses of lurasidone at Endpoint were superior to placebo on the BPRSd total score, and the CGI-S.
In a 6-week, placebo-controlled trial (N=180) involving a fixed dose of lurasidone (80 mg/day), lurasidone at Endpoint was superior to placebo on the BPRSd total score, and the CGI-S.
In a 6-week, placebo and active-controlled trial (N=473) involving two fixed doses of lurasidone (40 or 120 mg/day) and an active control (olanzapine), both lurasidone doses and the active control at Endpoint were superior to placebo on the PANSS total score, and the CGI-S.
In a 6-week, placebo-controlled trial (N=489) involving three fixed doses of lurasidone (40, 80 or 120 mg/day), only the 80 mg/day dose of lurasidone at Endpoint was superior to placebo on the PANSS total score, and the CGI-S.
In a 6-week, placebo and active-controlled trial (N=482) involving two fixed doses of lurasidone (80 or 160 mg/day) and an active control (quetiapine XR), both lurasidone doses and the active control at Endpoint were superior to placebo on the PANSS total score, and the CGI-S. (See Table 1.)
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Long-term Studies: The efficacy of lurasidone for the long-term treatment of schizophrenia was established in two studies in adult patients. One study was a double-blind, placebo-controlled, randomized withdrawal study in patients aged 18 to 75 years, inclusive, experiencing an acute episode of schizophrenia. A total of 676 patients entered the open label lurasidone stabilization phase (minimum of 12 weeks and maximum of 24 weeks).
A total of 285 patients completed the open-label phase, met the criteria for clinical stability, and were randomized into the double-blind phase (maximum of 28 weeks) where they received either lurasidone 40 or 80 mg/day or placebo. Patients treated with lurasidone experienced a statistically significant longer time to relapse than patients who received placebo.
One study was a 12-month, double-blind, parallel-group, active-controlled (quetiapine XR) study in patients with schizophrenia, aged 18 to 75 years, inclusive. A total of 218 patients who received flexible doses of either lurasidone (40, 80, 120, or 160 mg/day) or quetiapine XR (200, 400, 600, or 800 mg/day) were included in the non-inferiority analysis. Lurasidone was demonstrated to be non-inferior to quetiapine XR in time to relapse.
Adolescents: The efficacy of lurasidone in the treatment of schizophrenia in adolescent patients (13 to 17 years of age) was evaluated in one 6-week, placebo-controlled study of patients (N=327) who met DSM-IV criteria for schizophrenia. Both the 80 mg and 40 mg doses of lurasidone demonstrated superiority over placebo on the PANSS total score after 6 weeks of double-blind treatment (see Table 2).
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ECG Changes: Electrocardiogram (ECG) measurements were taken at various time points during the lurasidone clinical trial program. No post-baseline QT prolongations exceeding 500 msec were reported in patients treated with lurasidone. Within a subset of patients defined as having an increased cardiac risk, no potentially important changes in ECG parameters were observed. No cases of torsade de pointes or other severe cardiac arrhythmias were observed in the pre-marketing clinical program.
The effects of lurasidone on the QT/QTc interval were evaluated in a dedicated QT study involving 87 clinically stable patients with schizophrenia or schizoaffective disorder, who were treated with lurasidone doses of 120 mg daily, 600 mg daily, or ziprasidone 160 mg daily. Holter monitor-derived electrocardiographic assessments were obtained over an eight-hour period at baseline and steady state. No patients treated with lurasidone experienced QTc increases >60 msec from baseline, nor did any patient experience a QTc of >500 msec.
Pharmacokinetics: Adults: The activity of lurasidone is primarily due to the parent drug. The pharmacokinetics of lurasidone is dose-proportional within a total daily dose range of 20 mg to 160 mg. Steady-state concentrations of lurasidone are reached within 7 days of starting lurasidone. Following administration of 40 mg, the mean elimination half-life was 18 hours (7% coefficient of variation).
Children and adolescents: The pharmacokinetics of lurasidone, in pediatric patients 6-17 years of age, was similar to those in adults. There were no clinically relevant differences between genders in the pharmacokinetics of lurasidone in patients with schizophrenia.
Absorption: Lurasidone is absorbed and reaches peak serum concentrations in approximately 1-3 hours. It is estimated that 9-19% of an administered dose is absorbed.
In a food effect study, lurasidone mean C
max and AUC were about 3-times and 2-times, respectively, when administered with food compared to the levels observed under fasting conditions. Lurasidone exposure was not affected as meal size was increased from 350 to 1000 calories and was independent of meal fat content.
Distribution: Following administration of 40 mg of lurasidone, the mean apparent volume of distribution was 6173 L (17.2% coefficient of variation). Lurasidone is highly bound (~99%) to serum proteins.
Metabolism and elimination: Lurasidone is metabolized mainly via CYP3A4. The major biotransformation pathways are oxidative N-dealkylation, hydroxylation of norbornane ring, and S-oxidation. Lurasidone is metabolized into two non-major active metabolites (ID-14283 and ID-14326) and two major non-active metabolites (ID-20219 and ID-20220).
Total excretion of radioactivity in urine and feces combined was approximately 89%, with about 80% recovered in feces and 9% recovered in urine, after a single dose of [14C]-labeled lurasidone.
Following administration of 40 mg of lurasidone the mean (%CV) apparent clearance was 3902 mL/min (18.0% coefficient of variation).
Toxicology: Preclinical safety data: Reproductive toxicity: Lurasidone was not teratogenic in rats and rabbits. There are no adequate and well-controlled studies of lurasidone in pregnant women. No teratogenic effects were seen in studies in which pregnant rats and rabbits were given lurasidone during the period of organogenesis at doses up to 25 and 50 mg/kg/day, respectively. These doses are 1.5 and 6 times, in rats and rabbits respectively, the maximum recommended human dose (MRHD) of 160 mg/day based on body surface area. No adverse developmental effects were seen in a study in which pregnant rats were given lurasidone during the period of organogenesis and continuing through weaning at doses up to 10 mg/kg/day; this dose is approximately half of the MRHD based on body surface area.
Lurasidone was administered orally to female rats at doses of 0.1, 1.5, 15, or 150 mg/kg/day for 15 consecutive days prior to mating, during the mating period, and through day 7 of gestation. Estrus cycle irregularities were seen at 1.5 mg/kg and above; the no-effect dose of 0.1 mg/kg is approximately 0.006 times the MRHD of 160 mg/day based on body surface area. Fertility was reduced only at the highest dose and this was shown to be reversible after a 14 day drug-free period. The no-effect dose for reduced fertility was 15 mg/kg, which is 0.9 times the MRHD based on body surface area.
Fertility was not affected in male rats treated orally with lurasidone for 64 consecutive days prior to mating and during the mating period at doses up to 150 mg/kg/day (9 times the MRHD based on body surface area).
Mutagenicity: Lurasidone was not genotoxic in the Ames test, the in vitro chromosomal aberration test in Chinese Hamster Lung (CHL) cells, or the in vivo mouse bone marrow micronucleus test.
Carcinogenicity: Lifetime carcinogenicity studies were conducted in ICR mice and Sprague-Dawley rats. Lurasidone was administered orally at doses of 30, 100, 300, or 650 (the high dose was reduced from 1200 in males) mg/kg/day to ICR mice and 3, 12, or 36 (high dose reduced from 50) mg/kg/day to Sprague-Dawley rats. In the mouse study, there were increased incidences of malignant mammary gland tumors and pituitary gland adenomas in females at all doses; the lowest dose tested produced plasma levels (AUC) approximately equal to those in humans receiving the MRHD of 160 mg/day. No increases in tumors were seen in male mice up to the highest dose tested, which produced plasma levels (AUC) 14 times those in humans receiving the MRHD.
In rats, an increased incidence of mammary gland carcinomas was seen in females at the two higher doses; the no-effect dose of 3 mg/kg produced plasma levels (AUC) 0.4 times those in humans receiving the MRHD. No increases in tumors were seen in male rats up to highest dose tested, which produced plasma levels (AUC) 6 times those in human receiving the MRHD. Proliferative and/or neoplastic changes in the mammary and pituitary glands of rodents have been observed following chronic administration of antipsychotic drugs and are considered to be prolactin mediated. The relevance of this increased incidence of prolactin-mediated pituitary or mammary gland tumors in rodents in terms of human risk is unknown.