Clinical Pharmacology for Posfrea
Mechanism Of Action
Palonosetron is a 5-HT3 receptor antagonist with a strong binding affinity for this receptor and little or no affinity for other receptors.
Cancer chemotherapy may be associated with a high incidence of nausea and vomiting, particularly when certain agents, such as cisplatin, are used. 5-HT3 receptors are located on the nerve terminals of the vagus in the periphery and centrally in the chemoreceptor trigger zone of the area postrema. It is thought that chemotherapeutic agents produce nausea and vomiting by releasing serotonin from the enterochromaffin cells of the small intestine and that the released serotonin then activates 5-HT3 receptors located on vagal afferents to initiate the vomiting reflex.
Postoperative nausea and vomiting is influenced by multiple patient, surgical and anesthesia related factors and is triggered by release of 5-HT in a cascade of neuronal events involving both the central nervous system and the gastrointestinal tract. The 5-HT3 receptor has been demonstrated to selectively participate in the emetic response.
Pharmacodynamics
Cardiac Electrophysiology
The effect of intravenous palonosetron on blood pressure, heart rate, and ECG parameters including QTc were comparable to intravenous ondansetron and dolasetron in CINV clinical trials. In PONV clinical trials the effect of palonosetron on the QTc interval was no different from placebo. In non-clinical studies palonosetron possesses the ability to block ion channels involved in ventricular de- and re-polarization and to prolong action potential duration.
At a dose of 9 times the maximum recommended adult dose, POSFREA does not prolong the QT interval to any clinically relevant extent.
Pharmacokinetics
After intravenous dosing of palonosetron in healthy subjects and cancer patients, an initial decline in palonosetron plasma concentrations is followed by a slow elimination from the body. Mean maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC0-∞) are generally dose proportional over the dose range of 0.3 to 90 mcg/kg in healthy subjects and in cancer patients. Following a single intravenous dose of palonosetron at 3 mcg/kg (or 0.21 mg/70 kg) to six cancer patients, mean (±SD) maximum plasma concentration was estimated to be 5630 ± 5480 ng/L and mean AUC was 35.8 ± 20.9 h•mcg/L.
Following intravenous administration of palonosetron 0.25 mg once every other day for 3 doses in 11 cancer patients, the mean increase in plasma palonosetron concentration from Day 1 to Day 5 was 42±34%. Following intravenous administration of palonosetron 0.25 mg once daily for three days in 12 healthy subjects, the mean (±SD) increase in plasma palonosetron concentration from Day 1 to Day 3 was 110±45%.
After intravenous dosing of palonosetron in patients undergoing surgery (abdominal surgery or vaginal hysterectomy), the pharmacokinetic characteristics of palonosetron were similar to those observed in cancer patients.
Distribution
Palonosetron has a volume of distribution of approximately 8.3 ± 2.5 L/kg. Approximately 62% of palonosetron is bound to plasma proteins.
Elimination
After a single intravenous dose of 10 mcg/kg [14C]-palonosetron, approximately 80% of the dose was recovered within 144 hours in the urine with palonosetron representing approximately 40% of the administered dose. In healthy subjects, the total body clearance of palonosetron was 0.160 ± 0.035 L/h/kg and renal clearance was 0.067± 0.018 L/h/kg. Mean terminal elimination half-life is approximately 40 hours.
Metabolism
Palonosetron is eliminated by multiple routes with approximately 50% metabolized to form two primary metabolites: N-oxide-palonosetron and 6-S-hydroxy-palonosetron. These metabolites each have less than 1% of the 5-HT3 receptor antagonist activity of palonosetron. In vitro metabolism studies have suggested that CYP2D6 and to a lesser extent, CYP3A4 and CYP1A2 are involved in the metabolism of palonosetron. However, clinical pharmacokinetic parameters are not significantly different between poor and extensive metabolizers of CYP2D6 substrates.
Specific Populations
Pediatric Patients
Pharmacokinetic data was obtained from a subset of pediatric cancer patients that received 10 mcg/kg or 20 mcg/kg as a single intravenous dose of palonosetron. When the dose was increased from 10 mcg/kg to 20 mcg/kg a dose-proportional increase in mean AUC was observed. Peak plasma concentrations (CT) reported at the end of the 15-minute infusion of 20 mcg/kg were highly variable in all age groups and tended to be lower in patients less than six years than in older patients as shown in Table 4. The median half-life was 30 hours in overall age groups and ranged from about 20 to 30 hours across age groups after administration of 20 mcg/kg.
The total body clearance (L/h/kg) in patients 12 to 17 years old was similar to that in healthy adults. There are no apparent differences in volume of distribution when expressed as L/kg.
Table 4: Pharmacokinetics Parameters in Pediatric Cancer Patients following Intravenous Infusion of 20 mcg/kg Palonosetron Over 15 minutes
| PK Parametera |
Pediatric Age Group |
| Less than 2 years |
2 years to less than
6 years |
6 years to less than 12 years |
12 years to less than 17 years |
|
N=12 |
N=42 |
N=38 |
N=44 |
| CTb, ng/L |
9025 (197) |
9414 (252) |
16275 (203) |
11831 (176) |
|
|
N=5 |
N=7 |
N=10 |
| AUC 0-∞ , h·mcg/L |
|
103.5 (40.4) |
98.7 (47.7) |
124.5 (19.1) |
|
N=6 |
N=14 |
N=13 |
N=19 |
| Clearancec, L/h/kg |
0.31 (34.7) |
0.23 (51.3) |
0.19 (46.8) |
0.16 (27.8) |
| VssC, L/kg |
6.08 (36.5) |
5.29 (57.8) |
6.26 (40.0) |
6.20 (29.0) |
a Geometric Mean (CV) except for t1/2 which is median values
b CT is the plasma palonosetron concentration at the end of the 15-minute infusion
c Clearance and Vss calculated from 10 and 20 mcg/kg and are weight adjusted |
Racial Or Ethnic Groups
The pharmacokinetics of palonosetron were characterized in 24 healthy Japanese subjects over an intravenous dose range of 3 to 90 mcg/kg. Total body clearance was 25% higher in Japanese subjects compared to Whites, however, this increase is not considered to be clinically meaningful.
Patients With Renal Impairment
Mild to moderate renal impairment does not significantly affect palonosetron pharmacokinetic parameters. Total systemic exposure increased by approximately 28% in patients with severe renal impairment relative to healthy subjects. This increase is not considered clinically meaningful.
Patients With Hepatic Impairment
Hepatic impairment does not significantly affect total body clearance of palonosetron compared to the healthy subjects.
Drug Interaction Studies
In vitro studies indicated that palonosetron is not an inhibitor of CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2D6, CYP2E1 and CYP3A4/5 (CYP2C19 was not investigated) nor does it induce the activity of CYP1A2, CYP2D6, or CYP3A4/5. Therefore, the potential for clinically significant drug interactions with palonosetron appears to be low.
Dexamethasone
Coadministration of 0.25 mg palonosetron and 20 mg dexamethasone administered intravenously in healthy subjects revealed no pharmacokinetic drug-interactions between palonosetron and dexamethasone.
Oral Aprepitant
In an interaction study in healthy subjects where a single 0.25 mg intravenous dose of palonosetron was administered on day 1 and oral aprepitant for three days (125 mg/80 mg/80 mg), the pharmacokinetics of palonosetron were not significantly altered (AUC: no change, Cmax: 15% increase).
Metoclopramide
A study in healthy subjects involving a single 0.75 mg intravenous dose of palonosetron and steady state oral metoclopramide (10 mg four times daily) demonstrated no significant pharmacokinetic interaction.
Corticosteroids, Analgesics, Antiemetics/Antinauseants, Antispasmodics And Anticholinergic Agents
In controlled clinical trials, palonosetron has been safely administered with corticosteroids, analgesics, antiemetics/antinauseants, antispasmodics and anticholinergic agents.
Clinical Studies
The safety and efficacy of POSFREA have been established based on adequate and well-controlled adult studies of another intravenous formulation of palonosetron in CINV and PONV. Below is a display of the results of these adequate and well-controlled studies of palonosetron in these conditions.
Prevention Of Nausea And Vomiting Associated With MEC And HEC In Adults
Efficacy of a single intravenous dose of palonosetron in preventing acute and delayed nausea and vomiting associated with MEC or HEC were studied in four trials. In these double-blind studies, complete response rates (no emetic episodes and no rescue medication) and other efficacy parameters were assessed through at least 120 hours after administration of chemotherapy. The safety and efficacy of palonosetron in repeated courses of chemotherapy was also assessed.
Moderately Emetogenic Chemotherapy
Two double-blind trials (Study 1 and Study 2) involving 1132 patients compared a single dose of palonosetron with either a single-dose of ondansetron (Study 1) or dolasetron (Study 2) given 30 minutes prior to MEC, including carboplatin, cisplatin ≤ 50 mg/m2, cyclophosphamide <1500 mg/m2, doxorubicin > 25 mg/m2, epirubicin, irinotecan, and methotrexate >250 mg/m2. Concomitant corticosteroids were not administered prophylactically in Study 1 and were only used by 4 to 6% of patients in Study 2. The majority of patients in these studies were women (77%), White (65%) and naïve to previous chemotherapy (54%). The mean age was 55 years.
Highly Emetogenic Chemotherapy
A double-blind, dose-ranging trial evaluated the efficacy of a single intravenous dose of palonosetron from 0.3 to 90 mcg/kg (equivalent to < 0.1 mg to 6 mg fixed dose) in 161 chemotherapy-naïve adult cancer patients receiving HEC, either cisplatin ≥ 70 mg/m2 or cyclophosphamide > 1100 mg/m2. Concomitant corticosteroids were not administered prophylactically. Analysis of data from this trial indicates that 0.25 mg is the lowest effective dose in preventing acute nausea and vomiting associated with HEC.
A double-blind trial involving 667 patients compared a single intravenous dose of palonosetron with a single intravenous dose of ondansetron (Study 3) given 30 minutes prior to HEC, including cisplatin ≥ 60 mg/m2, cyclophosphamide > 1500 mg/m2, and dacarbazine. Corticosteroids were co-administered prophylactically before chemotherapy in 67% of patients. Of the 667 patients, 51% were women, 60% White, and 59% naïve to previous chemotherapy. The mean age was 52 years.
Efficacy Results
Studies 1, 2 and 3 show that palonosetron was effective in the prevention of nausea and vomiting associated with initial and repeat courses of MEC and HEC in the acute phase (0 to 24 hours) [Table 5]. Clinical superiority over other 5-HT3 receptor antagonists has not been adequately demonstrated in the acute phase. In Study 3, efficacy was greater when prophylactic corticosteroids were administered concomitantly.
Studies 1 and 2 show that palonosetron was effective in the prevention of nausea and vomiting associated with initial and repeat course of MEC in the delayed phase (24 to 120 hours) [Table 6] and overall phase (0 to 120 hours) [Table 7].
Table 5: Prevention of Acute Nausea and Vomiting (0 to 24 Hours) in Adults with Nausea and Vomiting Associated with MEC or HEC in Studies 1, 2 and 3: Complete Response Rates
| Chemotherapy |
Study |
Treatment Group |
Na |
% with Complete
Response |
p-value b |
97.5% Confidence Interval Palonosetron minus Comparator c |
| Moderately Emetogenic |
1 |
Palonosetron 0.25 mg
intravenously |
189 |
81 |
0.009 |
 |
Ondansetron 32 mg
intravenouslyd |
185 |
69 |
| 2 |
Palonosetron 0.25 mg
intravenously |
189 |
63 |
NS |
Dolasetron 100 mg
intravenously |
191 |
53 |
| Highly Emetogenic |
3 |
Palonosetron 0.25 mg
intravenously |
223 |
59 |
NS |
Ondansetron 32 mg
intravenouslyd |
221 |
57 |
a Intent-to-treat cohort
b 2-sided Fisher’s exact test. Significance level at α=0.025.
c These studies were designed to show non-inferiority. A lower bound greater than –15% demonstrates non-inferiority between palonosetron and comparator.
dOndansetron 32 mg intravenously was used in the clinical trial. Although this dose was used in the trial, it is no longer the currently recommended dose. Refer to the ondansetron prescribing information for the current recommended dose. |
Table 6: Prevention of Delayed Nausea and Vomiting (24 to 120 Hours) Associated with MEC in Adults in Studies 1 and 2: Complete Response Rates
| Chemotherapy |
Study |
Treatment Group |
Na |
% with Complete Response |
p-value b |
97.5% Confidence Interval Palonosetron minus Comparatorc |
| Moderately Emetogenic |
1 |
Palonosetron 0.25 mg
intravenously |
189 |
74 |
<0.001 |
 |
Ondansetron 32 mg
intravenouslyd |
185 |
55 |
| 2 |
Palonosetron 0.25 mg
intravenously |
189 |
54 |
0.004 |
Dolasetron 100 mg
intravenously |
191 |
39 |
aIntent-to-treat cohort
b 2-sided Fisher’s exact test. Significance level at α=0.025.
c These studies were designed to show non-inferiority. A lower bound greater than–15% demonstrates non-inferiority between palonosetron and comparator.
dOndansetron 32 mg intravenously was used in the clinical trial. Although this dose was used in the trial, it is no longer the currently recommended dose. Refer to the ondansetron prescribing information for the current recommended dose. |
Table 7: Prevention of Overall Nausea and Vomiting (0 to 120 Hours) Associated with MEC in Adults in Studies 1 and 2: Complete Response Rates
| Chemotherapy |
Study |
Treatment Group |
Na |
% with Complete Response |
p-valueb |
97.5% Confidence Interval Palonosetron minus Comparator c |
| Moderately Emetogenic |
1 |
Palonosetron 0.25 mg
intravenously |
189 |
69 |
<0.001 |
 |
Ondansetron 32 mg
intravenouslyd |
185 |
50 |
| 2 |
Palonosetron 0.25 mg
intravenously |
189 |
46 |
0.021 |
Dolasetron 100 mg
intravenously |
191 |
34 |
aIntent-to-treat cohort
b 2-sided Fisher’s exact test. Significance level at α=0.025.
cThese studies were designed to show non-inferiority. A lower bound greater than –15% demonstrates non-inferiority between palonosetron and comparator.
d Ondansetron 32 mg intravenously was used in the clinical trial. Although this dose was used in the trial, it is no longer the currently recommended dose. Refer to the ondansetron prescribing information for the current recommended dose. |
Prevention Of Nausea And Vomiting Associated With Emetogenic Chemotherapy, Including HEC In Pediatric Patients
One double-blind, active-controlled clinical trial was conducted in pediatric cancer patients. The total population (N = 327) had a mean age of 8.3 years (range two months to 16.9 years) and were 53% male; and 96% white. Patients were randomized and received a 20 mcg/kg (maximum 1.5 mg) intravenous infusion of palonosetron 30 minutes prior to the start of emetogenic chemotherapy (followed by placebo infusions four and eight hours after the dose of palonosetron) or 0.15 mg/kg of intravenous ondansetron 30 minutes prior to the start of emetogenic chemotherapy (followed by ondansetron 0.15 mg/kg infusions four and eight hours after the first dose of ondansetron, with a maximum total dose of 32 mg). Emetogenic chemotherapies administered included doxorubicin, cyclophosphamide (<1500 mg/m2), ifosfamide, cisplatin, dactinomycin, carboplatin, and daunorubicin. Adjuvant corticosteroids, including dexamethasone, were administered with chemotherapy in 55% of patients.
Complete Response in the acute phase of the first cycle of chemotherapy was defined as no vomiting, no retching, and no rescue medication in the first 24 hours after starting chemotherapy. Efficacy was based on demonstrating non-inferiority of intravenous palonosetron compared to intravenous ondansetron. Non-inferiority criteria were met if the lower bound of the 97.5% confidence interval for the difference in Complete Response rates of intravenous palonosetron minus intravenous ondansetron was larger than -15%. The non-inferiority margin was 15%.
Efficacy Results
As shown in Table 8, intravenous palonosetron 20 mcg/kg (maximum 1.5 mg) demonstrated non-inferiority to the active comparator during the 0 to 24-hour time interval.
Table 8: Prevention of Acute Nausea and Vomiting (0 to 24 Hours) Associated with Emetogenic Chemotherapy in Pediatric Patients: Complete Response Rates
Palonosetron
20 mcg/kg
intravenously
(N=165) |
Ondansetron
0.15 mg/kg for three
intravenous doses
(N=162) |
Difference [97.5% Confidence Interval]a:
Palonosetron minus intravenous
Ondansetron Comparator |
| 59.4% |
58.6% |
0.36% [-11.7%, 12.4%] |
| a To adjust for multiplicity of treatment groups, a lower-bound of a 97.5% confidence interval was used to compare to -15%, the negative value of the non-inferiority margin. |
In patients that received palonosetron at a lower dose than the recommended dose of 20 mcg/kg, non-inferiority criteria were not met.
Prevention Of Postoperative Nausea And Vomiting In Adults
In a multicenter, randomized, stratified, double-blind, parallel-group, clinical trial, palonosetron was compared to placebo for PONV in 546 patients undergoing abdominal and gynecological surgery. All patients received general anesthesia. The trial was conducted predominantly in the US in the out-patient setting for patients undergoing elective gynecologic or abdominal laparoscopic surgery and stratified at randomization for the following risk factors: gender, nonsmoking status, history of PONV and/or motion sickness.
Patients were randomized to receive a single dose of palonosetron 0.025 mg, 0.050 mg or 0.075 mg or placebo, each given intravenously immediately prior to induction of anesthesia.
Antiemetic activity of was evaluated during the 0 to 72-hour time period after surgery.
Of the 138 patients treated with palonosetron 0.075 mg and evaluated for efficacy, 96% were women; 66% had a history of PONV or motion sickness; 85% were nonsmokers. As for race, 63% were White, 20% were Black, 15% were Hispanic, and 1% were Asian. The age of patients ranged from 21 to 74 years, with a mean age of 38 years. Three patients were greater than 65 years of age.
Co-primary efficacy measures were Complete Response (CR) defined as no emetic episode and no use of rescue medication in 0 to 24 hours and 24 to 72 hours postoperatively.
Secondary efficacy endpoints included:
- Complete Response (CR) 0 to 48 hours and 0 to 72 hours
- Complete Control (CC) defined as CR and no more than mild nausea
- Severity of nausea (none, mild, moderate, severe)
The primary hypothesis was that at least one of the three palonosetron doses were superior to placebo.
Complete Response Rates for palonosetron 0.075 mg and placebo in this trial are described in the Table 9.
Table 9: Prevention of Postoperative Nausea and Vomiting in Adults: Complete Response Rates
| Treatment |
n/N (%) |
Palonosetron vs Placebo |
| Δ |
p-valuea |
| Co-primary Endpoints |
| Complete Response Rate (0 to 24 hours) |
Palonosetron 0.075 mg
intravenously |
59/138 (42.8%) |
16.8% |
0.004 |
| Placebo |
35/135 (25.9%) |
|
| Complete Response Rate (24 to 72 hours) |
Palonosetron 0.075 mg
intravenously |
67/138 (48.6%) |
7.8% |
0.188 |
| Placebo |
55/135 (40.7%) |
|
a To reach statistical significance for each co-primary endpoint, the required significance limit for the lowest p-value was p<0.017.
Δ Difference (%): palonosetron 0.075 mg minus placebo |
Palonosetron as a single dose of 0.075 mg reduced the severity of nausea compared to placebo. Analyses of other secondary endpoints indicate that palonosetron 0.075 mg was numerically better than placebo, however, statistical significance was not formally demonstrated.
A randomized, double-blind, multicenter, placebo-controlled, dose ranging study was performed to evaluate palonosetron for PONV following abdominal or vaginal hysterectomy. Five intravenous doses (0.1, 0.3, 1.0, 3.0 and 30 mcg/kg) were evaluated in a total of 381 intent-totreat patients. The primary efficacy measure was the proportion of patients with CR in the first 24 hours after recovery from surgery. The lowest effective dose of palonosetron was 1 mcg/kg (approximately 0.075 mg) which had a CR rate of 44% versus 19% for placebo, p=0.004 and significantly reduced the severity of nausea versus placebo, p=0.009.