Clinical Pharmacology for Pizensy
Mechanism Of Action
Lactitol exerts an osmotic effect, causing the influx of water into the small intestine leading to a laxative effect in the colon.
Pharmacodynamics
No formal pharmacodynamic studies have been conducted with PIZENSY.
Pharmacokinetics
Following a single oral dose of 20-gram PIZENSY in healthy adult subjects under fed conditions, the mean ± SD peak serum concentration (Cmax) is 776 ± 253 ng/mL, and the mean ± SD area under the curve (AUC) is 6,019 ± 1,771 ng*hr/mL.
Absorption
Lactitol is minimally absorbed systemically following oral administration. The mean ± SD time to reach peak serum concentration (Tmax) is 3.6 ± 1.2 hours following a single oral dose of 20-gram PIZENSY in healthy adult subjects under fed conditions.
Effect of Food
Cmax and AUC values increase greater than 2-fold under fasted conditions compared to fed conditions.
Elimination
The mean half-life of lactitol is 2.4 hours.
Excretion
Lactitol is minimally absorbed in the small intestine. Unabsorbed lactitol is expected to be degraded into organic acids in the colon and is minimally excreted in the feces.
Clinical Studies
Study 1
PIZENSY was evaluated in a double-blind, randomized, placebo-controlled, multicenter clinical study in adult patients with symptoms of CIC (NCT02819297). PIZENSY (20 grams once daily) was compared to placebo in a 6-month treatment period. Patients who developed persistent diarrhea or loose stools were allowed to reduce their dosage of study drug to 10 grams once daily. Patients had a mean age of 52 years (range 18 to 88 years); 76% were female, 60% were white, and 31% were black.
To be eligible for the study, patients were required to meet modified Rome II criteria for at least 12 weeks (which need not be consecutive) in the preceding 12 months. Rome II criteria were modified for the study to allow enrollment of patients having less than 3 defecations per week, rarely having a loose stool without the use of laxatives, and not meeting criteria for IBS-C. In addition, patients were required to report at least one of the following symptoms:
- Straining during at least 25% of defecations
- Lumpy or hard stool in at least 25% of defecations
- Sensation of incomplete evacuations for at least 25% of defecations
Patients who met these criteria were also required to demonstrate the following during the 2-week screening period:
- Average less than 3 complete spontaneous bowel movements (CSBMs) over the 2-week screening period. A spontaneous bowel movement (SBM) was defined as a bowel movement which had occurred with no rescue laxative use in the prior 24 hours, and a CSBM was defined as a SMB that is associated with a sense of complete evaluation.
- No more than one SBM with a Bristol Stool Form Scale (BSFS) of 6
- No SBMs with a BSFS of 7
The efficacy of PIZENSY was assessed using a responder analysis and change-from-baseline in the CSBM endpoint. Efficacy was assessed using information provided by patients after each bowel movement using an electronic diary.
The primary efficacy analysis was based on the first 12 weeks of the 6-month treatment period for 594 patients. A responder was defined as a patient who had at least 3 CSBMs in a given week and an increase of at least 1 CSBM from baseline in the same week for at least 9 weeks out of the first 12week treatment period and at least 3 of the last 4 weeks (Weeks 9-12). The responder rates are shown in Table 2.
Table 2: Efficacy Responder Rates in Placebo-Controlled Study (Study 1) in Adults with CIC
|
PIZENSY
N=291a |
Placebo
N=303 |
Treatment Difference
(95% CI) |
| Responderb |
25% |
13% |
12%c (6.0, 18.5) |
CI = confidence interval
a 74 of 291 patients in the PIZENSY group at least temporarily reduced their dose
b primary endpoint defined as a patient who had at least 3 CSBMs in a given week and an increase of at least 1 CSBM from baseline in the same week for at least 9 weeks out of the 12-week treatment period and at least 3 of the last 4 weeks of the study
c p-value <0.05 for difference from control |
A responder analysis based on Weeks 13 to 24 of the treatment period (i.e., the proportion of responders for at least 9 weeks of the last 12 weeks and at least 3 of the last 4 weeks) showed results similar to the responder analysis of the first 12 weeks.
Improvements in the mean frequency of CSBMs/week were seen at Week 1 with improvement generally maintained through Week 12. The PIZENSY group had a mean increase of 0.8 CSBM/week from baseline to Week 12 over the placebo group.
Study 2
PIZENSY (20 grams once daily) was compared to an active control (lubiprostone 24 mcg twice daily) in a double-blind, double-dummy design study in adult patient with symptoms of CIC (NCT02481947). Patients had a mean age of 46 years (range 18 to 87 years); 80% were female, 66% were white, and 29% were black. The primary endpoint was the same as Study 1. The frequency of CSBMs/week for the PIZENSY group was consistent with results from Study 1.
Other Studies
Studies of varying design describing the efficacy of lactitol in increasing the frequency of bowel movements during short-term treatment of less than 4 weeks in patients with symptoms of CIC have been published.