Pharmacotherapeutic group: Drugs for constipation, peripheral opioid receptor antagonists
ATC code: A06AH03
Mechanism of action and pharmacodynamic effects
Naloxegol is a PEGylated derivative of the mu-opioid receptor antagonist naloxone. PEGylation reduces naloxegol's passive permeability and also renders the compound a substrate for the P-glycoprotein transporter. Due to poorer permeability and increased efflux of naloxegol across the blood-brain barrier, related to P-gp substrate properties, the CNS penetration of naloxegol is minimal.
In vitro studies demonstrate that naloxegol is a full neutral antagonist at the mu-opioid receptor. Naloxegol acts by binding to mu-opioid receptors in the gastrointestinal (GI) tract targeting the underlying causes of OIC (i.e. reduced GI motility, hypertonicity and increased fluid absorption resulting from long-term opioid treatment).
Naloxegol functions as a peripherally-acting mu-opioid receptor antagonist in the GI tract, thereby decreasing the constipating effects of opioids without impacting opioid-mediated analgesic effects on the central nervous system.
Cardiac electrophysiology
In a thorough QT/QTc study, as defined by ICH E14 Guideline, there were no clinically important changes in HR, RR, QT, PR or QRS intervals or T wave morphology observed. In addition, no safety and tolerability concerns were identified in this study up to the highest dose given (150 mg). According to ICH E14 Guideline, this is considered a definitively negative thorough QT/QTc study.
Clinical efficacy and safety
OIC in patients with non-cancer related pain
The efficacy and safety of naloxegol in patients with OIC and non-cancer related pain were established in two replicate double-blind, placebo-controlled Clinical Studies (Kodiac 4 and Kodiac 5). Patients taking oral opioids at a minimum dose of 30 morphine milligram equivalent (mme) per day for at least 4 weeks before enrolment and self-reported OIC were eligible.
OIC was confirmed through a two week run in period and defined as < 3 spontaneous bowel movements (SBMs) per week on average with constipation symptoms associated with at least 25% of bowel movements. Patients were prohibited from using laxatives other than bisacodyl rescue laxative if they had not had a bowel movement for 72 hours. SBM was defined as a bowel movement without rescue laxative taken within the past 24 hours.
Patients with mean Numeric Rating Scale (NRS) pain scores equal to or higher than 7 were not studied due to the risk of confounding the efficacy as a result of uncontrolled pain. Patients who had a QTcF >500 msec at screening, had a recent history of myocardial infarction within 6 months before randomization, had symptomatic congestive heart failure, or had any other overt CV disease were excluded from the Clinical Studies.
Patients with moderate or severe hepatic insufficiency (Child's-Pugh Class B or C) were excluded from the Phase III Clinical Studies (Kodiac 4 and 5). Therefore, naloxegol has not been studied in OIC patients with moderate or severe hepatic impairment.
Both Clinical Studies were powered and stratified so that at least 50% of patients randomized to each treatment arm met baseline criteria to be categorized as a laxative inadequate responder (LIR).
Definition of laxative inadequate responder
To qualify as LIR, in the two weeks prior to first study visit patients had to have reported concurrent OIC symptoms of at least moderate severity whilst taking at least one laxative class for a minimum of four days during the pre-study period.
Efficacy
Response over 12 weeks in the LIR group
Efficacy and durability of effect were measured in the primary end-point as response over a 12-week treatment period to naloxegol as defined by ≥ 3 SBMs per week and a change from baseline of ≥ 1 SBM per week for at least 9 out of the 12 study weeks and 3 out of the last 4 weeks. The first of three multiplicity protected secondary endpoints was the 12-week responder rate in the LIR subgroup.
There was a statistically significant difference for the 25 mg dose versus placebo for the LIR subgroup responder rate in Kodiac 4 (p=0.002) and Kodiac 5 (p=0.014). Under multiplicity testing procedure, statistical significance for the 12.5 mg treatment group versus placebo in the LIR subgroup was observed in Kodiac 4 (p=0.028) but not in Kodiac 5 (p=0.074). In Kodiac 4, response rates in the placebo, 12.5 mg and 25 mg groups in the LIR subgroup were 28.8%, 42.6% and 48.7%, while in Kodiac 5, the corresponding response rates were 31.4, 42.4% and 46.8%. In pooled data from Kodiac 4 and Kodiac 5, responder rates in the LIR subgroup were 30.1% for placebo, 42.5% for the 12.5 mg dose, and 47.7% for the 25 mg dose, with the relative risk (95% CI) for treatment effect versus placebo of 1.410(1.106, 1.797) and 1.584(1.253, 2.001) for the 12.5 mg and 25 mg groups, respectively.
Response over 12 weeks in patients with an inadequate response to at least two classes of laxative
Response to naloxegol over 12 weeks was tested in a sub-group of patients with inadequate response to at least two laxative classes, corresponding to approximately 20% of patients randomized. In a pooled analysis of Kodiac 4 and Kodiac 5 (90, 88 and 99 patients in the placebo, 12.5 mg and 25 mg groups respectively), higher response rates in this population were observed for the 25 mg dose group compared with placebo (p=0.040). The responder rates in this population were placebo 30.0%, 12.5 mg 44.3% and 25 mg 44.4%.
Time to first spontaneous bowel movement
The time to first SBM in the LIR subgroup after taking the first dose was shorter for the 25 mg dose as compared to placebo in Kodiac 4 (p<0.001) and Kodiac 5 (p=0.002). The 12.5 mg dose in the LIR subgroup also demonstrated shorter time to first post-dose SBM as compared to placebo in Kodiac 4 (p=0.002) and Kodiac 5 (p<0.001). In Kodiac 4, placebo, 12.5 mg and 25 mg dose had median time to first post dose SBM of 43.4, 20.6, and 5.4 hours, respectively. In Kodiac 5 the corresponding times to first post dose SBM were 38.2, 12.8, and 18.1 hours, respectively.
Mean number of days per week with at least one SBM
There was an increase in the mean number of days per week with at least one SBM in the LIR subgroup for the 25 mg dose in Kodiak 4 and Kodiac 5 (p<0.001 in both studies) and for the 12.5 mg dose (p=0.006 in both studies).
OIC symptom improvement
The 25 mg dose in the LIR subgroup improved rectal straining (Kodiac 4 p=0.043, Kodiac 5 p<0.001). Stool consistency in the LIR subgroup as measured by the Bristol stool scale improved in Kodiac 5 versus placebo (p<0.001) but not in Kodiac 4 (p=0.156). The 25 mg dose in the LIR subgroup increased mean days per week compared with placebo with at least 1 complete spontaneous bowel movement (CSBM) in both studies (Kodiac 4 p=0.002, Kodiac 5 p<0.001).
Symptom responder end-point
A “symptom responder” was defined as meeting both the 12-week responder criteria and demonstrating improvement in pre-specified OIC symptoms and no deterioration in symptoms. In the LIR subgroup, the 25 mg dose increased the symptom responder rates in both studies as compared to placebo (Kodiac 4 p=0.001, Kodiac 5 p=0.005). The LIR subgroup symptom responder rates in Kodiac 4 for placebo, 12.5 mg and 25 mg arms were 24.6%, 36.5% and 45.3% and the symptom responder rates in Kodiac 5 were 25.6%, 33.6% and 42.7%.
Patient assessment of constipation symptoms (PAC-SYM) questionnaire
Naloxegol 25 mg dose in the LIR subgroup resulted in a greater improvement (change from baseline) of patient assessment of constipation symptoms (PAC-SYM) total scores compared with placebo in both studies at 12 weeks (Kodiac 4 p=0.023, Kodiac 5 p=0.002). The 12.5 mg dose in the LIR subgroup also resulted in greater improvement in total PAC SYM at week 12 compared with placebo in both studies (p= 0.020 and p=0.001 respectively). Naloxegol 25 mg dose, compared with placebo, also resulted in greater improvement (change from baseline) of week 12 PAC-SYM rectal domain scores in both studies (p=0.004 and p<0.001, Kodiac 4 and 5, respectively) and for the stool domain scores in Kodiac 4 (p=0.031) and Kodiac 5 (p<0.001). There was no relevant impact on abdominal symptoms in either study (p=0.256 and p=0.916, Kodiac 4 and 5, respectively).
Potential for interference with opioid-mediated analgesia
There were no clinically relevant differences between naloxegol 12.5 mg, 25 mg, and placebo in average pain intensity, daily opioid dose or in opioid withdrawal scores over the 12-week study.
In the 12-week Clinical Studies (Kodiac 4 and 5), the frequency of back pain AEs was 4.3% for naloxegol 25 mg versus 2.0% for placebo, and the frequency of extremity pain AEs was 2.2% for naloxegol 25 mg, versus 0.7% for placebo. In a long-term safety study (Kodiac 8), the frequency of AE reports of back pain was 8.9% for naloxegol 25 mg versus 8.8% for usual care. For extremity pain, the rate for naloxegol 25 mg was 3.5% versus 3.3% for usual care.
Safety and tolerability over an extended 12-week period
Kodiac 7 was a 12-week safety extension that allowed for patients from Kodiac 4 to continue the same blinded treatment for an additional 12 weeks (placebo, naloxegol 12.5 mg or 25 mg daily). The primary objective was to compare safety and tolerability among the three treatment groups for an additional 12 weeks (beyond that observed in Kodiac 4) using descriptive statistics. In this study, naloxegol at doses of 12.5 mg and 25 mg was generally safe and well tolerated as compared with placebo in the treatment of OIC patients with non-cancer related pain.
In all treatment groups, including placebo, improvements in PAC-SYM domains observed in Kodiac 4 were maintained for patients continuing in Kodiac 7.
Long-term safety and tolerability
Kodiac 8 was a Phase III, 52-week, multi-center, open-label, randomized, parallel group, safety and tolerability study of naloxegol versus usual care in the treatment of OIC in patients with non-cancer related pain. The primary objective was to assess long-term safety and tolerability for naloxegol 25 mg and to compare with usual care treatment using descriptive statistics.
Eligible patients were randomized in a 2:1 ratio to receive either naloxegol 25 mg daily (qd) or usual care treatment for OIC for 52 weeks. Patients assigned to usual care followed a laxative treatment regimen for OIC determined by the investigator according to best clinical judgment, excluding peripheral mu-opioid receptor antagonists.
Of the 844 patients who were randomized, 61.1% completed the study (defined as completing the 2-week follow-up visit after the 52-week treatment period). Overall, 393 and 317 patients had at least 6 and 12 months exposure to naloxegol 25 mg, respectively, in this study, which met the specified exposure requirements.
Long-term exposure to naloxegol 25 mg, up to 52 weeks, was generally safe and well tolerated in the treatment of OIC patients with non-cancer related pain. During the 52-week treatment period there were no important unexpected differences in the safety and tolerability findings between the naloxegol 25 mg treatment group and the usual care treatment group.
Paediatric population
The European Medicines Agency has deferred the obligation to submit the results of studies with Moventig in one or more subsets of the paediatric population in opioid induced constipation (see section 4.2 for information on paediatric use).