Comparison of Peripherally Acting Substance for Treatment of Detrusor Overactivity: What is New; What is in the Pipeline?

Comparison of pharmacokinetic variability of fesoterodine vs. tolterodine extended release in cytochrome P450 2D6 extensive and poor metabolizers

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Tolterodine and 5-hydroxymethyl tolterodine (5-HMT) are equipotent active moieties of tolterodine; 5-HMT is the singular active moiety of fesoterodine. The formation of 5-HMT from tolterodine occurs via CYP2D6, and some subjects are poor metabolizers CYP2D6. On the other hand, the formation of 5-HMT from fesoterodine occurs via ubiquitous esterases. Cross-study comparisons of data from phase 1 studies suggest that active moiety exposures are considerably more variable following tolterodine extended release vs. fesoterodine.

WHAT THIS STUDY ADDS

This head-to-head study confirmed the findings of reduced pharmacokinetic variability of fesoterodine and further delineates that tolterodine, and not 5-HMT, was the principal source of variability after administration of tolterodine extended release. The data suggest that fesoterodine delivers 5-HMT consistently, regardless of CYP2D6 status, with up to 40% higher bioavailability compared with tolterodine.

AIMS

Tolterodine and 5-hydroxymethyl tolterodine (5-HMT) are equipotent active moieties of tolterodine; 5-HMT is the singular active moiety of fesoterodine. Formation of 5-HMT from fesoterodine and tolterodine occurs via esterases and CYP2D6 respectively. This randomized, crossover, open-label, multiple-dose study in CYP2D6 extensive metabolizers (EMs) and poor metabolizers (PMs) compared the pharmacokinetics of fesoterodine vs. tolterodine extended release (ER).

METHODS

Subjects received fesoterodine and tolterodine ER with a ≥3-day washout period. Treatment comprised 4-mg once daily doses for 5 days escalated to 8-mg once daily for 5 days. Pharmacokinetics of active moieties were compared by drug, dose and genotype.

RESULTS

Active moiety exposures following fesoterodine and tolterodine ER increased proportional to dose in EMs and PMs. In EMs only, coefficients of variation for AUC and C(max) following fesoterodine (up to 46% and 48% respectively) were lower than those following tolterodine ER (up to 87% and 87% respectively). Following fesoterodine and tolterodine ER administration, active moiety exposures ranged up to sevenfold and 40-fold respectively. Mean urinary excretion of 5-HMT following fesoterodine 4 and 8 mg, respectively, was 0.44 and 0.89 mg in EMs and 0.60 and 1.32 mg in PMs. Following tolterodine ER 4 and 8 mg, it was 0.38 and 0.71 mg respectively (EMs only). Renal clearance was similar regardless of administered drug, dose or genotype.

CONCLUSIONS

Tolterodine, not 5-HMT, was the principal source of variability after tolterodine ER administration. Fesoterodine delivers 5-HMT with less variability than tolterodine, regardless of CYP2D6 status, with up to 40% higher bioavailability. The pharmacokinetics of fesoterodine were considerably less variable than TER.

Review of fesoterodine

INTRODUCTION

Overactive bladder syndrome is a common condition that adversely affects the quality of life. It is mainly treated with a combination of bladder retraining and antimuscarinics. In a quest to reduce the side effect profile of these drugs, whilst improving their efficacy, more bladder-selective antimuscarinics were developed. One of the more recent of these antimuscarinics which has come to the market is fesoterodine. This review examines the evidence of the safety and efficacy of this drug.

AREAS COVERED

A literature search performed identified two main multi-center trials which highlight the safety, efficacy and tolerability of fesoterodine. These together with the pharmacologic properties of the drug are discussed at length throughout the review. An expert opinion is then formulated based on the current evidence available and on comparison with other antimuscarinics.

EXPERT OPINION

It is concluded that fesoterodine has the added advantage of flexible dosing over some other antimuscarinics. It does, however, have a similar tolerability and side effect profile to other antimuscarinics and is, therefore, unlikely to revolutionize the treatment of the overactive bladder.

Effects of hepatic dysfunction on the single-dose pharmacokinetics of fesoterodine

Fesoterodine, a new antimuscarinic for the treatment of overactive bladder, is rapidly and extensively hydrolyzed by nonspecific esterases to its principal active moiety, 5-hydroxymethyl tolterodine (5-HMT). The elimination of 5-HMT involves metabolism and renal excretion. The plasma and urinary pharmacokinetics of 5-HMT and its inactive carboxy (SPM 5509), N-desisopropyl (SPM 7789), and carboxy-N-desisopropyl (SPM 7790) metabolites were investigated after a single oral dose of 8 mg of fesoterodine in 8 male subjects with moderate hepatic cirrhosis (Child-Turcotte-Pugh class B) and 8 matched healthy controls. The estimated mean ratios (95% confidence interval) of the area under the curve extrapolated to infinity after dosing (AUC(0-∞)), cumulative urinary excretion up to 48 hours after dosing (Ae(0-48)), maximum observed concentration (C(max)), and apparent terminal disposition half-life (t(1/2)) of 5-HMT for cirrhotic and healthy subjects were 2.2 (1.5-3.1), 2.5 (1.7-3.8), 1.4 (1.0-1.9), and 1.1 (0.8-1.3), respectively. In subjects with hepatic cirrhosis, AUC(0-∞) and Ae(0-48) of 5-HMT increased approximately 2-fold; the increase in C(max) was smaller, and t(1/2) was unaffected. AUC and C(max) of the inactive carboxy metabolites, SPM 5509 and SPM 7790, were reduced reciprocally by about 50%, whereas exposure to the dealkylated metabolite, SPM 7789, increased about 2-fold. Fesoterodine 8 mg was equally well tolerated in both groups. The results indicate that moderate hepatic cirrhosis reduces 5-HMT clearance, with an apparent effect on the carboxylation pathway and not on dealkylation.

The pharmacokinetic profile of fesoterodine 8 mg with daytime or nighttime dosing

PURPOSE

Diurnal variation can affect drug pharmacokinetics. Fesoterodine is a new antimuscarinic drug for the treatment of overactive bladder (OAB). We estimated the relative bioavailability of 5-hydroxymethyl tolterodine (5-HMT), the active metabolite of fesoterodine, following nighttime and daytime administration.

METHODS

In this randomized, open-label, two-period, two-treatment crossover, single-dose study, healthy subjects received daytime and nighttime oral dosing of fesoterodine 8-mg sustained-release tablets, separated by a minimum 60-h washout period. Blood samples for 5-HMT PK determination were collected before dosing and at specified intervals up to 48 h postdose. Safety was assessed by adverse event (AE) reports.

RESULTS

Fourteen subjects completed the study. Plasma concentration versus time profiles (AUC) of 5-HMT were similar for daytime and nighttime dosing. Mean AUC(infinity) 5-HMT values were 47.9 and 51.4 ng h/mL for nighttime and daytime dosing, respectively; the mean time to reach maximum concentration (C(max)) values were 3.9 and 5.0 ng/mL, respectively. Nighttime versus daytime AUC(infinity) and C(max) ratios of 5-HMT were 93 and 79%, respectively; 90% confidence intervals (CIs) indicated equivalence for AUC(infinity) but not for C(max). The median time to reach maximum concentration (T(max)) was 5.0 h for both dosing regimens, and the mean terminal elimination half-life (T((1/2))) was 5.9 and 5.7 h for nighttime and daytime dosing, respectively. Seven treatment-related AEs, most commonly headache, occurred in five subjects.

CONCLUSIONS

The AUC values for daytime and nighttime administration of fesoterodine were equivalent. The 21% reduction in the C(max) for nighttime dosing is unlikely to be clinically relevant. No safety issues were apparent. These results support both daytime and nighttime administration of fesoterodine for OAB treatment.

Effects of flexible-dose fesoterodine on overactive bladder symptoms and treatment satisfaction: an open-label study

AIMS

To evaluate the efficacy and tolerability of flexible-dose fesoterodine in subjects with overactive bladder (OAB) who were dissatisfied with previous tolterodine treatment.

METHODS

This was a 12-week, open-label, flexible-dose study of adults with OAB (> or = 8 micturitions and > or = 3 urgency episodes per 24 h) who had been treated with tolterodine (immediate- or extended-release) for OAB within 2 years of screening and reported dissatisfaction with tolterodine treatment. Subjects received fesoterodine 4 mg once daily for 4 weeks; thereafter, daily dosage was maintained at 4 mg or increased to 8 mg based on the subject's and physician's subjective assessment of efficacy and tolerability. Subjects completed 5-day diaries, the Patient Perception of Bladder Condition (PPBC) and the Overactive Bladder Questionnaire (OAB-q) at baseline and week 12 and rated treatment satisfaction at week 12 using the Treatment Satisfaction Question (TSQ). Safety and tolerability were assessed.

RESULTS

Among 516 subjects treated, approximately 50% opted for dose escalation to 8 mg at week 4. Significant improvements from baseline to week 12 were observed in micturitions, urgency urinary incontinence episodes, micturition-related urgency episodes and severe micturition-related urgency episodes per 24 h (all p < 0.0001). Approximately 80% of subjects who responded to the TSQ at week 12 reported satisfaction with treatment; 38% reported being very satisfied. Using the PPBC, 83% of subjects reported improvement at week 12 with 59% reporting improvement > or = 2 points. Significant improvements from baseline (p < 0.0001) exceeding the minimally important difference (10 points) were observed in OAB-q Symptom Bother and Health-Related Quality of Life (HRQL) scales and all four HRQL domains. Dry mouth (23%) and constipation (5%) were the most common adverse events; no safety issues were identified.

CONCLUSION

Flexible-dose fesoterodine significantly improved OAB symptoms, HRQL, and rates of treatment satisfaction and was well tolerated in subjects with OAB who were dissatisfied with prior tolterodine therapy.

Clinical Efficacy, Safety, and Tolerability of Once-Daily Fesoterodine in Subjects with Overactive Bladder

OBJECTIVE

To determine the efficacy, tolerability, and safety of fesoterodine in subjects with overactive bladder (OAB).

METHODS

This was a multicentre, randomised, double-blind, placebo- and active-controlled trial with tolterodine extended release (ER) to assess the efficacy and safety of fesoterodine. Eligible subjects (> or =18 yr) with increased micturition frequency and urgency and/or urgency urinary incontinence (UUI) were randomised to placebo, fesoterodine 4 mg, fesoterodine 8 mg, or tolterodine ER 4 mg for 12 wk. The primary efficacy variable was a change from baseline to week 12 in micturitions per 24 h. Co-primary end points included change from baseline to week 12 in UUI episodes per 24 h and Treatment Response ("yes" or "no," based on four-point treatment benefit scale). Secondary efficacy variables included mean volume voided per micturition, continent days per week, and number of urgency episodes.

RESULTS

At the end of treatment, subjects taking fesoterodine 4 and 8 mg had significant (p<0.05) and clinically relevant improvements versus placebo in the primary, co-primary, and most secondary efficacy variables. Tolterodine ER (active control) also provided significantly greater improvement than placebo for most efficacy variables, confirming the sensitivity of the study design. A more pronounced effect was observed with fesoterodine 8 mg at most end points.

CONCLUSIONS

Both doses of fesoterodine were significantly better than placebo in improving the symptoms of OAB and produced a significantly greater Treatment Response versus placebo. Efficacy was more pronounced with fesoterodine 8 mg compared with the other treatments. Active treatments were well tolerated.