Efficacy, safety, and tolerability of plecanatide in patients with irritable bowel syndrome with constipation: results of two phase 3 randomized clinical trials.

OBJECTIVES: Two identical, phase 3, randomized, double-blind, placebo-controlled trials evaluated the efficacy and safety of plecanatide in patients with irritable bowel syndrome with constipation (IBS-C). METHODS: Adults meeting Rome III criteria for IBS-C were randomized (1:1:1) to placebo or plecanatide (3 or 6 mg) for 12 weeks. The primary efficacy end point was the percentage of overall responders (patients reporting ≥30% reduction from baseline in worst abdominal pain plus an increase of ≥1 complete spontaneous bowel movement (CSBM)/week from baseline in the same week for ≥6 of 12 treatment weeks). Safety was assessed by adverse events (AEs). RESULTS: Overall, 2189 individuals were randomized across the two studies and 1879 completed the studies. Demographic and baseline characteristics were similar across treatment groups and between studies. The percentage of overall responders in Study 1 was 30.2% and 29.5% for plecanatide 3 and 6 mg, respectively, vs. 17.8% placebo (P < 0.001 for each dose vs. placebo), and in Study 2 was 21.5% (P = 0.009) and 24.0% (P < 0.001) for plecanatide 3 and 6 mg, respectively, compared to 14.2% for placebo. The percentage of sustained efficacy responders (overall responders plus weekly responders for ≥2 of last 4 weeks of the 12-week treatment period) was significantly greater for both doses of plecanatide vs. placebo across both studies. All secondary end points (stool frequency/consistency, straining, abdominal symptoms) showed statistically significant improvements compared with placebo. The most common AE was diarrhea (3 mg, 4.3%; 6 mg, 4.0%; placebo, 1.0%). Discontinuation due to diarrhea was infrequent (3 mg, 1.2%; 6 mg, 1.4%; placebo, 0). CONCLUSIONS: Plecanatide significantly improved both abdominal pain and constipation symptoms of IBS-C with minimal associated side effects and high levels of tolerability.

A Randomized Phase III Clinical Trial of Plecanatide, a Uroguanylin Analog, in Patients With Chronic Idiopathic Constipation.

OBJECTIVES: This study assessed the efficacy and safety of plecanatide, a guanylate cyclase-C (GC-C) agonist and the first uroguanylin analog approved for the treatment of chronic idiopathic constipation (CIC). METHODS: This phase III, multicenter, double-blind, placebo-controlled study randomized 1,394 patients with CIC. Patients received either plecanatide (3 or 6 mg) or placebo, orally, once daily, for 12 weeks. The primary efficacy endpoint was the percentage of patients who were durable overall complete spontaneous bowel movement (CSBM) responders over the 12-week treatment period. Patients were instructed to record their daily bowel movements, stool consistency scores, and abdominal symptoms in an electronic diary. Treatment-emergent adverse events (AEs) were collected. RESULTS: Each dose of plecanatide resulted in a significantly greater percentage of durable overall CSBM responders (21.0%, 3 mg; 19.5%, 6 mg) as compared with placebo (10.2%; P<0.001 for both). Plecanatide (3 and 6 mg) also significantly increased mean weekly CSBM frequency from baseline (increase of 2.5 and 2.2/week, respectively) vs. placebo (1.2/week; P<0.001 for both) and mean weekly spontaneous bowel movement frequency (increase of 3.2 and 3.1/week, respectively) vs. placebo (1.3/week; P<0.001, for both) over the 12-week treatment period. Both plecanatide doses significantly improved all secondary and additional efficacy endpoints. The most common AE, diarrhea, occurred in 1.3% (placebo), 5.9% (3 mg) and 5.7% (6 mg) of patients. CONCLUSIONS: Plecanatide significantly improved constipation and its related symptoms with a low rate of adverse events. These results suggest that plecanatide will be a useful treatment option in the management of CIC. ClinicalTrials.gov: NCT01982240.

Long-term treatment with plecanatide was safe and tolerable in patients with irritable bowel syndrome with constipation.

Objective: This open-label, multi-center, fixed-dose study (NCT02706483) evaluated the long-term safety and tolerability of plecanatide for the treatment of adults with irritable bowel syndrome with constipation (IBS-C).Methods: Safety and tolerability of once-daily plecanatide 6 mg for up to 53 weeks was assessed in patients with IBS-C who either had been enrolled in one of the phase 3 studies or were study-naïve but met eligibility criteria of the double-blind studies. Safety was assessed by treatment-emergent adverse events (AEs). Patient-reported questionnaires assessed overall IBS symptoms, treatment satisfaction, and desire for treatment continuation. No dose adjustments or treatment interruptions were permitted during the study.Results: Of the 2272 patients enrolled, 1842 (81.1%) completed the study. AEs were experienced by 27.3%, and 4.3% discontinued due to an AE. Most AEs were mild or moderate (90.3%). The incidence of diarrhea, the most commonly reported AE, was low (6.7%), and declined in frequency over time. Diarrhea was the most common cause of AE-related withdrawals (2.7% of patients). At week 53 or end of treatment, 88.2% of patients reported "significant" or "moderate" relief, 72.4% were "very" or "quite" satisfied with treatment, and 76.6% were "very" or "quite" likely to continue treatment.Conclusions: Plecanatide 6 mg was safe and well tolerated in patients with IBS-C treated for up to 53 weeks, with an overall safety profile similar to the 12-week IBS-C studies. Patients reported high rates of relief and satisfaction with treatment, and interest in continuing therapy.Trial registration: ClinicalTrials.gov identifier: NCT02706483.

Epitope-specific immunotherapy targeting CD4-positive T cells in coeliac disease: two randomised, double-blind, placebo-controlled phase 1 studies.

BACKGROUND: A gluten-free diet is the only means to manage coeliac disease, a permanent immune intolerance to gluten. We developed a therapeutic vaccine, Nexvax2, designed to treat coeliac disease. Nexvax2 is an adjuvant-free mix of three peptides that include immunodominant epitopes for gluten-specific CD4-positive T cells. The vaccine is intended to engage and render gluten-specific CD4-positive T cells unresponsive to further antigenic stimulation. We assessed the safety and pharmacodynamics of the vaccine in patients with coeliac disease on a gluten-free diet. METHODS: We did two randomised, double-blind, placebo-controlled, phase 1 studies at 12 community sites in Australia, New Zealand, and the USA, in HLA-DQ2·5-positive patients aged 18-70 years who had coeliac disease and were on a gluten-free diet. In the screening period for ascending dose cohorts, participants were randomly assigned (1:1) by central randomisation with a simple block method to a double-blind crossover, placebo-controlled oral gluten challenge. Participants with a negative interferon γ release assay to Nexvax2 peptides after the screening oral gluten challenge were discontinued before dosing. For the biopsy cohorts, the screening period included an endoscopy, and participants with duodenal histology who had a Marsh score of greater than 1 were discontinued before dosing. Participants were subsequently randomly assigned to either Nexvax2 or placebo in ascending dose cohorts (2:1) and in biopsy cohorts (1:1) by central randomisation with a simple block method. In the three-dose study, participants received either Nexvax2 60 µg, 90 µg, or 150 µg weekly, or placebo over 15 days; in a fourth biopsy cohort, patients received either Nexvax2 at the maximum tolerated dose (MTD) or placebo. In the 16-dose study, participants received Nexvax2 150 µg or 300 µg or placebo twice weekly over 53 days; in a third biopsy cohort, patients also received either Nexvax2 at the MTD or placebo. In the 4-week post-treatment period, ascending dose cohorts underwent a further double-blind crossover, placebo-controlled oral gluten challenge, which had a fixed sequence, and biopsy cohorts had a gastroscopy with duodenal biopsies and quantitative histology within 2 weeks without oral gluten challenge. Participants, investigators, and study staff were masked to the treatment assignment, except for the study pharmacist. The primary endpoint was the number and percentage of adverse events in the treatment period in an intention-to-treat analysis. Both trials were completed and closed before data analysis. Trials were registered with the Australian New Zealand Clinical Trials Registry, numbers ACTRN12612000355875 and ACTRN12613001331729. FINDINGS: Participants were enrolled from Nov 28, 2012, to Aug 14, 2014, in the three-dose study, and from Aug 3, 2012, to Sept 10, 2013, in the 16-dose study. Overall, 62 (57%) of 108 participants were randomly assigned after oral gluten challenge and 20 (71%) of 28 participants were randomly assigned after endoscopy. In the three-dose study, nine participants were randomly allocated to Nexvax2 60 µg and three to placebo (first cohort), nine were allocated to Nexvax2 90 µg and four to placebo (second cohort), eight were allocated to Nexvax2 150 µg and four to placebo (third cohort), and three were allocated to Nexvax2 150 µg and three to placebo (biopsy cohort). In the 16-dose study, eight participants were randomly allocated to Nexvax2 150 µg and four to placebo (first cohort), ten were allocated to Nexvax2 300 µg and three to placebo (second cohort), and seven were allocated to Nexvax2 150 µg and seven to placebo (biopsy cohort). The MTD for Nexvax2 was 150 µg because of transient, acute gastrointestinal adverse events with onset 2-5 h after initial doses of the vaccine, similar to those caused by gluten ingestion. In the ascending dose cohorts in the three-dose study, six (55%) of 11 placebo recipients, five (56%) of nine who received Nexvax2 60 µg, seven (78%) of nine who received Nexvax2 90 µg, and five (63%) of eight who received Nexvax2 150 µg had at least one treatment-emergent adverse event, as did all three (100%) placebo recipients and one (33%) of three Nexvax2 150 µg recipients in the biopsy cohort. In the ascending dose cohorts of the 16-dose study, five (71%) of seven placebo-treated participants, six (75%) of eight who received Nexvax2 150 µg, and all ten (100%) who received Nexvax2 300 µg had at least one treatment-emergent adverse event, as did six (86%) of seven placebo recipients and five (71%) of seven Nexvax2 150 µg recipients in the biopsy cohort. Vomiting, nausea, and headache were the only treatment-emergent adverse events that occurred in at least 5% of participants in either study. Among participants given the MTD, eight gastrointestinal treatment-emergent adverse events occurred in four (50%) of eight participants in the third cohort and none (0%) of three participants in the biopsy cohort in the three-dose study, and five events occurred in five (63%) of eight participants in the first cohort and three events in two (29%) of seven participants in the biopsy cohort of the 16-dose study. Median villous height to crypt depth ratio in distal duodenal biopsies was not significantly different between those who received the vaccine at the MTD on either schedule and those who received placebo. Of the participants who completed the post-treatment oral gluten challenge per protocol, interferon γ release assay to Nexvax2 peptides was negative (responders to treatment) in two (22%) of nine placebo-treated participants in the three-dose study versus two (33%) of six who received Nexvax2 60 µg, five (63%) of eight who received Nexvax2 90 µg, and six (100%) of six who received Nexvax2 150 µg (p=0·007); in the 16-dose study, none (0%) of five placebo-treated participants had a negative assay versus six (75%) of eight who received Nexvax2 150 µg (p=0·021). INTERPRETATION: The MTD of Nexvax2 was 150 µg for twice weekly intradermal administration over 8 weeks, which modified immune responsiveness to Nexvax2 peptides without deterioration in duodenal histology. The gastrointestinal symptoms that followed the first intradermal administration of the vaccine resembled those associated with oral gluten challenge. These findings support continued clinical development of this potential therapeutic vaccine for coeliac disease. FUNDING: ImmusanT.