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Howard JF, Nowak RJ, Wolfe GI, Freimer ML, Vu TH, Hinton JL, Benatar M, Duda PW, MacDougall JE, Farzaneh-Far R, Kaminski HJ, Barohn R, Dimachkie M, Pasnoor M, Farmakidis C, Liu T, Colgan S, Benatar MG, Bertorini T, Pillai R, Henegar R, Bromberg M, Gibson S, Janecki T, Freimer M, Elsheikh B, Matisak P, Genge A, Guidon A, David W, Habib AA, Mathew V, Mozaffar T, Hinton JL, Hewitt W, Barnett D, Sullivan P, Ho D, Howard JF, Traub RE, Chopra M, Kaminski HJ, Aly R, Bayat E, Abu-Rub M, Khan S, Lange D, Holzberg S, Khatri B, Lindman E, Olapo T, Sershon LM, Lisak RP, Bernitsas E, Jia K, Malik R, Lewis-Collins TD, Nicolle M, Nowak RJ, Sharma A, Roy B, Nye J, Pulley M, Berger A, Shabbir Y, Sachdev A, Patterson K, Siddiqi Z, Sivak M, Bratton J, Small G, Kohli A, Fetter M, Vu T, Lam L, Harvey B, Wolfe GI, Silvestri N, Patrick K, Zakalik K, Duda PW, MacDougall J, Farzaneh-Far R, Pontius A, Hoarty M. Clinical Effects of the Self-administered Subcutaneous Complement Inhibitor Zilucoplan in Patients With Moderate to Severe Generalized Myasthenia Gravis: Results of a Phase 2 Randomized, Double-Blind, Placebo-Controlled, Multicenter Clinical Trial. JAMA Neurol 2021; 77:582-592. [PMID: 32065623 PMCID: PMC7042797 DOI: 10.1001/jamaneurol.2019.5125] [Citation(s) in RCA: 113] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Question What are the clinical effects of zilucoplan, a subcutaneously self-administered macrocyclic peptide inhibitor of complement component 5, in a broad population of patients with moderate to severe acetylcholine receptor autoantibody–positive generalized myasthenia gravis? Findings In a randomized, double-blind, placebo-controlled, multicenter phase 2 trial, zilucoplan yielded rapid, clinically meaningful, statistically significant, and sustained improvements in the primary and key secondary end points. Near-complete complement inhibition was associated with a faster onset and greater magnitude of benefit than submaximal complement inhibition, and favorable safety and tolerability were observed. Meaning The findings support a potential therapeutic role for zilucoplan in generalized myasthenia gravis and further evaluation in a phase 3 study. Importance Many patients with generalized myasthenia gravis (gMG) have substantial clinical disability, persistent disease burden, and adverse effects attributable to chronic immunosuppression. Therefore, there is a significant need for targeted, well-tolerated therapies with the potential to improve disease control and enhance quality of life. Objective To evaluate the clinical effects of zilucoplan, a subcutaneously (SC) self-administered macrocyclic peptide inhibitor of complement component 5, in a broad population of patients with moderate to severe gMG. Design, Setting, and Participants This randomized, double-blind, placebo-controlled phase 2 clinical trial at 25 study sites across North America recruited participants between December 2017 and August 2018. Fifty-seven patients were screened, of whom 12 did not meet inclusion criteria and 1 was lost to follow-up after randomization but before receiving study drug, resulting in a total of 44 acetylcholine receptor autoantibody (AChR-Ab)–positive patients with gMG with baseline Quantitative Myasthenia Gravis (QMG) scores of at least 12, regardless of treatment history. Interventions Patients were randomized 1:1:1 to a daily SC self-injection of placebo, 0.1-mg/kg zilucoplan, or 0.3-mg/kg zilucoplan for 12 weeks. Main Outcomes and Measures The primary and key secondary end points were the change from baseline to week 12 in QMG and MG Activities of Daily Living scores, respectively. Significance testing was prespecified at a 1-sided α of .10. Safety and tolerability were also assessed. Results The study of 44 patients was well balanced across the 3 treatment arms with respect to key demographic and disease-specific variables. The mean age of patients across all 3 treatment groups ranged from 45.5 to 54.6 years and most patients were white (average proportions across 3 treatment groups: 78.6%-86.7%). Clinically meaningful and statistically significant improvements in primary and key secondary efficacy end points were observed. Zilucoplan at a dose of 0.3 mg/kg SC daily resulted in a mean reduction from baseline of 6.0 points in the QMG score (placebo-corrected change, –2.8; P = .05) and 3.4 points in the MG Activities of Daily Living score (placebo-corrected change, –2.3; P = .04). Clinically meaningful and statistically significant improvements were also observed in other secondary end points, the MG Composite and MG Quality-of-Life scores. Outcomes for the 0.1-mg/kg SC daily dose were also statistically significant but slower in onset and less pronounced than with the 0.3-mg/kg dose. Rescue therapy (intravenous immunoglobulin or plasma exchange) was required in 3 of 15, 1 of 15, and 0 of 14 participants in the placebo, 0.1-mg/kg zilucoplan, and 0.3-mg/kg zilucoplan arms, respectively. Zilucoplan was observed to have a favorable safety and tolerability profile. Conclusions and Relevance Zilucoplan yielded rapid, meaningful, and sustained improvements over 12 weeks in a broad population of patients with moderate to severe AChR-Ab–positive gMG. Near-complete complement inhibition appeared superior to submaximal inhibition. The observed safety and tolerability profile of zilucoplan was favorable. Trial Registration ClinicalTrials.gov Identifier: NCT03315130.
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Affiliation(s)
| | | | | | | | | | | | | | - Petra W Duda
- Ra Pharmaceuticals Inc, Cambridge, Massachusetts
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- Montreal Neurological Institute, Montreal, Quebec, Canada
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- Lahey Hospital, Burlington, Massachusetts
| | | | | | | | | | - Radwa Aly
- George Washington University, Washington, DC
| | - Elham Bayat
- George Washington University, Washington, DC
| | | | - Shaida Khan
- University of Texas Southwestern, Dallas, Irving
| | - Dale Lange
- Hospital for Special Surgery, New York, New York
| | | | - Bhupendra Khatri
- Center for Neurological Disorders, St Francis Hospital at Ascension, Milwaukee, Wisconsin
| | - Emily Lindman
- Center for Neurological Disorders, St Francis Hospital at Ascension, Milwaukee, Wisconsin
| | - Tayo Olapo
- Center for Neurological Disorders, St Francis Hospital at Ascension, Milwaukee, Wisconsin
| | - Lisa M Sershon
- Center for Neurological Disorders, St Francis Hospital at Ascension, Milwaukee, Wisconsin
| | | | | | - Kelly Jia
- Wayne State University, Detroit, Michigan
| | | | | | | | | | | | - Bhaskar Roy
- Yale School of Medicine, New Haven, Connecticut
| | - Joan Nye
- Yale School of Medicine, New Haven, Connecticut
| | | | | | | | | | | | | | - Mark Sivak
- Mount Sinai Hospital, New York, New York
| | | | - George Small
- Allegheny Neurological Associates, Pittsburgh, Pennsylvania
| | - Anem Kohli
- Allegheny Neurological Associates, Pittsburgh, Pennsylvania
| | - Mary Fetter
- Allegheny Neurological Associates, Pittsburgh, Pennsylvania
| | - Tuan Vu
- University of South Florida, Tampa
| | - Lucy Lam
- University of South Florida, Tampa
| | | | | | | | | | | | - Petra W Duda
- Ra Pharmaceuticals Inc, Cambridge, Massachusetts
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Camilleri M, Lembo AJ, Lavins BJ, MacDougall JE, Carson RT, Williams VS, Nelson LM, Shiff SJ, Currie MG, Kurtz CB, Johnston JM. Comparison of adequate relief with symptom, global, and responder endpoints in linaclotide phase 3 trials in IBS-C. United European Gastroenterol J 2015; 3:53-62. [PMID: 25653859 DOI: 10.1177/2050640614555946] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 09/23/2014] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Optimal clinical trial endpoints for irritable bowel syndrome with constipation (IBS-C) are uncertain. OBJECTIVE The objective of this article is to compare adequate relief (AR) to abdominal/bowel symptoms, global endpoints, and FDA and EMA responder criteria; and to use AR as an anchor to assess clinically meaningful change (CMC) in IBS-C symptoms. METHODS Using pooled 12-week data from two phase 3 linaclotide clinical trials, daily abdominal/bowel symptoms and weekly global assessments were correlated with AR. Symptom CMC thresholds were estimated using AR as an anchor. Agreement between AR and FDA/EMA responder criteria was assessed. RESULTS Correlations of AR with percentage change in abdominal symptoms, bowel symptoms, and global endpoints ranged from 0.48-0.54, 0.32-0.39, and 0.61-0.71, respectively. Using AR as an anchor, CMC thresholds were 29% improvement in abdominal pain, 29% improvement in abdominal discomfort, and 0.7/week increase in CSBMs, similar to thresholds for IBS-C responder endpoints recommended by the FDA and EMA. There was considerable agreement of weekly responder rates between AR and the FDA and EMA endpoints (on average, 70%-76% and 71%-82% of weeks with agreement, respectively). CONCLUSIONS AR bridges IBS-C clinical trials, putting into perspective the disparate primary endpoints recommended by professional societies and regulatory authorities, and allowing researchers, practitioners, and regulators to compare trial results.
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Affiliation(s)
- Michael Camilleri
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
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Rao SSC, Quigley EMM, Shiff SJ, Lavins BJ, Kurtz CB, MacDougall JE, Currie MG, Johnston JM. Effect of linaclotide on severe abdominal symptoms in patients with irritable bowel syndrome with constipation. Clin Gastroenterol Hepatol 2014; 12:616-23. [PMID: 24075889 DOI: 10.1016/j.cgh.2013.09.022] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 09/06/2013] [Accepted: 09/08/2013] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS Patients with irritable bowel syndrome with constipation (IBS-C) have abdominal symptoms that vary in severity. Linaclotide, a guanylate cyclase-C agonist, improves abdominal and bowel symptoms in these patients. We examined the prevalence of severe abdominal symptoms in patients with IBS-C and assessed the effects of linaclotide on abdominal symptoms, global measures, and quality of life (QOL). METHODS In two phase 3 trials, patients who met modified Rome II criteria for IBS-C were randomly assigned to groups given oral, once-daily linaclotide (290 μg) or placebo for 12 weeks. During the baseline (2 weeks prior to treatment) and treatment periods, patients rated abdominal pain, discomfort, bloating, fullness, and cramping daily (from 0 = none to 10 = very severe). Linaclotide's effects on abdominal symptoms, global measures, and IBS-related QOL were assessed in subpopulations of patients who rated specific individual abdominal symptoms as severe (≥ 7.0) at baseline. RESULTS In the intent-to-treat population (1602 patients; 797 receiving placebo and 805 receiving linaclotide), baseline prevalence values for severe abdominal symptoms were 44% for bloating, 44% for fullness, 32% for discomfort, 23% for pain, and 22% for cramping, with considerable overlap among symptoms. In patients with severe symptoms, linaclotide reduced all abdominal symptoms; mean changes from baseline severity scores ranged from -2.7 to -3.4 for linaclotide vs -1.4 to -1.9 for placebo (P < .0001). Linaclotide improved global measures (P < .0001) and IBS-QOL scores (P < .01) compared with placebo. Diarrhea was the most common adverse event of linaclotide in patients with severe abdominal symptoms (18.8%-21.0%). CONCLUSIONS Of 5 severe abdominal symptoms assessed, bloating and fullness were most prevalent in patients with IBS-C. Linaclotide significantly improved all abdominal symptoms, global measures, and IBS-QOL in subpopulations of IBS-C patients with severe abdominal symptoms. Clinicaltrials.gov NUMBERS NCT00938717, NCT00948818.
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Affiliation(s)
- Satish S C Rao
- Section of Gastroenterology and Hepatology, Georgia Regents University, Augusta, Georgia
| | - Eamonn M M Quigley
- Gastroenterology Division, Houston Methodist Hospital and Weill Cornell Medical College, Houston, Texas
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Lacy BE, Lembo AJ, MacDougall JE, Shiff SJ, Kurtz CB, Currie MG, Johnston JM. Responders vs clinical response: a critical analysis of data from linaclotide phase 3 clinical trials in IBS-C. Neurogastroenterol Motil 2014; 26:326-33. [PMID: 24382134 PMCID: PMC4282394 DOI: 10.1111/nmo.12264] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 10/29/2013] [Indexed: 12/15/2022]
Abstract
BACKGROUND US Food and Drug Administration (FDA) set a rigorous standard for defining patient responders in irritable bowel syndrome-C (IBS-C; i.e., FDA's Responder Endpoint) for regulatory approval. However, this endpoint's utility for health-care practitioners to assess clinical response has not been determined. We analyzed pooled IBS-C linaclotide trial data to evaluate clinically significant responses in linaclotide-treated patients who did not meet the FDA responder definition. METHODS Percentages of FDA non-responders reporting improvement in abdominal pain, bowel function and/or global relief measures were determined using pooled data from two linaclotide Phase 3 IBS-C trials. KEY RESULTS 1602 IBS-C patients enrolled; 34% of linaclotide-treated and 17% of placebo-treated patients met the FDA Responder Endpoint (p < 0.0001). Among FDA non-responders at week 12, 63% of linaclotide-treated patients reported their abdominal pain was at least somewhat relieved, compared with 48% of placebo-treated patients. For stool frequency, 62% of linaclotide-treated patients reported that they were at least somewhat improved at week 12, compared with 46% of placebo-treated patients. For global IBS symptoms, 65% of linaclotide-treated patients reported at least some IBS-symptom relief, 43% reported adequate relief of IBS symptoms, and 57% reported being satisfied with linaclotide treatment, vs placebo rates of 48%, 34%, and 41% respectively. CONCLUSIONS & INFERENCES Most linaclotide-treated IBS-C patients who were FDA non-responders reported some improvement in abdominal pain and stool frequency, and global relief/satisfaction. In addition to the FDA Responder Endpoint, differing response thresholds and symptom-specific change from baseline should be considered by clinicians for a complete understanding of clinical response to linaclotide and other IBS-C therapies.
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Affiliation(s)
- B E Lacy
- Division of Gastroenterology & Hepatology, Dartmouth-Hitchcock Medical CenterLebanon, NH, USA
| | - A J Lembo
- Division of Gastroenterology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical SchoolBoston, MA, USA
| | - J E MacDougall
- Research & Development, Ironwood PharmaceuticalsCambridge, MA, USA
| | - S J Shiff
- Clinical Development, Forest Research InstituteJersey City, NJ, USA
| | - C B Kurtz
- Research & Development, Ironwood PharmaceuticalsCambridge, MA, USA
| | - M G Currie
- Research & Development, Ironwood PharmaceuticalsCambridge, MA, USA
| | - J M Johnston
- Research & Development, Ironwood PharmaceuticalsCambridge, MA, USA
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Castro J, Harrington AM, Hughes PA, Martin CM, Ge P, Shea CM, Jin H, Jacobson S, Hannig G, Mann E, Cohen MB, MacDougall JE, Lavins BJ, Kurtz CB, Silos-Santiago I, Johnston JM, Currie MG, Blackshaw LA, Brierley SM. Linaclotide inhibits colonic nociceptors and relieves abdominal pain via guanylate cyclase-C and extracellular cyclic guanosine 3',5'-monophosphate. Gastroenterology 2013; 145:1334-46.e1-11. [PMID: 23958540 DOI: 10.1053/j.gastro.2013.08.017] [Citation(s) in RCA: 190] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 08/02/2013] [Accepted: 08/13/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND & AIMS Linaclotide is a minimally absorbed agonist of guanylate cyclase-C (GUCY2C or GC-C) that reduces symptoms associated with irritable bowel syndrome with constipation (IBS-C). Little is known about the mechanism by which linaclotide reduces abdominal pain in patients with IBS-C. METHODS We determined the effects of linaclotide on colonic sensory afferents in healthy mice and those with chronic visceral hypersensitivity. We assessed pain transmission by measuring activation of dorsal horn neurons in the spinal cord in response to noxious colorectal distention. Levels of Gucy2c messenger RNA were measured in tissues from mice using quantitative reverse transcription polymerase chain reaction and in situ hybridization. We used human intestinal cell lines to measure release of cyclic guanosine-3',5'-monophosphate (cGMP) by linaclotide. We performed a post-hoc analysis of data from a phase III, double-blind, parallel-group study in which 805 patients with IBS-C were randomly assigned to groups given an oral placebo or 290 μg linaclotide once daily for 26 weeks. We quantified changes in IBS-C symptoms, including abdominal pain. RESULTS In mice, linaclotide inhibited colonic nociceptors with greater efficacy during chronic visceral hypersensitivity. Intra-colonic administration of linaclotide reduced signaling of noxious colorectal distention to the spinal cord. The colonic mucosa, but not neurons, was found to express linaclotide's target, GC-C. The downstream effector of GC-C, cGMP, was released after administration of linaclotide and also inhibited nociceptors. The effects of linaclotide were lost in Gucy2c(-/-) mice and prevented by inhibiting cGMP transporters or removing the mucosa. During 26 weeks of linaclotide administration, a significantly greater percentage of patients (70%) had at least a 30% reduction in abdominal pain compared with patients given placebo (50%). CONCLUSIONS We have identified an analgesic mechanism of linaclotide: it activates GC-C expressed on mucosal epithelial cells, resulting in the production and release of cGMP. This extracellular cGMP acts on and inhibits nociceptors, thereby reducing nociception. We also found that linaclotide reduces chronic abdominal pain in patients with IBS-C.
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Affiliation(s)
- Joel Castro
- Nerve-Gut Research Laboratory, Discipline of Medicine, Faculty of Health Sciences, The University of Adelaide, Adelaide, South Australia, Australia; Department of Gastroenterology and Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, South Australia, Australia
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Lembo AJ, Schneier HA, Shiff SJ, Kurtz CB, MacDougall JE, Jia XD, Shao JZ, Lavins BJ, Currie MG, Fitch DA, Jeglinski BI, Eng P, Fox SM, Johnston JM. Two randomized trials of linaclotide for chronic constipation. N Engl J Med 2011; 365:527-36. [PMID: 21830967 DOI: 10.1056/nejmoa1010863] [Citation(s) in RCA: 244] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Linaclotide is a minimally absorbed peptide agonist of the guanylate cyclase C receptor. In two trials, we aimed to determine the efficacy and safety of linaclotide in patients with chronic constipation. METHODS We conducted two randomized, 12-week, multicenter, double-blind, parallel-group, placebo-controlled, dual-dose trials (Trials 303 and 01) involving 1276 patients with chronic constipation. Patients received either placebo or linaclotide, 145 μg or 290 μg, once daily for 12 weeks. The primary efficacy end point was three or more complete spontaneous bowel movements (CSBMs) per week and an increase of one or more CSBMs from baseline during at least 9 of the 12 weeks. Adverse events were also monitored. RESULTS For Trials 303 and 01, respectively, the primary end point was reached by 21.2% and 16.0% of the patients who received 145 μg of linaclotide and by 19.4% and 21.3% of the patients who received 290 μg of linaclotide, as compared with 3.3% and 6.0% of those who received placebo (P<0.01 for all comparisons of linaclotide with placebo). Improvements in all secondary end points were significantly greater in both linaclotide groups than in the placebo groups. The incidence of adverse events was similar among all study groups, with the exception of diarrhea, which led to discontinuation of treatment in 4.2% of patients in both linaclotide groups. CONCLUSIONS In these two 12-week trials, linaclotide significantly reduced bowel and abdominal symptoms in patients with chronic constipation. Additional studies are needed to evaluate the potential long-term risks and benefits of linaclotide in chronic constipation. (Funded by Ironwood Pharmaceuticals and Forest Research Institute; ClinicalTrials.gov numbers, NCT00765882 and NCT00730015.).
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Affiliation(s)
- Anthony J Lembo
- Department of Medicine, Division of Gastroenterology, Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, MA, USA
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Johnston JM, Kurtz CB, Drossman DA, Lembo AJ, Jeglinski BI, MacDougall JE, Antonelli SM, Currie MG. Pilot study on the effect of linaclotide in patients with chronic constipation. Am J Gastroenterol 2009; 104:125-32. [PMID: 19098860 DOI: 10.1038/ajg.2008.59] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVES Chronic constipation is a common gastrointestinal disorder with limited treatment options. Oral administration of linaclotide, a novel peptide agonist of guanylate cyclase-C receptors, has been shown in animal studies to stimulate intestinal fluid secretion and transit. In Phase 1 studies in healthy human volunteers, linaclotide was well-tolerated, increased bowel movement frequency, and loosened stool consistency. METHODS This randomized, double-blind, placebo-controlled pilot study evaluated the safety, tolerability, and exploratory efficacy of oral linaclotide in 42 patients with chronic constipation. Patients were randomized to linaclotide (100, 300, or 1,000 microg) or placebo once daily for 2 weeks. Bowel habits (stool frequency, consistency, straining, completeness of evacuation) and degree of abdominal discomfort were monitored daily using an interactive voice response system. Patient-reported outcomes of severity of constipation and overall relief were evaluated weekly. RESULTS Linaclotide treatment produced dose-dependent increases from the pretreatment baseline values in weekly complete spontaneous bowel movement frequency (range: 2.2-3.2), stool consistency scores (range: 1.1-2.6, 7-point scale), and straining scores (range: 0.4-1.5, 7-point scale); corresponding placebo increases were 1.3, 0.4, 0.4, respectively. Clinical improvements were also demonstrated in abdominal discomfort, severity of constipation, and overall relief. Compared to placebo, linaclotide 100 microg/day significantly increased spontaneous bowel movement frequency, and linaclotide 1,000 microg/day significantly improved stool consistency (P<0.05). Adverse events were primarily gastrointestinal, with diarrhea being the most common. CONCLUSIONS In this pilot study, linaclotide treatment improved bowel habits and symptoms of patients with chronic constipation. Further randomized controlled trials are warranted.
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Abstract
The linear mixed model has become a widely used tool for longitudinal analysis of continuous variables. The use of regression splines in these models offers the analyst additional flexibility in the formulation of descriptive analyses, exploratory analyses and hypothesis-driven confirmatory analyses. We propose a method for fitting piecewise polynomial regression splines with varying polynomial order in the fixed effects and/or random effects of the linear mixed model. The polynomial segments are explicitly constrained by side conditions for continuity and some smoothness at the points where they join. By using a reparameterization of this explicitly constrained linear mixed model, an implicitly constrained linear mixed model is constructed that simplifies implementation of fixed-knot regression splines. The proposed approach is relatively simple, handles splines in one variable or multiple variables, and can be easily programmed using existing commercial software such as SAS or S-plus. The method is illustrated using two examples: an analysis of longitudinal viral load data from a study of subjects with acute HIV-1 infection and an analysis of 24-hour ambulatory blood pressure profiles.
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Affiliation(s)
- Lloyd J Edwards
- Department of Biostatistics, The University of North Carolina, Chapel Hill, 27599, USA.
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Vitale G, Bull LM, Morris RE, Cheetham AK, Toby BH, Coe CG, MacDougall JE. Combined Neutron and X-ray Powder Diffraction Study of Zeolite Ca LSX and a 2H NMR Study of Its Complex with Benzene. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100043a058] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
BACKGROUND Adolescent dating violence is a public health problem. The public health approach to prevention is to identify predictors of problem behaviors and develop interventions to eliminate or reduce those predictors with the intention of altering the chain of causation. Longitudinal data are preferred for identifying predictors of behavior but all dating violence studies have used cross-sectional data. We use longitudinal data to examine predictors of adolescent dating violence from several domains guided by an ecological perspective. METHODS Eighty percent (N = 1,965) of the 8th- and 9th-graders in one county completed baseline questionnaires in school and 90% (N = 1,759) of those adolescents completed questionnaires again 1&1/2 years later. Proportional odds models were used to identify cross-sectional correlates and longitudinal predictors of dating violence perpetration that occurred between baseline and follow-up. RESULTS Most of the study variables were correlated with dating violence in cross-sectional analyses. Having friends who are victims of dating violence, using alcohol, and being of a race other than white predicted dating violence perpetration by females. Holding attitudes that are accepting of dating violence predicted dating violence perpetration by males. CONCLUSION The findings suggest that intervention strategies should vary for males and females and that when basing interventions on cross-sectional findings, scarce resources may be stretched to address persons who may not truly be at risk of beginning to perpetrate dating violence.
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Affiliation(s)
- V A Foshee
- Department of Health Behavior and Health Education, School of Public Health, 317 Rosenau Hall, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7400.
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Abstract
OBJECTIVES An earlier report described desirable 1-month follow-up effects of the Safe Dates program on psychological, physical, and sexual dating violence. Mediators of the program-behavior relationship also were identified. The present report describes the 1-year follow-up effects of the Safe Dates program. METHODS Fourteen schools were in the randomized experiment. Data were gathered by questionnaires in schools before program activities and 1 year after the program ended. RESULTS The short-term behavioral effects had disappeared at 1 year, but effects on mediating variables such as dating violence norms, conflict management skills, and awareness of community services for dating violence were maintained. CONCLUSIONS The findings are considered in the context of why program effects might have decayed and the possible role of boosters for effect maintenance.
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Affiliation(s)
- V A Foshee
- School of Public Health, University of North Carolina at Chapel Hill 27599-7400, USA.
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