Diabetes Care 31:1816-1823, 2008 DOI: 10.2337/dc08-0029 © 2008 by the American Diabetes Association
Sustained Weight Loss Following 12-Month Pramlintide Treatment as an Adjunct to Lifestyle Intervention in Obesity
1 Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana Corresponding author: Christian Weyer, cweyer{at}amylin.com
OBJECTIVE—To assess long-term weight loss efficacy and safety of pramlintide used at different dosing regimens and in conjunction with lifestyle intervention (LSI). RESEARCH DESIGN AND METHODS—In a 4-month, double-blind, placebo-controlled, dose-ranging study, 411 obese subjects were randomized to receive pramlintide (six arms: 120, 240, and 360 µg b.i.d. and t.i.d.) or placebo in conjunction with a structured LSI program geared toward weight loss. Of the 4-month evaluable subjects (n = 270), 77% opted to continue preexisting treatment during an 8-month single-blind extension (LSI geared toward weight maintenance).
RESULTS—At month 4, mean weight loss from baseline in the pramlintide arms ranged from 3.8 ± 0.7 to 6.1 ± 0.8 kg (2.8 ± 0.8 kg with placebo). By month 12, initial 4-month weight loss was regained in the placebo group but was maintained in all but the 120-µg b.i.d. group. Placebo-corrected weight loss with 120 µg t.i.d. and 360 µg b.i.d. averaged 3.2 ± 1.2 kg (3.1 ± 1.1% body wt) and 3.3 ± 1.1 kg (3.1 ± 1.0% body wt), respectively, at month 4 (both P < 0.01; 4-month evaluable n = 270) and 6.1 ± 2.1 kg (5.6 ± 2.1% body wt) and 7.2 ± 2.3 kg (6.8 ± 2.3% body wt), respectively, at month 12 (both P < 0.01; 12-month evaluable n = 146). At month 12, 40 and 43% of subjects treated with 120 µg t.i.d. and 360 µg b.i.d., respectively, achieved CONCLUSIONS—When used over 12 months as an adjunct to LSI, pramlintide treatment, with low-dose three-times-daily or higher-dose two-times-daily regimens, helped obese subjects achieve greater initial weight loss and enhanced long-term maintenance of weight loss.
To date, efforts to develop obesity pharmacotherapies aimed at reducing food intake and body weight have largely focused on small-molecule anorectics, an approach that has repeatedly been hampered by safety concerns (1). Peptide hormones originating from pancreas and gut regulate meal size and body weight by acting as short-term (episodic) signals (2). In contrast to small molecules, peptide hormones do not readily diffuse the blood-brain barrier to penetrate the entire central nervous system. Moreover, they act by enhancing signaling through specific, naturally occurring pathways that regulate food intake as opposed to acting more generally on multiple neuronal processes, for example, by altering synaptic concentrations of neurotransmitters. Based on these characteristics, peptide hormone therapeutics are potential alternatives to centrally-acting small-molecule anorectics. Amylin, a 37–amino acid β-cell hormone cosecreted with insulin in response to meals, reduces food intake and body weight in rodents and may fulfill the criteria for a peripheral satiation hormone (3–6). Pramlintide, a synthetic analog of human amylin, has been extensively studied as an antihyperglycemic treatment and is currently under investigation as a potential treatment for obesity.
In two studies in obese subjects, pramlintide (120 µg single doses or 180 µg t.i.d. before meals for 6-weeks) reduced ad libitum food intake (7,8). Compared with placebo, pramlintide significantly reduced 24-h caloric intake (by
Pramlintide's weight effects in obese subjects were initially assessed in a 16-week, randomized, double-blind, placebo-controlled, nonforced dose-escalation study. In this study, in which 88% of subjects escalated to the maximum dose (240 µg t.i.d.), pramlintide induced a placebo-corrected reduction in weight of 3.7% (P < 0.001), with 31% of pramlintide-treated subjects achieving To evaluate the weight loss efficacy and safety of pramlintide across a range of doses, across different dose frequencies, in conjunction with LSI, and over 1 year, we conducted a 4-month dose-ranging study (main study) evaluating six pramlintide arms (120, 240, and 360 µg b.i.d. and t.i.d.) in conjunction with lifestyle intervention (LSI) and then implemented an 8-month single-blind extension protocol in which subjects continued their preassigned treatment.
Main double-blind study This was a 4-month, multicenter (24 centers in the U.S.), randomized, double-blind, placebo-controlled, dose-ranging study. Following a 1-week placebo lead-in, 411 obese subjects were randomized (1:6) to receive placebo three times daily or pramlintide (120, 240, and 360 µg b.i.d. and t.i.d.) via subcutaneous injection 15 min before morning, midday, and evening meals in conjunction with LSI. To maintain dose-frequency blinding, subjects receiving pramlintide twice daily also received placebo before midday meals. Pramlintide was initiated at 120 µg and increased in 120 µg increments every 2 weeks until the assigned maintenance dose was reached (online appendix Fig. 1, available at http://dx.doi.org/10.2337/dc08-0029).
Single-blind extension study
LSI program
Study participants Exclusion criteria included clinically active cardiac disease, diabetes, poorly controlled hypertension (sitting blood pressure >160/95 mmHg), hepatic disease, malignant disease within 5 years of screening, major depressive or psychotic disorders, eating disorders, gastrointestinal disorders, current enrollment in a weight loss program, and use of excluded concomitant medications including steroids and antiobesity, antipsychotic, antiepileptic, and certain antidepressant agents (including monoamine oxidase inhibitors, bupropion, tricyclic antidepressants, and tetracyclic antidepressants). Subjects on stable doses of selective serotonin reuptake inhibitors and serotonin-norepinephrine reuptake inhibitors, except for sibutramine, were permitted to enroll. The study protocol was approved by the institutional review board of each study site or by a centralized institutional review board. All patients provided written informed consent before the main study and extension. This study was conducted in accordance with the principles described in the Declaration of Helsinki (1964), including all amendments up to and including the 1996 South African revision.
Study end points
Statistical analysis Summaries of safety and tolerability were conducted separately for each study using the corresponding ITT population. Changes in body weight and waist circumference were analyzed separately for each study using the corresponding ITT and evaluable populations. Missing data for the ITT populations were imputed using the last observation carried forward (LOCF) method. LOCF was implemented separately for each study using the corresponding ITT population. Subgroup analyses were conducted by the occurrence of treatment-emergent nausea in the ITT population.
Changes in body weight from baseline were analyzed using a general linear model including factors for treatment group, study site, sex, baseline BMI stratum (<35,
Baseline characteristics and subject disposition Double-blind study. In the main double-blind study, 408 (the ITT population) of the 411 subjects randomized to placebo or one of six pramlintide arms started the study medication. Withdrawal rates were slightly lower for the pooled pramlintide group (31%) than for placebo (37%) (Table 1). Overall withdrawal rates and reasons for withdrawal were generally similar between all pramlintide treatment arms.
Single-blind extension. Of the eligible subjects (4-month evaluable n = 270), 77% opted to participate in the single-blind extension. By month 12, withdrawal rates were 26% for pramlintide-treated versus 37% for placebo-administered subjects (Table 1). Baseline characteristics of subjects participating in the single-blind extension were well balanced across arms in each study (Table 1).
Body weight and waist circumference
Single-blind extension. In the extension (12-month evaluable n = 146), initial weight loss was largely regained in the placebo group but maintained or continued in all but the pramlintide 120 µg b.i.d. arm (Fig. 1A and B). Excluding 120 µg b.i.d., weight loss from baseline to month 12 in the pramlintide arms ranged from 6.3 ± 3.5 to 8.0 ± 2.0 kg (evaluable 6.0 ± 2.8 to 7.9 ± 1.9%; ITT-LOCF 6.1 ± 2.4 to 6.8 ± 1.4 kg [5.5 ± 2.0 to 6.6 ± 1.3%]) versus 0.8 ± 1.3 kg (evaluable 1.1 ± 1.3%; ITT-LOCF 2.4 ± 1.1 kg [2.2 ± 1.0%]) with placebo. Pramlintide 120 µg t.i.d., 240 µg t.i.d., and 360 µg b.i.d. and t.i.d. achieved statistically significant weight loss versus placebo (12-month evaluable and 12-month ITT-LOCF P < 0.05) (Fig. 1A and B). In these arms, 41–65% of pramlintide-treated subjects achieved 5% weight loss from baseline to month 12 (placebo 18%) (Fig. 2A). In the lowest doses from each dosing regimen achieving statistically significant absolute weight loss in the 4-month double-blind study, 40 and 43% of subjects receiving 120 µg t.i.d. and 360 µg b.i.d. achieved 10% weight loss at month 12 (placebo 12%) (Fig. 2B). Similar to at month 4, reductions in weight appeared dose dependent for the pramlintide twice daily but not three times daily arms. Subjects treated with pramlintide 120 µg t.i.d., 240 µg t.i.d., and 360 µg b.i.d. also experienced significant reductions in waist circumference versus placebo (P < 0.05) (online appendix Table 1).
Despite close-to-normal mean baseline values for lipoprotein profiles and blood pressure in this obese but relatively healthy study population, fasting lipid concentrations and blood pressure trended toward improvements with pramlintide treatment (online appendix Table 1).
Safety and tolerability During the single-blind extension, the incidence of nausea ranged from 0 to 9% in the pramlintide treatment arms vsersus 0% for placebo (online appendix Table 2). There were no reports of severe nausea or withdrawals due to nausea. The most frequent adverse event in the extension was upper respiratory tract infection (11.5% in the pooled pramlintide treatment group and 14.8% with placebo). Weight loss was dissociated from nausea, as subjects who did not experience nausea during the study achieved reductions in body weight similar to those in the overall population (online appendix Fig. 1).
Consistent with their objectives, the present study and extension provide important new insights into the safety and weight loss efficacy of pramlintide over a range of doses and dose frequencies. Our findings show that pramlintide in conjunction with LSI induces weight loss that is durable up to 12 months.
Dose range and frequency
The aforementioned dose-ranging findings may be explained by pramlintide's pharmacokinetic profile. Following injection, plasma pramlintide peaks at With respect to dose selection for future studies, our results indicate that adequate weight loss efficacy and safety can be achieved with both three-times- and twice-daily regimens. Although 120 µg t.i.d. is commensurate with the pramlintide dosing regimen currently approved for the treatment of type 2 diabetes (12), in the present study in obese subjects without diabetes, 360 µg b.i.d. emerged as an equally effective dose for weight loss. Although the incidence of nausea was slightly greater with 360 µg b.i.d. than with the lower 120 µg t.i.d. regimen, nausea was generally mild and transient and no other safety issues were identified at this higher dose.
LSI Rather than choosing a specific, prescriptive low-calorie diet or exercise program, the present study used LEARN, a well-established and flexible program aimed at making gradual changes in lifestyle, including healthy eating and behavior modification. LEARN has been extensively studied in nonpharmacological and pharmacological intervention studies (10,15).
Durability of weight loss Consistent with clinical practice experience, the initial weight loss obtained with LSI alone (placebo) was not maintained but was followed by gradual weight regain. Unlike placebo, 4-month weight loss was maintained over 12 months in all but the lowest pramlintide twice-daily arm. This is consistent with findings from 1-year pramlintide diabetes studies, which also showed durable weight loss over 1 year (12,16,17).
Assessment of the durability of pramlintide-induced weight loss in the present study is limited by several factors. These include a relatively high attrition rate, a common, well-recognized problem in obesity pharmacotherapy studies (18), and the possibility of self-selection bias. Of note, subjects were not initially recruited for a long-term study, and only
Safety and tolerability Previous studies have suggested that amylin analogs, such as pramlintide, may be viable components of a combinatorial peptide approach to obesity treatment (21). In diet-induced obese rats, amylin induced synergistic, fat-specific weight loss when coadministered with leptin, a long-term adiposity signal (22). In a recently published, 24-week translational clinical research study in overweight/obese subjects, combination treatment with pramlintide (360 µg b.i.d.) and recombinant human leptin (R-met-Hu-Leptin, meterleptin, 5 mg b.i.d.) resulted in 12.7% mean weight loss from enrollment, significantly more than treatment with pramlintide or meterleptin alone (8.1 and 8.4%, respectively; P < 0.001) (22). Further development of a pramlintide/meterleptin combination product for obesity is currently underway. In conclusion, although larger longer-term confirmatory studies are required to determine its efficacy and safety for weight loss, alone or in combination, clinical findings obtained to date support the potential of pramlintide as part of a novel, integrated neurohormonal approach for the management of obesity.
Principal investigators: A. Ahmann, V. Aroda, L. Aronne, C. Bowden (former PI: B. Troupin), D. Carter, J. Ferguson, K. Fujioka, J. Geohas, D. Kereiakes, E. Klein, S. Klein, D. Krieger, S. Miller, T. Moretto, M. Pierson, J. Pullman, S. Schwartz, J. Shapiro, D. Smith, S. Smith, T. Wadden, R. Weinstein, F. Whitehouse, and J. Zavoral. Participating centers: American Health Network; Big Sky Clinical Research; Capital Clinical Research Center; Comprehensive Weight Control Program; CSRA Partners in Health; Diabetes & Glandular Disease Research Associates; Diablo Clinical Research, Inc.; Henry Ford Health System; The Lindner Clinical Trial Center; Miami Research Associates; Pennington Biomedical Research Center; Philadelphia Health Associates; Profil Institute for Clinical Research, Inc.; Radiant Research Austin, Portland, Minneapolis, Kansas City, Chicago, and Salt Lake City-64th South; SAM Clinical Research; Scripps Clinic; University of Pennsylvania Weight & Eating Disorders Program; VA San Diego Healthcare System; and Washington University School of Medicine.
We are indebted to the subjects and investigators and to Shereen McIntyre, Jonathan Kornstein, Szecho Lin, Ya Huang, Rich Dopson, Lily Chen, Jackie Benson, and Christine Schulteis for their excellent assistance in the conduct, reporting, and quality control. Some data from this study were presented at the 67th Annual Meeting of the American Diabetes Association, 22–26 June 2007, Chicago, Illinois; the 43rd Annual Meeting of the European Association for the Study of Diabetes, 17–21 September 2007, Amsterdam, the Netherlands; and NAASO, The Obesity Society Annual Scientific Meeting, 20–24 October 2007, Ernest N. Morial Convention Center, New Orleans, Louisiana.
Published ahead of print at http://care.diabetesjournals.org on 20 June 2008. Clinical trial reg. nos. NCT00112021 and NCT00189514, clinicaltrials.gov. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C Section 1734 solely to indicate this fact. Received for publication January 4, 2008. Accepted for publication June 13, 2008.
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