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. 2025 Jun 25:1-73.
doi: 10.3310/SKHT8119. Online ahead of print.

The quantity, quality and findings of network meta-analyses evaluating the effectiveness of GLP-1 RAs for weight loss: a scoping review

Michael Nunns  1 , Samantha Febrey  1 , Jill Buckland  1 , Rebecca Abbott  1   2 , Rebecca Whear  1   2 , Alison Bethel  1   2 , Kate Boddy  1 , Liz Shaw  1 , Jo Thompson Coon  1   2 , G J Melendez-Torres  1
Affiliations

The quantity, quality and findings of network meta-analyses evaluating the effectiveness of GLP-1 RAs for weight loss: a scoping review

Michael Nunns et al. Health Technol Assess. .

Abstract

Background: Glucagon-like peptide 1 receptor agonists are a class of drug originally developed to treat type 2 diabetes but now increasingly used for weight loss, especially in people living with obesity. Despite an abundance of evidence about the effectiveness and safety of glucagon-like peptide 1 receptor agonists for weight loss, network meta-analyses are inconsistent in their quality and scope, and this is a fast-moving field.

Objectives: We sought to identify the most recent network meta-analyses evaluating the effectiveness of glucagon-like peptide 1 receptor agonists for weight loss; critically appraise included network meta-analyses; provide an overview of the quality and findings of existing network meta-analyses, and identify any pertinent gaps in the evidence; and consider the value of updating the most recent, comprehensive and high-quality network meta-analyses.

Methods: On 6 June 2023, we searched MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews and Epistemonikos for systematic reviews with network meta-analyses published since 2020 in adults (18 or above) with body mass index ≥ 25 (or ≥ 23 for Asian populations), including at least one relevant glucagon-like peptide 1 receptor agonist and weight loss outcomes. We screened and selected reviews in duplicate and independently, and appraised reviews using a modified A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR-2) and a network meta-analysis reliability checklist. The highest-quality reviews were then extracted in depth, and the most relevant network meta-analysis models identified, focusing on weight loss and safety outcomes. A top-up search for trials published since October 2022 was also undertaken to identify relevant trials not included in published network meta-analyses. A further search for new network meta-analyses was conducted on 26 September 2024.

Results: Of 22 systematic reviews identified, 14 were prioritised for analysis as the remaining 8 reviews were rated as low or critically low quality. We focused on network meta-analyses of weight loss outcomes measured at 6 months, 12 months, longer than 12 months or over a mix of time points. At 6 months, subcutaneous tirzepatide was the most effective drug associated with 9 kg (at 5 mg) to 12 kg (at 15 mg) of weight loss. However, the largest effects were seen for subcutaneous semaglutide 2.4 mg, which was associated with between 11.5 and 12.5 kg of weight loss, though this came from two network meta-analyses, both informed by six trials, and both merging findings across multiple time points. The relative effectiveness among glucagon-like peptide 1 receptor agonists followed a pattern suggested by their performance against placebo, with tirzepatide and semaglutide standing out as the most effective drugs for weight loss. No network meta-analyses compared tirzepatide and semaglutide 2.4 mg. The drugs associated with the greatest weight loss, tirzepatide and semaglutide 2.4 mg, were generally associated with increased risk of safety issues compared to placebo. The update trial search identified 11 new trials, which, though largely small, could make a new network meta-analysis useful. The update search for network meta-analyses yielded 13 new includes. Among other novel comparisons, tirzepatide was indirectly compared with semaglutide 2.4 mg, outperforming it at 15 mg, but not 5 or 10 mg. Data again came from merged time points.

Discussion: To our knowledge, this is the first review of network meta-analyses of glucagon-like peptide 1 receptor agonists. The evidence presented regarding weight loss is in general agreement with the wider literature, though data on tirzepatide were not as resounding as reported in some meta-analyses.

Limitations: Current network meta-analyses of glucagon-like peptide 1 receptor agonists with weight loss outcomes often lack clarity about the network meta-analysis methods, such as which trials were included. The tendency to combine multiple doses of drugs, and to merge findings from multiple time points, limits our understanding of dose and time effects.

Future work: Head-to-head trials of tirzepatide versus semaglutide 2.4 mg are required to determine their relative effectiveness and safety, as the two most promising options for weight loss, as are longer-term trials to establish the effectiveness and safety of glucagon-like peptide 1 receptor agonists when taken for durations of > 72 weeks.

Funding: This article presents independent research funded by the National Institute for Health and Care Research (NIHR) Evidence Synthesis programme as award number NIHR159924.

Keywords: GLUCAGON-LIKE PEPTIDE 1 RECEPTOR AGONISTS; NETWORK META-ANALYSIS; SAFETY; SCOPING REVIEW; WEIGHT LOSS.

Plain language summary

Some drugs that are used to treat diabetes have also been found to lower weight. We sought to review the evidence about whether they are safe and effective options for weight loss in people who are overweight or obese. We summarised recent research about six diabetic treatment drugs: semaglutide, liraglutide, tirzepatide, lixisenatide, exenatide and dulaglutide. The research we summarised looked at experiments on those drugs and compared them in something called a network meta-analysis. Essentially, this tells us about which drug is most effective, even if nobody has done an experiment to directly compare two drugs. We also looked at evidence about the safety and side effects of taking the drugs, because members of the public told us this was important. There were 22 pieces of evidence that compared the drugs of interest. Of these, we assessed 14 as being reliable enough to take data from. Two injectable drugs (semaglutide 2.4 mg and tirzepatide 10 and 15 mg) were most effective, and people taking these drugs could lose between 11.2 and 12.5 kg of weight compared to not taking any drugs (this is defined as taking a placebo). All drugs had some side effects, with things like nausea and upset stomach being common. Some more serious effects caused people to stop treatment. No one drug was particularly worse than others. There was a lack of information about long-term effectiveness and safety, and several limitations to the studies we reviewed. The drugs we reviewed have huge potential for managing a global issue, but it is important to know how effective and safe they are. Our research showed the drugs can help people lose weight, but not without some risk of side effects. More experiments are needed to help to build the evidence about these drugs.

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References

    1. World Health Organization. Factsheet: Obesity and Overweight. Geneva: World Health Organization; 2021. URL: www.who.int/news-room/fact-sheets/detail/obesity-and-overweight (accessed 31 October 2023).
    1. NHS Digital. Statistics on Obesity, Physical Activity and Diet, England, 2020. NHS Digital; 2020. URL: https://digital.nhs.uk/data-and-information/publications/statistical/sta... (accessed 12 October 2023).
    1. Department of Health and Social Care. Policy Paper: Tackling Obesity: Empowering Adults and Children to Live Healthier Lives. London: Department of Health and Social Care; 2020. URL: www.gov.uk/government/publications/tackling-obesity-government-strategy/... (accessed 20 October 2023).
    1. Andreasen CR, Andersen A, Knop FK, Vilsbøll T. How glucagon-like peptide 1 receptor agonists work. Endocr Connect 2021;10:R200–12. https://doi.org/10.1530/ec-21-0130 - PMC - PubMed
    1. National Institute for Health and Clinical Excellence. Tirzepatide for Treating Type 2 Diabetes. Technology Appraisal Guidance [TA924]. London: National Institute for Health and Clinical Excellence (NICE); 2023. URL: www.nice.org.uk/guidance/TA924 (accessed 2 November 2023).

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