A new ACR Open Rheumatology study ↗ tracking GLP-1 receptor agonist initiation in 60,198 patients with rheumatic and musculoskeletal diseases (RMDs) reports that the drug class went from 0.1% of RMD prescriptions in 2018 to 6.8% in 2024. At 12 months, semaglutide ↗ users lost an average of 5.8% body weight; tirzepatide ↗ users lost 8.2%, a 2.2 percentage-point real-world advantage that confirms the head-to-head superiority pivotal trials suggested. Patients without diabetes lost 1.8% more weight than those with diabetes, an additional differentiator that prescribers in this population should hold.
The data set. American College of Rheumatology's Rheumatology Informatics System for Effectiveness (RISE) registry, retrospective cohort design, adults with RMD prescribed semaglutide (72%) or tirzepatide (28%) between 2018 and 2024. Mean age 57. Mean BMI 36.4. 80.5% female (RMD populations are heavily female because most autoimmune RMDs are sex-skewed). 54.9% had comorbid diabetes. Patients with an evaluation-and-management visit before their first GLP-1 prescription were classified as new users for the primary analysis. The 12-month weight-change endpoint used multivariable linear regression with logistic models for ≥5%, ≥10%, and ≥15% weight-loss thresholds.
The growth trajectory. 0.1% of RMD patients on GLP-1 RAs in 2018. 6.8% in 2024. A 68-fold increase over six years. The growth tracks the broader GLP-1 commercial trajectory but reflects the specific patient population's disease burden: RMD patients are typically older and heavier than the general obesity population, with substantial comorbidity burden and concurrent immunomodulator use that affects weight management strategies. The decision to start a GLP-1 in this population includes considerations the general obesity-treatment population does not face.
The TZP-vs-SEM comparison. 8.2% vs 5.8% mean weight loss at 12 months, treatment difference 2.2 percentage points (95% CI 1.9-2.5). The pivotal SURMOUNT and STEP trials suggested a similar magnitude of advantage for tirzepatide over semaglutide in head-to-head obesity populations; the RMD real-world cohort confirms it in patients with substantial comorbidity. The 2.2-point real-world difference is meaningful: at the population level, it translates to an additional three to four pounds for an average-weight RMD patient over 12 months.
The diabetes-status differential. Patients without diabetes lost 1.8% more weight than those with diabetes (CI 1.5-2.1). The pattern is well-established in the broader obesity-trial literature: T2D patients have blunted weight-loss responses to GLP-1 drugs compared with non-diabetic obesity patients, reflecting differences in baseline metabolic state, insulin resistance, and possibly receptor sensitivity. The new study confirms this in the RMD population, which is the relevant clinical context for rheumatologists deciding which patients are most likely to benefit.
What this means for rheumatology practice. RMD patients carry elevated cardiovascular risk and frequently struggle with weight management because chronic pain and disease activity limit physical activity options. The 5.8% to 8.2% weight loss range represents clinically meaningful benefit in this population, with the additional caveat that GLP-1 GI tolerability may interact with disease-modifying antirheumatic drugs (DMARDs) and biologics that have their own GI burden. The 6.8% prescription penetration in 2024 is below what the underlying clinical eligibility would support, suggesting room for further uptake as rheumatologists become more comfortable with the class.
What this is not. A clinical trial. The retrospective registry design supports real-world utilization analysis but cannot establish causality, control for confounding, or compare the GLP-1 class against alternative weight-loss strategies (bariatric surgery, structured weight-management programs). Patients selecting into GLP-1 therapy in the RMD population may differ systematically from non-prescription patients in ways that affect weight-change outcomes.
The platform read. The GLP-1R ↗ and GIPR ↗ target pages on peptidemodel anchor the metabolic-disease coverage. The TZP-vs-SEM real-world differential at 2.2 percentage points reflects what dual-receptor agonism delivers in chronic-condition populations, which is the design principle the platform's GLP-1(7-36) amide ↗ card and the broader multi-agonist target pages support as ongoing reference material.
What 2027 has to clarify. Whether GLP-1 prescriptions in RMD continue growing past the 6.8% baseline as additional efficacy data accumulate. Whether the drug-drug interaction profile with DMARDs and biologics produces meaningful adverse signals in larger longitudinal cohorts. And whether the TZP-vs-SEM differential in RMD persists or compresses as both drugs reach steady-state market penetration.