Substance + claimed effects

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are a class of injectable peptide drugs that mimic an endogenous gut incretin hormone released after eating. The original therapeutic frame was glycaemic control in type 2 diabetes (exenatide, liraglutide); the second wave was weight loss in obesity (semaglutide 2.4 mg as Wegovy, tirzepatide as Zepbound — the latter is technically a dual GIP/GLP-1 agonist but is grouped clinically with this class). This entry covers the third wave: the effects that show up independent of, or layered on top of, the weight-loss mechanism. The brief specifically calls out cardiovascular events, kidney outcomes, sleep apnea, addiction-related behaviours, and metabolic markers; each has now been tested in at least one phase-3 randomised trial, most published in NEJM between 2016 and 2025. Weight loss is treated as a separate substance in the catalogue.

Evidence by addressing question

mechanism

GLP-1 receptors are expressed in pancreatic beta cells (the original target — augments glucose-dependent insulin secretion, suppresses glucagon), but also in stomach (slows gastric emptying), kidney (natriuresis, podocyte protection), heart and vasculature (endothelial effects, reduced inflammation), and — critically for the addiction signal — in CNS nuclei controlling appetite and reward: the arcuate nucleus of the hypothalamus, the nucleus tractus solitarius, and the mesolimbic dopamine pathway including the ventral tegmental area and nucleus accumbens. Activation of POMC/CART neurons and suppression of NPY/AgRP neurons drives satiety; activation of GLP-1 receptors in the VTA/NAc attenuates dopaminergic responses to highly palatable food and to drugs of abuse (ethanol, nicotine, cocaine, opioids in rodent models).

For the cardiovascular signal specifically, mediation analysis of SELECT showed only about a third of the MACE benefit was attributable to waist-circumference reduction Ryan 2025; the remainder is hypothesised to derive from direct anti-inflammatory effects (lower hsCRP), blood-pressure reduction (~5 mmHg systolic), lipid-profile improvement (lower triglycerides, modest LDL-C decline), reduced atherogenic ApoB-containing lipoproteins, and possibly direct vascular effects on plaque inflammation. For HFpEF, the SUMMIT secondary analysis implicated reduced plasma volume and end-organ congestion as proximate mechanisms Packer 2025. For kidneys, glomerular hyperfiltration is reduced, podocyte stress lowered, and inflammatory tubulointerstitial damage attenuated.

evidence

Cardiovascular — diabetes population. The class signal was established by the diabetes CVOT programme. LEADER (liraglutide, n=9,340, T2D + high CV risk): 13% relative risk reduction in 3-point MACE (HR 0.87, 95% CI 0.78–0.97), 22% reduction in CV death Marso 2016a. SUSTAIN-6 (semaglutide subcutaneous, n=3,297, T2D): 26% relative reduction in MACE (HR 0.74, 95% CI 0.58–0.95), driven by stroke Marso 2016b.

Cardiovascular — non-diabetic obesity. The landmark trial. SELECT (semaglutide 2.4 mg, n=17,604, BMI ≥27 + established CVD, no diabetes): MACE 6.5% vs 8.0% (HR 0.80, 95% CI 0.72–0.90, p<0.001) over a mean ~40 months; NNT 67 over the trial Lincoff 2023. The prespecified adiposity mediation analysis is the key second-order finding: benefit was consistent across all baseline-BMI strata and only ~33% of the MACE reduction was statistically mediated by waist-circumference change — the remainder is independent of weight loss Ryan 2025. This is what makes "beyond weight loss" a defensible frame and not marketing.

Heart failure with preserved EF. STEP-HFpEF (semaglutide 2.4 mg, n=529, HFpEF + obesity, no diabetes): KCCQ-CSS improved by 16.6 vs 8.7 points (estimated difference 7.8, p<0.001) and 6-minute walk distance by 21.5 m more than placebo over 52 weeks Kosiborod 2023. SUMMIT (tirzepatide, n=731, HFpEF + obesity, mixed diabetes status): composite of CV death or worsening HF event reduced 38% (HR 0.62, 95% CI 0.41–0.95); KCCQ-CSS improvement 6.9 points greater vs placebo Packer 2025. SUMMIT is the first GLP-class trial to show a hard heart-failure event reduction in HFpEF, a syndrome with almost no effective pharmacotherapy historically.

Kidney. FLOW (semaglutide 1.0 mg, n=3,533, T2D + CKD with albuminuria, on RAS inhibitor; stopped early for efficacy): composite of kidney failure, >50% eGFR loss, kidney death, or CV death reduced 24% (HR 0.76, 95% CI 0.66–0.88, p=0.0003); annual eGFR slope shallower by 1.16 mL/min/1.73 m²/year; MACE down 18%; all-cause mortality down 20% Perkovic 2024. This is the first GLP-1 trial with kidney as the primary endpoint and adds a third major mortality-reducing kidney drug to RAS-blockade and SGLT2 inhibitors.

Sleep apnea. SURMOUNT-OSA — two parallel phase-3 trials of tirzepatide in moderate-severe OSA + obesity. Trial 1 (no PAP, n=234): AHI fell 25.3 events/hour on tirzepatide vs 5.3 on placebo (estimated difference −20.0, p<0.001). Trial 2 (on PAP, n=235): AHI fell 29.3/hour vs 5.5/hour (difference −23.8, p<0.001). Hypoxic burden, hsCRP, and systolic BP all improved. About half the tirzepatide arm achieved AHI <5 or AHI 5–14 without daytime symptoms — i.e. functional remission of OSA Malhotra 2024. AHI reduction is roughly proportional to weight loss in this population, so the OSA effect is largely (though not entirely) weight-mediated; the magnitude is nonetheless what no prior OSA pharmacotherapy has achieved.

Addiction-related behaviours. The first adequately-powered RCT is Hendershot 2025: phase-2 double-blind trial of low-dose semaglutide (0.25 → 0.5 mg, well below diabetes/obesity doses) in n=48 non-treatment-seeking adults with alcohol use disorder over 9 weeks. Primary outcome (laboratory self-administration of alcohol post-treatment): grams consumed and breath alcohol concentration both lower on semaglutide. Secondary: weekly craving down significantly; smaller subgroup of smokers reduced cigarettes per day; reductions in heavy-drinking days emerged but not all weekly-consumption measures hit significance Hendershot 2025. Pharmacoepidemiologic studies of T2D patients on GLP-1s show roughly 50% lower opioid-overdose incidence vs other antidiabetic agents and 18–25% lower incidence of new substance use disorders across alcohol, cannabis, cocaine, nicotine, opioids — consistent with a class effect on mesolimbic reward, but confounded by healthier-user bias.

Metabolic markers. Across SURPASS (tirzepatide in T2D) and SURMOUNT (tirzepatide in obesity) programmes: HbA_1c reductions of 2.0–2.5 percentage points at the highest dose, systolic BP down ~6–8 mmHg, triglycerides down ~25%, hsCRP cut roughly in half, modest LDL-C reduction. Semaglutide produces similar though slightly smaller magnitudes. These changes track with weight loss but, per SELECT mediation analysis, are not fully explained by it.

protocol

All current GLP-1 RAs at this writing are injectable (oral semaglutide exists for T2D at lower potency; oral non-peptide GLP-1 agonists like orforglipron are in late-stage trials). Dosing is once-weekly for semaglutide (Wegovy/Ozempic) and tirzepatide (Zepbound/Mounjaro); once-daily for liraglutide (now largely superseded). All require a slow titration — usually four monthly steps over 16–20 weeks — to manage GI side effects. The target maintenance doses for the non-glycaemic indications are: semaglutide 2.4 mg/week (CV, HFpEF), 1.0 mg/week (kidney, in T2D), 0.5 mg/week effective in the alcohol trial; tirzepatide titrated to 10 or 15 mg/week (OSA, HFpEF). The interventions in every successful trial were on top of standard background therapy (statins, RAS inhibitors, beta-blockers, etc.) — these are add-on agents, not replacements.

contraindications

Boxed warning across the class: personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 (rodent C-cell tumour signal; no consistent human signal but the warning is conservative). Pancreatitis history is a relative contraindication — pancreatitis rates in trials are 0.1–0.3% absolute and not consistently higher than placebo, but mechanism plausibility and case reports keep this on the list. Gallbladder disease risk is elevated, particularly with rapid weight loss. Diabetic gastroparesis is a relative contraindication given gastric emptying delay. Pregnancy and breastfeeding: no human safety data; class is contraindicated and discontinuation 2 months before conception is advised. Combining with insulin or sulfonylureas raises hypoglycaemia risk in diabetics. The European Medicines Agency reviewed a suicidal-ideation signal from spontaneous reports in 2023; the FDA in 2025 requested removal of the boxed warning after finding no signal in clinical trial data or large pharmacoepidemiologic cohorts FDA 2025 Wang 2024.

failure-modes

Discontinuation reverses most gains. STEP 4 withdrawal: continuing semaglutide produced an additional 7.9% weight loss; switching to placebo regained 6.9% in 48 weeks Rubino 2021. STEP 1 trial extension: within a year of stopping, participants regained roughly two-thirds of weight lost and cardiometabolic improvements (BP, lipids, HbA1c) reverted toward baseline Wilding 2022. The CV, kidney, OSA, and HFpEF benefits all observed in trials were on-treatment effects; the durability of "beyond-weight-loss" benefits after discontinuation is not established.

Lean mass loss. About 25–40% of total weight lost on GLP-1s is lean mass, primarily skeletal muscle, when no concurrent resistance training or high protein intake is in place. This is roughly the proportion seen with diet-induced weight loss generally, not unique to the drug — but the absolute magnitude is larger because the total weight loss is larger. Adequately powered resistance training (2–3 sessions/week) and ≥1.2 g protein/kg/day blunts the loss substantially.

GI tolerability dropout. Nausea, vomiting, diarrhoea, constipation are dose-limiting in 5–15% of trial participants. Mostly resolves with slower titration; small fraction never tolerate.

Compounded peptides. US shortage-driven compounding pharmacies sold non-FDA-reviewed semaglutide and tirzepatide at lower prices through 2024–2025; impurity and dosing-error reports accumulated. With shortage now resolved, compounding for these molecules is no longer FDA-permitted.

misconceptions

"It's just a weight loss drug." SELECT's mediation analysis (only ~33% of MACE benefit explained by waist-circumference change) is the cleanest refutation. The CV benefit appears at non-weight-loss doses in diabetics (LEADER, SUSTAIN-6). The kidney benefit in FLOW is barely weight-mediated.

"You'll be on it forever." Probably yes if the goal is sustained weight loss, possibly yes for the CV/kidney indications (the trials studied continuous use); we don't yet know if a finite course of GLP-1 imprints durable benefit after stopping. STEP extension data suggest not, for weight; the question for hard CV outcomes is open.

"It only works in obese people." Diabetes CVOTs predate the obesity programme; benefit holds across BMI in SELECT Ryan 2025. The Hendershot AUD trial used low doses without requiring obesity.

"GLP-1 causes depression." Spontaneous report signal investigated by EMA and FDA; large pharmacoepidemiologic studies and the FDA's 2025 review found no causal signal FDA 2025.

audience

The clearest beneficiaries by trial data:

• Adults with established atherosclerotic CVD plus BMI ≥27 (SELECT population) — strongest evidence for adding it on for secondary prevention.
• Adults with T2D plus CKD (eGFR 25–75 + albuminuria) on RAS inhibitor (FLOW population) — first-line addition.
• Adults with moderate-severe OSA + obesity who don't tolerate or fully benefit from CPAP (SURMOUNT-OSA).
• Adults with symptomatic HFpEF + obesity (STEP-HFpEF, SUMMIT).
• Adults with T2D and high CV risk (LEADER, SUSTAIN-6).

Population variability in addiction signals — see §5.

practicalities

Prescription required, all current formulations. List prices at writing (late 2025/early 2026): semaglutide 2.4 mg (Wegovy) ~$675/month wholesale after Nov 2025 cut from ~$1,350; tirzepatide (Zepbound) similar trajectory; with US savings-card or self-pay programmes, $199–$400/month is accessible for many. Medicare pricing ~$245/month from 2026 negotiated list. Insurance coverage for weight loss alone remains spotty; coverage when prescribed for diabetes is standard; coverage for the CV, kidney, or OSA indication is currently expanding as new labels are added. Cold-chain storage; supply-chain disruptions through 2023–2024 are mostly resolved.

history

Exendin-4, isolated from the Gila monster's saliva in the 1990s, was the prototype peptide; synthesised as exenatide and approved in the US in 2005 for T2D. Liraglutide (Victoza, T2D 2010; Saxenda, obesity 2014). The shift from glycaemic-control framing to weight-loss framing to cardiovascular-prevention framing tracks three RCT waves: SUSTAIN/LEADER (~2016, diabetes + heart), STEP/SURMOUNT (~2021, obesity), SELECT/FLOW/SURMOUNT-OSA/STEP-HFpEF/SUMMIT (2023–2025, the "beyond weight loss" wave). The class is on track to become one of the most-prescribed drug families of the next decade.

The credibility range

Optimist case

Five separate phase-3 NEJM trials in the last 24 months have hit primary endpoints across five different organ systems: vascular (SELECT), renal (FLOW), pulmonary (SURMOUNT-OSA), cardiac (SUMMIT), and the prior diabetes CVOTs (LEADER, SUSTAIN-6). The CV benefit in non-diabetic obesity (SELECT) is largely independent of weight loss — meaning these molecules have intrinsic atheroprotective, anti-inflammatory, or vascular effects that operate beyond the metabolic improvements. Combined with the diabetes-cohort signal showing CV benefit at glycaemic-control doses, the case that GLP-1 RAs are a fundamentally pleiotropic class — like statins or ACE inhibitors in their breadth — is well-supported. Add the addiction signal (mechanistically grounded in mesolimbic GLP-1 receptors, supported by a placebo-controlled AUD trial and consistent pharmacoepidemiology) and this becomes a generational drug class. The CV NNT (~67 over 3 years in SELECT) is comparable to high-intensity statins in primary prevention; the FLOW kidney effect is comparable to SGLT2 inhibitors in CKD.

Skeptic case

Every trial was sponsored by the molecule's manufacturer (Novo Nordisk for semaglutide, Eli Lilly for tirzepatide); the publication and PR ecosystem around these drugs is among the most aggressive in pharma. Effect sizes for hard endpoints, while real, are modest (20% relative MACE reduction is large by population-health standards but not transformative for individual patients; ARR ~1.5% over 3 years). The dose-response between weight loss and CV benefit is weaker than expected if weight loss were the operative mechanism — but that could equally mean the analyses haven't found the right marker, not that the drug has "extra" benefits. Trial populations are highly selected (motivated, mostly white, mostly Western, low dropout); real-world adherence will be lower and benefits attenuated. Long-term safety beyond 4–5 years is unknown for the non-glycaemic indications. Discontinuation reverses most gains, meaning the implicit recommendation is lifelong injection of an expensive drug — a public-health proposition that is not obviously affordable or sustainable at population scale. Muscle mass loss is a real concern in older populations, where the risk-benefit calculus is sensitive to sarcopenia. The "GLP-1 cures everything" framing in lay media is way ahead of what the evidence supports, especially for the addiction signal (one phase-2 trial with n=48).

Author's call

The cardiovascular and renal benefits are settled science at this point — multiple replicating large RCTs, consistent direction, mechanistic plausibility, and partial independence from the weight-loss pathway. evidence: 5, controversy: 2 (residual debate about which mechanism does the work, not about whether it works). The HFpEF signal is now two trials; durable. The OSA effect is dramatic but largely weight-mediated (still: clinically meaningful, since the weight loss is reliable). The addiction signal is the most exciting and most uncertain — promising mechanism, supportive pharmacoepidemiology, but one small RCT; treat as hypothesis-generating, not actionable yet. The substance is one of the highest-impact pharmaceutical advances of the last 25 years for cardiovascular and renal prevention in adults with metabolic disease, and reasonable people can argue about appropriate population-level use. The catch — lifelong injection, high cost, lean mass loss, discontinuation rebound — is real and shapes both effort and cost scoring.

Stakeholder + incentive map

• Manufacturers — Novo Nordisk (semaglutide franchise), Eli Lilly (tirzepatide franchise). Highly motivated to expand indications; trial designs and disclosure are mostly clean, but the broader narrative is sponsor-shaped.
• Cardiology / nephrology / endocrinology guideline bodies — incorporating SELECT and FLOW into 2024–2025 guideline updates (ESC, ADA, KDIGO).
• Compounding pharmacies — financial incentive to keep the shortage frame alive; now largely shut out by FDA.
• Payors — pushing back hard on weight-loss coverage; expanding coverage as indications shift to CV/kidney/HF where cost-effectiveness models look better.
• Online communities — heavy patient organising around access, dosing protocols, side-effect management; substantial signal value but also commercial cross-currents (telehealth clinics, microdosing influencers).
• Bariatric surgery field — competitive pressure; many bariatric programmes now offer GLP-1 as first-line or bridge.
• Skeptic camp — long-term safety advocates, sarcopenia researchers, addiction-medicine specialists wary of off-label hype on the substance-use signal.

Population variability

• Diabetes status — CV benefit holds across diabetic and non-diabetic obese populations. Kidney trials limited to T2D; FLOW analogues in non-diabetic CKD are not yet reported.
• Sex — Trials underrepresent women in older diabetes CVOTs; SELECT was 28% female; subgroup analyses do not show heterogeneity.
• Ethnicity — Trial populations skew white; effect sizes in Asian populations may differ given different baseline BMI thresholds and metabolic phenotypes (tirzepatide trials in East Asia suggest preserved efficacy).
• BMI band — Benefit consistent across BMI categories in SELECT mediation analysis Ryan 2025; the addiction trials used non-obesity dosing in non-obese patients.
• Age — STEP-HFpEF age-spectrum analysis showed preserved benefit in older adults but with higher discontinuation. Sarcopenia risk is age-dependent.
• Baseline cardiovascular risk — Greater absolute benefit in higher-risk populations (established CVD in SELECT, advanced CKD in FLOW).

Knowledge gaps

• Cardiovascular benefit in primary prevention (no prior CV event, no CKD, no diabetes) — not tested.
• Kidney benefit in non-diabetic CKD — trial pending.
• Durability of CV/kidney benefit after discontinuation — uncertain; trial extensions ongoing.
• Addiction signal — needs phase-3 RCTs at treatment-seeking doses with longer follow-up and abstinence endpoints.
• Long-term safety beyond 4–5 years — particularly pancreatic, thyroid, sarcopenia signals over a decade.
• Effects in adolescents (limited data) and elderly >75 (underrepresented).
• Oral non-peptide GLP-1 agonists (orforglipron etc.) — whether the "beyond weight loss" effects transfer to oral formulations at scale.
• Combination with SGLT2 inhibitors — additive vs overlapping benefits in CKD/HF (FLOW subgroup analysis suggests additive).

Scope. The brief named five consequences: cardiovascular events, kidney outcomes, sleep apnea, addiction-related behaviours, and metabolic markers. All five are covered in the body. Weight loss itself is intentionally excluded — treated as a separate entry per the project convention, and the brief explicitly framed this entry as "beyond weight reduction." Glycaemic control in type 2 diabetes is mentioned as the historical indication but not built out, since that lives in standard diabetes care rather than the "beyond weight loss" frame the entry is meant to occupy.

Rating difficulties.

• mood scored 2 rather than 0 or 3. The addiction-behaviour signal is real but rests on one small RCT (n=48) plus pharmacoepidemiology; the felt-mood effect outside addiction contexts is not clean. Bumping above 2 would over-claim from a single small trial.
• energy scored 2 because it lifts in symptomatic populations (HFpEF, OSA) but is not a general-population energy intervention. Healthy users do not report a consistent energy gain, and GI nausea during titration cuts the other way for the first months.
• longevity scored 4 not 5. The mortality reductions are large for a drug class (20% all-cause in FLOW, 19% CV mortality in SELECT) but the populations are high-risk; we don't have evidence in primary prevention. A 5 would imply population-level mortality bending across all comers.
• beauty_cumulative scored 1 rather than 0. Body-composition shifts over years have a slow appearance effect, but rapid fat loss is associated with the "Ozempic face" cosmetic downside; net effect is small and not the reason to take it.
• controversy scored 2. The CV/kidney/HFpEF benefits are accepted across cardiology, nephrology, sleep medicine. Real ongoing debate exists on long-term safety, muscle loss, durability after discontinuation, and the addiction signal — but not on whether the drug works. A 3 would imply competing camps on efficacy, which is no longer the state of the field.

Hard decisions during the write.

• Action set to decide rather than do. Prescription-only, indication-specific, requires clinician engagement and trade-off discussion. do would mis-signal a self-directed action.
• Cadence weekly. Daily liraglutide is now largely superseded; the molecules with the new trial data (semaglutide, tirzepatide) are weekly. Oral once-daily orforglipron is in pipeline but not yet on shelves.
• Contraindications. Added thyroid-condition for MTC/MEN2, diabetes-medication for the hypoglycaemia risk when combining with sulfonylureas or insulin, plus pregnancy and breastfeeding. Did not add kidney-disease — the trial evidence shows benefit in CKD, not harm.
• Addiction signal positioned cautiously. The mesolimbic mechanism is strong and the Hendershot 2025 trial is well-conducted, but n=48 is hypothesis-strength, not actionable. The article frames it that way; the dossier walks the broader pharmacoepidemiology more fully.

Separate-entry candidates flagged by this write.

• The weight-loss case itself — already implicitly planned.
• SGLT2 inhibitors as the parallel modern cardiometabolic class; pairs with this one.
• HFpEF as a condition entry (chronicity, symptom forecast, treatment ladder).
• ApoB and Lp(a) — risk-marker entries that intersect with GLP-1 lipid effects.
• Bariatric surgery as the historical comparator.
• "Ozempic face" / sarcopenic weight loss as a more general topic on weight-loss body-composition outcomes.

Future-link candidates. Once those exist: cross-link from this entry's out-of-scope section.

Status. Set to draft. The addiction angle in particular benefits from a reviewer with substance-use clinical context confirming the framing is honest about the strength of one phase-2 trial.