Insulin

Insulin is the original peptide therapy and the reference molecule for everything else on this site. The therapeutic arc begins with Banting, Best, Collip, Campbell, and Fletcher, Canadian Medical Association Journal 1922, 12:141–146 — the Toronto group's preliminary report of "pancreatic extracts in the treatment of diabetes mellitus," following the January 11, 1922 administration of an early extract at Toronto General Hospital and the refined Collip preparation of January 23, 1922 that produced the first unambiguous clinical response. Within twelve months Eli Lilly had a commercial product; over the following decades insulin was sequenced (Sanger, 1955), chemically synthesized (Katsoyannis and Du, 1963–1965), and crystallographically solved (Hodgkin, 1969). The recombinant human insulin produced by Genentech in 1979 became the first commercial recombinant-DNA drug when Humulin reached the U.S. market in 1982 — the technological precondition for somatropin, glucagon, every GLP-1 receptor agonist, and effectively every peptide drug in the modern formulary.

The clinical evidence base is the deepest of any peptide therapy. The Diabetes Control and Complications Trial (DCCT 1993) randomized 1,441 type 1 diabetes patients to intensive or conventional insulin therapy for a mean 6.5-year follow-up; intensive therapy reduced retinopathy development by 76% in primary prevention and slowed progression by 54% in secondary prevention, with concordant 39–60% reductions in microalbuminuria, clinical nephropathy, and clinical neuropathy. The UK Prospective Diabetes Study (UKPDS 33 1998) randomized 3,867 newly-diagnosed type 2 diabetes patients to intensive glucose control (sulfonylurea or insulin) versus conventional dietary therapy and reported a 25% reduction in microvascular endpoints over median 10-year follow-up. Together the two trials established that glycemic control matters, that insulin can deliver it, and that microvascular complications respond to sustained glycemic-burden reduction — the framework against which every subsequent diabetes-therapeutics trial is benchmarked.

The cardiovascular and cancer-safety record has been built across the following two decades. The ORIGIN trial (Gerstein, Bosch, Dagenais et al., N Engl J Med 2012, 367:319–328, n=12,537 with dysglycemia, 6.2-year median follow-up) reported a neutral effect of glargine on cardiovascular outcomes and no excess cancer at any site — the rebuttal to the breast-cancer signal raised in Hemkens, Grouven, Bender et al., Diabetologia 2009, 52:1732–1744, a German registry of 127,031 patients that had reported a dose-dependent association between glargine and malignancy. The DEVOTE trial (Marso, McGuire, Zinman et al., N Engl J Med 2017, 377:723–732, n=7,637, high-CV-risk type 2 diabetes) showed degludec non-inferior to glargine U100 on major adverse cardiovascular events and superior on severe hypoglycemia (4.9% vs 6.6%) — the basis for the modern preference for degludec over older basal analogs.

The once-weekly analog is the most significant insulin development of 2024–2026. The ONWARDS Phase 3 program for icodec spans six trials; the two most consequential are ONWARDS-1 (Rosenstock, Bain, Gowda et al., N Engl J Med 2023, 389:297–308, insulin-naïve type 2 diabetes, n=984, weekly icodec vs daily glargine U100, superior HbA1c reduction at 52 weeks with slightly higher clinically-significant hypoglycemia) and ONWARDS-2 (Philis-Tsimikas, Asong, Franek et al., Lancet Diabetes Endocrinol 2023, 11:414–425, basal-insulin-treated type 2 diabetes, n=526, switching from daily degludec to weekly icodec, superior HbA1c reduction at 26 weeks). Weekly basal insulin and weekly GLP-1 receptor agonists together reframe diabetes management as a once-weekly subcutaneous-injection paradigm, with daily multi-dose regimens reserved for type 1 disease and type 2 patients requiring prandial coverage. The FDA approved Awiqli for adult type 2 diabetes in March 2026 after a 2024 complete response letter citing hypoglycemia concerns in type 1 disease; EU and Swiss approvals preceded the US approval by approximately 18 months.

The biohacker context for insulin sits in a different register from most peptides on this site. Insulin is occasionally injected by competitive bodybuilders post-workout in the belief that pharmacological hyperinsulinemia enhances glucose and amino-acid delivery to muscle. The case-report literature is consistent: Evans and Lynch, Br J Sports Med 2003, 37:356–357 documented severe hypoglycemia in a non-diabetic bodybuilder injecting insulin for muscle-mass purposes; Heidet, Abdel Wahab, Ebadi et al., J Emerg Med 2019, 56:279–281 reported a 30-year-old bodybuilder presenting in coma from cryptic insulin injection. Insulin is the single most lethal pharmacological agent in the bodybuilding-enhancement category — more dangerous than any anabolic steroid, GH product, or peptide on this site — because the therapeutic-to-toxic ratio is narrow, severe hypoglycemia develops over minutes rather than hours, and the dose producing a marginal anabolic effect is close to the dose producing neuroglycopenic catastrophe. The peptide alternatives surveyed in the muscle preservation decision guide have nothing approaching this rapid-lethality profile in a non-diabetic person.

The GLP-1 receptor agonist era has reshaped insulin's clinical role substantially. A decade ago the standard type-2-diabetes escalation pathway after metformin failure ran through sulfonylureas to basal insulin to basal-bolus regimens; the GLP-1 receptor pharmacology dossier describes how that pathway has now been displaced for many patients by GLP-1 RAs and dual-agonists (liraglutide, semaglutide, tirzepatide) as second-line therapy. GLP-1 RAs lower glucose without the hypoglycemia and weight-gain liabilities that constrain insulin titration, and the cardiovascular outcome trials in the GLP-1 class (LEADER) have built an evidence base insulin does not match. Insulin remains essential in type 1 diabetes — where the pathophysiology is absolute deficiency and replacement is the entire therapeutic strategy — and in advanced type 2 disease beyond what any oral or GLP-1-class agent can supplement.

Modern type 1 management has shifted decisively toward closed-loop systems. The iDCL trial (Brown et al. 2019, n=168, Tandem Control-IQ vs sensor-augmented pump) reported an 11-percentage-point improvement in time-in-range at six months — the regulatory basis for the current hybrid closed-loop ecosystem (Control-IQ, Medtronic 780G, Beta Bionics iLet). Pumps universally use rapid-acting analog with algorithm-modulated basal delivery; weekly icodec sits outside this paradigm and will likely remain a non-pump option. On the access side, Semglee (insulin glargine-yfgn) became the first FDA-approved interchangeable insulin biosimilar in July 2021, substitutable for Lantus at the pharmacy without prescriber intervention; the Davies, Dahl, Heise et al., Diabet Med 2017, 34:1340–1353 review framed the earlier European biosimilar entrance. The biosimilar pathway has begun to constrain originator pricing without producing the compression observed in monoclonal-antibody biosimilars, particularly after the 2023 $35 monthly insulin cap for Medicare beneficiaries.

The honest framing has three parts. Insulin is the most clinically-validated peptide therapy ever marketed, with a century of safety data in indicated populations. The modern analog and once-weekly era extends but does not displace the underlying receptor pharmacology characterized through the 1970s–1990s; the analog-versus-human-insulin question is pharmacokinetic predictability and hypoglycemia risk rather than fundamental mechanism. And insulin's role in 2026 is being reshaped from the outside by the GLP-1 RA class — a rebalancing that will continue across the coming decade as outcome trials accumulate.