Semaglutide outcome trials

Three questions, three populations

In STEP 1, adults with overweight or obesity and without diabetes had a mean body-weight change of minus 14.9 per cent at week 68 with semaglutide, against minus 2.4 per cent with placebo. That is the weight-management result.

SELECT enrolled 17,604 adults with pre-existing cardiovascular disease and overweight or obesity, without diabetes. Major adverse cardiovascular events were reduced: hazard ratio 0.80, with a 95 per cent confidence interval of 0.72 to 0.90 and P less than 0.001. For health beyond the scales, SELECT is my strongest exhibit, with the cardiovascular disease that defined the participants kept in view.

FLOW studied 3,533 participants with type 2 diabetes and chronic kidney disease. Its major kidney-disease endpoint combined kidney failure, a fall in eGFR of 50 per cent or more, or death from kidney or cardiovascular causes. The hazard ratio was 0.76, with a 95 per cent confidence interval of 0.66 to 0.88.

These are separate questions, with separate entry criteria. Bringing them together enlarges the clinical picture without making every result apply to every person.

Appetite biology

Semaglutide is a modified copy of GLP-1, a gut hormone involved in glucose control and appetite. Its modifications resist enzymatic breakdown and attach a fatty side chain that binds albumin reversibly. That design extends its circulation to about a week. Its GLP-1 receptor activity supports glucose-dependent insulin secretion, suppresses inappropriate glucagon release and affects appetite circuitry, alongside slower gastric emptying; the safety review describes the pharmacological context.

The albumin connection makes it a useful neighbour for CJC-1295, whose attachment is covalent. Both albumin attachments seem ingenious to me. The completed outcome studies make semaglutide's clinical account much more substantial than the chemical resemblance alone would suggest.

A head-to-head weight trial

Semaglutide also has evidence that complicates its reputation. In SURMOUNT-5, a direct comparison involving 751 adults with obesity, mean weight change at 72 weeks was minus 20.2 per cent with tirzepatide and minus 13.7 per cent with semaglutide, with P less than 0.001.

I welcome a comparison that can make an established medicine look less exceptional on a particular outcome. This one concerns mean weight loss in that trial. The cardiovascular and kidney results above come from different studies and remain questions in their own right.

The tolerability cost

The semaglutide safety review describes predominantly mild-to-moderate, transient gastrointestinal effects, with nausea in roughly a third of patients and increased biliary-disease risk. Digestive intolerance is a leading reason for discontinuation and clusters around dose escalation.

The boxed warning concerns thyroid C-cell tumours observed in rodents. A personal or family history of medullary thyroid carcinoma or MEN-2 is a contraindication; a clear increase in human thyroid cancer has not been established. Acute pancreatitis is a class warning, and rapid glucose correction in people with pre-existing diabetic retinopathy carries its own concern. Pregnancy is a contraindication. Those qualifications deserve space even beside a strong outcome record.

Reports of quieter “food noise,” fewer cravings, sulfurous burps, bowel changes and fatigue are anecdotal accounts. They can convey the texture of an experience, while clinical evidence supplies a different kind of information about benefits and harms.

Semaglutide is an approved prescription medicine for several indications. A compounded semaglutide preparation has no FDA approval, and research material does not inherit the identity or quality of the manufactured product used in a trial. I trust these clinical findings within the studied medicine, setting and population.