Mounjaro is the brand name for tirzepatide, a synthetic peptide that activates two receptors. The Mounjaro prescribing information names tirzepatide as the active ingredient and describes the injection as a once-weekly agonist at the receptors for glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1).
The name on the pen is the product. A single-dose pen holds 0.5 mL of one chain, based on the GIP sequence, with a twenty-carbon fatty diacid attached so the chain binds albumin and can be dosed once a week. The injection is subcutaneous. One active ingredient, tirzepatide, activates both receptors. Where the word peptide is a shop category, it usually means a dry vial.
Tirzepatide is metabolized by proteolytic cleavage of the peptide backbone, beta-oxidation of the C20 fatty diacid and amide hydrolysis.
A GIP sequence is modified to act on two receptors
The description is a parts list. Tirzepatide contains aminoisobutyric acid at positions 2 and 13, a C-terminal amide, and a lysine at position 20 attached to 1,20-eicosanedioic acid through a linker. The molecular weight is 4813.53 daltons. The empirical formula is C225H348N48O68. Aminoisobutyric acid is not one of the twenty amino acids used to build ordinary human proteins. With the C-terminal amide and the fatty diacid, that residue is what turns a GIP-based chain into a synthetic peptide. The label gives the fatty diacid a job: it enables albumin binding and prolongs the half-life. Tirzepatide is 99 percent bound to plasma albumin. The elimination half-life is about five days.
The metabolism line is what settles the peptide question in the label's own words. Proteolytic cleavage cuts the peptide backbone. Beta-oxidation breaks down the C20 fatty diacid. The amide is hydrolyzed. Intact tirzepatide is not observed in urine or feces.
A single-dose pen or vial contains the drug in 0.5 mL, at 2.5, 5, 7.5, 10, 12.5, or 15 mg. The solution is clear and colorless to slightly yellow. Alongside tirzepatide, that presentation contains sodium chloride (4.1 mg), sodium phosphate dibasic heptahydrate (0.7 mg), and water for injection. The multi-dose vial and the single-patient-use KwikPen hold four doses in 2.4 mL, and benzyl alcohol, glycerin, and phenol join the inactive ingredients. Tirzepatide is the active ingredient in the single-dose pen, the vial, and the KwikPen alike.
In circulation the chain selectively binds and activates both the GIP receptor and the GLP-1 receptor, the targets of the native hormones. The same passage says it enhances first- and second-phase insulin secretion and reduces glucagon, both in a glucose-dependent manner. The sequence itself is the subject of the tirzepatide page. The pen holds one modified peptide, a measured volume, and the inactive ingredients in the solution.
SURPASS-2 compared the pen with semaglutide 1 mg
The indications are a diabetes label. Mounjaro is indicated as an adjunct to diet and exercise to improve glycemic control in adults and in pediatric patients 10 years of age and older with type 2 diabetes mellitus, and to reduce the risk of major adverse cardiovascular events — cardiovascular death, non-fatal myocardial infarction, or non-fatal stroke — in adults with type 2 diabetes mellitus who are at high risk for these events. The trial tables also record a change in body weight. The indications stay with glucose and cardiovascular risk.
SURPASS-2 is the comparison that belongs next to an Ozempic question, and it is narrower than a pairing of brand names. It was a 40-week trial, open-label, and double-blind only with respect to the Mounjaro dose assignment. It randomized 1,879 adults with type 2 diabetes mellitus and inadequate glycemic control on stable doses of metformin alone, to Mounjaro 5, 10, or 15 mg once weekly or to semaglutide 1 mg once weekly. The Mounjaro label names that comparator as semaglutide. Ozempic is semaglutide, and its maintenance doses are 0.5 mg, 1 mg, and 2 mg, so 1 mg is one of those maintenance doses, with 2 mg above it. What the Ozempic pen contains is covered in Is Ozempic a peptide?.
Table 5 is the week-40 result. In the modified intent-to-treat columns, 469 patients were on Mounjaro 15 mg and 468 were on semaglutide 1 mg. The least-squares mean change in HbA1c was -2.3 percentage points on 15 mg and -1.9 percentage points on semaglutide 1 mg, from a baseline mean of 8.3 percent in both columns. The estimated difference versus semaglutide was -0.5 percentage points (95 percent confidence interval -0.6 to -0.3). Least-squares mean body weight fell 11.2 kg on 15 mg and 5.7 kg on semaglutide 1 mg, a difference of -5.5 kg (95 percent confidence interval -6.4 to -4.6). Both differences carry the table's mark of a p-value below 0.001 for superiority versus semaglutide, adjusted for multiplicity. The label states that 10 mg and 15 mg produced a statistically significant reduction in HbA1c compared with semaglutide 1 mg. Adults already on metformin, one semaglutide dose, 40 weeks.
A second brand does not make a second molecule
Zepbound is the weight-management brand of the same molecule. The Zepbound prescribing information indicates tirzepatide, in combination with a reduced-calorie diet and increased physical activity, to reduce excess body weight and maintain weight reduction long term in adults with obesity or adults with overweight in the presence of at least one weight-related comorbid condition, and to treat moderate to severe obstructive sleep apnea in adults with obesity.
In a storefront, peptide tends to mean a dry vial and a purity claim. Mounjaro is a sterile solution, a strength in milligrams, and a list of inactive ingredients. The contents have a description: a GIP sequence, aminoisobutyric acid at positions 2 and 13, a C-terminal amide, a C20 fatty diacid on lysine 20, molecular weight 4813.53 daltons. That description is the pen. A vial with tirzepatide written on the glass still has to match it.