Foundayo vs Tirzepatide (Zepbound): Weight Loss at Each Dose, From Both FDA Labels

Foundayo (orforglipron) is a once-daily tablet. Tirzepatide (Zepbound) is a once-weekly injection.1,2 Orforglipron acts on the GLP-1 receptor; tirzepatide acts on GIP and GLP-1 receptors.1,2 Zepbound is approved for moderate to severe obstructive sleep apnea in adults with obesity.2 Adults without diabetes lost 11.1% of body weight at week 72 on Foundayo 17.2 mg versus 2.1% on placebo (Foundayo label, April 2026), and 20.9% on Zepbound 15 mg versus 3.1% (Zepbound label, August 2026), counting everyone who started.1,2

Tirzepatide was already approved as Mounjaro, to improve blood sugar in adults with type 2 diabetes, when the FDA approved Zepbound in November 2023.3

The table draws on the Foundayo label (April 2026), the Zepbound label (August 2026) and the FDA notice that approved Zepbound (November 2023); the weight-loss row counts everyone who started.1,2,3

For the tablet, the next step is on how to get Foundayo online.

Zepbound (tirzepatide) caused more weight loss than Foundayo (orforglipron) at every dose, in separate placebo trials. In SURMOUNT-1 (Zepbound label, August 2026), adults with obesity or overweight and no diabetes lost 15.0%, 19.5% and 20.9% of body weight at week 72 on 5, 10 and 15 mg, versus 3.1% on placebo, counting everyone who started.2 ATTAIN-1 (Foundayo label, April 2026), counted the same way, gave 7.4%, 8.3% and 11.1% on 5.5, 9 and 17.2 mg, versus 2.1%.1

Both trials ran 72 weeks in adults with obesity, or overweight plus a weight-related condition, without type 2 diabetes: ATTAIN-1 enrolled 3,127 adults (Foundayo label, April 2026) and SURMOUNT-1 enrolled 2,539 (Zepbound label, August 2026).1,2 Each row counts everyone who started.

The labels also report who lost at least 20% of body weight by week 72, counting everyone who started: 18.4% on Foundayo 17.2 mg versus 2.9% on placebo,1 and 30.0%, 50.1% and 56.7% on Zepbound 5, 10 and 15 mg versus 3.1% on placebo.2

The numbers come from two separate trials, each against placebo. They are not a direct test of one drug against the other. The Foundayo vs Zepbound comparison sets the two drugs side by side.

The Foundayo (orforglipron) and Zepbound (tirzepatide) labels both report more gastrointestinal adverse reactions on the drug than on placebo, and both carry a boxed warning about thyroid C-cell tumors.1,2 In pooled Foundayo trials, gastrointestinal adverse reactions occurred in 60%, 68% and 69% on 5.5, 9 and 17.2 mg, versus 37% on placebo (Foundayo label, April 2026).1 In pooled SURMOUNT-1 and SURMOUNT-2, 56% of Zepbound patients at every dose had them, versus 30% on placebo (Zepbound label, August 2026).2

The rates below come from the pooled trials in the Foundayo label (April 2026) and the pooled SURMOUNT-1 and SURMOUNT-2 trials in the Zepbound label (August 2026).1,2

Across the Foundayo trials, 8% of patients on the drug stopped for adverse reactions, versus 3% on placebo.1 Both labels say nausea, vomiting and diarrhea were more common during dose escalation and decreased over time.1,2

The boxed warnings rest on different animal findings. The Zepbound label says tirzepatide causes thyroid C-cell tumors in rats, that the effect rises with dose and with time on the drug, and that human relevance is unknown.2 The Foundayo label says orforglipron is not pharmacologically active in rats or mice and did not produce tumors in rodents, but Foundayo carries the class boxed warning, and the human relevance of the rodent finding has not been determined.1

This article is for information only and is not medical advice. Talk to a licensed clinician before you start, change or stop a medicine.