---
title: "STEP 1: Semaglutide Phase 3 Results | Primara Labs"
url: https://www.primaralabs.com/research/trials/step-1
source: Primara Labs, markdown mirror of the HTML page
---

# STEP 1

In STEP 1, a phase 3 trial of semaglutide in adults with BMI of 30 or greater (27 or greater with at least one weight-related coexisting condition), without diabetes (n=1,961), mean body weight fell 14.9% on 2.4 mg over 68 weeks, against 2.4% on placebo (treatment-policy estimand; Wilding JPH et al. N Engl J Med 2021;384:989-1002).

Primara Labs sells some of the compounds covered here. Every figure on this page links to its source and the date it was checked.

Updated 24 September 2026

Semaglutide Explained: STEP, SUSTAIN and SELECT Trials (Philippines)2:07·[Transcript and chapters](https://www.primaralabs.com/videos/semaglutide)

## Results

Mean percent change in body weight by arm, as each source reports it. Navy bars are the trial arms, grey bars the comparator. Bars from different trials are not a head-to-head comparison: populations, durations and estimands differ.

## Side effects reported

STEP 1: Discontinuation for adverse events is not given in the abstract; discontinuation for gastrointestinal adverse events was 4.5% against 0.8% on placebo.

Design

## Trial design and sources

Compound

Semaglutide

Phase

3

Population

Adults with BMI of 30 or greater (27 or greater with at least one weight-related coexisting condition), without diabetes

Participants randomised

1,961

Duration

68 weeks

Primary endpoint

Coprimary: percentage change in body weight and weight reduction of at least 5% (week 68)

Estimand

treatment-policy

Read out

10 February 2021

Discontinuation for adverse events is not given in the abstract; discontinuation for gastrointestinal adverse events was 4.5% against 0.8% on placebo. The estimand is described in the abstract (effects regardless of treatment discontinuation or rescue) without being named.

-   Wilding JPH et al. N Engl J Med 2021;384:989-1002 [open](https://doi.org/10.1056/NEJMoa2032183) · checked 23 September 2026
-   ClinicalTrials.gov NCT03548935 [open](https://clinicaltrials.gov/study/NCT03548935) · checked 23 September 2026
-   Registry: NCT03548935

Questions

## STEP 1, answered

### What did STEP 1 find?

In STEP 1, a phase 3 trial of semaglutide in adults with BMI of 30 or greater (27 or greater with at least one weight-related coexisting condition), without diabetes (n=1,961), mean body weight fell 14.9% on 2.4 mg over 68 weeks, against 2.4% on placebo (treatment-policy estimand; Wilding JPH et al. N Engl J Med 2021;384:989-1002).

### What side effects were reported in STEP 1?

STEP 1: Discontinuation for adverse events is not given in the abstract; discontinuation for gastrointestinal adverse events was 4.5% against 0.8% on placebo.

Related

## More on semaglutide

-   [STEP 2](https://www.primaralabs.com/research/trials/step-2)
-   [STEP 3](https://www.primaralabs.com/research/trials/step-3)
-   [STEP 4](https://www.primaralabs.com/research/trials/step-4)
-   [STEP 5](https://www.primaralabs.com/research/trials/step-5)
-   [STEP 8](https://www.primaralabs.com/research/trials/step-8)
-   [SELECT](https://www.primaralabs.com/research/trials/select)
-   [SURMOUNT-5](https://www.primaralabs.com/research/trials/surmount-5)
-   [Evidence Map: Semaglutide](https://www.primaralabs.com/research/evidence#semaglutide)
-   [Semaglutide 15mg](https://www.primaralabs.com/marketplace/semaglutide-15mg)