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A Phase 3 Study of Once‑Monthly PF‑08653944 vs Placebo for Weight Loss in Adults with Overweight or Obesity

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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study focuses on adults who have Overweight or Obesity. The medication being tested is called PF-08653944 and is given as a subcutaneous injection once a month; a matching placebo that contains no active drug is also used.

The purpose is to determine whether the monthly treatment can achieve greater weight loss than the placebo over a period of about 72 weeks. Participants are randomly assigned to receive either the medication at one of several dose levels or the placebo, and neither the participants nor the study staff know which is administered. Injections are given every four weeks, and participants attend regular clinic visits where their weight, waist size, blood pressure, and physical function are measured.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial enrollment

    After signing the informed consent form, the patient becomes a participant in the study.

  2. Step 2

    Baseline visit

    The patient attends a clinic visit where body weight, waist circumference, and blood pressure are measured.

    A questionnaire that assesses physical function and quality of life (iwqol-lite-ct) is completed.

    Blood samples may be taken to establish health status before treatment begins.

  3. Step 3

    Randomization

    The patient is assigned, in a double‑blind manner, to receive either pf-08653944 or a matching placebo.

    The assignment is unknown to both the patient and the study staff.

  4. Step 4

    Monthly dosing period

    The patient receives a subcutaneous injection of the study medication once every month.

    The injection is given for a total of 72 weeks (approximately 1.5 years).

    The exact dose and volume are defined by the study protocol and are administered by a qualified professional.

  5. Step 5

    Regular follow‑up visits

    At each monthly visit, the patient’s body weight, waist circumference, and systolic blood pressure (sbp) are recorded.

    The patient completes the iwqol-lite-ct physical function questionnaire to track changes in quality of life.

    Any side effects or health concerns are discussed with the study team.

  6. Step 6

    Interim safety monitoring

    Throughout the 72‑week period, the patient reports any adverse events or new symptoms to the study staff.

    The study staff evaluates safety information and may adjust care as needed, while maintaining the blind.

  7. Step 7

    Final visit at week 72

    The patient attends a final clinic visit where the same measurements taken at baseline are repeated.

    The primary outcome, percent change in body weight from baseline, is calculated.

    Secondary outcomes, including absolute body weight change, waist circumference change, sbp change, and the iwqol-lite-ct score change, are also recorded.

  8. Step 8

    Study completion

    After the final assessments, the patient stops receiving study medication.

    The patient may be offered standard care or follow‑up as recommended by their health provider.

Who can join the trial?

10 criteria

  • You must be at least 18 years old (or meet the local minimum age for giving consent).
  • You may be either a man or a woman.
  • You must be able to understand the study and give written permission to take part.
  • Your body mass index (BMI) at the screening visit must be 30 kg/m² or higher. This means you are classified as obese.
  • If your BMI is between 27.0 and 30.0 kg/m², you must also have at least one of the following weight‑related health conditions:
  • Hypertension – a condition where the blood pressure is higher than normal.
  • Dyslipidemia – high levels of cholesterol or other fats in the blood.
  • Obstructive sleep apnea – a disorder where breathing stops briefly during sleep.
  • Cardiovascular disease – problems affecting the heart or blood vessels.
  • Type 2 diabetes (T2D) – a condition where the body does not use sugar properly, leading to high blood sugar.

Who cannot join the trial?

4 criteria

  • If you have gained or lost more than 5% of your body weight in the last 90 days, you cannot join the study.
  • Having type 1 diabetes or any type of diabetes other than type 2 diabetes (except a past case of pregnancy‑related diabetes that is now resolved) makes you ineligible.
  • A past episode of acute (sudden) or chronic (long‑lasting) pancreatitis excludes you, unless it was caused by gallstones and you have already had a cholecystectomy (surgical removal of the gallbladder).
  • If you or a close family member (parent, sibling, or child) has had medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia type 2 (MEN‑2), you cannot take part.
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Investigated drugs

PF-08653944 is an experimental medicine being tested for weight loss. It is given as a solution that is injected under the skin once a month. In this study, participants receive the injection to see if it can help them lose body weight over a period of about a year. Researchers are checking how well it works and whether it is safe for adults who are overweight or have obesity.

What is already known about the treatment

  • PF-08653944

    PF-08653944 is given as a subcutaneous injection of a clear solution for injection, meaning it is delivered under the skin using a small needle. It is an investigational peptide that is currently in Phase 3 clinical trials and has not yet received regulatory approval. The drug is being studied to help adults who are overweight or have obesity lose weight. It works by mimicking a natural hormone that signals the brain to reduce appetite and increase energy use, and it is classified as a peptide hormone analog.

  • Placebo to match PF-08653944

    The placebo is administered in the same way as PF-08653944, as a subcutaneous injection of a solution that looks identical but contains no active ingredient. It is used only as a control in the trial and is not an approved medication. The purpose of the placebo is to allow researchers to compare the safety and weight‑loss effects of PF-08653944 against an inactive substance in people with overweight or obesity. It is classified simply as an inert placebo with no therapeutic action.

Investigated diseases

  • Overweight

    A condition in which a person carries more body weight than is considered optimal for health, usually reflected by a body‑mass index (BMI) between 25 and 29.9. It develops gradually when energy intake consistently exceeds energy expenditure, causing a slow increase in body fat. If the imbalance continues, the excess weight can progress toward higher BMI categories.

  • Obesity

    A condition characterized by excessive accumulation of body fat, typically defined by a BMI of 30 or greater. It often results from prolonged periods of caloric surplus combined with limited physical activity. Over time, the amount of stored fat tends to increase, leading to further elevation of BMI and associated metabolic changes.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-525318-75-00Protocol codeC6491013Estimated enrolment954 patientsSponsorPfizer Inc.

sourced from the EU Clinical Trials Register and site verification

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