A Phase 2/3 interventional study of Continuous Positive Airway Pressure and Tirzepatide in Sleep Apnoea, Obesity & Overweight and Sleep Apnea Syndrome, Obstructive, sponsored by Woolcock Institute of Medical Research. Not yet recruiting at 1 site in Australia. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-29.
Sponsored by Woolcock Institute of Medical Research · Phase 2/3, Interventional, and Treatment
When used, continuous positive airway pressure (CPAP) is an effective treatment for obstructive sleep apnea (OSA), a condition that is mainly caused by overweight and obesity. However, CPAP is plagued by poor adherence and high rates of discontinued use leaving most patients undertreated and at risk of serious health complications. This study aims to test whether new effective weight loss pharmacotherapy is superior to CPAP for alleviating OSA and improving health outcomes.
The TIRZE-PAP study is a parallel randomised superiority trial comparing weight loss with weekly tirzepatide (15mg or the maximum tolerated dose) versus CPAP, in 256 people with moderate-severe OSA (AHI≥15/hr) and overweight or obesity (BMI: ≥27kg/m2). Participants allocated to CPAP will receive therapy as per usual care by their treating physician. Participants allocated to tirzepatide will undergo a 20-week stepped titration with a monthly increase of dose to a maximum 15mg (or maximum tolerated) by week 20. Outcomes will be collected over two 28-day periods commencing at baseline (pre-intervention weeks -4 to 0) and at follow-up (post-intervention weeks 48 to 52).
Exclusion Criteria:
OSA or other respiratory related criteria:
Glycaemia related criteria:
Obesity related criteria:
Other criteria:
Device: Continuous Positive Airway Pressure
Drug: Tirzepatide
Participants allocated to CPAP will be managed by their caring sleep physician as per their normal practice. Participants may also be counselled on losing weight with diet and exercise as per usual practice.
Patients allocated to weight loss with tirzepatide will be managed by the study dietitian. The tirzepatide formulation is administered subcutaneously once weekly using single-use injection pens. Participants will undergo a 20-week dose escalation phase followed by a dose maintenance phase for the remainder of the 12-month study period.
Breathing Disturbance Index (BDI)
BDI is the primary severity metric of OSA in the trial which is measured by the number of breathing disturbances per hour of sleep. This is measured using contactless mattress-based OSA monitors (SleepTracker-AI) that can automatically and reliably measure true OSA alleviation every night for the entire period of sleep.
Time frame: The mean BDI measured over 28 nights of monitoring is calculated for baseline (Weeks -4 to 0) and follow-up (Weeks 48 to 52)
Hypoxia - Oxygen Desaturation Index (ODI 3%)
ODI 3% is calculated as the number of oxygen desaturation events ≥3% per hour as a percentage of time in bed, estimated using at-home oximetry (RingConn Gen 2).
Time frame: ODI 3% will be determined as a mean of 7-10 nights of data acquired at baseline and a mean of 7-10 nights of data acquired at 12month follow-up.
Patient-Reported Outcomes Measurement Information System (PROMIS) Sleep-Related Impairment Short Form 8a Score
The PROMIS Sleep-Related Impairment Short Form 8a Score is used to assess participant-reported levels of alertness, sleepiness, and tiredness and the functional impairments associated with sleep problems or reduced alertness over the past 7 days.
Time frame: Collected at Baseline and 3,6,9 and 12 months.
Epworth Sleepiness Scale (ESS)
Subjective sleepiness scored out of 24 measured using an 8-item questionnaire.
Time frame: Collected at Baseline and 3,6,9 and 12 months.
Ambulatory Blood Pressure - Sleep Systolic Blood Pressure (SBP)
Sleep SBP is measured hourly, using an ambulatory blood pressure monitor, for a self-reported sleep period.
Time frame: Baseline and Week 52
Cardiometabolic Fasted Blood Markers - Low-Density Lipoproteins (LDL)
Low-density lipoproteins are measured from fasted venous blood.
Time frame: Screening and Week 52
Cardiometabolic Fasted Blood Markers - HbA1c
HbA1c, or glycated haemoglobin, assesses long-term glycaemic control. It is measured from fasted venous blood.
Time frame: Screening and Week 52
Hypoxic Burden
This is an oximetry-derived measurement using established algorithms. Hypoxic burden measures are quantified from nightly at-home oximetry acquired using an oximeter device (RingConn Gen 2).
Time frame: The mean nightly hypoxic burden measured over 7-10 nights of monitoring is calculated for baseline and 12 month follow-up.
Short Form Functional Outcomes of Sleep Questionnaire (FOSQ-10)
The FOSQ-10 is used to assess the impact of sleep disorders/excessive sleepiness on daily functioning.
Time frame: Baseline and 3, 6, 9 and 12 months.
Cardiometabolic Fasted Blood Markers - Glucose
Glucose is measured from fasted venous blood.
Time frame: Screening and Week 52
Cardiometabolic Fasted Blood Markers - Triglycerides [TAG]
Triglycerides are measured from fasted venous blood.
Time frame: Screening and Week 52
Cardiometabolic Fasted Blood Markers - High-Density Lipoproteins (HDL)
High-density lipoproteins are measured from fasted venous blood.
Time frame: Screening and Week 52
Cardiometabolic Fasted Blood Markers - Total Cholesterol
Total cholesterol is measured from fasted venous blood.
Time frame: Screening and Week 52
Ambulatory Blood Pressure - Sleep Diastolic Blood Pressure (DBP)
Sleep DBP is measured hourly over 24 hours using an ambulatory blood pressure monitor, segmented for a self-reported sleep period.
Time frame: Baseline and Week 52
Ambulatory Blood Pressure - Wake Systolic Blood Pressure (SBP)
Wake SBP is measured hourly over 24 hours using an ambulatory blood pressure monitor, segmented for a self-reported wake period.
Time frame: Baseline and Week 52
Ambulatory Blood Pressure - Wake Diastolic Blood Pressure (DBP)
Wake DBP is measured hourly over 24 hours using an ambulatory blood pressure monitor, segmented for a self-reported wake period.
Time frame: Baseline and Week 52
Ambulatory Blood Pressure - 24-hour Mean Arterial Pressure (MAP)
24-hour MAP is calculated hourly over 24 hours using an ambulatory blood pressure monitor. MAP = DBP + (SBP - DBP)/3
Time frame: Baseline and Week 52
Office Blood Pressure - Systolic Blood Pressure (SBP)
SBP is measured using an automated blood pressure machine after sitting quietly for 5 minutes.
Time frame: Baseline and Week 52
Office Blood Pressure - Diastolic Blood Pressure (DBP)
DBP is measured using an automated blood pressure machine after sitting quietly for 5 minutes.
Time frame: Baseline and Week 52
Anthropometry - Body Mass Index (kg/m^2)
BMI is calculated as weight in kilograms, divided by height measured in metres squared.
Time frame: Baseline and Week 52
Anthropometry - Weight (kg)
Weight is measured in kilograms.
Time frame: Baseline and Week 52
Anthropometry - Body Weight (% change)
Change in Weight is calculated as a percentage of change from baseline to 52-weeks.
Time frame: Baseline and Week 52
Anthropometry - Waist Circumference
Waist circumference is measured in centimetres, using a tape measure positioned in line with the superior iliac crest of the hip.
Time frame: Baseline and Week 52
Anthropometry - Neck Circumference
Neck circumference is measured in centimetres, using a tape measure positioned inferior to the laryngeal prominence.
Time frame: Baseline and Week 52
CAmbridge Neuropsychological Test Automated Battery (CANTAB) Multitasking Test
The Multitasking Test is used to assess executive functioning and cued attentional set shifting.
Time frame: Baseline and Week 52
CANTAB Spatial Working Memory Task
The Spatial Working Memory Task is used to assess working memory and strategy and is applicable in the assessment of general cognitive function.
Time frame: Baseline and Week 52
Psychomotor Vigilance Task (PVT)
The PVT is used to assess a participant's level of alertness.
Time frame: Baseline and Week 52
Blood-Based Neurodegeneration Biomarkers - Amyloid Beta
Amyloid Beta, a peptide associated with Alzheimer's disease, is measured from fasted venous blood.
Time frame: Baseline and Week 52
Blood-Based Neurodegeneration Biomarkers - Phosphorylated Tau
Phosphorylated Tau \[p-Tau-217\], a tau protein with added phosphate groups, is measured from fasted venous blood.
Time frame: Baseline and Week 52
Blood-Based Neurodegeneration Biomarkers - Glial Fibrillary Acidic Protein (GFAP)
GFAP, a structural protein found in astrocytic cells, is measured from fasted venous blood.
Time frame: Baseline and Week 52
Hypoxia - Time Spent With SpO2<88%
Time spent with SpO2\<88% is calculated as the time spent with oxygen saturation below 88% as a percentage of time in bed, estimated using at-home oximetry.
Time frame: Hypoxia outcomes will be determined as a mean of 7-10 nights of data acquired at baseline and a mean of 7-10 nights of data acquired at 12months.
Hypoxia - Minimum SpO2
Minimum SpO2 is calculated as the minimum oxygen saturation reached during time in bed, estimated using at-home oximetry.
Time frame: Hypoxia outcomes will be determined as a mean of 7-10 nights of data acquired at baseline and a mean of 7-10 nights of data acquired at 12 month follow-up
Hypoxia - Average Desaturation
Average desaturation is calculated as the mean of all desaturation events \>=3% during time in bed, estimated using at-home oximetry.
Time frame: Hypoxia outcomes will be determined as a mean of 7-10 nights of data acquired at baseline and a mean of 7-10 nights of data acquired at 12 month follow-up
Breathing Disturbance Index (BDI)
BDI is measured by the number of breathing disturbances per hour of sleep using contactless mattress-based OSA monitors (SleepTracker-AI).
Time frame: Nightly for 12-month treatment duration.
Anthropometry - Weight (Self-Measured)
Weight (kg) - self-measured at home
Time frame: At Baseline, 3, 6, and 9 months
Plan to share: Yes — Non-identifiable IPD will be shared upon reasonable request to the Principal Investigators.
Supporting information: Study protocol, Sap, Icf, Csr, Analytic code
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Woolcock Institute of Medical Research