Adults 2 Weeks to 8 Months, any sex, with Respiratory Tract Infection or Respiratory Syncytial Virus. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Percentage of Participants Who Experienced At Least One Solicited Injection Site Adverse Event (AE)Primary· Up to Day 5
An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. Solicited injection site AEs were monitored from Day 1 to Day 5.
with solicited injection site adverse events
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
3
Panel B: Pre-term Clesrovimab 50mg
3
Panel C: Pre-term Clesrovimab 75mg
3
Panel D1 and D2: Pre-term Clesrovimab 100mg
2
Panel E1 and E2: Full-term Clesrovimab 100mg
2
Placebo
2
without solicited injection site adverse events
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
3
Panel B: Pre-term Clesrovimab 50mg
30
Panel C: Pre-term Clesrovimab 75mg
37
Panel D1 and D2: Pre-term Clesrovimab 100mg
30
Panel E1 and E2: Full-term Clesrovimab 100mg
30
Placebo
36
Percentage of Participants Who Experienced At Least One Solicited Systemic Adverse Event (AE)Primary· Up to Day 5
An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. Solicited systemic AEs were monitored from Day 1 to Day 5.
with solicited systemic adverse events
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
2
Panel B: Pre-term Clesrovimab 50mg
8
Panel C: Pre-term Clesrovimab 75mg
9
Panel D1 and D2: Pre-term Clesrovimab 100mg
2
Panel E1 and E2: Full-term Clesrovimab 100mg
3
Placebo
9
without solicited systemic adverse events
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
4
Panel B: Pre-term Clesrovimab 50mg
25
Panel C: Pre-term Clesrovimab 75mg
31
Panel D1 and D2: Pre-term Clesrovimab 100mg
30
Panel E1 and E2: Full-term Clesrovimab 100mg
29
Placebo
29
Percentage of Participants Who Experienced At Least One Serious Adverse Event (SAE)Primary· Up to Day 545
An SAE is any untoward medical occurrence that, at any dose, results in death; is life-threatening; requires inpatient hospitalization or prolongation of existing hospitalization; results in persistent or significant injury/incapacity; is a congenital anomaly/birth defect; or is an other important medical event.
with serious adverse events (SAE)
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
1
Panel B: Pre-term Clesrovimab 50mg
4
Panel C: Pre-term Clesrovimab 75mg
1
Panel D1 and D2: Pre-term Clesrovimab 100mg
3
Panel E1 and E2: Full-term Clesrovimab 100mg
6
Placebo
6
without SAE
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
5
Panel B: Pre-term Clesrovimab 50mg
29
Panel C: Pre-term Clesrovimab 75mg
39
Panel D1 and D2: Pre-term Clesrovimab 100mg
29
Panel E1 and E2: Full-term Clesrovimab 100mg
26
Placebo
32
Area Under the Serum-Concentration Time Curve From Zero to Infinity (AUC0-∞)Secondary· At designated time points (up to 1 year post-dose)
AUC0-∞ is a measure of the extrapolated mean concentration in serum from dosing to infinity.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
1560
± 43.5
Panel B: Pre-term Clesrovimab 50mg
3520
± 22.8
Panel C: Pre-term Clesrovimab 75mg
5510
± 22.4
Panel D1 and D2: Pre-term Clesrovimab 100mg
6790
± 25.4
Panel E1 and E2: Full-term Clesrovimab 100mg
5690
± 15.9
Maximum Serum Concentration (Cmax) of ClesrovimabSecondary· At designated time points (up to 1 year post-dose)
Cmax is the highest observed serum drug concentration.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
26.3
± 19.3
Panel B: Pre-term Clesrovimab 50mg
61.7
± 21.8
Panel C: Pre-term Clesrovimab 75mg
94.5
± 20.5
Panel D1 and D2: Pre-term Clesrovimab 100mg
117
± 23.5
Panel E1 and E2: Full-term Clesrovimab 100mg
99.9
± 13.7
Time to Maximum Serum Concentration (Tmax) of ClesrovimabSecondary· At designated time points (up to 1 year post-dose)
Tmax is the time taken to reach the maximum observed plasma (Cmax) concentration of Clesrovimab.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
4.0
3.8 – 4.60
Panel B: Pre-term Clesrovimab 50mg
4.20
3.70 – 5.30
Panel C: Pre-term Clesrovimab 75mg
4.20
3.00 – 5.80
Panel D1 and D2: Pre-term Clesrovimab 100mg
4.10
3.70 – 6.00
Panel E1 and E2: Full-term Clesrovimab 100mg
4.10
3.70 – 4.90
Apparent Terminal Half-life (t1/2) of ClesrovimabSecondary· At designated time points (up to 1 year post-dose)
t1/2 is the time required for 50% of drug to be cleared from serum.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
48.8
± 34.6
Panel B: Pre-term Clesrovimab 50mg
44.6
± 10.9
Panel C: Pre-term Clesrovimab 75mg
46.1
± 15.1
Panel D1 and D2: Pre-term Clesrovimab 100mg
45.2
± 13.7
Panel E1 and E2: Full-term Clesrovimab 100mg
43.0
± 9.72
Serum Concentration of Clesrovimab on Day 7 (C7days)Secondary· Day 7
Serum concentration of clesrovimab was measured on Day 7.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
24.4
± 20.4
Panel B: Pre-term Clesrovimab 50mg
57.8
± 21.6
Panel C: Pre-term Clesrovimab 75mg
88.1
± 20.4
Panel D1 and D2: Pre-term Clesrovimab 100mg
109
± 23.0
Panel E1 and E2: Full-term Clesrovimab 100mg
92.8
± 13.3
Serum Concentration of Clesrovimab on Day 14 (C14days)Secondary· Day 14
Serum concentration of clesrovimab was measured on Day 14.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
19.4
± 22.1
Panel B: Pre-term Clesrovimab 50mg
46.8
± 20.6
Panel C: Pre-term Clesrovimab 75mg
71.1
± 19.7
Panel D1 and D2: Pre-term Clesrovimab 100mg
88.6
± 21.8
Panel E1 and E2: Full-term Clesrovimab 100mg
75.4
± 12.9
Serum Concentration of Clesrovimab on Day 90 (C90days)Secondary· Day 90
Serum concentration of clesrovimab was measured on Day 90.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
5.60
± 49.5
Panel B: Pre-term Clesrovimab 50mg
13.0
± 25.4
Panel C: Pre-term Clesrovimab 75mg
20.4
± 25.8
Panel D1 and D2: Pre-term Clesrovimab 100mg
25.2
± 28.6
Panel E1 and E2: Full-term Clesrovimab 100mg
21.1
± 18.8
Serum Concentration of Clesrovimab on Day 150 (C150days)Secondary· Day 150
Serum concentration of clesrovimab was measured on Day 150.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
2.24
± 80.6
Panel B: Pre-term Clesrovimab 50mg
4.98
± 34.2
Panel C: Pre-term Clesrovimab 75mg
8.05
± 37.7
Panel D1 and D2: Pre-term Clesrovimab 100mg
9.70
± 40.2
Panel E1 and E2: Full-term Clesrovimab 100mg
7.96
± 26.7
Serum Concentration of Clesrovimab on Day 365 (C365days)Secondary· Day 365
Serum concentration of clesrovimab was measured on Day 365.
Group
Value
95% CI
Panel A: Preterm Clesrovimab 20mg
0.0953
± 362
Panel B: Pre-term Clesrovimab 50mg
0.177
± 79.4
Panel C: Pre-term Clesrovimab 75mg
0.313
± 107
Panel D1 and D2: Pre-term Clesrovimab 100mg
0.355
± 104
Panel E1 and E2: Full-term Clesrovimab 100mg
0.248
± 63.1
Adverse events — posted to ClinicalTrials.gov
Time frame: Up to Day 545.
Reporting threshold: 5%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics, and incidence of anti-drug antibodies (ADAs) of single ascending doses of clesrovimab in healthy pre-term (born at 29 to 35 weeks gestational age) and full-term (born at \>35 weeks gestational age) infants. Participants will be randomized into 1 of 4 dose escalation panels (Panels A to D); an additional panel (Panel E) of full-term infants will receive the same dose as Panel D. Key safety and tolerability variables will be reviewed after each dose panel prior to administering the next-highest dose.
Publications & conference data
8 peer-reviewed publications reference this trial (live from Europe PMC):
NCT04938830 — Clesrovimab (MK-1654) in Infants and Children at Increased Risk for Severe Respiratory Syncytial Virus (RSV) Disease (MK
· Phase 3
· completed
NCT04767373 — Efficacy and Safety of Clesrovimab (MK-1654) in Infants (MK-1654-004)
· Phase 2, PHASE3
· completed
NCT04086472 — Phase 2a Respiratory Syncytial Virus (RSV) Human Challenge Study of Clesrovimab (MK-1654) in Healthy Participants (MK-16
· Phase 2
· completed
Other Merck Sharp & Dohme LLC trials
Trials by the same sponsor.
NCT07224477 — A Clinical Study of V540A in Healthy Female Participants (V540A-005)
· Phase 2
· not yet recruiting
NCT07302347 — A Study of Pembrolizumab in Japanese Pediatric Participants With Solid Tumors or Lymphomas and Japanese Adult Participan
· Phase 1, PHASE2
· recruiting
NCT07528508 — A Clinical Trial in Healthy Participants to Study the Effect of a Single Dose of MK-8527 on Levels of Methadone (MK-8527
· Phase 1
· not yet recruiting
NCT07513376 — A Clinical Trial of Adjuvant Intismeran (V940) With or Without Pembrolizumab Coformulated With Berahyaluronidase Alfa (M
· Phase 3
· not yet recruiting
NCT07532304 — A Clinical Trial of MK-4646 With Bictegravir/Emtricitabine/Tenofovir Alafenamide and Dolutegravir in Healthy Adult Parti
· Phase 1
· not yet recruiting
Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Merck Sharp & Dohme LLC
Last refreshed: 14 January 2025
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT03524118.