A Clinical Study of V503 in Chinese Females Who Have Previously Received a Bivalent Human Papillomavirus (HPV) Vaccine (V503-108)

A Phase 3 Randomized, Placebo-Controlled, Double-Blind Study to Evaluate the Immunogenicity and Safety of V503 in Chinese Females Aged 10 to 45 Years Who Have Previously Received a Bivalent Human Papillomavirus (HPV) Vaccine

Researchers want to learn if V503 (also called the 9-valent human papillomavirus [9vHPV] vaccine, recombinant) can induce an immune response to HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58 in Chinese females who previously received the bivalent HPV (2vHPV) vaccine.

The 9vHPV vaccine protects against diseases caused by 9 types of HPV (6, 11, 16, 18, 31, 33, 45, 52, and 58) and the 2vHPV vaccine protects against diseases caused by 2 types of HPV (16 and 18).

The goals of the trial are to learn:

• If the 9vHPV vaccine can induce an immune response to HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58 in participants who received the 2vHPV vaccine
• About the safety of the 9vHPV vaccine in prior 2vHPV vaccine recipients

Study Overview

• Status: Not yet recruiting
• Conditions: Papillomavirus Infections
• Intervention / Treatment: Biological: V503; Biological: Placebo

• Study Type: Interventional
• Enrollment (Estimated): 930
• Phase: Phase 3

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

The main inclusion criteria include but are not limited to the following:

• For participants to be enrolled in prior 2vHPV (bivalent human papillomavirus [HPV] vaccine) vaccine groups: has received at least one dose of any one of the three currently marketed 2vHPV vaccines, with the last dose administered at least one year prior to Day 1.
• For participants to be enrolled in HPV vaccine naïve groups: has never received any HPV vaccine.

Exclusion Criteria:

The main exclusion criteria include but are not limited to the following:

• Has known thrombocytopenia or any coagulation disorder that would contraindicate intramuscular injections.
• Has a history of abnormal Pap test showing low-grade squamous intraepithelial lesion (LSIL), high-grade squamous intraepithelial lesion (HSIL) or atypical squamous cells - undetermined significance (ASC-US), atypical squamous cells - cannot exclude HSIL (ASC-H), atypical glandular cells, or biopsy showing CIN, AIS, or cervical cancer.
• Has a history of external genital wart, vulvar intraepithelial neoplasia (VIN), vaginal intraepithelial neoplasia (VaIN), AIN, vulvar cancer, vaginal cancer, or anal cancer.
• Has a history of a positive test for HPV (including HPV types not in the vaccine).
• Is currently immunocompromised or has been diagnosed as having congenital or acquired immunodeficiency, human immunodeficiency virus (HIV) infection, lymphoma, leukemia, systemic lupus erythematosus (SLE), rheumatoid arthritis, juvenile rheumatoid arthritis (JRA), inflammatory bowel disease, or other autoimmune condition.
• Has a history of splenectomy.
• Has received, is receiving, or plans to receive the following immunosuppressive therapies: radiation therapy, cyclophosphamide, azathioprine, methotrexate, any chemotherapy, cyclosporin, leflunomide (Arava™), tumor necrosis factor alpha (TNF-α) antagonists, monoclonal antibody therapies (including rituximab [Rituxan™]), intravenous gamma globulin (IVIG), antilymphocyte sera, or other therapy known to interfere with the immune response. With regard to systemic corticosteroids, a participant will be excluded if the participant is currently receiving steroid therapy, has recently (defined as within 2 weeks of enrollment) received such therapy, or has received 2 or more courses of corticosteroids (orally or parenterally) lasting at least 1 week within 12 months prior to enrollment. Participants using inhaled, nasal, or topical corticosteroids are considered eligible for the study.
• Has received, is receiving, or plans to receive any immune globulin product (including RhoGAM™ [Ortho-Clinical Diagnostics]) or blood derived product other than IVIG.
• Has participated in an HPV vaccine clinical trial and has received either active agent or placebo.
• Has received any marketed HPV vaccine other than the 2vHPV vaccines.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Prior 2vHPV Vaccine Recipients Receiving V503; Participants will receive V503 at Day 1, Month 2, and Month 6	Biological: V503; V503 (9-vHPV vaccine [Types 6, 11, 16, 18, 31, 33, 45, 52, and 58]) administered as a 0.5-mL intramuscular (IM) injection on Day 1, Month 2, and Month 6; Other Names: GARDASIL®9; 9-valent HPV Vaccine
Placebo Comparator: Prior 2vHPV Vaccine Recipients Receiving Placebo; Participants will receive Placebo at Day 1, Month 2, and Month 6	Biological: Placebo; Saline administered as a 0.5-mL IM injection on Day 1, Month 2, and Month 6
Experimental: HPV Vaccine-Naïve Participants Receiving V503; Participants will receive V503 at Day 1, Month 2, and Month 6	Biological: V503; V503 (9-vHPV vaccine [Types 6, 11, 16, 18, 31, 33, 45, 52, and 58]) administered as a 0.5-mL intramuscular (IM) injection on Day 1, Month 2, and Month 6; Other Names: GARDASIL®9; 9-valent HPV Vaccine
Placebo Comparator: HPV Vaccine-Naïve Participants Receiving Placebo; Participants will receive Placebo at Day 1, Month 2, and Month 6	Biological: Placebo; Saline administered as a 0.5-mL IM injection on Day 1, Month 2, and Month 6

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of Participants Who Are Seropositive by Competitive Luminex Immunoassay (cLIA) to HPV Types 6, 11, 31, 33, 45, 52, and 58 (Month 7)	The percentage of participants who are seropositive for HPV types 6, 11, 31, 33, 45, 52, and 58 in the Prior 2vHPV Vaccine Recipients Receiving V503 group will be determined using cLIA. Seropositivity is defined as having a titer at or above the prespecified seropositivity cutoff for a given HPV type.	Up to approximately 1 month post vaccination 3 (Up to approximately Month 7)
Percentage of Participants Who Experience at Least 1 Solicited Injection-site Adverse Event (AE)	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. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. AEs such as redness/erythema, swelling, pain, and induration at the injection site are recorded. The percentage of participants who experience 1 or more injection-site AE will be reported.	Up to approximately Day 8 post any vaccination
Percentage of Participants Who Experience at Least 1 Solicited Systemic AE	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. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. Systemic AEs are those not categorized as injection-site AEs. The percentage of participants who experience 1 or more systemic AE will be reported.	Up to approximately Day 8 post any vaccination
Percentage of Participants Who Experience at Least 1 Serious AE (SAE)	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. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a study intervention. An SAE is an AE that results in death, is life threatening, results in a persistent or significant disability or incapacity, results in or prolongs an existing hospitalization, is a congenital anomaly or birth defect, or is another important medical event. The percentage of participants who experience 1 or more SAEs will be reported.	Up to approximately Month 12

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of Participants Who Are Seropositive by cLIA to HPV Types 6, 11, 16, 18, 31, 33, 45, 52, and 58	The percentage of participants who are seropositive for HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58 will be determined using cLIA. Seropositivity is defined as having a titer at or above the prespecified seropositivity cutoff for a given HPV type.	Up to approximately 1 month post vaccination (Up to approximately 7 months)
cLIA Geometric Mean Titers (GMTs) for HPV Types 6, 11, 16, 18, 31, 33, 45, 52, and 58	Antibodies to HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58 will be measured using a cLIA. Antibody titers will be expressed as milli Merck Units/milliliter (mMU/mL).	Up to approximately 1 month post vaccination (Up to approximately 7 months)
Difference in Percentage of Participants Who Are Seropositive by cLIA to HPV Types 6, 11, 16, 18, 31, 33, 45, 52, and 58 Between Prior 2vHPV Vaccine Recipients and HPV Vaccine-Naïve Participants	The percentage of participants who are seropositive for HPV types 6, 11, 16, 18, 31, 33, 45, 52, and 58 will be determined using cLIA. Seropositivity is defined as having a titer at or above the prespecified seropositivity cutoff for a given HPV type. The difference in seropositivity percentages between participants who previously received a 2vHPV vaccine and subsequently receive V503 and participants who were HPV vaccine-naïve and receive V503 will be evaluated.	Up to approximately 1 month post vaccination (Up to approximately 7 months)

Collaborators and Investigators

• Sponsor: Merck Sharp & Dohme LLC
• Investigators: Study Director: Medical Director, Merck Sharp & Dohme LLC

Publications and helpful links

Helpful Links

• Merck Clinical Trials Information

Study record dates

Study Major Dates

• Study Start (Estimated): October 9, 2026
• Primary Completion (Estimated): December 18, 2027
• Study Completion (Estimated): December 22, 2028

Study Registration Dates

• First Submitted: August 21, 2026
• First Submitted That Met QC Criteria: August 21, 2026
• First Posted (Actual): August 25, 2026

Study Record Updates

• Last Update Posted (Actual): September 4, 2026
• Last Update Submitted That Met QC Criteria: September 3, 2026
• Last Verified: September 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Pathologic Processes; Disease Attributes; Infections; Virus Diseases; Communicable Diseases; Sexually Transmitted Diseases, Viral; Sexually Transmitted Diseases; DNA Virus Infections; Tumor Virus Infections; Pathological Conditions, Signs and Symptoms; Papillomavirus Infections
• Other Study ID Numbers: V503-108

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: https://trialstransparency.msdclinicaltrials.com/pdf/ProcedureAccessClinicalTrialData.pdf

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No