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Endometrial CarcinomaPhase 3SAPPHIRENCT07860450

Two Part (Phase1b/ Phase3) Trial of Subcutaneous Dostarlimab Plus Carboplatin-Paclitaxel in Participants With Primary Advanced or Recurrent Endometrial Cancer

A Phase 3 study testing Dostarlimab and Carboplatin and paclitaxel in people with Endometrial Carcinoma and Neoplasms, Endometrial, run by GlaxoSmithKline.

Not yet recruiting

Opening soon. The study is approved but enrolment has not started yet. Sites may already take enquiries.

Sites and contacts
Official record
Search all trials

Trial summary

This is an open-label study, meaning both the researchers and participants will know which treatment is being given. The study has two parts. In Part 1, researchers will identify the most suitable SC dose. Read more about this study

Who is it for?
Ages 18 years and older, women only
Conditions the study is for
Endometrial Carcinoma, Neoplasms, Endometrial
What is being tested?
Dostarlimab and Carboplatin and paclitaxel
Type of treatment
Injection or infusion
Could I receive a placebo?
No, everyone receives an active treatment
How many people
378 participants
Where
No sites listed yet
Study dates
12 Nov 2026to 5 Nov 2032
Phase
Phase 3
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 years and older
  • Women only
  • No healthy volunteers
  • Adult, Older adult

Who may be able to join

  • Participant is at least 18 years of age (or the legal age of consent in the jurisdiction in which the trial is taking place) at the time of signing the Informed Consent Form (ICF).
  • Participant has primary Stage III or Stage IV disease or first recurrent EC.
  • Participant must have a documented Mismatch repair (MMR)/Microsatellite Instability (MSI) status.
  • Participant is capable of giving signed informed consent, including compliance with the requirements and restrictions listed in the ICF and in the protocol.
  • Participant has an Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 for Part 1 and an ECOG performance status of 0 or 1 for Part 2.
  • Participant has adequate organ function.

Who cannot join

  • Participant has history of or active autoimmune disease that has required systemic treatments within the 2 years prior to screening.
  • Participant has a history of severe allergic and/or anaphylactic reactions to chimeric, human or humanized antibodies, fusion proteins, or known hypersensitivity to carboplatin, paclitaxel or dostarlimab components or excipients.
  • Participant has received prior therapy with anti-programmed death protein 1 (PD-1), anti-programmed cell death ligand 1 (PD-L1), or anti-PD-L2 agent.
  • Participant has known uncontrolled brain or central nervous system (CNS) metastases.

Trial locations and contacts

No sites are listed yet. Contact the study team or a site near you to ask about taking part.

US GSK Clinical Trials Call Center contact

877-379-3718

GSKClinicalSupportHD@gsk.com

EU GSK Clinical Trials Call Center contact

+44 (0) 20 89904466

GSKClinicalSupportHD@gsk.com

About this study

Official title: An Open-label, Multicenter, 2-Part Study: A Phase 1b Dose Selection Followed by a Randomized Phase 3 to Evaluate the Pharmacokinetics, Efficacy, and Safety of Subcutaneous Dostarlimab Plus Carboplatin-Paclitaxel Versus Intravenous Dostarlimab Plus Carboplatin-Paclitaxel in Participants With Primary Advanced or Recurrent Endometrial Cancer (SAPPHIRE)

This is an open-label study, meaning both the researchers and participants will know which treatment is being given.

The study has two parts. In Part 1, researchers will identify the most suitable SC dose. In Part 2, participants will be randomly assigned by chance to receive dostarlimab as either an SC injection or an IV infusion. All participants will also receive carboplatin and paclitaxel. Treatment may continue for up to 3 years, with participants closely monitored throughout the study.

Being tested
Dostarlimab, Carboplatin and paclitaxel
Keywords
Endometrial Carcinoma, Dostarlimab, Carboplatin-Paclitaxel
Medical subject headings
Endometrial Neoplasms

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • DostarlimabBiological

    Dostarlimab will be administered as SC injection and IV infusion

  • Carboplatin and paclitaxelDrug

    Carboplatin and paclitaxel will be administered as an IV infusion

Study groups in NCT07860450
Study groupRoleWhat they receive
Part 1 (Phase 1b) SC dostarlimab and IV dostarlimabExperimentalParticipants will receive SC dostarlimab in Cohorts 1, 2, 4, 5 and 6, at different doses, to determine the doses of SC dostarlimab that will yield drug exposures comparable to approved IV dosing regimens. Participants in Cohort 3 will receive IV dostarlimab. Participants in all cohorts will receive carboplatin and paclitaxel. After 6 cycles, all participants will receive IV dostarlimab for up to 3 years until progression, death, or intolerable toxicities.
Receives: Biological: Dostarlimab; Drug: Carboplatin and paclitaxel
Part 2 (Phase 3): SC dostarlimab (experimental) or IV dostarlimab (standard of care)ExperimentalEligible participants will be randomly assigned to receive either SC dostarlimab or IV dostarlimab (standard of care arm) in a 1:1 ratio. Participants randomized to the experimental arm will receive SC dostarlimab in combination with carboplatin and paclitaxel for 6 cycles, followed by SC dostarlimab monotherapy for up to 3 years of treatment in total. Participants randomized to the standard of care arm will receive IV dostarlimab in combination with carboplatin and paclitaxel for 6 cycles, followed by IV dostarlimab monotherapy for up to 3 years of treatment in total.
Receives: Biological: Dostarlimab; Drug: Carboplatin and paclitaxel

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. Part 1: Serum Trough Concentration (Ctrough) After First Dose of Dostarlimab

    Measured: Up to 42 days

  2. Part 1: Area Under the Concentration-time Curve (AUC) of Dostarlimab

    Measured: Up to 42 days

  3. Part 2: Observed Ctrough of Dostarlimab

    Measured: Up to 168 days

  4. Part 2: Model-predicted (MP) AUC of Dostarlimab

    Measured: Up to 21 days

  5. Part 2: MP AUC of Dostarlimab

    Measured: Up to 168 days

Secondary outcomes (16)

  1. Part 1: Ctrough of Dostarlimab

    Measured: Up to 42 days

  2. Part 1: AUC of Dostarlimab

    Measured: Up to 42 days

  3. Part 1: Maximum Observed Concentration (Cmax) of Dostarlimab

    Measured: Up to 42 days

  4. Part 1: Time to Peak Drug Concentration (Tmax) of Dostarlimab

    Measured: Up to 42 days

  5. Parts 1 and 2: Number of Participants Experiencing Adverse Events (AEs), Serious AEs (SAEs), Treatment-emergent AEs (TEAEs) and Immune-mediated AEs (imAEs)

    Measured: Up to 39 months

  6. Parts 1 and 2: Number of Participants with TEAEs Leading to Infusion or Injection Interruption, Dose Modifications, Trial Intervention Discontinuation, or Death

    Measured: Up to 39 months

  7. Parts 1 and 2: Confirmed Overall Response Rate (ORR)

    Confirmed ORR is defined as the percentage of participants reaching confirmed complete response (CR) or confirmed partial response (PR) per RECIST 1.1 by blinded independent central review (BICR) and investigator assessment

    Measured: Up to 3 years

  8. Parts 1 and 2: Duration of Response (DoR)

    DoR per RECIST 1.1 by BICR and investigator assessment is defined as the time from the date of first documented objective response of CR or PR that is subsequently confirmed until the date of first documented progressive disease (PD) or death due to any cause, whichever comes first

    Measured: Up to 3 years

  9. Parts 1 and 2: Progression-free Survival (PFS)

    PFS is defined as the time from the date of randomization to the date of first documented objective tumor progression per RECIST 1.1 by BICR and investigator assessment or death due to any cause, whichever comes first

    Measured: Up to 3 years

  10. Parts 1 and 2: Overall Survival (OS)

    OS is defined as the time from the date of randomization to the date of death due to any cause

    Measured: Up to 3 years

  11. Part 1: Number of Participants with Antidrug Antibody (ADAs) against Dostarlimab

    Measured: Up to 39 months

  12. Part 2: Number of Participants with ADAs against Dostarlimab

    Measured: Up to 3 years

  13. Part 2: MP Ctrough of Dostarlimab

    Measured: Up to 168 days

  14. Part 2: MP Ctrough at Steady State of Dostarlimab

    Measured: Up to 168 days

  15. Part 2: MP AUC at Steady State of Dostarlimab

    Measured: Up to 168 days

  16. Part 2: MP Cmax of Dostarlimab

    Measured: Up to 168 days

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted6 Oct 2026
  2. Study start12 Nov 2026 (estimated)
  3. Primary completion5 Nov 2030 (estimated)
  4. Study completion5 Nov 2032 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase 3
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Sequential
Masking
None (open label)
Enrolment
378 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT07860450
Sponsor's protocol ID
300118
Other IDs
2025-525060-15-00, EN-35, GOG-3125, 2025
Acronym
SAPPHIRE
Status last verified
Oct 2026
First submitted
30 Sep 2026
Last updated
19 Oct 2026
Results posted
No
Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
Individual data sharing
Yes: Study Sponsor will assess requests from qualified researchers for anonymized individual patient-level data and related study documents. Data sharing is subject to certain criteria, conditions, and exceptions. For further information, refer to https://www.gsk-studyregister.com/gsk-patient-level-data-sharing-july2025.pdf

Questions about this trial

What is this clinical trial studying?

A Phase 3 study testing Dostarlimab and Carboplatin and paclitaxel in people with Endometrial Carcinoma and Neoplasms, Endometrial, run by GlaxoSmithKline.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 6 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: opening soon, as of the sponsor's last update on 19 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact US GSK Clinical Trials Call Center (877-379-3718, GSKClinicalSupportHD@gsk.com), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Part 1: Serum Trough Concentration (Ctrough) After First Dose of Dostarlimab (time frame: Up to 42 days). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT07860450.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 Oct 2026.

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