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.
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
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.
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.
- Conditions
- Endometrial Carcinoma, Neoplasms, Endometrial
- 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 group | Role | What they receive |
|---|---|---|
| Part 1 (Phase 1b) SC dostarlimab and IV dostarlimab | Experimental | Participants 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) | Experimental | Eligible 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.
Part 1: Serum Trough Concentration (Ctrough) After First Dose of Dostarlimab
Measured: Up to 42 days
Part 1: Area Under the Concentration-time Curve (AUC) of Dostarlimab
Measured: Up to 42 days
Part 2: Observed Ctrough of Dostarlimab
Measured: Up to 168 days
Part 2: Model-predicted (MP) AUC of Dostarlimab
Measured: Up to 21 days
Part 2: MP AUC of Dostarlimab
Measured: Up to 168 days
Secondary outcomes (16)
Part 1: Ctrough of Dostarlimab
Measured: Up to 42 days
Part 1: AUC of Dostarlimab
Measured: Up to 42 days
Part 1: Maximum Observed Concentration (Cmax) of Dostarlimab
Measured: Up to 42 days
Part 1: Time to Peak Drug Concentration (Tmax) of Dostarlimab
Measured: Up to 42 days
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
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
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
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
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
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
Part 1: Number of Participants with Antidrug Antibody (ADAs) against Dostarlimab
Measured: Up to 39 months
Part 2: Number of Participants with ADAs against Dostarlimab
Measured: Up to 3 years
Part 2: MP Ctrough of Dostarlimab
Measured: Up to 168 days
Part 2: MP Ctrough at Steady State of Dostarlimab
Measured: Up to 168 days
Part 2: MP AUC at Steady State of Dostarlimab
Measured: Up to 168 days
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.
- First posted6 Oct 2026
- Study start12 Nov 2026 (estimated)
- Primary completion5 Nov 2030 (estimated)
- Study completion5 Nov 2032 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Endometrial CarcinomaStudies of the same condition, open and under way.
- More trials run by GlaxoSmithKlineThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
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)
Sponsor and investigators
- Lead sponsor
- GlaxoSmithKline
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- GSK Clinical Trials, Study director, GlaxoSmithKline
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