A Phase 3 interventional study of Arm A: Gedatolisib + Palbociclib + Fulvestrant and Arm B: Ribociclib + Fulvestrant in Breast Cancer, sponsored by Celcuity Inc. Recruiting at 239 sites in 25 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-09.
Sponsored by Celcuity Inc · Phase 3, Interventional, and Treatment
This is a Phase 3, open-label, randomized, clinical trial evaluating the efficacy and safety of gedatolisib and palbociclib plus endocrine therapy for the treatment of patients with locally advanced or metastatic HR+/HER2- advanced breast cancer.
This is a Phase 3, open-label, randomized clinical trial evaluating the efficacy and safety of gedatolisib plus endocrine therapy and palbociclib versus endocrine therapy and ribociclib for the treatment of patients with advanced (inoperable) or metastatic hormone receptor positive, human epidermal growth factor receptor 2 negative (HR+/HER2-) breast cancer. Following completion of the screening procedures to determine eligibility, patients will be assigned manually according to their endocrine sensitivity status to either Study 1 (endocrine-resistant) or Study 2 (endocrine-sensitive) and subsequently be randomized 1:1 to either investigational treatment or standard-of-care control.
Study 1 is expected to enroll approximately 440 subjects with treatment-naïve endocrine-resistant ABC whose cancer progressed while receiving or within 12 months of completing adjuvant endocrine therapy. The trial will evaluate the efficacy and safety of the investigational arm (gedatolisib combined with palbociclib and fulvestrant - Arm A) compared to the control arm (ribociclib combined with fulvestrant - Arm B).
Study 2 is expected to enroll approximately 740 subjects with treatment-naïve endocrine-sensitive ABC whose cancer relapsed or progressed 12 months or more after completion of adjuvant endocrine therapy, or those with de novo metastatic disease without prior endocrine therapy exposure. The trial will evaluate the efficacy and safety of the investigational arm (gedatolisib combined with palbociclib and letrozole - Arm C) compared to the control arm (ribociclib combined with letrozole - Arm D).
Gedatolisib is an intravenously administered pan-PI3K/mTOR inhibitor. Palbociclib and ribociclib are CDK4/6 inhibitors. Fulvestrant is a selective estrogen receptor degrader (SERD). Letrozole is an aromatase inhibitor (AI).
14,825 studies on the registry are indexed under Breast Neoplasms; 3,319 are open to participants now.
This study's planned enrollment of 1,180 is above the median of 72 across 10,896 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →Celcuity Inc is the lead sponsor of 5 studies on the registry; 3 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Permitted prior therapies:
i. Study 1: if disease progression was on or within event occurred >6 months of discontinuation after completion of CDK4/6 inhibitor portion of treatment.
ii. Study 2: if disease progression event occurred >12 months after completion of CDK4/6 inhibitor portion of treatment.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HER2
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adjuvant and neoadjuvant
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Biopsy and archival tissue
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Measurable disease
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Leptomeningeal disease
Cancer that has spread to the leptomeninges, the thin layers covering the brain and spinal cord, and the fluid between them. It is not the same as brain metastases.
Criteria often treat it separately, and many studies leave it out even where treated brain metastases are allowed.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Subjects with treatment-naïve endocrine-resistant ABC.
Drug: Arm A: Gedatolisib + Palbociclib + Fulvestrant
Subjects with treatment-naïve endocrine-resistant ABC.
Drug: Arm B: Ribociclib + Fulvestrant
Subjects with treatment-naïve endocrine-sensitive ABC.
Drug: Arm C: Gedatolisib + Palbociclib + Letrozole
Subjects with treatment-naïve endocrine-sensitive ABC.
Drug: Arm D: Ribociclib + Letrozole
Drug pages: Gedatolisib · Palbociclib · Fulvestrant
Drug: Gedatolisib Participants will receive intravenous (IV) gedatolisib once weekly for 3 weeks (Days 1, 8, 15) followed by 1 week off Other Names: • PF-05212384 Drug: Palbociclib Participants will receive oral palbociclib on days 1-21 of each 28-day cycle. Other Names: • IBRANCE Drug: Fulvestrant Participants will receive intramuscular (IM) fulvestrant every 2 weeks during Cycle 1 and then every 4 weeks Other Names: • Faslodex
Also known as: PF-05212384, IBRANCE, Faslodex
Drug pages: Ribociclib · Fulvestrant
Drug: Ribociclib Participants will receive oral ribociclib on Days 1-21 of each 28-day cycle Other Names: • KISQALI® Drug: Fulvestrant Participants will receive intramuscular (IM) fulvestrant approximately every 2 weeks during Cycle 1 then approximately every 4 weeks Other Names: • Faslodex
Also known as: KISQALI®, Faslodex
Drug pages: Gedatolisib · Palbociclib · Letrozole
Drug: Gedatolisib Participants will receive intravenous (IV) gedatolisib once weekly for 3 weeks (Days 1, 8, 15) followed by 1 week off Drug: Palbociclib Participants will receive oral palbociclib on days 1-21 of each 28-day cycle. Drug: Letrozole Participants will receive oral letrozole daily.
Also known as: PF-05212384, IBRANCE, FEMARA
Drug: Ribociclib Participants will receive oral ribociclib on Days 1-21 of each 28-day cycle Drug: Letrozole Participants will receive oral letrozole daily.
Also known as: KISQALI®, FEMARA
Progression Free Survival (PFS)
PFS is defined as the time from randomization to death or the first documented progression, whichever occurs first, confirmed by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 criteria, as determined based on blinded independent central review (BICR)
Time frame: From date of randomization to the date of death due to any cause, up to approximately 48 months
Overall Survival (OS)
OS is defined as the length of time from randomization until the date of death from any cause method, where PFS is defined as the time from randomization to death or the first documented progression, whichever occurs first, confirmed by Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 criteria, as determined based on blinded independent central review (BICR)
Time frame: From date of randomization to the date of death due to any cause, up to approximately 48 months
Overall Response Rate (ORR)
Percentage of subjects who achieved an objective response according to RECIST v1.1 criteria (complete response \[CR\] or partial response \[PR\]) as assessed by BICR)
Time frame: Up to approximately 48 months
Duration of Response (DOR)
Time from the assessment of initial response (PR or better) to death or first documented radiologically confirmed disease progression as assessed by BICR, whichever occurs first
Time frame: Up to approximately 48 months
Time to Response (TTR)
Time to Response (TTR)
Time frame: Time from randomization to the first assessment of PR or better as assessed by BICR
Clinical Benefit Rate (CBR)
Percentage of subjects with CR or PR; or with stable disease (SD) lasting \>24 weeks as assessed by BICR
Time frame: Up to approximately 48 months
Quality of Life (QOL) Functional Assessment of Cancer Therapy - Breast Trial Outcome Index (FACT-B TOI)
Time frame: From baseline to 30 Day Safety Follow-up
Adverse Events
Type, incidence, severity (as graded by the NCI CTCAE v5.0), seriousness, and relationship to study medications of Adverse Events and any laboratory abnormalities
Time frame: Up to approximately 48 months
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Started Jul 2025 (actual). Primary completion is estimated for Mar 2029, 44 months after the start.
Of 272 industry-sponsored phase 3 interventional studies under Breast Neoplasms, half reached primary completion within 40 months of starting (the median), counting those still running; a quarter within 28 and three quarters within 63. This study's planned 44 months is close to that.
Counting every sponsor, half of 600 studies reached it within 59 months; a quarter within 36 and three quarters within 96.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drugs tested here: Gedatolisib · Palbociclib · Fulvestrant · Letrozole
Celcuity Inc