A Phase 1 interventional study of G1T48 and Palbociclib in Carcinoma, Ductal, Breast, Breast Cancer Female and Breast Neoplasm, sponsored by G1 Therapeutics, Inc.. Completed at 15 sites in 7 countries. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-21.
Sponsored by G1 Therapeutics, Inc. (part of Pharmacosmos A/S) · Phase 1, Interventional, and Treatment
Among 50 studies in Carcinoma, Ductal, Breast with a site in United States — 4 open to participants now, 9 under way, 2 of them phase 3. Carcinoma, Ductal, Breast · United States.
Among the 50 studies in Carcinoma, Ductal, Breast with a site in United States, this one is the 13th largest by enrollment of the 42 interventional ones that give a count, is one of 2 that started in 2018, is one of 8 in phase 1, and was the 43rd registered.
86 studies on the registry are indexed under Carcinoma, Ductal, Breast; 7 are open to participants now.
Browse Carcinoma, Ductal, Breast studies →4 of the 50 studies in Carcinoma, Ductal, Breast with a site in United States are open now. Recruiting first, the newest first:
Natera, Inc. · Sites in United States
Ages 18+
Memorial Sloan Kettering Cancer Center · Sites in United States
Ages 18+
Memorial Sloan Kettering Cancer Center · Sites in United States
Ages 45+ · Women only
Stanford University · Sites in United States
Ages 18+ · Women only
A study can be open while its sites in United States have not opened yet or have stopped. Only those recruiting at a site in United States →
Of the 7 Carcinoma, Ductal, Breast studies recruiting now, 5 set no upper age limit and 2 stop at 75 or younger; none take children under 18; none take healthy volunteers.
This study: 18 Years and older · female · no healthy volunteers.
The full table on the hub →This tab as a report to print or save as PDF → With an account.
50 studies; the count open now beside each. This study's row is marked.
A study in two phases is counted once above. Listed by phase, each with its combined phases: Phase 1 11 · Phase 2 16 · Phase 3 7
First in 1997; this study’s year is marked. 2 started in 2018.
By drug class, each counting the studies that test any of its medicines:
This study's enrollment of 107 is above the median of 92 across 69 interventional studies indexed under Carcinoma, Ductal, Breast.
Median enrollment 48 across the 42 interventional studies, 74 across the 5 observational. Of the 37 that completed or were terminated, 11 (30%) have results posted.
This tab as a report to print or save as PDF → With an account.
7 of 50 have an industry lead sponsor. The 10 most frequent:
This study is registered under G1 Therapeutics, Inc., one of the names counted as Pharmacosmos A/S. Under that name alone:
G1 Therapeutics, Inc. is the lead sponsor of 16 studies on the registry; none are open to participants now.
Of its 12 completed or terminated interventional studies of FDA-regulated products, 10 (83%) have results posted.
Pharmacosmos A/S has 2 studies filed under Carcinoma, Ductal, Breast — fewer than ten, so there is no comparison to draw.
5 of the studies in Carcinoma, Ductal, Breast with a site in United States that are under way reach primary completion within a year, 1 of them phase 3. Phase 3 first, then by date:
| Study | Primary completion |
|---|---|
| NCT01953588Phase 3Alliance for Clinical Trials in OncologyFulvestrant and/or Anastrozole in Treating Postmenopausal Patients With Stage II-III Breast Cancer Undergoing Surgery | 2027-04-01 |
| NCT03909282Stanford UniversitySurgical Excision vs Neoadjuvant Radiotherapy+Delayed Surgical Excision of Ductal Carcinoma | 2026-12 |
| NCT00909909Rutgers, The State University of New JerseyRadiation Therapy in Treating Women With Early Stage Breast Cancer | 2027-07 |
| NCT05837767Memorial Sloan Kettering Cancer CenterA Study of Radiation Therapy to Treat Solid Tumor Cancer That Has Spread to Soft Tissue | 2027-07-24 |
| NCT04084730Memorial Sloan Kettering Cancer CenterStudy of 3-Day Partial Breast Radiation Therapy in Women With Breast Cancer | 2027-08-30 |
Add all 5 to your calendar (.ics) → With an account.
Among the 50 studies in Carcinoma, Ductal, Breast with a site in United States, from their registry updates:
Nothing recorded among them since 2026-09-25.
This tab as a report to print or save as PDF → With an account.
This is a study to investigate the potential clinical benefit of G1T48 as an oral selective estrogen receptor degrader (SERD) alone and in combination with palbociclib, a cyclin dependent kinase 4/6 (CDK 4/6) inhibitor, in patients with estrogen receptor-positive, HER2-negative metastatic breast cancer.
The study is an open-label design, consisting of 3 parts: dose-finding portion including food effect (Part 1), G1T48 monotherapy expansion portion (Part 2), and G1T48 in combination with palbociclib expansion portion (Part 3). All parts include 3 study phases: Screening Phase, Treatment Phase, and Survival Follow-up Phase. The Treatment Phase begins on the day of first dose with study treatment and completes at the Post-Treatment Visit. Approximately, 184 patients may be enrolled in the study.
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.
For Parts 1 and 2, patients must satisfy 1 of the following criteria for prior therapy:
For Part 3, patients must satisfy 1 of the following criteria for prior therapy:
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.
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).
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.
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
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.
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.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
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.
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.
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.
Line of therapy
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
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.
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.
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.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
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.
Patients in Part 1 will receive a single oral dose of G1T48 on Cycle 1 Day -3 and will begin once-daily dosing on Cycle 1 Day 1. The initial dose cohort shall receive an identified starting dose and subsequent cohorts shall receive higher doses based on the safety and PK (pharmacokinetic(s)) data obtained from the previous dose levels.
Drug: G1T48
In Part 1, additional G1T48 cohort(s) of 8 patients may be enrolled to assess the effect of different fat content meals (eg, high fat, moderate fat, or low-fat) on the rate and extent of the absorption of G1T48. Patients will receive a single oral dose of G1T48 on Cycle 1 Day -10 and on Cycle 1 Day -3. Patients will begin G1T48 once-daily dosing on Cycle 1 Day 1.
Drug: G1T48
Patients in Part 2 will receive G1T48 once-daily at the dose determined in Part 1.
Drug: G1T48
Patients in Part 3 will receive G1T48 once-daily at the dose determined in Part 2 in combination with palbociclib once-daily on Days 1 to 21 of each 28-day cycle.
Drug: G1T48 · Drug: Palbociclib
oral SERD
Also known as: Rintodestrant
CDK 4/6 Inhibitor
Also known as: Ibrance
Dose Limiting Toxicity
Time frame: Cycle 1 Day -3 to Cycle 1 Day 28
Recommended Phase 2 dose
G1T48 alone and in combination with palbociclib; progression-free survival (PFS)
Time frame: 12 months
Number of Treatment Related Adverse Event, including Abnormal Laboratory Events
All AEs, including clinical laboratory, vitals signs, physical examinations and ECGs will be analyzed in all patients receiving study drug(s) from the signing of the informed consent until 30 days after the last dose of study medication(s).
Time frame: 21 months
Tumor response based on RECIST, Version 1.1
G1T48 alone and in combination with palbociclib;
Time frame: 21 months
Effect of food on bioavailability of G1T48
Time frame: Part 1, Cycle 1 Day -10 to Cycle 1 Day 1.
Pharmacokinetics of G1T48 and metabolites: Maximum Plasma Concentration (Cmax)
Time frame: Part 1, Cycle 1 Day -3 to Cycle 2 Day 1. Part 2, Cycle 2 Day 1 to Cycle 3 Day 1. Part 3, Cycle 2 Day 1 to Cycle 3 Day 1.
Pharmacokinetics of G1T48 and metabolites: Area under Curve - plasma concentration (AUC)
Time frame: Part 1, Cycle 1 Day -3 to Cycle 2 Day 1. Part 2, Cycle 2 Day 1 to Cycle 3 Day 1. Part 3, Cycle 2 Day 1 to Cycle 3 Day 1.
Pharmacokinetics of G1T48 and metabolites: Plasma: terminal half life (T1/2)
Time frame: Part 1, Cycle 1 Day -3 to Cycle 2 Day 1. Part 2, Cycle 2 Day 1 to Cycle 3 Day 1. Part 3, Cycle 2 Day 1 to Cycle 3 Day 1.
Pharmacokinetics of G1T48 and metabolites: Plasma - Volume of distribution
Time frame: Part 1, Cycle 1 Day -3 to Cycle 2 Day 1. Part 2, Cycle 2 Day 1 to Cycle 3 Day 1. Part 3, Cycle 2 Day 1 to Cycle 3 Day 1.
Pharmacokinetics of palbociclib: Plasma - Trough concentration
Time frame: Part 3, Cycle 2 Day 1 to Cycle 3 Day 1.
Ran from May 2018 to primary completion in Sep 2022, 52 months.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Sep 2026. You cannot join it, but the record below documents what was studied.
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