GS-5829 in Combination With Fulvestrant or Exemestane in Women With Advanced Estrogen Receptor Positive, HER2 Negative-Breast Cancer

Phase 1

Terminated

Conditions: Advanced Estrogen Receptor Positive HER2- Breast Cancer

Interventions: Drug: GS-5829
Drug: Exemestane
Drug: Fulvestrant

Registration Number: NCT02983604

Lead Sponsor: Gilead Sciences

Brief Summary: The primary objectives of the Phase 1b Dose Escalation part of this study are to characterize the safety and tolerability of GS-5829 in combination with exemestane or fulvestrant and to determine the maximum tolerated dose (MTD) or the recommended Phase 2 dose of GS-5829 in combination with fulvestrant in women with advanced estrogen receptor positive, HER2-negative (ER+/HER2-) breast cancer.

The primary objective of the Randomized Phase 2 Dose Expansion portion of this study is to evaluate the efficacy of GS-5829 in combination with fulvestrant compared to fulvestrant alone in women with advanced ER+/HER2- breast cancer.

This study was terminated early and the Phase 2 portion of the study was not conducted.

Detailed Description: Not available

Recruitment & Eligibility

Status: TERMINATED

Sex: Female

Target Recruitment: 14

Inclusion Criteria

Histologically or cytologically confirmed breast cancer with evidence of metastatic or locally advanced disease not amenable to resection or radiation therapy with curative intent and who have progressed during treatment with at least one prior hormonal therapy
- Phase 1b Dose Escalation - Individuals may have had unlimited prior hormonal therapy and a total of 2 prior chemotherapy regimens (adjuvant chemotherapy is considered 1 regimen). Individuals may have progressed on fulvestrant or exemestane.
- Randomized Phase 2 Dose Expansion - Individuals may have disease progression during treatment or within 12 months of completion of endocrine therapy (tamoxifen, and/or AI) in the adjuvant setting, or disease progression during treatment with endocrine therapy (tamoxifen, AI or CDK4/6 inhibitor plus AI) for advanced/metastatic disease. Individuals may have had unlimited prior hormonal therapy, but must be naive to fulvestrant in the metastatic setting. A total of 2 prior chemotherapies are allowed, however, only one for metastatic disease is permitted.
Documentation of ER positive (≥ 1% positive stained cells by local standards) based on the most recent tumor biopsy, unless bone-only disease
Documented HER2-negative tumor based on local testing on most recent tumor biopsy (immunohistochemistry score 0/1+ or negative by in situ hybridization HER2/CP17 ratio < 2 or for single probe assessment HER2 copy number < 4)
Post-, pre- or peri-menopausal women considered to be in the post-menopausal state as defined by one of the following:
- Age ≥ 60 years
- Age < 60 years and cessation of regular menses for at least 12 consecutive months in the absence of chemotherapy, tamoxifen, toremifene, or ovarian suppression and serum estradiol and follicle-stimulating hormone (FSH) level within the post-menopausal range
- Prior bilateral oophorectomy
- Pre-/peri-menopausal women can be enrolled if amenable to be treated with the luteinizing-hormone releasing hormone (LHRH) agonist, goserelin. Individuals must have commenced treatment with goserelin or an alternative LHRH agonist at least 4 weeks prior to Cycle 1 Day 1 (C1D1). If individuals have received an alternative LHRH agonist prior to study entry, they must switch to goserelin on or before Cycle 1 Day 1 (C1D1) for the duration of the study
Measurable disease defined per RECIST v. 1.1, or bone-only disease must have a lytic or mixed lytic blastic lesion that can be accurately assessed by computed tomography (CT) or magnetic resonance imaging (MRI). Individuals with bone-only disease and blastic-only metastases are not eligible
All acute toxic effects of any prior antitumor therapy resolved to Grade ≤ 1 before the start of study drug dosing (with the exception of alopecia [Grade 1 or 2 permitted] and neurotoxicity [Grade 1 or 2 permitted])
Eastern Cooperative Oncology Group (ECOG) Performance Status of ≤ 1
Life expectancy of ≥ 3 months, in the opinion of the investigator
Adequate organ function defined as follows:
- Hematologic: Platelets ≥ 100 x 10^9/L; Hemoglobin ≥ 9.0 g/dL; absolute neutrophil count (ANC) ≥ 1.5 x 10^9/L (without platelet transfusion or any granulocytic growth factors within previous 7 days of the hematologic laboratory values obtained at screening visit)
- Hepatic: aspartate transaminase (AST) / alanine transaminase (ALT) ≤ 2.5 x upper limit of normal (ULN) (if liver metastases are present, ≤ 5 x ULN); total or conjugated bilirubin ≤ 1.5 x ULN
- Renal: Serum Creatinine ≤ 1.5 x ULN or creatinine clearance (CrCl) ≥ 60 mL/min as calculated by the Cockroft-Gault method
Coagulation: International Normalized Ratio (INR) ≤ 1.2
Negative serum pregnancy test
Females of childbearing potential who engage in heterosexual intercourse must agree to use protocol specified method(s) of contraception as described in the study protocol
Females who are nursing must agree to discontinue nursing before the first dose of GS-5829
Able and willing to provide written informed consent to participate in the study

Key

Exclusion Criteria

History or evidence of clinically significant disorder, condition, or disease that, in the opinion of the investigator or the Gilead medical monitor would pose a risk to individual safety or interfere with the study evaluations, procedures, or completion
Known brain metastasis or leptomeningeal disease (Note: if treated and stable at least 6 months prior to enrollment, individual is eligible).
Uncontrolled intercurrent illness including, but not limited to, active uncontrolled infection, active or chronic bleeding event within 28 days prior to C1D1, uncontrolled cardiac arrhythmia, or psychiatric illness/social situation that would limit compliance with study requirements as judged by treating physician
Myocardial infarction, symptomatic congestive heart failure (New York Heart Association Classification > Class II), unstable angina, or serious uncontrolled cardiac arrhythmia within the last 6 months of C1D1
Major surgery, defined as any surgical procedure that involves general anesthesia and a significant incision (i.e., larger than what is required for placement of central venous access, percutaneous feeding tube) within 28 days of C1D1
Impairment of gastrointestinal (GI) function or GI disease that may significantly alter the absorption of GS-5829, including any unresolved nausea, vomiting, or diarrhea that is Common Terminology Criteria for Adverse Events (CTCAE) Grade > 1
Minor surgical procedure(s) within 7 days of enrollment or randomization, or not yet recovered from prior surgery (placement of central venous access device, fine needle aspiration, or endoscopic biliary stent ≥ 1 day before enrollment or randomization is acceptable)
History of a concurrent or second malignancy, except for: adequately treated local basal cell or squamous cell carcinoma of the skin; cervical carcinoma in situ; superficial bladder cancer; adequately treated Stage 1 or 2 cancer currently in complete remission; any other cancer that has been in complete remission for ≥ 5 years
Anti-tumor therapy (chemotherapy, chemoradiation, radiation, antibody therapy, molecular targeted therapy) within 21 days or 5 half-lives whichever is longer, of C1D1 (6 weeks for nitrosoureas, mitomycin C, or molecular agents with t1/2 > 10 days); 5 half-lives of any investigational drug; concurrent use of goserelin for pre-/peri-menopausal breast cancer and exemestane or fulvestrant per the protocol are permitted
History of long QT syndrome or whose corrected QT interval (QTc) measured (Fridericia method) at screening is prolonged (> 470 ms). Individuals who screen fail due to this criterion are not eligible to be re-screened
Prior exposure to any bromodomain (BET) inhibitors
Known hypersensitivity to the study drugs (GS 5829, fulvestrant or exemestane), the metabolites, or formulation excipients
Immunotherapy within 6 months of C1D1
Evidence of bleeding diathesis or clinically significant bleeding, within 28 days of C1D1 or history of hemoptysis of > 2.5 mL/1 teaspoon within 6 months of C1D1
Anticoagulation/antiplatelet therapy within 7 days of C1D1, including acetylsalicylic acid, low molecular weight heparin, or warfarin
Known human immunodeficiency virus (HIV) infection
Hepatitis B surface Antigen (HBsAg) positive
Hepatitis C virus (HCV) antibody positive with HCV RNA positive
Use of moderate/strong cytochrome P450 (CYP)3A4 inhibitors or moderate/strong CYP3A4 inducers within 2 weeks prior to C1D1
History of high grade esophageal or gastric varices

Note: Other protocol defined Inclusion/Exclusion criteria may apply.

Study & Design

Study Type: INTERVENTIONAL

Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
GS-5829 + exemestane (Phase 1b)	GS-5829	Participants will be sequentially enrolled at progressively higher dose levels of GS-5829 (up to 9 mg) in combination with exemestane and may continue with treatment until disease progression, unacceptable toxicity, withdrawal of consent, or death, whichever comes first.
GS-5829 + fulvestrant (Phase 1b)	GS-5829	Participants will be sequentially enrolled at progressively higher dose levels of GS-5829 (up to 9 mg) in combination with fulvestrant and may continue with treatment until disease progression, unacceptable toxicity, withdrawal of consent, or death, whichever comes first.
GS-5829 + fulvestrant (Phase 2)	GS-5829	Participants will receive GS-5829 (dose determined from Phase 1b) + fulvestrant until disease progression, unacceptable toxicity, withdrawal of consent, or death, whichever comes first.
GS-5829 + exemestane (Phase 1b)	Exemestane	Participants will be sequentially enrolled at progressively higher dose levels of GS-5829 (up to 9 mg) in combination with exemestane and may continue with treatment until disease progression, unacceptable toxicity, withdrawal of consent, or death, whichever comes first.
GS-5829 + fulvestrant (Phase 1b)	Fulvestrant	Participants will be sequentially enrolled at progressively higher dose levels of GS-5829 (up to 9 mg) in combination with fulvestrant and may continue with treatment until disease progression, unacceptable toxicity, withdrawal of consent, or death, whichever comes first.
GS-5829 + fulvestrant (Phase 2)	Fulvestrant	Participants will receive GS-5829 (dose determined from Phase 1b) + fulvestrant until disease progression, unacceptable toxicity, withdrawal of consent, or death, whichever comes first.
Fulvestrant (Phase 2)	Fulvestrant	Participants will receive fulvestrant alone until disease progression, unacceptable toxicity, withdrawal of consent, or death, whichever comes first.

Primary Outcome Measures

Name	Time	Method
Phase 1b Dose Escalation: Number of Participants Experiencing Dose Limiting Toxicities (DLTs) Through Day 28 at Each Dose Level of GS-5829	Baseline up to 28 days	A DLT was a toxicity as defined below: * Grade ≥ 4 neutropenia * Grade ≥ 3 neutropenia with fever * Grade ≥ 3 thrombocytopenia * Grade ≥ 2 bleeding (e.g., gastrointestinal, respiratory, epistaxis, purpura) * Grade ≥ 3 or higher non-hematologic toxicity, except: * Grade 3 nausea or emesis with maximum duration of 48 hours on adequate medical therapy * Grade 3 diarrhea which persists for \< 72 hours in the absence of adequate medical therapy * Grade ≥ 2 non-hematologic treatment-emergent adverse event (TEAE) that in the opinion of the investigator is of potential clinical significance such that further dose escalation would expose participants to unacceptable risk * Treatment interruption of ≥ 7 days due to unresolved toxicity * Grade 3 or Grade 4 elevation in aspartate transaminase (AST) or alanine transaminase (ALT) associated with a Grade 2 elevation in bilirubin that is at least possibly related to study drug
Randomized Phase 2 Dose Expansion: Progression-Free Survival	Baseline up to 2 years	Progression-Free Survival (PFS) was defined as the interval from date of randomization to the earlier of the first documented confirmed disease progression or death from any cause.

Secondary Outcome Measures

Name	Time	Method
Randomized Phase 2 Dose Expansion: Overall Response Rate	Baseline up to 2 years	Overall response rate (ORR) was defined as the proportion of participants who achieve complete response (CR) or partial response (PR), based on Response Evaluation Criteria in Solid Tumors (RECIST) v. 1.1 study progression criteria.
Randomized Phase 2 Dose Expansion: Clinical Benefit Rate	Baseline up to 2 years	Clinical benefit rate (CBR) was defined as the proportion of participants who achieve CR, PR, or stable disease that lasts for \> 24 weeks based on RECIST v. 1.1 study progression criteria.
Randomized Phase 2 Dose Expansion: Overall Survival	Baseline up to 2 years	Overall survival was defined as the interval from date of randomization to date of death from any cause.
Phase 1b Dose Escalation: PK Parameter: AUCtau of GS-5829	Predose, 0.5, 1, 2, 3, 4, 6, 8, and 24 hours postdose on Day 15	AUCtau is defined as concentration of drug over time (the area under the concentration verses time curve over the dosing interval).
Phase 1b Dose Escalation: Pharmacokinetic (PK) Parameter: Cmax of GS-5829	Predose, 0.5, 1, 2, 3, 4, 6, 8, and 24 hours postdose on Days 1 and 15	Cmax is defined as the maximum observed concentration of drug.
Randomized Phase 2 Dose Expansion: Overall Safety Profile as Assessed by the Percentage of Participants Experiencing Any Adverse Events (AEs), Grade 3 or 4 AEs, Treatment-Related AEs, or Abnormalities in Laboratory Tests or Electrocardiograms	Baseline up to 2 years

Trial Locations

Locations (6): Stanford Women's Cancer Center
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Stanford, California, United States
Allina Health, Virginia Piper Cancer Institute
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Minneapolis, Minnesota, United States
Medical Oncology Associates, PS (dba Summit Cancer Centers)
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Spokane, Washington, United States
Dana Farber Cancer Institute
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Boston, Massachusetts, United States
The Sarah Cannon Research Institute
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Nashville, Tennessee, United States
Baylor University Medical Center
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Houston, Texas, United States