18 and older, female only, with Advanced Estrogen Receptor Positive HER2- Breast Cancer. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Phase 1b Dose Escalation: Number of Participants Experiencing Dose Limiting Toxicities (DLTs) Through Day 28 at Each Dose Level of GS-5829Primary· 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
Group
Value
95% CI
GS-5829 4 mg + Exemestane
1
GS-5829 4 mg + Fulvestrant
0
GS-5829 6 mg + Fulvestrant
0
GS-5829 9 mg + Fulvestrant
0
Phase 1b Dose Escalation: Pharmacokinetic (PK) Parameter: Cmax of GS-5829Secondary· 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.
Day 1
Group
Value
95% CI
GS-5829 4 mg + Exemestane
318.25
± 107.844
GS-5829 4 mg + Fulvestrant
247.00
± 3.464
GS-5829 6 mg + Fulvestrant
244.00
± 9.000
GS-5829 9 mg + Fulvestrant
518.00
± 60.811
Day 15
Group
Value
95% CI
GS-5829 4 mg + Exemestane
389.666
± 105.6424
GS-5829 4 mg + Fulvestrant
370.333
± 52.5483
GS-5829 6 mg + Fulvestrant
375.666
± 67.0919
GS-5829 9 mg + Fulvestrant
634.000
± 46.6690
Phase 1b Dose Escalation: PK Parameter: AUCtau of GS-5829Secondary· 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).
Group
Value
95% CI
GS-5829 4 mg + Exemestane
4989.809
± 1655.8737
GS-5829 4 mg + Fulvestrant
5218.820
± 1326.2407
GS-5829 6 mg + Fulvestrant
3937.709
± 667.4396
GS-5829 9 mg + Fulvestrant
7638.847
± 938.3444
Adverse events — posted to ClinicalTrials.gov
Time frame: First dose date to last dose date (average: 14.5 weeks; maximum: 53 weeks) plus 30 days.
Reporting threshold: 5%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
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.
Publications & conference data
8 peer-reviewed publications reference this trial (live from Europe PMC):
NCT07115368 — Study of GS-1219 in Participants With HIV-1
· Phase 1
· terminated
NCT06784973 — Study of Obeldesivir to Treat Children With Respiratory Syncytial Virus (RSV) Infection
· Phase 2
· terminated
NCT06683482 — A Qualitative Study on Advanced Breast Cancer Patients and Their Caregivers in Spain
· completed
NCT06613685 — Study of Oral Weekly GS-1720 and GS-4182 Compared With Biktarvy in People With HIV-1 Who Have Not Been Treated
· Phase 2, PHASE3
· terminated
NCT06585150 — Study of Obeldesivir to Treat Nonhospitalized Adults With Acute Respiratory Syncytial Virus (RSV) Infection
· Phase 2
· terminated
Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by Gilead Sciences
Last refreshed: 7 August 2019
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT02983604.