A Study to Compare the Steady-State Bioavailability of Injectable Letrozole SIE and Oral Letrozole in Post-Menopausal Women With Hormone Receptor Positive Early Breast Cancer
SIE-1
An Open-Label, One-Sequence Study to Evaluate the Steady-State Comparative Bioavailability of Quarterly Letrozole SIE and Once Daily 2.5 mg Oral Letrozole (Femara®) in Post-Menopausal Women Treated With Endocrine Therapy for Hormone Receptor-Positive Early Breast Cancer. (SIE-1)
Planned date reported by the registry; this milestone is not confirmed as achieved.
Study Completion
October 2028
Estimated
Planned date reported by the registry; this milestone is not confirmed as achieved.
Brief Summary
The study aims to compare the amount of the drug letrozole that gets into the bloodstream after multiple doses of the quarterly injection Letrozole SIE, versus multiple doses of the standard oral daily tablet of letrozole (Femara®), in women who have gone through menopause and have received treatment for hormone receptor-positive early breast cancer. Participants must have completed at least five years of hormone therapy with at least two of those years with letrozole before starting their participation in the study. Women who have completed four years of hormone therapy are also eligible if their doctor considers them at low risk of cancer returning.
Registry Overview
Registry-reported information. Elapsed time and enrollment totals alone do not measure study progress or recruitment pace.
Recruitment status
recruiting
Estimated enrollment
120 participants
Study completion date
October 2028
Estimated
Planned date reported by the registry; this milestone is not confirmed as achieved.
Listed locations
4 countries · 21 sites
Trial Relationships
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Related Scientific Literature
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Study Timeline
Dates and qualifiers reported by the registry. Estimated dates do not confirm that a milestone has occurred.
First Submitted
January 22, 2026
Actual (reported)
First Posted
February 10, 2026
Actual (reported)
Study Start
June 8, 2026
Actual (reported)
Primary Completion
May 2028
Estimated
Planned date reported by the registry; this milestone is not confirmed as achieved.
Study Completion
October 2028
Estimated
Planned date reported by the registry; this milestone is not confirmed as achieved.
Letrozole SIEEarly breast cancerPharmacokineticsBioavailabilitySafetyEndocrine therapyInjectable
Outcome Measures
Primary Outcomes (1)
Area under the concentration-time curve within a dosing interval at Steady-State (SS AUCtau)
Individual and mean area under the concentration-time curve within a dosing interval at steady-state
After multiple doses of Letrozole SIE until Day 281 TP2 and after multiple doses of US-sourced oral Femara® or EU-sourced oral Femara® on Day 14 TP1
Secondary Outcomes (14)
Adverse Events
From the time of obtaining signed informed consent until the final follow-up visit on Day 281 (or Day 421 for the subset of participants in the Extension Period)
Injection site reactions
At pre-dose and 1 hour after each Letrozole SIE administration in TP2
Study Arms (2)
US-sourced oral Femara®
EXPERIMENTAL
Drug: US-sourced oral Femara® + Letrozole SIE
EU-sourced oral Femara®
EXPERIMENTAL
Drug: EU sourced oral Femara® + Letrozole SIE
Interventions
US-sourced oral Femara® + Letrozole SIEDrug
US-sourced Femara® 2.5 mg/day oral for 14 days (treatment period 1) + quarterly injectable Letrozole SIE (treatment period 2)
US-sourced oral Femara®
EU sourced oral Femara® + Letrozole SIEDrug
EU-sourced oral Femara® 2.5 mg/day for 14 days (treatment period 1) + quarterly injectable Letrozole SIE (treatment period 2)
EU-sourced oral Femara®
Eligibility Criteria
Age18 Years - 80 Years
Sexfemale
Healthy VolunteersNo
Age GroupsAdult (18-64), Older Adult (65+)
You may qualify if:
Women with weight of ≥50 kg and a Body Mass Index (BMI) ≥19 kg/m2 and ≤39 kg/m2
Planned date reported by the registry; this milestone is not confirmed as achieved.
Injection-related pain score
From baseline TP2 to the follow-up visit on Day 281
Bone mineral density (BMD) by dual energy x-ray absorptiometry (DXA)
From screening to Day 281 TP2
Average plasma drug concentration during a dosing interval at Steady-State (SS Cave)
After multiple doses of Letrozole SIE until Day 281 TP2 and after multiple doses of US-sourced oral Femara® or EU-sourced oral Femara® at Day 14 TP1
+9 more secondary outcomes
Other Outcomes (2)
Hormone supression
From screening to the final follow-up visit on Day 281 (or Day 421 for the subset of participants in the Extension Period)
CYP2A6 genotyping
From screening to final follow-up visit Day 281 (or Day 421 for the subset of participants in the Extension Period)
Registry-reported names are shown in full. Names without a link have not yet been matched to a Syfrah profile.
Women with confirmed diagnosis of HR+/HER2- or HR+/HER2+ early stage breast cancer who have completed at least 5 years of endocrine therapy, at least 2 years of which were with letrozole. Participants at a low risk of relapse, as assessed by the investigator, can also be eligible after completing 4 years of adjuvant endocrine therapy, at least 2 of which were with letrozole.
Women in good health.
Women who have undergone breast imaging per applicable guidelines (e.g., mammogram) within the last 12 months with no evidence of malignancy (documentation required), and if not done, must be willing to have 1 performed prior to baseline.
You may not qualify if:
Presence of an uncontrolled, unstable, clinically significant medical condition.
Have used estrogen or progesterone systemic or topical therapy, oral contraceptives, androgens, LH-releasing hormone analogs, prolactin inhibitors, or antiandrogens within 3 months prior to screening.
Use of inducers or inhibitors of CYP3A4 and CYP2A6.
Diagnosed with osteoporosis.
Preexisting cardiovascular disease
Positive result for hepatitis B surface antigen, hepatitis B core antibody, hepatitis C antibody, or HIV antibodies.
Contact the study team to confirm eligibility.
Investigational Site number SRB-004
Belgrade, 11000, Serbia
RECRUITING
Investigational Site number SRB-002
Belgrade, 11080, Serbia
RECRUITING
Investigational Site number SRB-001
Kamenitz, 21204, Serbia
RECRUITING
Investigational Site number SRB-003
Kragujevac, 34000, Serbia
RECRUITING
Investigational Site number SRB-005
Niš, 18000, Serbia
RECRUITING
Hospital Universitario Fundación Alcorcón (Investigational Site number ESP-015)
Alcorcón, 28922, Spain
RECRUITING
NEXT Oncology. Phase I Unit / IOB - Hospital Quironsalud Barcelona (Investigational Site number ESP-002)
Barcelona, 08023, Spain
RECRUITING
Hospital Universitario Virgen de las Nieves (Investigational Site number ESP-011)
Granada, 18014, Spain
RECRUITING
Hospital Universitario de Jaén (HUJ) (Investigational Site number ESP-005)
Jaén, 23007, Spain
RECRUITING
Complejo Asistencial Universitario de León - Hospital de León (Investigational Site number ESP-013)
León, 24071, Spain
RECRUITING
Hospital Universitario Arnau de Vilanova de Lleida (Investigational Site number ESP-003)
Lleida, 25198, Spain
RECRUITING
Althaia Xarxa Assistencial Universitària de Manresa F.P (Investigational Site number ESP-012)
Manresa, 08243, Spain
RECRUITING
Hospital Quirónsalud Málaga (Investigational Site number ESP-001)
Málaga, 29004, Spain
RECRUITING
Hospital Clínico Universitario Virgen de la Arrixaca (Investigational Site number ESP-009)
Murcia, 30120, Spain
RECRUITING
NEXT Oncology Phase I Unit - Hospital Universitario Quironsalud Madrid (Investigational Site number ESP-008)
Pozuelo de Alarcón, 28223, Spain
RECRUITING
Hospital Universitari Sant Joan de Reus (Investigational Site number ESP-004)
Reus, 43204, Spain
RECRUITING
Consorci Corporació Sanitària Parc Taulí - Hospital de Sabadell (Investigational Site number ESP-006)
Sabadell, 08208, Spain
RECRUITING
Hospital Clinico Universitario Santiago de Compostela (Investigational Site number ESP-007)
Santiago de Compostela, 15705, Spain
RECRUITING
Study Completion
October 2028
Estimated
Planned date reported by the registry; this milestone is not confirmed as achieved.
Last Updated
October 9, 2026
Record last verified: 2026-10
Source records
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