Last Update: Aug 27, 2026 An Open-label, Multi-center, Phase I/Ib Study of IEV407 as a Single Agent and in Combination With Endocrine Therapy in Patients With Advanced Hormone Receptor Positive, HER2- Negative Breast Cancer ClinicalTrials.gov Identifier: [NCT07604571](https://clinicaltrials.gov/ct2/show/NCT07604571) Novartis Reference Number:CIEV407A12101 [See if you Pre-qualify](#trial-eligibility "See if you Pre-qualify") All compounds are either investigational or being studied for (a) new use(s). Efficacy and safety have not been established. There is no guarantee that they will become commercially available for the use(s) under investigation. ## Study Description The purpose of this study is to evaluate the safety, tolerability and preliminary activity of IEV407 as a single agent and in combination with endocrine therapy (fulvestrant or letrozole) in patients with advanced hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-negative) breast cancer. This is a first-in-human, open-label, phase I/Ib, multi-center study consisting of a dose escalation part of IEV407 as a single agent (SA) and in combination with endocrine therapy (fulvestrant or letrozole) followed by a dose expansion part in patients with advanced breast cancer (aBC). The study will start with the evaluation of IEV407 as a SA. Following evaluation of IEV407 in combination with fulvestrant through dose escalation and establishment of a recommended dose and/or dose ranges for optimization (RD/DRO), the study may proceed to the Phase Ib expansion part to evaluate the combination treatment of IEV407 with fulvestrant. If more than one treatment arm is open concurrently in the dose expansion part, a randomization schedule will be employed for patient allocation. Condition Advanced HR+/HER2- Breast Cancer Phase Phase1 Overall Status Recruiting Number of Participants194 Start Date May 28, 2026 Completion Date Jun 08, 2032 Gender All Age(s) 18 Years - (Adult, Older Adult) ## Interventions Drug ### Fulvestrant Intramuscular injection. Approved medication. Drug ### IEV407 Oral administration Drug ### Letrozole Oral administration. Approved medication. ## Eligibility Criteria Inclusion Criteria: \* Age ≥ 18 years old \* Patients with one of the following indications: \* Dose escalation (IEV407 single agent and in combination with fulvestrant or letrozole): HR+/HER2- aBC with disease progression on or following, or have been intolerant to, at least one line of endocrine-based therapy in combination with a CDK4/6 inhibitor and at least one additional line of systemic therapy in the unresectable/metastatic setting and not be a candidate for any available standard therapy, in the investigator's judgement. \\- Dose expansion of IEV407 in combination with fulvestrant: HR+/HER2- aBC with disease progression on or following, or have been intolerant to, endocrine-based therapy in combination with a CDK4/6 inhibitor. They must not have received more than two prior lines of endocrine-based therapy in the unresectable/metastatic setting. Prior cytotoxic chemotherapy and/or antibody-drug conjugate therapies in the unresectable/metastatic setting are not allowed. Exclusion Criteria: \* Patients with inadequate bone marrow and/or organ functions with out-of-range laboratory values. \* Impaired cardiac function or clinically significant cardiac disease. \* Concurrent use of hormone replacement therapy. \* Women of childbearing potential who are unwilling to use highly effective contraception methods, pregnant or nursing women. \* For the combination treatment of IEV407 with fulvestrant or letrozole: Patients with symptomatic visceral disease or any disease burden that makes the patient ineligible for endocrine-based therapy. Other protocol-defined inclusion/exclusion criteria may apply. Canada #### Novartis Investigative Site Recruiting Toronto,Ontario,M5g 2m9,Canada Japan #### Novartis Investigative Site Recruiting Hirakata,Osaka,5731191,Japan Singapore #### Novartis Investigative Site Recruiting Singapore,119074,Singapore United States #### Mary Crowley Cancer Research Recruiting Dallas,Texas,75251,United States ###### Pramitha Kondancheri Phone: [+1 972 566 3000]() Email: ###### Reva Schneider #### Yale New Haven Hospital Recruiting New Haven,Connecticut,06520,United States ###### Carl Brown Email: ###### Jing Du ## Worldwide Contacts If the location of your choosing does not feature any contact detail, please reach out using the information below. #### Novartis Pharmaceuticals Phone: [ +41613241111](tel:+41613241111) Email: [](mailto:) #### Novartis Pharmaceuticals Phone: [ 1-888-669-6682](tel:1-888-669-6682) Email: