Elacestrant + Trastuzumab Deruxtecan

Selective estrogen receptor degrader (SERD), film-coated tablet, taken orally per protocol.

HER2-directed antibody-drug conjugate, vial, via intravenous (into the vein) infusion per standard of care

This phase Ib/II, open-label, single-arm, investigator-initiated study is to evaluate the safety and efficacy of elacestrant in combination with trastuzumab deruxtecan (T-DXd) in participants with hormone receptor-positive (HR+), HER2-low or HER2-ultralow, metastatic breast cancer that is resistant to prior CDK4/6 inhibitor and endocrine therapy. This is a Phase I/II clinical trial.

The goal of this study is to evaluate the safety and efficacy of elacestrant in combination with trastuzumab deruxtecan (T-DXd) in participants with hormone receptor-positive (HR+), HER2-low or HER2-ultralow, metastatic breast cancer that is resistant to prior CDK4/6 inhibitor and endocrine therapy.

The names of the study drugs involved in this study are: * Elacestrant (a type of selective estrogen receptor degrader) * Trastuzumab deruxtecan (a type of standard of care antibody drug conjugate)

Live record on ClinicalTrials.gov →

• Participants must have a histologically or cytologically confirmed diagnosis of HR+/HER2-low metastatic or unresectable locally advanced breast cancer, defined as ER ≥ 10%, any PR in the most recent sample and HER2-low (IHC 1+ or IHC 2+ and ISH non-amplified) or HER2-ultralow (IHC 0 and any membranous staining on any prior primary or metastatic sample). Cutoff values for positive/negative HER2 staining should be in accordance with current ASCO/CAP (American Society of Clinical Oncology/College of American Pathologists) guidelines.76
• Participants must have had prior CDK4/6 inhibitor and may have any number of prior endocrine based therapies in the metastatic setting.
• Participants may have progressed on up to 1 prior line of prior chemotherapy or ADC in the metastatic setting.
• Participants must have measurable disease per RECIST 1.1 criteria. See Section 11 for the definition of measurable disease. Participants must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for non-nodal lesions and short axis for nodal lesions) as ≥20 mm (≥2 cm) by chest x-ray or as ≥10 mm (≥1 cm) with CT scan, MRI, or calipers by clinical exam. See Section 12 (Measurement of Effect) for the evaluation of measurable disease.
• Participants must have known ESR1 mutation status in tumor or ctDNA within 6 months of enrollment to the trial. Participants must have Guardant360 CDx testing for ESR1-mutation status if status has not been validated within 60 days of registration.
• Women or men age ≥18 years are eligible.

Inclusion criteria as written on the registry, trimmed. The full list, with exclusions, is on the live record.