DESTINY-Breast 08 will investigate the safety, tolerability, PK and preliminary anti-tumour activity of T-DXd in combination with other therapies in patients with Metastatic HER2-low Advanced or Metastatic Breast Cancer

This study is modular in design allowing assessment of the safety, tolerability, PK and preliminary anti-tumour activity of T-DXd in combination with other therapies. Combination-treatment modules will have 2 parts: a dose-finding phase (Part 1), and a dose expansion phase (Part 2); the Part 2 dose-expansion phase will use the RP2D determined in Part 1.

The target population of interest in this study is patients with HER2-low (IHC 1+ or IHC 2+/ISH -) (as per ASCO/CAP 2018 guidelines) advanced/MBC. Part 1 of each module will enroll patients with locally confirmed HER2-low advanced/MBC in second-line or later (≥ 2L) settings

Part 2 of each module will enroll patients with HER2-low MBC who have either not received prior treatment, or received only 1 prior treatment (depending on the module-specific exclusion criteria) for advanced/metastatic disease

Key Inclusion Criteria:

• Patients must be at least 18 years of age

• Male or female patients who have pathologically documented breast cancer that:

  1. Has a history of HER2-low expression, defined as IHC 2+/ISH- or IHC 1+ (ISH- or untested) with a validated assay
  2. Is documented as HR+ (either ER and/or PgR positive [ER or PgR ≥1%]) or ER and PgR negative (ER and PgR <1%) per ASCO/CAP guidelines in the metastatic setting

• Patient must have adequate tumor sample for biomarker assessment

• ECOG Performance Status of 0 or 1

For patients with HR+ disease:

Part 1: At least 1 prior treatment line of ET with or without a targeted therapy (such as CDK4/6, mTOR or PI3-K inhibitors), and at least 1 prior line of chemotherapy for MBC are required.

Part 2: Only 1 prior treatment line of ET with or without a targeted therapy (such as CDK4/6, mTOR or PI3-K inhibitors) for MBC is allowed. No prior chemotherapy in the metastatic setting is allowed. Note there are no patients with HR+ disease in Part 2 of Modules 2 and 3.

For patients with HR- disease:

Part 1: At least 1 prior line of chemotherapy for MBC is required. Note there are no patients with HR- disease in Part 1 of Modules 4 and 5.

Part 2: For Module 2, no prior lines of therapy for MBC are allowed, and for Modules 1 and 3, only 1 prior line of chemotherapy for MBC is allowed. Note there are no patients with HR- disease in Part 2 of Modules 4 and 5.

Key Exclusion Criteria:

• Uncontrolled intercurrent illness
• Uncontrolled or siginificant cardiovascular disease
• History of (non-infectious) ILD/pneumonitis that required steroids, has current ILD/pneumonitis, or where suspected ILD/pneumonitis cannot be ruled out by imaging at screening.
• Lung-specific intercurrent clinically significant illnesses
• Has spinal cord compression or clinically active central nervous system metastases
• Active primary immunodeficiency
• Uncontrolled infection requiring IV antibiotics, antivirals, or antifungals
• Prior treatment with ADC that comprises of an exatecan derivative that is a topoisomerase I inhibitor.

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal. All request will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure. Yes, indicates that AZ are accepting requests for IPD, but this does not mean all requests will be shared.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA Pharma Data Sharing Principles. For details of our timelines, please rerefer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the deidentified individual patient-level data in an approved sponsored tool . Signed Data Sharing Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information. Additionally, all users will need to accept the terms and conditions of the SAS MSE to gain access. For additional details, please review the Disclosure Statements at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.