A Study to Investigate Mechanisms of Resistance to Breast Cancer Therapies

General Inclusion Criteria:

• Willingness to undergo a procedure to obtain tumor tissue (e.g. biopsy) and blooddraw

• Diagnosis of HER2+, HR+ (for cohort R1) or triple negative breast cancer (for cohortT1) as per local assessment

• Availability of an archival tumor tissue (most recent pre-treatment tumor tissue ispreferred)

• Unequivocally growing tumor lesion (progressive lesion) that is accessible forresection, excision or core needle biopsy

• Discontinuation of prior anti-cancer treatment outlined below should not be longerthan 4 weeks from participation in this study

Inclusion criteria for participants in the cohorts studying acquired resistance

• Participant had undergone regular monitoring for disease progression as per localpractice (preferably every 3-6 months) while on most recent breast cancer therapy

• Accessible tumor lesion that newly appeared or a lesion that started to regrow whilethe participant was at least 6 months on therapy

Inclusion criteria for participants in the cohort studying primary resistance

• Accessible tumor lesion that continued to increase in size or a newly appearinglesion (as confirmed by routine tumor assessment) while treated for at least 4 weeksbut less than 6 months on therapy

Exclusion Criteria:

• Any risks factors that increase the risk of complications associated with theprocedure to obtain tumor tissue (e.g. bleeding disorders)

• Any serious medical condition or abnormality in clinical laboratory tests thatprecludes an individual's safe participation in and completion of the study

• Participant has started treatment with subsequent anti-cancer therapy

• Participants whose progressive tumor lesion that is targeted for biopsy/resection isin the bone

• Discontinuation of treatment was due to a reason other than disease progression