The study consists of a screening period of 28 days, a treatment period. Local or central testing of PIK3CA mutation in blood or tumor tissue must be performed using an approved polymerase chain reaction (PCR)-based or next generation sequencing (NGS) assay at a clinical laboratory. Patients with confirmed eligibility criteria and PIK3CA mutant breast cancer will be randomized in a 1:1 ratio to receive:
Neoadjuvant treatment with dual anti-HER2 blockade consisting of ready-to-use fixed-dose combination of pertuzumab and trastuzumab as subcutaneous (PH-FDC SC) formulation q3w and nab-paclitaxel (125 mg/m2 on days 1, 8, and 15) in 3-week cycle for total 6 cycles
* with inavolisib (6 cycles) or
* without inavolisib. In both study arms, treatment will be given until surgery/core-biopsy, disease progression, unacceptable toxicity, or withdrawal of consent of the patient.
All patients will undergo surgery or biopsy after completing study therapy to assess pCR rate.