Open-Label Umbrella Study to Evaluate Safety and Efficacy of Sapanisertib and Serabelisib (PIKTOR) in Various Combinations in Patients With HR+/HER2- Advanced or Metastatic Breast Cancer

Inclusion Criteria: * Histologically confirmed diagnosis of HR+/HER2- breast cancer. * Documented evidence of advanced or recurrent disease that is not amenable to surgery/radiation for curative intent. * Participant has received at least one prior systemic therapy. * At least 1 measurable or evaluable target lesion according to RECIST v1.1 * Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 1 at Screening. * Non-pregnant, non-lactating females who are postmenopausal, surgically sterile or who agree to use effective contraceptive methods. Exclusion Criteria: * Participants with triple-negative breast cancer. * Participants with central nervous system metastases are not eligible, unless they have completed local therapy and have discontinued the use of corticosteroids for this indication for at least 4 weeks before starting treatment in this study. * Active malignancy (except for breast cancer, definitively treated in-situ carcinomas \[e.g., breast, cervix, bladder\], or basal or squamous cell carcinoma of the skin) within the past 24 months prior to treatment. Fully resected localized malignancies are eligible. * Gastric feeding tube (gastrostomy tube), gastrointestinal malabsorption, gastrointestinal anastomosis, bowel obstruction, or any other condition that might affect the absorption of study treatment. * Significant cardiovascular impairment. * Active, uncontrolled infection. * Concurrent participation in another therapeutic clinical trial. * Prior radiation therapy within 21 days prior to start of study treatment. * Participants who have received a prior PI3K, AKT, mTORC1/2, or dual PI3K/mTOR inhibitor. * Strong CYP3A4 inhibitors, strong CYP1A2 inhibitors or CYP1A2 inducers, or clinically significant CYP3A4 inducers within 7 days before the first dose of study intervention, or participants who require treatment with strong CYP3A4 inhibitors or inducers during the study. * Prolongation of QTc interval to \>480 ms. * Type 1 or Type 2 diabetes mellitus on insulin.