The study is a Phase 1b/2, multi-center, open-label, dose escalation trial evaluating the safety and preliminary efficacy of sapanisertib and serabelisib (PIKTOR) with fulvestrant and/or other anticancer therapies in participants with HR+/HER2- advanced/metastatic breast cancer.

The study is a Phase 1b/2, multi-center, open-label, dose escalation trial evaluating the safety and preliminary efficacy of sapanisertib and serabelisib (PIKTOR) with fulvestrant and/or other anticancer therapies in participants with HR+/HER2- advanced/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.