This is an umbrella study evaluating the efficacy and safety of multiple treatment combinations in participants with metastatic or inoperable locally advanced breast cancer.

The study will be performed in two stages. During Stage 1, seven cohorts will be enrolled in parallel in this study:

Cohort 1 will consist of programmed death-ligand 1 (PD-L1)-positive participants who have received no prior systemic therapy for metastatic or inoperable locally advanced triple-negative breast cancer (TNBC) (first-line \[1L\] PD-L1+ cohort).

Cohort 2 will consist of participants who had disease progression during or following 1L treatment with chemotherapy for metastatic or inoperable locally-advanced TNBC and have not received cancer immunotherapy (CIT) (second-line \[2L\] CIT-nave cohort).

Cohort 3, 5, 6 and 7 will consist of participants with locally advanced or metastatic hormone receptor-positive (HR+), human epidermal growth factor receptor 2 (HER2)-negative disease with one or more PIK3CA mutations.

Cohort 4 will consist of participants with locally advanced or metastatic HER2+ /HER2-low disease with one or more PIK3CA mutations who had disease progression on standard-of-care therapies (HER2+ /HER2-low cohort).

In each cohort, eligible participants will initially be assigned to one of several treatment arms (Stage 1). During Stage 2, participants in the 2L CIT-nave cohort who experience disease progression, loss of clinical benefit, or unacceptable toxicity during Stage 1 may be eligible to continue treatment with a different treatment combination, provided Stage 2 is open for enrollment and all eligibility criteria are met.

The purpose of this study is to learn about the safety and effects of the study medicine PF-07248144 when given along with fulvestrant for the possible treatment of HR-positive, HER2-negative advanced or metastatic breast cancer.

HR-positive breast cancer cells have proteins on their surface called receptors that bind to hormones like estrogen and progesterone (female sex hormones). These hormones can promote the growth of cancer cells.

HER2-negative describes cells that have a small amount or none of a protein called HER2 on their surface. In normal cells, HER2 helps control cell growth. Cancer cells that are HER2-negative may grow more slowly and are less likely to recur (come back) or spread to other parts of the body than cancer cells that have a large amount of HER2 on their surface.

Advanced cancer is a term that is often used to describe cancer that is unlikely to be cured.

Metastatic cancer is the type where the cancer cells spread from one part of the body to another.

This study is seeking for participants whose breast cancer has gotten worsen after receiving cyclin dependent kinase (CDK) 4/6 inhibitor-based therapy.

Half of participants in this study will receive their usual study treatment, everolimus with endocrine therapy (either exemestane or fulvestrant) for HR-positive/HER2-negative advanced or metastatic breast cancer (A/mBC). The study doctor will discuss which hormone therapy is right for the participant before treatment begins.

PF-07248144 is a tablet that will be taken by mouth at home every day in a 28-day cycle. Fulvestrant will be given as two injections (one injection in the buttock) at visits to the study clinic. Everolimus and exemestane are also tablets and will be taken by mouth at home every day in a 28-day cycle.

The study will compare the experiences of people receiving PF-07248144 in combination with fulvestrant to those of the people who do not. This will help see if PF-07248144 in combination with fulvestrant is safe and effective.

This is a Phase 1b/2, open-label, parallel-arms pilot study in men and post-menopausal women with hormone receptor positive (HR+), HER2- advanced or metastatic breast cancer with an alteration in the PI3K pathway, including a mutation of the PIK3CA gene, PTEN loss, or AKT1 mutation, designed to determine the safety of evexomostat (SDX-7320) plus standard of care treatment alpelisib (BYL-719) or capivasertib and fulvestrant (each combined, the 'triplet therapy'), to measure the severity and number of hyperglycemic events, and to assess clinical, anti-tumor benefit of the triplet therapy.

The purpose of this study is:

* to characterize the safety of the triplet drug combination consisting of either alpelisib or capivasertib (per the treating oncologist's choice) and fulvestrant plus evexomostat,
* to test whether evexomostat, when given in combination with either alpelisib or capivasertib and fulvestrant will reduce the number and severity of hyperglycemic events and/or reduce the number or dose of anti-diabetic medications needed to control the hyperglycemia for metabolically normal patients and those deemed at risk for capivasertib and alpelisib-induced hyperglycemia (insulin resistance, as measured by HOMA-IR, baseline elevated HbA1c or well-controlled type 2 diabetes), and
* to assess preliminary anti-tumor efficacy for each combination and changes in key biomarkers and quality of life in this patient population.

This phase 3 clinical trial compares the safety and efficacy of palazestrant (OP-1250) to the standard-of-care options of fulvestrant or an aromatase inhibitor in women and men with breast cancer whose disease has advanced on one endocrine therapy in combination with a CDK4/6 inhibitor.