Study to Assess the Safety and Tolerability of PF-07220060 in Combination With PF-07104091 in Participants With Breast Cancers or Solid Tumors and to Assess the Safety and Tolerability of PF-07220060 and PF-07104091 in Combination With Endocrine Therapy in Participants With Breast Cancer.

Inclusion Criteria

Part 1: Breast Cancer (BC)
HR+, HER2- BC
Refractory HR-positive/HER2-positive BC
Part 1: Solid Tumors other than BC
Part 2:
HR-positive/HER2-negative BC
Lesion:
Part 1: evaluable lesion (including skin or bone lesion only)
Part 2: measurable lesion per RECIST v1.1
Prior systemic Treatment
Part 1: HR-positive/HER2-negative BC
At least 1 line of SOC, including CDK4/6 inhibitor therapy and Endocrine Therapy, for advanced or metastatic disease.
Prior chemotherapy in the metastatic setting is allowed.
Part 1: HR-positive/HER2-positive BC
At least 1 prior treatment of approved HER2 targeting therapy.
Part 1: Solid Tumors other than BC
Participants with no standard therapy available or for which no local regulatory approved standard therapy is available that would confer significant clinical benefit in the medical judgement of the investigator.
Part 2A: At least 1 prior systemic therapy for advanced or metastatic disease, including CDK4/6 inhibitor treatment and ET.
Parts 2A and 2B: At least 1 prior endocrine therapy for advanced or metastatic disease.
Part 2B: Up to 1 prior line of chemotherapy for advanced/metastatic disease is allowed.
General Inclusion Criteria
Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0 or 1
Adequate renal, liver, and bone marrow function
Resolved acute effects of any prior therapy to baseline severity

Exclusion Criteria:

All Study Parts: Permanent treatment discontinuation from prior CDK 4 and/or CDK2 inhibitor due to treatment related toxicity.
Part 2B: Prior treatment with any CDK 4/6 inhibitor, or fulvestrant, or everolimus.
Parts 2B and 2C: Prior treatment with any CDK4/6 inhibitor for advanced disease.
Part 2C: Prior neoadjuvant or adjuvant treatment with a nonsteroidal aromatase inhibitor AI (ie, anastrozole or letrozole) with disease recurrence while on or within 12 months of completing treatment.
Prior irradiation to >25% of the bone marrow
Current use of drugs which have a risk for QTc prolongation
Current use or anticipated need for food or drugs that are known strong CYP3A4/5, strong UGT2B7 or UGT1A9 inhibitors or inducers

Participation in other studies involving investigational drug(s) within 4 weeks prior to study entry

Participants with any other active malignancy within 3 years prior to enrollment except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ of the cervix, Bowen's disease
Major surgery within 4 weeks prior to study entry
Radiation therapy within 4 weeks prior to study entry.
Clinically important hypertension
Known or suspected hypersensitivity to PF-07220060, PF-07104091, letrozole, fulvestrant, or goserelin (or equivalent to induce chemical menopause if applicable)
Known abnormalities in coagulation. Anticoagulation with subcutaneous heparin or prophylactic doses of anticoagulant are allowed
Known active uncontrolled or symptomatic central nervous system (CNS) metastases
Active inflammatory GI disease
Current use or anticipated need for Proton Pump Inhibitors (PPI) within 14 days prior to first dose of the study intervention
Previous high-dose chemotherapy requiring stem cell rescue
Participants with active, uncontrolled bacterial, fungal, or viral infection, including hepatitis B virus (HBV), hepatitis C virus (HCV), and known human immunodeficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) related illness
Other protocol specific exclusion criteria may apply