To assess the safety and tolerability of increasing doses of PF-07104091 and to estimate the Maximum Tolerated Dose (MTD) and/or select the Recommended Phase 2 dose (RP2D) for PF-07104091 as a single agent in participants with advanced or metastatic small cell lung, breast and ovarian cancers.

Study C4161001 is a Phase 1, open label, multi dose, multi center, dose escalation, safety, pharmacokinetic (PK) and pharmacodynamic study of PF-07104091 in adult patients with advanced or metastatic small cell lung cancer (SCLC), advanced platinum resistant epithelial ovarian cancer/fallopian tube cancer/primary peritoneal cancer, locally recurrent/advanced or metastatic triple negative breast cancer (TNBC), HR-positive HER2-negative advanced or mBC, advanced or metastatic non-small cell lung cancer (NSCLC). This two part study will assess the safety and tolerability of increasing dose levels of PF-07104091 in Part 1, and establish the recommended Phase 2 dose (RP2D) in Part 2.

Inclusion Criteria:

• Participants with HR-positive HER2-negative advanced or metastatic breast cancer (received at least two prior lines in the advanced or metastatic setting including one prior line of combined CDK4/6 inhibitor and endocrine therapy and no more than two prior lines of cytotoxic chemotherapy)
• Participants with locally recurrent/advanced or metastatic TNBC who have received up to 2 prior lines of chemotherapy in the advanced or metastatic setting
• Participants with advanced platinum resistant epithelial ovarian cancer (EOC)/fallopian tube cancer/primary peritoneal cancer (PPC) (histologically or cytologically proven) who have received at least 1 systemic anti-cancer therapy containing a platinum analog
• Participants with cytological diagnosis of advanced/metastatic SCLC
• Participants with or cytological diagnosis of advanced/metastatic NSCLC
• Participants with HR-positive HER2-negative advanced or metastatic breast cancer (second line plus setting) (histologically or cytologically proven).
• Participants entering the study in the expansion cohort have at least one measurable lesion as defined by RECIST version 1.1 that has not been previously irradiated
• Performance Status 0 or 1
• Adequate bone marrow, hematological, kidney and liver function
• Resolved acute effects of any prior therapy to baseline severity

Exclusion Criteria:

• Participants with known symptomatic brain metastases requiring steroids
• Participants with any other active malignancy within 3 years prior to enrollment
• Major surgery within 3 weeks prior to study entry
• Radiation therapy within 3 weeks prior to study entry.
• Systemic anti cancer therapy within 4 weeks prior to study
• Prior irradiation to >25% of the bone marrow
• Participants with active, uncontrolled bacterial, fungal, or viral infection, including HBV, HCV, and known HIV or AIDS related illness
• Active COVID-19/SARS-CoV2 infection
• Baseline 12 lead ECG that demonstrates clinically relevant abnormalities that may affect participant safety or interpretation of study results
• Any of the following in the previous 6 months: myocardial infarction, long QT syndrome, Torsade de Pointes, arrhythmias, serious conduction system abnormalities, unstable angina, coronary/peripheral artery bypass graft, symptomatic CHF, New York Heart Association class III or IV, cerebrovascular accident, transient ischemic attack, symptomatic pulmonary embolism, and/or other clinical significant episode of thrombo embolic disease.
• Anticoagulation with vitamin K antagonists or factor Xa inhibitors is not allowed.
• Hypertension that cannot be controlled by medications
• Participation in other studies involving investigational drug(s) within 2 weeks prior to study entry.
• Known or suspected hypersensitivity to active ingredient/excipients in PF 07104091.
• Active inflammatory gastrointestinal disease, chronic diarrhea, known diverticular disease or previous gastric resection or lap band surgery.
• Participants with advanced/metastatic, symptomatic, visceral spread, that are at risk of life threatening complications in the short
• Participants with an indwelling catheter that has an external component such as those used for drainage of effusion(s) or central venous catheter that is externally
• Previous high dose chemotherapy requiring stem cell rescue
• Known abnormalities in coagulation such as bleeding diathesis, or treatment with anticoagulants precluding intramuscular injections of goserelin (if applicable).
• Current use or anticipated need for food or drugs that are known strong CYP3A4/5 or UGT1A9 inhibitors or inducers
• Current use or anticipated need for drugs that are known sensitive UGT1A1 substrates with narrow therapeutic
• Serum pregnancy test positive at screening
• Other medical or psychiatric condition

Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.