Phase 1/2a Dose Escalation, Finding and Expansion Study Evaluating Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Anti-Tumor Activity of PF-07104091 as a Single Agent and in Combination Therapy

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.

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