ZN-c3 for the Treatment of Metastatic Triple-Negative Breast Cancer and Advanced Ovarian Cancer

Inclusion Criteria:

* Participant must provide written informed consent before any study-specific procedures or interventions are performed
* Participants aged \>= 18 years
* Participants with biopsy proven metastatic TNBC defined as:

  * Estrogen receptor (ER) \< 10%, progesterone receptor (PR) \< 10%
  * HER2 non-amplified by College of American Pathologists (CAP) guidelines
* Participants with biopsy proven advanced ovarian cancer (including primary peritoneal and fallopian tube cancers)
* Prior PARP inhibitor therapy allowed
* Participants must have at least one measurable site of disease as defined by Response Evaluation Criteria in Solid Tumors (RECIST) version (v) 1.1 that is amendable to biopsy
* Participants must have received at least one standard of care line of therapy in the recurrent setting
* Eastern Cooperative Oncology Group (ECOG) performance status (PS) =\< 2
* Prior treatment related toxicities resolved to =\< grade 1 (except neuropathy, alopecia or skin pigmentation)
* Absolute neutrophil count (ANC) \>= 1.5 x 10\^9/L; excluding measurements obtained within 7 days after daily administration of filgrastim/sargramostim or within 3 weeks after administration of pegfilgrastim
* Platelet count \>= 100 x 10\^9/L; excluding measurements obtained within 3 days after transfusion of platelets
* Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) =\< 3 × upper limit of normal (ULN). If liver function abnormalities are due to underlying liver metastases, AST and ALT =\< 5 x ULN
* Total serum bilirubin =\< 1.5 x ULN or =\< 3 x ULN in the case of Gilbert's disease
* Serum creatinine =\< 1.5 x ULN or creatinine clearance (CrCl) \>= 60 mL/min
* Participants of childbearing potential must have a negative serum beta human chorionic gonadotropin (beta-hCG) test
* Participants of childbearing potential must agree to use an effective method of contraception per institutional standard prior to the first dose and for 90 days after the last dose of ZN-c3
* Willingness and ability to comply with scheduled visits, treatment plan, laboratory tests and other study procedures, including pretreatment and on-treatment biopsies
* Willingness to practice adequate sun protection (use of sunscreen or sun-protective clothing or limitation of sun exposure)

Exclusion Criteria:

* Prior Wee-1 inhibitor exposure
* Any of the following treatment interventions within the specified time frame prior to cycle 1 day 1:

  * Major surgery within 28 days (the surgical incision should be fully healed prior to study drug administration)
  * Radiation therapy within 21 days; however, if the radiation portal covered =\< 5% of the bone marrow reserve, the subject is eligible irrespective of the end date of radiotherapy
  * Autologous or allogeneic stem cell transplant within 3 months
  * Current use of an investigational agent that is not expected to be cleared by the first dosing of study drug or that has demonstrated to have prolonged side effects
  * Prescription, non-prescription drugs or food known as moderate to strong inducers of CYP3A within 2 weeks
* A serious illness or medical condition(s) including, but not limited to, the following:

  * Symptomatic brain metastases
  * Leptomeningeal disease that requires or is anticipated to require immediate treatment
  * Myocardial impairment of any cause (e.g., cardiomyopathy, ischemic heart disease, significant valvular dysfunction, hypertensive heart disease, and congestive heart failure) resulting in heart failure by New York Heart Association Criteria (class III or IV)
  * Other severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or study drug administration, or may interfere with the interpretation of study results, and in the judgment of the investigator would make the subject inappropriate for entry into this study
  * Significant gastrointestinal abnormalities, including an inability to take oral medication, requirement for intravenous (IV) alimentation, active peptic ulcer, chronic diarrhea or vomiting considered to be clinically significant in the judgment of the Investigator, or prior surgical procedures affecting absorption
  * Active or uncontrolled infection. Subjects with an infection receiving treatment (antibiotic, antifungal or antiviral treatment) may be entered into the study but must be afebrile and hemodynamically stable for \>= 72 hours
* Unresolved toxicity of grade \> 1 attributed to any prior therapies (excluding grade 2 neuropathy, alopecia or skin pigmentation)
* Known hypersensitivity to any drugs similar to ZN-c3 in class
* Participants that are pregnant or lactating (including the cessation of lactation) or those of childbearing potential who have a positive serum pregnancy test within 14 days prior to cycle 1 day 1
* Participants with active (uncontrolled, metastatic) second malignancies or requiring therapy
* 12-lead electrocardiogram (ECG) demonstrating a corrected QT interval using Fridericia's formula (QTcF) of \> 480 msec, except for subjects with atrioventricular pacemakers or other conditions (e.g., right bundle branch block) that render the QT measurement invalid
* Any history or current evidence of congenital long QT syndrome
* Participant requiring any medications that can lead to significant QT prolongation
* Participant requires administration of strong and moderate CYP3A4 inhibitors and inducers as well as strong and moderate P-glycoprotein (P-gp) inhibitors
* Participants with any condition that, in the opinion of the investigator, could jeopardize the participant's safety or adherence to the study protocol
* For TNBC cohort only, participants with tumors showing androgen receptor (AR) \>= 80% by immunohistochemistry are excluded