Replication fork speed assessed by DNA fiber assays in PDO models. Responder defined as participants achieving complete response (CR) or partial response (PR) based on RECISTv1.1 criteria. Wilcoxon rank sum tests will be used to compare the percentage change in replication fork speed with exposure to WEE1 inhibition in co-clinical models between overall response responder and non-responder.

Replication fork speed assessed by DNA fiber assays in PDO models. PFS6 is a binary endpoint where patients that are alive and progression free (per RECIST 1.1) at 6 months are considered responders. All other patients (those that died or progressed prior to 6 months or those with less than 6 months of follow-up for progression) are considered non-responders. Wilcoxon rank sum tests will be used to compare the percentage change in replication fork speed with exposure to WEE1 inhibition in co-clinical models between overall response responder and non-responder.

Participants who achieve partial response (PR) or complete response (CR) per RECIST v1.1 criteria.

To determine the safety and tolerability of ZN-c3 in subjects with recurrent or persistent USC.

To investigate the antitumor activity of ZN-c3 in subjects with recurrent or persistent USC

Detailed DLT consideration outline in protocol section 5.4. Toxicities are to be assess according to the CTCAE v5. Management and dose modifications associated with the above adverse events outlined in protocol section 6.

The MTD is defined as the highest dose level with ≤1 DLT in a cohort of 6 participants. See previous primary outcome measure for the DLT definition. If 0 out of 3 participants experience DLT, next dose level will be proceeded. If \>=1 out of the group suffer DLT, dose escalation will be stopped and 3 additional participants will be entered at the next lowest dose level. If \<=1 out of 6 DLTs, this dose level is considered as MTD.

ORR was defined as the proportion of participants achieving complete response (CR) or partial response (PR) on treatment based on RECIST 1.1 criteria. Per RECIST 1.1 for target lesions: CR is complete disappearance of all target lesions and PR is at least a 30% decrease in the sum of longest diameter (LD) of target lesions, taking as reference baseline sum LD. PR or better overall response assumes at a minimum incomplete response/stable disease (SD) for the evaluation of non-target lesions and absence of new lesions.

Incidence and severity of Dose Limiting Toxicities (DLTs) in DLT-evaluable subjects during Cycle 1

Frequency and severity of AEs and dose modifications

ORR as defined by the revised RECIST Guideline version 1.1 and assessed by ICR.

EFS at 18 weeks is defined as time from study enrollment until date of disease progression, or detection of disease at a previously uninvolved site, or date of death of the subjects at 18 weeks.

Incidence and severity of adverse events (AEs)

Incidence and severity of dose-limiting toxicities (DLTs)

Incidence and severity of adverse events (AEs) Incidence of dose interruptions, reductions, and discontinuations due to treatment-related AEs

To investigate the safety and tolerability of single agent ZN-c3, including identification of the maximum tolerated dose (MTD)/recommended Phase 2 dose (RP2D), based on the incidence and severity of adverse events (AEs) and dose-limiting toxicities (DLTs) in DLT-evaluable subjects.

To characterize and compare the PK (Cmax.) of ZN-c3 following a single dose of ZN-c3 under fed and fasting conditions.

To investigate the clinical activity of WEE1 inhibition based on the objective response rate (ORR) as defined by the revised Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1