A Study to Investigate the Safety and Preliminary Efficacy of GSK5460025 Alone or in Combination With Other Anti-cancer Agents in Participants With Solid Tumors

Inclusion Criteria:

* Has a histologically diagnosed advanced (unresectable, metastatic or recurrent) solid tumor
* Has a known dMMR/MSI-H status as determined by a certified local laboratory at the time of Pre-screening or has an unknown Mismatch repair (MMR)/ Microsatellite Instability (MSI) status at the time of Pre-screening and MMR/MSI status will be determined by central reference laboratory
* Provides an archival or fresh (preferred) formalin fixed, paraffin embedded (FFPE) sample
* Intends to receive GSK5460025 as next treatment
* Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2
* Is expected to have a minimum of 3 months life expectancy
* Has adequate organ function, as defined in the protocol

Part 1 inclusion criteria:

• Has histologically diagnosed advanced (unresectable, metastatic or recurrent) solid tumor and has exhausted all standard of care treatment options

Part 2 inclusion criteria:

* Has histologically diagnosed advanced (unresectable, metastatic or recurrent) Colorectal cancer (CRC) or Endometrial cancer (EC)
* Has received at least 1 but no more than 3 lines of systemic anticancer therapy for their advanced (unresectable, metastatic or recurrent) disease including at least one line of Immune checkpoint inhibitors (ICI) therapy
* Has measurable disease (i.e., at least 1 target lesion) during the Screening period per RECIST 1.1, as determined by the investigator

Exclusion Criteria:

* Has not recovered (i.e., to Grade ≤1 or to baseline) from prior anticancer therapy-induced Adverse Events (AEs)
* Has received prior treatment with a Werner (WRN) inhibitor or Nucleotide Excision Repair Targeting (NERT) agent.
* Is unable to swallow and retain orally administered study treatment
* Has untreated or progressed metastases in brain or CNS
* Has a known additional malignancy that progressed or required active treatment within the last 2 years because reoccurrence of another malignancy would confound interpretation by RECIST 1.1 criteria. Exceptions include basal or squamous cell carcinomas of the skin or in situ carcinomas \[e.g., breast, cervix, bladder\] that have been resected with no evidence of metastatic disease.
* Has any impairment of gastrointestinal function or gastrointestinal disease that may significantly alter the absorption of study drugs
* Has cirrhosis or current unstable liver or biliary disease
* Has known hypersensitivity to any of the study interventions or any of their excipients