All participants in Phase 1 Part 1A (Dose Escalation) who received at least 1 dose of XTX202 and experienced a DLT. DLTs were defined as the following: * Any treatment-related Grade ≥ 3 toxicity * Any Grade febrile neutropenia * The following nonhematologic exceptions: * Grade 3 nausea or vomiting lasting \< 3 days * Grade 3 fatigue lasting \< 7 days * Any treatment-related toxicity that resulted in a treatment delay of ≥ 7 days

Treatment-emergent adverse event (TEAE) is defined as any adverse event that starts or increases in severity on or after the first dose of study drug and no later than 90 days after the last dose of study drug. Adverse events are graded using the NCI CTCAE version 5.0.

Percentage of participants who achieved at least one confirmed Complete Response (CR) or Partial Response (PR). Response is based on Investigator assessment according to RECIST v1.1. In the analysis set used for ORR, participants are assigned to a treatment group based on the initial dose received. In the Participant Flow module, participants are assigned to a treatment group based on the highest dose received. One participant in Phase 2 Part 2B initially received XTX202 1.4 mg/kg, then increased the dose to 4.0 mg/kg at a later cycle and was therefore included in the XTX202 4.0 mg/kg dose group.

Number of participants that experienced a clinical laboratory test abnormality. Abnormalities considered are those Grade 3-4 events with a \>= 1 grade increase from baseline. Baseline is defined as the last available measurement taken prior to the first administration of study treatment. Laboratory data is graded using the NCI CTCAE version 5.0. Participants are included only once, in the highest level of CTCAE Grade.

Number of participants that experienced a clinical laboratory test abnormality. Abnormalities considered are those Grade 3-4 events with a \>= 1 grade increase from baseline. Baseline is defined as the last available measurement taken prior to the first administration of study treatment. Laboratory data is graded using the NCI CTCAE version 5.0. Participants are included only once, in the highest level of CTCAE Grade.

Number of participants with shift from baseline in laboratory results. Baseline is defined as the last available measurement taken prior to the first administration of study treatment. Participants with both baseline and at least one postbaseline result are included. Participants are included only once, in the highest level of CTCAE Grade. Missing = number of patients with missing baseline and/or post baseline laboratory value.

Number of participants with shift from baseline in laboratory results. Baseline is defined as the last available measurement taken prior to the first administration of study treatment. Participants with both baseline and at least one postbaseline result are included. Participants are included only once, in the highest level of CTCAE Grade. Missing = number of patients with missing baseline and/or post baseline laboratory value. Missing = number of patients with missing baseline and/or post baseline laboratory value