This is a first-in-human, multicenter, Phase 1/2, open-label study designed to evaluate the safety and tolerability of XTX501 as monotherapy in participants with metastatic non-small cell lung cancer (NSCLC) and select advanced solid tumors.

This is a first-in-human, Phase 1/2, multicenter, open-label study designed to evaluate the safety, tolerability, PK, pharmacodynamics, immunogenicity, and antitumor activity of XTX501, an investigational bispecific PD-1/masked IL-2 in participants with metastatic NSCLC and select advanced solid tumors.

Phase 1, Part 1A will examine XTX501 monotherapy in a Bayesian Optimal Interval design to determine the maximum tolerated dose up to 10 dose regimens.

Phase 1, Part 1B will further evaluate the safety and antitumor activity of XTX501 at dose regimens under consideration for the recommended Phase 2 dose(s).

Phase 2 will further evaluate the efficacy of the selected recommended Phase 2 dose(s).

Inclusion Criteria:

• Measurable disease at baseline per RECIST v1.1

• ECOG performance status of 0 or 1

• Adequate organ function

• Metastatic NSCLC:

  • Must have histologically confirmed metastatic NSCLC.
  • Tumor must have been assessed for EGFR and ALK per local standard of practice; patients with these driver mutations are excluded.
  • Patients with tumors known to have the following alterations are excluded: ROS1, RET, MET, HER-2, NTRK 1/2/3.
  • Patients must have previously derived clinical benefit from a PD-1/PD-L1 inhibitor or PD-1/PDL-1 bispecific without progression for at least 6 months.

Exclusion Criteria:

• Prior treatment with IL-2
• History of significant pulmonary disease
• History of clinically significant cardiovascular disease
• Active CNS metastases
• Pregnant or breastfeeding

In Phase 1, participants with select additional solid tumor types may be enrolled.