A First-in-human, Multicenter, Open-label, Dose Escalation and Dose Expansion Phase 1 Study in Patients with Advanced Solid Tumors to Evaluate the Safety of Intravenously Administered ALG.APV-527

ALG.APV-527 binds to both its targets, 4-1BB and 5T4. ALG.APV-527 has the potential to activate T cells and NK cells that are present in the TME in patients with various 5T4-expressing solid malignancies.

In this study, the sponsor and investigators want to learn:

• How much of the study agent can be given with an acceptable level of side effects
• The effects of the study agent (good and bad)
• How much of the study agent is absorbed into the blood and how fast it is removed
• How the study agent is acting on your body
• If research tests can be used in the future to predict who will benefit from ALG.APV527

This is a dose escalation/expansion study. Dose Escalation means that the amount of the study agent given will be increased in each group of research participants to find the most appropriate dose for further study.

In the dose expansion part of the study, a larger number of people receive the study agent dose determined to be appropriate in the dose escalation part of the study.

This study has two regimens. If you are enrolled into regimen 1, you will receive the study agent once every 2 weeks as an infusion into your vein (IV infusion). If you are enrolled into regimen 2, you will receive the study agent once every 3 weeks as an IV infusion.

The study agent will be given over 2 hours for the first infusion. If well tolerated, this can be shortened to 1 hour for subsequent infusions. You will be observed for 8 hours after your first infusion and for 2 hours after subsequent infusions for safety monitoring.

The dose and frequency of the study agent you receive will be determined by when you enroll into the study.