A Phase 1, Open-Label, Multiple-Ascending Dose Study of the Safety and Tolerability of CTX-471 Administered Either as a Monotherapy or in Combination with Pembrolizumab in Patients with Inadequate Responses to PD-1/PD-L1 Checkpoint Inhibitors in Metastatic or Locally Advanced Malignancies

CTX-471 is a fully humanized IgG4 agonist antibody for CD-137, also known as 4-1BB, a costimulatory factor for T cells and NK cells.

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

• How much of the study agent alone or in combination with Pembrolizumab can be given with an acceptable level of side effects
• The effects of the study agent alone or in combination with Pembrolizumab (good and bad)
• How much of the study agent alone or in combination with Pembrolizumab is absorbed into the blood and how fast it is removed
• How proteins that indicate the status of your disease are affected with use of the study agent alone or in combination with Pembrolizumab
• If your body develops proteins that work against the study agent alone or in combination with Pembrolizumab
• If research tests can be used in the future to predict who will benefit from CTX-471

This is a dose escalation/expansion study. This means that in the dose escalation part of the study, 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.

Research participants will be assigned to receive the study agent alone or in combination with Pembrolizumab. The study agent will be given once every 2 weeks as an IV (intravenous, meaning into a vein) infusion over 60 minutes. Pembrolizumab will be given once every 6 weeks as an IV (intravenous, meaning into a vein) infusion over 30 minutes.