A Phase 1, Open-Label, Multicenter Study of JANX007 in Subjects With Metastatic Castration-Resistant Prostate Cancer

JANX007 is a Tumor Activated T Cell Engager therapuetic targeting prostate-specific membrane antigen (PSMA) for the treatment of metastatic castration-resistant prostate cancer.

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 level of certain molecules (biomarkers) in your blood changes over time while receiving the study agent

This is a dose escalation/expansion study and will be conducted in 3 parts. The purpose of Part 1 is to determine what is the safe dose of the study agent that can be administered and show signs of tumor killing capabilities.  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, part 2 and part 3, a larger number of people receive the study agent dose determined to be appropriate in the dose escalation part of the study.  The dose regimens will be selected based on the dose from Part 2 that showed the best tolerability and potential tumor destroying ability.

The study agent administration will be given weekly in cycles of 21 days.  Alternative dosing schedules, every 2 weeks or every 3 weeks, (including a step dose regimen with JANX007 administered on Day 1, Day 4 and Day 8 in the first week of Cycle 1, called 4-day step) may be implemented depending on when you enroll into the study. Your doctor will let you know what dosing schedule you will follow.

This study involves observation / hospitalization in Medical City Dallas Hospital. After your first dose on Cycle 1 Day 1, you will be hospitalized in Medical City Dallas for 24-48 hours. If the first dose is well tolerated, you will only need to be observed for 2 hours after each infusion.