A Phase I/II, Open-label Study to Investigate the Safety, Tolerability, Pharmacokinetics, and Preliminary Efficacy of FB849 Administered in Subjects with Advanced Solid Tumors Alone and in Combination with Pembrolizumab

• FB849 is a HPK1 inhibitor

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

• How much of the study drug can be given with an acceptable level of side effects
• The effects of the study drug (good and bad)
• How much of the study drug is absorbed into the blood and how fast it is removed
• How the study drug is acting on your body

The study will include four parts (Phase Ia, Phase Ib, Phase IIa, and Phase IIb). You will be enrolled to only one phase of the study.

In Phase Ia, about 8 groups of participants will receive different, increasing doses of the study drug to determine which dose is safe and tolerable, and to also determine the preliminary maximum tolerated dose and/or recommended dose to be given to participants in Phase Ib.

Phase Ib is the dose escalation phase. Dose expansion means that a larger number of participants will be given the highest dose from the dose escalation phase (Phase Ia) determined to have the least side effects and to be the most tolerable.

In Phase IIa, about 2 different groups of participants will receive different, increasing doses of the study drug in combination with Pembrolizumab to determine which dose is safe and tolerable, and to determine the maximum dose tolerated and/or recommended to be given in Phase IIb.

In Phase IIb, 3 or more groups of participants will receive the recommended dose of the study drug that was determined to be safe and tolerable in combination with Pembrolizumab. Phase IIb will continue to evaluate the safety and tolerability of the study drug as well as determine the effectiveness of the recommended study drug dose from Phase Ib.

The study regimen will be given in cycles. Each cycle is 21 days long. If you meet the requirements to be in the study, you will receive the study drug on Day 1 of each cycle in the clinic.