A Phase 1 Study Evaluating the Safety, Tolerability, and Efficacy of BL-B01D1 in Subjects With Metastatic or Unresectable Non-Small Cell Lung Cancer and Other Solid Tumors

EGFR x HER3 bispecific antibody-drug conjugate

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 BL-B01D1

This study will be conducted in two different schedules (Cohort A and Cohort B) and three parts (dose escalation, dose finding, and dose expansion). Each cohort includes different dose groups. Which cohort (A or B) and part you will enter and which dose you will receive will depend on when you enter the study. The dose you receive may be too low to have an effect on your disease, or so high that it causes side effects. Your study doctor will inform you which schedule and part you will be enrolled in.

Part 1: Dose Escalation

The purpose of part 1 of this study is to determine the dose of the study drug that works, can be tolerated, and is least harmful.

• Cohort A: The study drug will be given intravenously (slow injection into a vein) every 3 weeks (Day 1 and Day 8 of a 21-day cycle).
• Cohort B: The study drug will be given intravenously every 3 weeks on Day 1.

Part 2: Dose Finding

The purpose of Part 2 is to determine the recommended dose and schedule at which BL-B01D1 can be tolerated. Approximately 60 participants will be enrolled in Part 1 and Part 2 combined.

Part 3: Dose Expansion

Once Part 1 (dose escalation) and Part 2 (dose finding) are complete and 2 or more recommended dose expansion (RDE) doses and schedules are determined, Part 3 (dose expansion) will begin. The purpose of Part 3 is to determine if the study drug works, is safe and tolerable at the RDE dose and schedule. If you enter the study in Part 3, you will be randomly assigned by chance (like the flip of a coin) into one of the 2 or more cohorts. You will have an equal chance of being assigned to each cohort in Part 3 of the study. There will be approximately 20 participants per cohort.