Safety, PK and Efficacy of QXL138AM in Patients With Solid Tumors and Multiple Myeloma

This is an open-label, multicenter, first in human (FIH) Phase 1a/1b study of QXL138AM in participants with locally advanced unresectable and/or metastatic solid tumors and multiple myeloma. This study will be conducted in two parts (A and B) and each part has two sub-parts for tumor type (1 and 2).

Part A1 - Dose Escalation in Solid Tumors The following solid tumor types will initially be enrolled in this part: ovarian, pancreatic, urothelial, renal, hepatocellular, gastrointestinal, lung, prostate, and breast cancer.

Dose escalation will use a standard 3+3 design, where 3 to 6 participants with advanced solid tumors will be enrolled sequentially into each cohort/dose level with the exception of Cohort 1 and 2. For Cohorts 1 and 2, given the very low starting dose, only one participant is planned for each level unless a participant experiences a Grade 2 or higher adverse event not clearly and incontrovertibly related to disease progression or an extraneous factor. If such a Grade 2 or higher event occurs in Cohort 1 or 2, dose escalation will switch to a standard 3+3 design. Dose escalation will continue until the MTD or RDE is determined in participants with solid tumors, referred to as the RDE-ST. At this point, the two solid tumor types for dose expansion will be selected for Part B1 and may begin at the RDE-ST.

The proposed dose levels are defined in the table below. Cohort No. of Participants Dose Level (Q2W) (mg/kg)

1. 1-6 0.001
2. 1-6 0.003
3. 3-6 0.01
4. 3-6 0.03
5. 3-6 0.1
6. 3-6 0.3
7. 3-6 1
8. 3-6 2
9. 3-6 4 Infusions will be administered via syringe pump or IV bag (depending on the dose) and administered over a 30-60-minute (± 10 minutes) duration.

Part A2 - Dose Escalation in Multiple Myeloma Dose escalation in multiple myeloma will commence when the RDE-ST for solid tumors has been identified, or if there are signs of anti-tumor activity in Part A1 as determined by the Sponsor.

Dose escalation will use a standard 3+3 design, where 3 to 6 participants with multiple myeloma will be enrolled sequentially into dose escalation cohorts starting at one dose level below the RDE-ST determined from solid tumor dose escalation (RDE-ST-1). Alternatively, if signs of anti-tumor activity in Part A1 are observed, the Sponsor may elect to initiate dose escalation in multiple myeloma at one dose level below the highest dose already deemed safe in Part A1. If two of the first six participants in the first multiple myeloma cohort experience a DLT, then the dose will be further reduced by one level (RDE-ST-2). Once the RDE for multiple myeloma patients is determined, it will be referred to as the RDE-MM and dose expansion may begin in patients with multiple myeloma at this dose.

Part B1: Dose Expansion in Solid Tumors When the RDE-ST has been identified by the SRC from Part A1, the study may continue to Part B1 dose expansion to further explore the safety and anti-tumor activity of QXL138AM in solid tumors. Dose expansion will enroll two cohorts of 20 participants each in two solid tumor indications identified from Part A1. In each cohort, patients will be randomized 1:1 to receive the RDE-ST dose or 1 dose lower. The Sponsor may opt to enroll additional participants up to a maximum of 40 in each cohort if signs of anti-tumor activity are observed.

Part B2: Dose Expansion in Multiple Myeloma When the RDE-MM in multiple myeloma has been identified by the SRC from Part A2, the study may continue to Part B2 dose expansion to further explore the safety and anti-tumor activity of QXL138AM in patients with multiple myeloma. Up to 20 participants will be treated at the RDE-MM identified in Part A2. Patients will be randomized 1:1 to receive the RDE-MM dose or 1 dose lower.