Inclusion: Solid tumor patients (Part 2a: SCLC; Part 2b: NSCLC/HR+HER2- breast cancer) with measurable disease, ECOG ≤2, prior therapy failure. Breast cancer patients must have CDK4/6 inhibitor failure; NSCLC patients require targeted therapy if actionable mutations present. Exclusion: Active CNS metastases, Grade≥2 neuropathy, unresolved toxicities, active hepatitis/HIV, significant cardiac history, or hypersensitivity to study drug components. Taxane-exposed patients require 2-month washout.

Eligible participants must have IMWG-defined multiple myeloma requiring systemic therapy, age ≥18 years, ECOG 0-1, life expectancy >3 months, ≥2 prior lines of therapy (including IMiD and PI), measurable disease, adequate organ function, and negative pregnancy test. Key exclusions include recent malignancies (past 3 years), active CNS disease, severe infections, HIV/HBV/HCV positivity, prior allogeneic transplant, significant pulmonary/cardiovascular comorbidities, or pregnancy/breastfeeding.

All patients (N = 35) were included in response analyses. Five patients (14.29%) overall achieved a PR per investigator assessment,with no patients achieving a CR. One patient each had a PR in the 0.20 and 0.30 mg/kg Q3W dose groups, and 3 patients in the 0.40 mg/kg Q9W dose group, fourteen (40.00%) patients achieved stable disease as their best overall response,and 5 had no or an non-evaluable posttreatment scan.

Nineteen patients had tumor samples that were able to be assessed for DLL3 expression by immunohistochemistry. DLL3-positive expression by immunohistochemistry (DLL3 >0%) was confirmed in 17 patients; 5 were DLL3 high (75.00% DLL3 positive cells). Of DLL3-positive patients, 2 (11.80%) achieved a PR, including 1 patient in the 0.20 mg/kg Q3W cohort and 1 DLL3-high patient in the 0.40 mg/kg Q9W cohort.