Eligible participants are adults (≥18 years) with advanced/metastatic HER2-expressing solid tumors (IHC 1+/2+/3+ or HER2 mutations) who failed or are intolerant to standard therapy. Key inclusion criteria: ECOG 0-1, adequate organ function, measurable lesions per RECIST 1.1, and washout from prior therapies. Exclusion criteria include uncontrolled brain metastases, cardiovascular disease, significant pulmonary conditions, prior topoisomerase I inhibitor-ADCs, active infections (HIV/HBV/HCV), pregnancy, and unresolved toxicity >Grade 1 from prior treatments.

The pharmacokinetics (PK) of GQ1005 will be assessed via maximum concentration (Cmax), time to peak concentration (Tmax), and area under the curve (AUC). Antitumor efficacy measures include overall response rate (ORR), duration of response (DOR), disease control rate (DCR), time-to-response (TTR), progression-free survival (PFS), and overall survival (OS), all evaluated per RECIST 1.1. Immunogenicity will be assessed by anti-drug antibody (ADA) formation.

Eligible participants are adults (≥18 years) with advanced/metastatic HER2-expressing solid tumors (IHC 1+/2+/3+ or HER2 mutations) who failed or are intolerant to standard therapy. Key inclusion criteria: ECOG 0-1, adequate organ function, measurable lesions per RECIST 1.1, and washout from prior therapies. Exclusion criteria include uncontrolled brain metastases, cardiovascular disease, significant pulmonary conditions, prior topoisomerase I inhibitor-ADCs, active infections (HIV/HBV/HCV), pregnancy, and unresolved toxicity >Grade 1 from prior treatments.

The pharmacokinetics (PK) of GQ1005 will be assessed via maximum concentration (Cmax), time to peak concentration (Tmax), and area under the curve (AUC). Antitumor efficacy measures include overall response rate (ORR), duration of response (DOR), disease control rate (DCR), time-to-response (TTR), progression-free survival (PFS), and overall survival (OS), all evaluated per RECIST 1.1. Immunogenicity will be assessed by anti-drug antibody (ADA) formation.

Eligible patients are adults (≥18) with HER2+ advanced/metastatic solid tumors (breast, gastric/GEJ, or other) refractory to standard therapy, ECOG 0-1, LVEF≥50%, and adequate organ function, excluding those with active brain metastases, significant cardiac/pulmonary disease, unresolved toxicities (>Grade 1), uncontrolled infections, or prior cumulative anthracycline dose >360mg/m2 doxorubicin-equivalent.

Eligible patients must be &ge;19 years old with ECOG 0-1, adequate organ function (hematologic/renal/hepatic), and negative pregnancy status. Key exclusions include trastuzumab intolerance, active CNS metastases, unresolved Grade &ge;2 toxicities, recent anticancer therapies (<3 weeks), significant cardiopulmonary dysfunction (LVEF<50%, NYHA II-IV), active infections (HIV/HBV/HCV), or other malignancies within 5 years (except specified cured cancers).

The study evaluates safety endpoints including dose-limiting toxicities (DLTs) during the 21-day assessment period to determine maximum tolerated dose (MTD) or recommended phase II dose (RP2D), along with treatment-emergent adverse events (TEAEs) graded by CTCAE v4.03 with special focus on immune-related adverse events (irAEs) monitored for up to 4 weeks post-treatment.

Eligible patients must be &ge;19 years old with ECOG 0-1, adequate organ function (hematologic/renal/hepatic), and negative pregnancy status. Key exclusions include trastuzumab intolerance, active CNS metastases, unresolved Grade &ge;2 toxicities, recent anticancer therapies (<3 weeks), significant cardiopulmonary dysfunction (LVEF<50%, NYHA II-IV), active infections (HIV/HBV/HCV), or other malignancies within 5 years (except specified cured cancers).

The study evaluates safety endpoints including dose-limiting toxicities (DLTs) during the 21-day assessment period to determine maximum tolerated dose (MTD) or recommended phase II dose (RP2D), along with treatment-emergent adverse events (TEAEs) graded by CTCAE v4.03 with special focus on immune-related adverse events (irAEs) monitored for up to 4 weeks post-treatment.

Key eligibility: Adults (&ge;18) with HER2+ metastatic solid tumors, ECOG 0-2 (dose escalation)/0-1 (expansion), adequate organ function (ANC&ge;1500, platelets&ge;100K, bilirubin&le;1.5&times;ULN, CrCl&ge;60). Exclusions: Grade&ge;3 antibody hypersensitivity, CNS metastases, active HBV/HCV/HIV, recent anticancer therapy, pregnancy, or uncontrolled comorbidities.

Part 1 (dose escalation): Participants received an infusion of ADCT-502, at escalating doses. Part 1 continued until the maximum tolerated dose or the recommended dose (s) and schedule (s) for expansion were determined.Part 2 (expansion): Participants were due to be assigned to the recommended dose level of ADCT-502 as identified in Part 1 by the Dose Escalation Steering Committee.