This is a first-in-human, multicenter, open-label, single-arm, dose-escalation Phase 1 study evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity, and preliminary antitumor activity of D3L-002 monotherapy in subjects with advanced solid tumors. D3L-002 will be administered as an intravenous infusion every 3 weeks (Q3W) in 21-day cycles. Approximately 24 subjects will be enrolled. Dose escalation will follow a Bayesian Optimal Interval (BOIN) design to determine the maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D).