Phosphatidylserine　is　a　crucial　component　of　the　cell　membrane,　typically　localized　to　the　inner　leaflet　of　the　lipid　bilayer.　In　neoplastic　cells,　phosphatidylserine　is　aberrantly　externalized,　rendering　it　a　promising　biomarker　for　the　development　of　targeted　oncological　therapeutics.　We　previously　elucidated　the　crystal　structure　of　phosphatidylserine　bound　to　the　C2　domain　of　lactadherin　(LAC)　and　revealed　calcium-independent　binding　with　nanomolar　affinity　(Kd　=　3.3　±　0.5　nM).　Expanding　upon　our　previous　work,　here　we　developed　a　novel　targeted　therapeutic　platform　by　genetically　fusing　LAC　with　human　serum　albumin　(HSA).　This　engineered　LAC-HSA　fusion　protein　synergistically　integrates　phosphatidylserine-targeting　specificity　with　HSA＇s　pharmacokinetic　advantages,　including　an　extended　plasma　half-life　and　drug　delivery　capabilities.　To　validate　its　therapeutic　potential,　we　incorporated　a　potent　cytotoxic　agent　(zinc　monocarboxyphthalocyanine,　CPZ)　into　LAC-HSA　via　a　non-covalent　strategy.　In　vitro,　the　LAC-HSA　fusion　protein　selectively　bound　to　phosphatidylserine-exposed　tumor　cells,　enhancing　the　uptake　of　encoded　cytotoxic　agent　(3-fold　higher　than　the　non-targeted　control),　thereby　improving　tumor　cell-killing　efficacy.　In　vivo,　in　the　mouse　solid　tumor　model,　the　targeted　therapy　group　showed　a　3-fold　reduction　in　tumor　volume　compared　to　the　non-targeted　treatment　group.　These　results　clearly　demonstrate　that　LAC-HSA　is　an　effective　phosphatidylserine-targeting　drug　carrier.　©　2025　Elsevier　B.V.