Background/Objectives: Hemophilia A (HA) is caused by coagulation factor VIII (FVIII) deficiency, but its clinical heterogeneity suggests that biological alterations beyond impaired hemostasis may contribute to disease expression. This study aimed to characterize F8 knockout (F8-KO)-associated molecular changes and identify drug repositioning candidates with therapeutic potential for HA. Methods: An F8-KO human umbilical vein endothelial cell model was generated using CRISPR/Cas9 and profiled by RNA sequencing and data-independent acquisition (DIA) proteomics. Integrated multi-omics, enrichment, and protein–protein interaction analyses informed drug repositioning using Connectivity Map (CMap), EpiMed, and DrugBank. Valproic acid (VPA) was evaluated using cell viability assays, RT-qPCR, transcriptomic profiling, and H3K27ac CUT&Tag. Results: Integrated transcriptomic and proteomic analysis identified 113 shared genes with predominantly concordant changes, and network-based analysis prioritized genes involved in endothelial homeostasis and inflammatory regulation. Drug repositioning identified VPA and irbesartan across three screening sources. VPA increased CD274 mRNA expression, partially reversed F8-KO-associated transcriptional alterations, and remodeled H3K27ac-associated regulatory programs involving vascular homeostasis- and inflammation-related pathways. Conclusions: VPA may modulate F8 deficiency-associated endothelial molecular alterations and represents a drug-repositioning candidate for HA. These findings may offer a new perspective for exploring potential therapeutic strategies beyond conventional correction of the coagulation defect.