pH-Responsive Erdafitinib Liposomes with FGFR3 Targeting for Intravesical Bladder Cancer Therapy

Fibroblast growth factor receptor 3 (FGFR3) is a key oncogenic driver in bladder cancer (BCa). Although erdafitinib, the pioneering FGFR3 inhibitor, is approved for clinic use, its oral administration frequently causes inadequate therapeutic effect and side effects. Here, we report a pH-responsive and erdafitinib-loaded liposomal nanosystem with surface modification of anti-FGFR3 antibodies (Phl-erda@Ab), which demonstrates improved antitumor effects in intravesical instillation therapy. In RT112 cells, we evaluated targeted uptake and antiproliferative activity. In vivo, we assessed intravesical retention, antitumor efficacy, and histopathological markers (TUNEL, Ki67) in a BCa xenograft BALB/C nude mouse model, alongside systemic safety profiling. The Phl-erda@Ab exhibited sharp pH sensitivity, releasing 49% of the drug payload within 1 h at pH 5.3 while maintaining minimal release at pH 7.4 and 6.5. Liposome retention after intravesical instillation was doubled compared with non-targeted Phl-erda in mice. The Phl-erda@Ab intravesical therapy demonstrated effective antitumor activity, including maximal necrosis, the highest TUNEL-positive apoptotic index, and the lowest Ki67 proliferation index, compared to other groups. No significant pathological damage to major organs was observed. In summary, Phl-erda@Ab enables FGFR3-targeted, pH-triggered intravesical delivery with enhanced intravesical retention, improved antitumor activity, and favorable local safety, providing preclinical evidence to support clinical translation in FGFR3-overexpressing BCa.