Non-muscle invasive bladder cancer (NMIBC) is commonly treated with Intravesical Bacillus Calmette-Guerin (BCG) immunotherapy. However, up to 70% of patients experience lower urinary tract symptoms (LUTS) including bladder pain, urinary urgency, and frequency, which reduce quality of life and lead up to 20% of patients to discontinue therapy. Phenazopyridine (PAP), a urinary tract analgesic is clinically effective in relieving LUTS associated with urinary tract infection (UTI). As BCG-induced LUTS share similarities with UTI symptoms, PAP may also provide symptomatic relief during BCG therapy. However, its effects on BCG efficacy remain unknown.
This study aims to determine whether PAP alleviates BCG-immunotherapy LUTS, without compromising necessary BCG mechanisms and impairing efficacy of the treatment.

Female Mice (N=10) were treated with weekly intravesical instillations of BCG (1.2x107CFU) or BCG + PAP (300μM) for six weeks. One day after the final treatment, bladders were collected for assessment of immune cell population via flow cytometry. Changes in bladder sensory signalling were assessed using ex-vivo bladder afferent nerve recordings in the absence and presence of PAP (100μM). To evaluate whether PAP altered BCG efficacy, urothelial cancer cell lines (MB49, T24 and UMUC3) were exposed to BCG for 2hrs (MOI 3) with or without PAP (10-300μM). BCG-induced apoptosis (Annexin V/PI) was assessed by flow cytometry, while BCG internalisation was quantified via qPCR and immunohistochemistry.

BCG treatment increased expression of key inflammatory pathways and increased the overall CD45+ immune cell population in the bladder. PAP had no significant impact on infiltration of immune cell subtypes, including Neutrophils, Natural Killer cells and Dendritic cells during BCG treatment. In-vitro, BCG induced early and late apoptosis in vitro in urothelial cells (p<0.001), and this effect was not altered by PAP (p>0.05). qPCR and immunohistochemistry similarly showed that BCG internalisation was unaffected by PAP. Importantly, PAP significantly inhibited BCG-induced bladder afferent hypersensitivity  ex vivo (P<0.01, N=5/group).

This study shows that the urinary tract analgesic, PAP, does not significantly impact the apoptotic, internalisation BCG in-vitro or the measured immune responses in-vivo, but is effective in reducing BCG induced bladder afferent hypersensitivity ex vivo. These results suggest that PAP may be used as an adjunct therapeutic with BCG-Immunotherapy for NMIBC, to relieve associated LUTS without impacting mechanisms associated with effective BCG treatment.

LUTS are a common and clinically significant side effect of BCG-immunotherapy for NMIBC, affecting up to 70% of patients. As these symptoms are associated with increased bladder afferent sensitivity, targeting afferent signalling with PAP may offer a novel adjunct approach for symptom management during BCG treatment.

Continence 19S (2026) 102695
DOI: 10.1016/j.cont.2026.102695