Immunostimulation in the urinary bladder by local application ofNocardia rubra cell wall skeleton preparation (Rubratin) for superficial bladder cancer immunotherapy — a phase I/II study

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Abstract
Objectives: Twelve patients with superficial papillary transitional cell carcinoma of the bladder (pTa, pT1) were treated with six consecutive weekly intravesical instillations of Rubratin (in a dose of 1.5, 3.0, or 4.5 mg), a cell wall skeleton preparation ofNocardia rubra (NCW). The main objective of this study was to look for local immunomodulating effects of NCW and in the first four patients the effect on a marker lesion was also investigated. Methods: Local immunostimulation in all 12 patients was determined by (1) measurement of cytokine induction [interleukin 1 β (IL1 β), IL2, IL6, and tumor necrosis factor alpha (TNFα)], (2) leukocyte influx into the urine, and (3) phenotypic analysis of the lymphocyte fraction of these leukocytes. Results: Significantly elevated levels of Rubratin-induced IL1β (P < 0.001), IL2 (P < 0.001), IL6 (P < 0.01), and TNFα (P < 0.001) were found compared to control pretherapy levels. Rubratin also induced leukocyte influx into the urine. Fluorescence-activated cell sorter (FRCS) analysis of the urinary leukocytes indicated T-cell activation (IL2 receptor and HLA-DR expression), while in two out of five patients the CD4/CD8 ratios were increased. Urinary cytokine induction by Rubratin was comparable with cytokine induction observed in non-responding bacillus Calmette-Guérin (BCG) patients (recurrent tumor within 6 months), but less compared with responding BCG patients (no recurrent tumor within 6 months). Clinical results showed no response on the marker lesion and in five out of eight patients early recurrence was found after complete transurethral resection (TUR) of the bladder tumors. This biological response modifier caused no local or systemic side effects at the doses used. Conclusion: Although local immunostimulation by intravesical Rubratin administration can be induced, the amount of immunocompetent cells attracted to the bladder is not as high as observed in BCG-responding patients, resulting in lower amounts of cytokines produced. This could also explain the lack of clinical efficacy.

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