Imiquimod Injection to Rabbit Vocal Folds: A Preliminary, Preclinical Investigation

Objective: Given the recalcitrant nature of recurrent respiratory papillomatosis, targeted therapies to reduce disease burden are fundamental to improved patient care paradigms. We seek to demonstrate the safety of imiquimod injection into vocal fold mucosa by evaluating the degree of laryngeal edema, histopathologic changes to vocal fold structure, and serologic interferon α (IFNα) levels following injection. Study Design: Preclinical. Setting: Academic institution. Subjects and Methods: Six New Zealand White rabbits underwent unilateral injection of 100 µg of sterile imiquimod (1 µg/µL), with 100 µL of normal saline injected into the contralateral vocal fold. Direct laryngoscopy was performed on days 3, 7, and 30 following injection. Larynges from 3 rabbits were harvested on postinjection day 7 for histologic analysis. The remaining 3 rabbit larynges were harvested on day 30. Serial serum samples were drawn for IFNα quantification via immunoassay. Results: No signs of respiratory distress were observed at any point. Vocal fold appearance was not clinically divergent between imiquimod and control conditions via serial direct laryngoscopic evaluation. No inflammatory lesions or scarring were identified following injection. Histology showed no signs of acute inflammatory processes or changes in the control or imiquimod injection groups. Serum IFNα increased at days 3 and 7 following imiquimod injection (P <.0001 and P =.0368, respectively), before returning to baseline by day 14. Conclusions: Vocal fold imiquimod injection did not result in notable morbidity in this preclinical model. However, serum IFNα concentrations increased transiently. These data are critical to advance the therapeutic utility of this compound, particularly in the setting of recurrent respiratory papillomatosis.