Symptom severity in patients with human rhinovirus (HRV)-induced respiratory illness is associated with elevated levels of the inflammatory cytokines interleukin-6 (IL-6) and IL-8. AG7088 is a novel, irreversible inhibitor of the HRV 3C protease. In this study, AG7088 was tested for its antiviral activity and ability to inhibit the production of IL-6 and IL-8 in a human bronchial epithelial cell line, BEAS-2B. Infection of BEAS-2B cells with HRV 14 resulted in the production of both infectious virus and the cytokines IL-6 and IL-8. Treatment of HRV 14-infected cells with AG7088 resulted in a statistically significant (P, <0.05) dose-dependent reduction in the levels of infectious virus as well as IL-6 and IL-8 released into the cell supernatant compared to the results obtained for compound-free infected cells. AG7088 was also able to inhibit the replication of HRV 2 and 16 in BEAS-2B cells. In time-of-addition studies, AG7088 could be added as late as 14 to 26 h after HRV 14 infection of BEAS-2B cells and still result in a statistically significant (P, <0.05) reduction in the levels of infectious virus, IL-6, and IL-8 compared to the results obtained for compound-free infected cells. These findings have implications for the development of an antirhinovirus agent that may not only block virus replication but also diminish symptoms.Human rhinoviruses (HRV), which include over 100 different virus serotypes, are responsible for a significant portion of common colds experienced each year (reviewed in references 7, 26, and 34). In patients with underlying respiratory disorders, HRV infections may lead to sinusitis, otitis media, and lower-respiratory-tract illnesses and also may lead to exacerbations of asthma, cystic fibrosis, and bronchitis (3). Many of the clinical symptoms observed in patients with HRV-induced respiratory illness, such as sore throat, nasal congestion, sneezing, and runny nose, are associated with elevated cytokine levels that can be detected in nasal washings (27,31,33). In addition, experimental HRV infections have been shown to produce an increase in the levels of one or more of the inflammatory cytokines and mediators, including interleukin-6 (IL-6), IL-8, IL-1, kinins, tumor necrosis factor, histamine, and soluble intercellular adhesion molecule 1 (ICAM-1) (32,38,45; R. B. Turner, K. Weingand, C. H. Yeh, et al. Abstr. 36th Intersci. Conf. Antimicrob. Agents Chemother. abstr. H-48, 1996). Increased levels of both IL-6 (45) and IL-8 (39; Turner et al., 36th ICAAC) have been associated with symptom severity in HRV-infected patients.Although a number of compounds have shown in vitro activity against HRV, no antiviral agent has been shown to be effective against disease caused by HRV infection in vivo (1,2,8,15,17,28). To date, only one agent, pirodavir, has been shown to be effective when administered at the time of HRV challenge but not when given 24 h after HRV infection (19). Recent reports have described a new class of compounds directed toward a novel target, the HRV 3C protease (10-14, ...