S3183 Effect of Azo Bonded 5-ASA and 4-APAA on DNBS-Induced Colitis in Rats

Abstract

INTRODUCTION: Azo chemistry, enables drug delivery to the colon, where bacterial azo reductases can cleave the bond, liberating the two moieties. In all commercial IBD azo preparations, the only active moiety is 5-ASA, an anti-inflammatory agent. Delivering two different active moieties such as anti-inflammatory and an immunomodulator may improve efficacy. 4-aminophenylacetic acid (4-APAA), has been used in Japan for the past 10 years in the treatment of Rheumatoid Arthritis. It has an available amino group for azo bonding. 4-APAA is known to reduce TNF-α, IL-1β, MMP-1 production and to reduce the adhesion of T cells. We herein report the effect of azo bonded 5-ASA + 4-APAA on experimental colitis in rats. METHODS: Experimental colitis—on Day 0, a catheter was inserted rectally into the colon and the irritant, an ethanolic solution of 2,4 dinitrobenzenesulfonic acid (DNBS) was instilled at a volume of 0.5 mL. Concentration of DNBS was 60 mg/mL in 30% ethanol for a total dose of 30 mg DNBS. Animals—30 adult male Lewis rats (weighting 200–250 g) were divided into 5 groups of 6 animals each: (1) Vehicle; (2) Vehicle + DNBS; (3) 5-ASA 100 mg/kg/day + DNBS; (4) 4-APAA 99 mg/kg/day + DNBS; (5) Azo bonded 5-ASA + 4-APAA 199 mg/kg + DNBS. All groups received rectal bid doses of test compounds for the 4 days following induction of colitis. Animals were sacrificed on day 5 and animals were scored for the presence and severity of intestinal lesions (0 to 2 scale). Colon: body weight ratios were also determined. Statistics – t-test was used and P < 0.05 was deemed as significant. RESULTS: Compared to the vehicle/DNBS group, adhesion scores were reduced by 17%, 25%, and 38% in the 5-ASA, 4-APAA and azo bonded 5-ASA + 4-APAA groups respectively. The azo bonded 5-ASA + 4-APAA group was also better than the 5-ASA group. Compared to the vehicle/DNBS group, the average net colon to body weight ratio was reduced by 31.8%, 31.3 % and 31.1 % in the 5-ASA, 4-APAA and azo bonded 5-ASA + 4-APAA groups respectively. No significant difference was observed between the groups. CONCLUSION: The main findings of the present study are that rectally administered 4-APAA alone and azo bonded 5-ASA + 4-APAA are effective inhibitors of experimental colitis in a rat model and that this effect is of similar magnitude to the of 5-ASA. The azo bonded 5-ASA + 4-APAA also trended to better than each component separately, therefore may be a better alternative than single moiety azo preparations.Figure 1.: DNBS Colitis Adhesion Score.