A Novel Approach to the Discovery of Non-systemic Anti-inflammatory Steroids; Antedrug

Therapeutic use of anti-inflammatory steroids is limited due primarily to their systemic suppressive effects on pituitary function and the immune system.. To overcome the clinical limitation, a new approach toward the discovery of non-systemic anti-inflammatory steroids is based upon the antedrug concept introduced by this laboratory. The new concept describes locally active agents which are designed to undergo a predictable biotransformation to inactive metabolites upon entry into systemic circulation from the applied site. Thus, true antedrugs are devoid of systemic adverse effects. In a continuing effort, 16$\alpha$-carboxylate and isoxazoline derivatives of prednisolone have been synthesized and screened. In the croton oil-induced ear edema bioassay, the following relative potencies were obtained setting hydrocortisone=1.0; 3a, 1.5; 3b, 3.1; 4a, 4.0; 4b, 12.2; 5b, 8.2; 6b, 11.2; 7a, 1.9; 7b, 4.1; 8a, 3.3; 8b 6.8; 9a, 0.7; 9b 8.6; 10a 2.6; 10b, 7.4. Results of the five-day bioassay indicated that, in contrast to the parent compound, the novel steroidal antedrugs did not significantly alter body weight gain, thymus weights, adrenal weights or plasma corticosterone levels. Taken together, the antedrug concept appears to be a fundamentally sound strategy for the separation of local anti-inflammatory activity form systemic adverse effects.