LFA-1 (leukocyte function-associated antigen-1), is a member of the beta2-integrin family and is expressed on all leukocytes. This letter describes the discovery and preliminary SAR of spirocyclic hydantoin based LFA-1 antagonists that culminated in the identification of analog 8 as a clinical candidate. We also report the first example of the efficacy of a small molecule LFA-1 antagonist in combination with CTLA-4Ig in an animal model of transplant rejection.
Leukocyte function-associated antigen-1 (LFA-1), also known as CD11a/CD18 or alpha(L)beta(2), belongs to the beta(2) integrin subfamily and is constitutively expressed on all leukocytes. The major ligands of LFA-1 include three intercellular adhesion molecules 1, 2, and 3 (ICAM 1, 2, and 3). The interactions between LFA-1 and the ICAMs are critical for cell adhesion, and preclinical animal studies and clinical data from the humanized anti-LFA-1 antibody efalizumab have provided proof-of-concept for LFA-1 as an immunological target. This article will detail the structure-activity relationships (SAR) leading to a novel second generation series of highly potent spirocyclic hydantoin antagonists of LFA-1. With significantly enhanced in vitro and ex vivo potency relative to our first clinical compound (1), as well as demonstrated in vivo activity and an acceptable pharmacokinetic and safety profile, 6-((5S,9R)-9-(4-cyanophenyl)-3-(3,5-dichlorophenyl)-1-methyl-2,4-dioxo-1,3,7-triazaspiro-[4.4]nonan-7-yl)nicotinic acid (2e) was selected to advance into clinical trials.
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