- Katz B, Luong C, Ho J, Somoza J, Gjerstad E, Tang J, et al. Dissecting and designing inhibitor selectivity determinants at the S1 site using an artificial Ala190 protease (Ala190 uPA). J Mol Biol. 2004;344:527-47 pubmed..The 6-fluoro-5-amidinobenzimidzole, CA-11, is more than 1000-fold selective against natural Ala190 protease anti-targets, and more than 100-fold selective against other Ser190 anti-targets. ..