sentence: Besides , more MDM2 inhibitors , such as RITA ( 134 ) , PRIMA1 ( 135 ) HLI373 ( 148 ) , HLI98 ( 149 ) , MEL23 and MEL24 ( 150 ) , and RO8994 ( 136 ) have been discovered to target MDM2 directly , thereby enhancing p53 activity and exhibiting anti-cancer ability.MDMX / HDMX ( murine / humans double minute X) shares significant homology with MDM2 and is also a negative regulator of p53 .