The present invention relates to inhibitors of MALT1 proteolytic and/or autoproteolytic activity. More specifically, it relates to compounds such as, but not limited to peptide derivates such as Z-LSSR-CHO (see SEQ ID NO:1), Z-LSSR-CMK (see SEQ ID NO:1), Z-GASR-CHO (see SEQ ID NO:2), and Z-GASR-CMK (see SEQ ID NO:2), and small compounds such as 5-{[5-(3-chloro-4-methylphenyl)-2-furyl]methylene}-2-thioxodihydro-4,6(1H,5H)-pyrimidinedione and variants thereof, and the use of those compounds for the preparation of a medicament. The invention relates further to a method to screen for inhibitors of the MALT1 proteolytic and/or autoproteolytic activity.