Cathepsin S inhibitors

A compound of formula (I):

• wherein
• R1 is H, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, aryl, heteroaryl, ORa, SRa, NRaRb, N(Ra)C(O)Rb, N(Ra)C(O)ORb, C(O)Ra, COORa, OC(O)Ra, C(S)Ra, C(O)NRaRb, C(S)NRaRb, N(Ra)C(S)Rb, or N(Ra)N(Rb)C(O)Rc, in which each of Ra, Rb, and Rc, independently, is H, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, aryl, or heteroaryl, or Ra and Rb together with the nitrogen atom or nitrogen atoms to which they are attached form heterocycloalkyl, heterocycloalkenyl, or heteroaryl;
• each of R2 and R3, independently, is H, cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, aryl, heteroaryl, or alkyl optionally substituted with cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, aryl, or heteroaryl;
• and
• each of R4 and R5, independently, is H, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, heterocycloalkyl, heterocycloalkenyl, aryl, or heteroaryl, or R4 and R5 together with the nitrogen atom to which they are attached form heterocycloalkyl, heterocycloalkenyl, or heteroaryl.