TABLE 4.

Proteasome inhibitors in clinical testing

Inhibitor	Class	IC50 In Vitro Peptidase Activity			Half-Life	Route	Binding	Reference
		CT-L	C-L	T-L
		nM			min
Bortezomib	Boronate	7.9	53	590	110	i.v./s.c.	Slowly reversible	Cauhan et al. (2005)
Carfilzomib	Epoxyketone	6	2400	3600	<30	i.v.	Irreversible	Kuhn et al. (2007)
Ixazomib	Boronate	3.4	31	3500	18	p.o.	Reversible	Cauhan et al. (2005), Kupperman et al. (2010)
Marizomib	β-lactone	3.5	430	28	10–15	i.v.	Irreversible	Feling et al. (2003)
Oprozomib	Epoxyketone	36 (β5)	ND	ND	30–90	p.o.	Irreversible	Zhou et al. (2009), Roccaro et al. (2010)
		82 (β5i)

C-L, caspase-like activity (β1); CT-L, chymotrypsin-like activity (β5); ND, not determined; T-L, trypsin-like activity (β2).