Carfilzomib

Carfilzomib (Kyprolis) is an FDA-approved second-generation tetrapeptide epoxyketone proteasome inhibitor used for the treatment of relapsed or refractory multiple myeloma. Unlike bortezomib, it binds the proteasome irreversibly, conferring greater selectivity and potency. It is approved as monotherapy and in combination with lenalidomide plus dexamethasone or daratumumab plus dexamethasone.

Carfilzomib is a tetrapeptide epoxyketone that covalently and irreversibly inhibits the chymotrypsin-like (CT-L) proteolytic activity of the 20S proteasome catalytic core. The alpha,beta-epoxyketone pharmacophore forms a morpholine adduct with the N-terminal threonine of the beta5 subunit, permanently inactivating the active site. Proteasome inhibition leads to accumulation of poly-ubiquitinated proteins, triggering endoplasmic reticulum stress, activation of the unfolded protein response, upregulation of pro-apoptotic proteins such as NOXA and BIM, and suppression of NF-κB-mediated pro-survival signaling. Because it binds irreversibly, carfilzomib's pharmacodynamic effect outlasts its short plasma half-life. Compared to bortezomib, it has minimal off-target activity against serine proteases, which reduces peripheral neuropathy.

Carfilzomib received accelerated FDA approval in 2012 for patients with relapsed/refractory multiple myeloma after at least two prior therapies. The ASPIRE trial (carfilzomib + lenalidomide + dexamethasone vs. lenalidomide + dexamethasone) showed a 26.3-month median PFS vs. 17.6 months (HR 0.69). The ENDEAVOR trial demonstrated superiority over bortezomib-dexamethasone. Cardiovascular toxicity, particularly hypertension and cardiac failure, is the primary dose-limiting concern and requires monitoring.