Carfilzomib

Mechanism

Carfilzomib is a synthetic tetrapeptide epoxyketone that irreversibly inhibits the 20S proteasome core particle. It specifically and irreversibly binds the chymotrypsin-like (β5) and, at higher doses, the caspase-like (β1) and trypsin-like (β2) subunits of the 20S proteasome.

The epoxyketone pharmacophore forms a covalent, morpholine-like adduct with the N-terminal threonine hydroxyl and amino groups of the proteasome β-subunit — an interaction highly specific to the proteasome (not seen with other protease classes, which explains the reduced off-target toxicity compared with bortezomib).

Irreversible binding means proteasome activity only recovers through new proteasome synthesis (de novo proteasome biogenesis, approximately 24–48 hours). This provides more sustained proteasome suppression than the reversible inhibitor bortezomib.

Consequences of proteasome inhibition:

1. Accumulation of misfolded/damaged proteins → endoplasmic reticulum stress → unfolded protein response → apoptosis (especially in malignant plasma cells with high protein synthesis load).
2. Stabilisation of pro-apoptotic proteins (e.g., Noxa, Bim) and NF-κB inhibitor IκB → reduced NF-κB signalling → reduced survival and drug resistance signalling.
3. Cell cycle arrest through accumulation of CDK inhibitors (p21, p27).

Malignant plasma cells are selectively vulnerable due to their high immunoglobulin synthesis, making them dependent on proteasomal degradation for protein quality control.

Evidence base

ASPIRE Trial (KRd vs Rd)

In relapsed multiple myeloma, adding carfilzomib to lenalidomide-dexamethasone improved median PFS from 17.6 to 26.3 months (HR 0.69, p<0.001) and showed an overall survival benefit. The overall response rate was 87% vs 67% (Stewart et al., NEJM, 2015).

ENDEAVOR Trial (Kd vs Vd)

Direct head-to-head comparison of carfilzomib-dexamethasone vs bortezomib-dexamethasone showed superior PFS (18.7 vs 9.4 months, HR 0.53, p<0.0001) and overall survival. Carfilzomib was associated with less peripheral neuropathy (Grade ≥3: 6% vs 32%) but more hypertension and cardiac events (Dimopoulos et al., Lancet Oncol, 2016).

CANDOR Trial (DKRd vs KRd)

Adding daratumumab to KRd improved PFS in relapsed/refractory myeloma, with updated results confirming sustained benefit (Usmani et al., Lancet Haematol, 2024).

Safety Profile

Carfilzomib's key differentiators from bortezomib: significantly less peripheral neuropathy (due to irreversible β5 subunit selectivity), but increased cardiovascular toxicity (cardiac failure, hypertension, dyspnoea). Pre-existing cardiovascular disease requires careful risk-benefit assessment.

Protocols

KRd Regimen (Relapsed Myeloma)

• Cycle 1: Carfilzomib 20 mg/m² IV on Days 1, 2 (escorting dose); 56 mg/m² on Days 8, 9, 15, 16.
• Cycles 2–18: 56 mg/m² IV on Days 1, 2, 8, 9, 15, 16 of each 28-day cycle.
• With lenalidomide 25 mg PO Days 1–21, dexamethasone weekly.

Kd Regimen (Relapsed Myeloma)

• Cycle 1: 20 mg/m² IV Days 1, 2; 56 mg/m² Days 8, 9, 15, 16.
• Cycles 2+: 56 mg/m² IV Days 1, 2, 8, 9, 15, 16 of each 28-day cycle.
• With dexamethasone 20 mg weekly.

Administration

• 10-minute IV infusion (or 30-minute in some protocols).
• Pre-medicate with dexamethasone before each dose.
• Hydration recommended to reduce renal toxicity.

Dose Modifications

• Cardiac events (HF, arrhythmia): hold or discontinue based on severity.
• Renal impairment: monitor closely; dose modification for CrCl <15 mL/min.
• Hepatic impairment: reduce dose for moderate impairment.

All dosing reflects the licensed UK SmPC and NICE-approved protocols. This is a POM; administration occurs under specialist haematology supervision. This profile is for research and educational purposes only.

UK legal status

Carfilzomib is a prescription-only medicine (POM) in the UK under the Human Medicines Regulations 2012. It is licensed for relapsed and refractory multiple myeloma in combination with lenalidomide and dexamethasone (KRd) or with dexamethasone alone (Kd). NICE recommends carfilzomib for relapsed myeloma in these combinations (TA457). The licensed product (Kyprolis) holds a UK marketing authorisation regulated by the MHRA. Supply without a valid prescription is unlawful. It is not classified as a controlled substance under the Misuse of Drugs Act 1971.

Vendor notes

As a licensed POM, carfilzomib is supplied through hospital oncology pharmacies upon prescription. It is not available from research peptide vendors. Peptide Data does not list vendors for this compound.