High-Dose Carfilzomib Recaptures Response in Relapsed/Refractory Multiple Myeloma Resistant to Low-Dose Carfilzomib By Co-Inhibiting β2 Subunit of Proteasome Complex: The First in Human Evidence
Background Proteasome, a complex involved in the intracellular protein degradation, consists of multiple subunits, but only three subunits have enzymatic activity to cleave and degrade proteins, namely β1, β2 and β5. Carfilzomib (CFZ), a second-generation proteasome inhibitor (PI), can induce cell d...
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Veröffentlicht in: | Blood 2021-11, Vol.138 (Supplement 1), p.818-818 |
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Sprache: | eng |
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Zusammenfassung: | Background
Proteasome, a complex involved in the intracellular protein degradation, consists of multiple subunits, but only three subunits have enzymatic activity to cleave and degrade proteins, namely β1, β2 and β5. Carfilzomib (CFZ), a second-generation proteasome inhibitor (PI), can induce cell death by selective and irreversible inhibition of β5 subunit of proteasome. Preclinical data suggested that high-dose CFZ could co-inhibit predominantly β2 proteasome activity, followed by β1 inhibition (Besse et al, Cell Chem Biol. 2019). Over the past few years, CFZ has become a corner stone for multiple myeloma (MM) therapy. Currently, CFZ is approved by the FDA in different dosing schedules in combination with lenalidomide or daratumumab and dexamethasone. However, the optimal CFZ dosing is still a matter of debate, with the approved dosage ranging from 20to 70mg/m 2 in different regimens. In addition, if response can be recaptured by escalating CFZ dose in patients progressing from low-dose CFZ has yet to be determined. The aim of our current study was to analyse the profile of proteasome inhibition in the respective dose cohorts and to elucidate if high-dose CFZ could recapture response in patients resistant to low-dose CFZ.
Methods
We prospectively collected clinical data and peripheral blood mononuclear cells (PBMC) of 32 patients with relapsed/refractory (RR) MM before and 1-8 hours after CFZ administration. PBMC were lysed and labelled for the activity of individual proteasome subunits using activity based proteasome probes and the proteasome subunits were separated using SDS-PAGE. The activity of constitutive and immunoproteasome β1, β2 and β5 subunits was evaluated by densitometry analysis and combination of the activity of constitutive and immunoproteasome individual subunit was used for further analysis.
Results
Overall, six, nine, twelve and five patients received CFZ at a dose of 20, 27, 36 and 56 mg/m 2, respectively. As expected, the total activity of proteasome decreased with higher doses of CFZ. Significant inhibition (median inhibition > 50%) of β5 subunit was observed already at 20 mg/m 2 dose, while β2 subunit started to be co-inhibited only at a dose of ≥27 mg/m 2. Significant co-inhibition of β2 activity was seen at 36 mg/m 2 dose, at which also β1 subunit started to be co-inhibited. Finally, at 56 mg/m 2, the activity of all active subunits was inhibited with a median inhibition of > 50%, with the strongest inhibition of the β5 subunit, |
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ISSN: | 0006-4971 1528-0020 |
DOI: | 10.1182/blood-2021-147170 |