Siegel, David S.

AbstractA population pharmacokinetic (PK) model and exposure–response (E‐R) analysis was developed using data collected from 5 phase 1b/2 and 2 phase 3 studies in subjects with multiple myeloma. Subjects receiving intravenous infusion on 2 consecutive days each week for 3 weeks (days 1, 2, 8, 9, 15, and 16) in each cycle at doses ranging from 15 to 20/56 mg/m2 (20 mg/m2 in cycle 1 and, if tolerated, escalated to 56 mg/m2 on day 8 of cycle 1). The population PK analysis indicated that among all the covariates tested, the only statistically significant covariate was body surface area on carfilzomib clearance; however, this covariate was unlikely to be clinically significant. Despite inclusion of different populations (relapsed or relapsed/refractory), treatments (carfilzomib monotherapy or combination therapy), infusion lengths (2 to 10 minutes or 30 minutes), and different doses, the E‐R analysis of efficacy showed that after adjusting for baseline characteristics, higher area under the concentration–time curve was associated with improved overall response rate (ORR), from 15 to 20/56 mg/m2. No positive relationships between maximum concentration and ORR were identified, indicating that ORR would not be expected to be impacted by infusion length. For safety end points, no statistically significant relationship between exposure and increasing risk of adverse events was identified. The results of an E‐R analysis provided strong support for a carfilzomib dose at 20/56 mg/m2 as a 30‐minute infusion for monotherapy and combination therapy. This article illustrates an example of application of E‐R analysis to support labeling dose recommendation in the absence of extensive clinical data.

Purpose To determine the effects of carfilzomib, lenalidomide, and dexamethasone (KRd) versus lenalidomide and dexamethasone (Rd) on health-related quality of life (HR-QoL) in the Carfilzomib, Lenalidomide, and Dexamethasone Versus Lenalidomide and Dexamethasone for the Treatment of Patients With Relapsed Multiple Myeloma (ASPIRE) trial. Methods Patients with relapsed multiple myeloma were randomly assigned to receive KRd or Rd. The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire C30 and myeloma-specific module were administered at baseline; day 1 of cycles 3, 6, 12, and 18; and after treatment. The Global Health Status/Quality of Life (GHS/QoL) scale and seven subscales (fatigue, nausea and vomiting, pain, physical functioning, role functioning, disease symptoms, and adverse effects of treatment) were compared between groups using a mixed model for repeated measures. The percentages of responders with ≥ 5- or 15-point GHS/QoL improvement at each cycle were compared between groups. Results Baseline questionnaire compliance was excellent (94.1% of randomly assigned patients). KRd patients had higher GHS/QoL scores versus Rd patients over 18 treatment cycles (two-sided P < .001). The minimal important difference was met at cycle 12 (5.6 points) and approached at cycle 18 (4.8 points). There was no difference between groups for the other prespecified subscales from ASPIRE. A higher proportion of KRd patients met the GHS/QoL responder definition (≥ 5-point improvement) with statistical differences at cycle 12 (KRd v Rd patients, 25.5% v 17.4%, respectively) and 18 (KRd v Rd patients, 24.2% v 12.9%, respectively). Conclusion KRd improves GHS/QoL without negatively affecting patient-reported symptoms when compared with Rd. These data further support the benefit of KRd in patients with relapsed multiple myeloma.

Key Points KRd has a favorable benefit-risk profile compared with Rd, regardless of baseline cytogenetic risk status, in patients with relapsed MM. KRd improves but does not abrogate the poor prognosis associated with high-risk cytogenetics in patients with relapsed MM.

SummaryWhile proteasome inhibition is a validated therapeutic approach for multiple myeloma (MM), inhibition of individual constitutive proteasome (c20S) and immunoproteasome (i20S) subunits has not been fully explored owing to a lack of effective tools. We utilized the novel proteasome constitutive/immunoproteasome subunit enzyme‐linked immunosorbent (ProCISE) assay to quantify proteasome subunit occupancy in samples from five phase I/II and II trials before and after treatment with the proteasome inhibitor carfilzomib. Following the first carfilzomib dose (15–56 mg/m2), dose‐dependent inhibition of c20S and i20S chymotrypsin‐like active sites was observed [whole blood: ≥67%; peripheral blood mononuclear cells (PBMCs): ≥75%]. A similar inhibition profile was observed in bone marrow–derived CD138+ tumour cells. Carfilzomib‐induced proteasome inhibition was durable, with minimal recovery in PBMCs after 24 h but near‐complete recovery between cycles. Importantly, the ProCISE assay can be used to quantify occupancy of individual c20S and i20S subunits. We observed a relationship between MM patient response (n = 29), carfilzomib dose and occupancy of multiple i20S subunits, where greater occupancy was associated with an increased likelihood of achieving a clinical response at higher doses. ProCISE represents a new tool for measuring proteasome inhibitor activity in clinical trials and relating drug action to patient outcomes.

AbstractThe International Myeloma Working Group consensus updates the definition for high-risk (HR) multiple myeloma based on cytogenetics Several cytogenetic abnormalities such as t(4;14), del(17/17p), t(14;16), t(14;20), nonhyperdiploidy, and gain(1q) were identified that confer poor prognosis. The prognosis of patients showing these abnormalities may vary with the choice of therapy. Treatment strategies have shown promise for HR cytogenetic diseases, such as proteasome inhibition in combination with lenalidomide/pomalidomide, double autologous stem cell transplant plus bortezomib, or combination of immunotherapy with lenalidomide or pomalidomide. Careful analysis of cytogenetic subgroups in trials comparing different treatments remains an important goal. Cross-trial comparisons may provide insight into the effect of new drugs in patients with cytogenetic abnormalities. However, to achieve this, consensus on definitions of analytical techniques, proportion of abnormal cells, and treatment regimens is needed. Based on data available today, bortezomib and carfilzomib treatment appear to improve complete response, progression-free survival, and overall survival in t(4;14) and del(17/17p), whereas lenalidomide may be associated with improved progression-free survival in t(4;14) and del(17/17p). Patients with multiple adverse cytogenetic abnormalities do not benefit from these agents. FISH data are implemented in the revised International Staging System for risk stratification.

Key Points Pomalidomide plus low-dose dexamethasone significantly improved PFS vs pomalidomide alone in relapsed and refractory multiple myeloma. Pomalidomide plus low-dose dexamethasone is an important new treatment option for RRMM patients who have received multiple prior therapies.

SummaryCarfilzomib is a next‐generation proteasome inhibitor that selectively and irreversibly binds to its target. In clinical studies, carfilzomib has shown efficacy in patients with relapsed and/or refractory multiple myeloma (MM) and has demonstrated a tolerable safety profile. In this phase 2, open‐label, multicentre clinical trial, 35 patients with relapsed and/or refractory MM following 1–3 prior therapies, including at least one bortezomib‐based regimen, received carfilzomib 20 mg/m2 in a twice‐weekly, consecutive‐day dosing schedule for ≤12 monthly cycles. The best overall response rate (ORR) was 17·1% and the clinical benefit response rate (ORR + minimal response) was 31·4%. The median duration of response was >10·6 months and the median time to progression was 4·6 months. The most common adverse events were fatigue (62·9%), nausea (60·0%), and vomiting (42·9%). No exacerbation of baseline peripheral neuropathy was observed. Single‐agent carfilzomib was generally well tolerated for up to 12 treatment cycles and showed activity in patients with relapsed and/or refractory MM who had received prior treatment with bortezomib. These data, combined with an acceptable toxicity profile, support the potential use of carfilzomib in patients with relapsed and/or refractory MM and warrant continued investigation of carfilzomib as single agent or in combination with other agents.

AbstractCarfilzomib is a next-generation, selective proteasome inhibitor being evaluated for the treatment of relapsed and refractory multiple myeloma. In this open-label, single-arm phase 2 study (PX-171-003-A1), patients received single-agent carfilzomib 20 mg/m2 intravenously twice weekly for 3 of 4 weeks in cycle 1, then 27 mg/m2 for ≤ 12 cycles. The primary endpoint was overall response rate (≥ partial response). Secondary endpoints included clinical benefit response rate (≥ minimal response), duration of response, progression-free survival, overall survival, and safety. A total of 266 patients were evaluable for safety, 257 for efficacy; 95% were refractory to their last therapy; 80% were refractory or intolerant to both bortezomib and lenalidomide. Patients had median of 5 prior lines of therapy, including bortezomib, lenalidomide, and thalidomide. Overall response rate was 23.7% with median duration of response of 7.8 months. Median overall survival was 15.6 months. Adverse events (AEs) were manageable without cumulative toxicities. Common AEs were fatigue (49%), anemia (46%), nausea (45%), and thrombocytopenia (39%). Thirty-three patients (12.4%) experienced peripheral neuropathy, primarily grades 1 or 2. Thirty-three patients (12.4%) withdrew because of an AE. Durable responses and an acceptable tolerability profile in this heavily pretreated population demonstrate the potential of carfilzomib to offer meaningful clinical benefit. This trial was registered at www.clinicaltrials.gov as #NCT00511238.

Abstract Carfilzomib is a selective proteasome inhibitor that binds irreversibly to its target. In phase 1 studies, carfilzomib elicited promising responses and an acceptable toxicity profile in patients with relapsed and/or refractory multiple myeloma (R/R MM). In the present phase 2, multicenter, open-label study, 129 bortezomib-naive patients with R/R MM (median of 2 prior therapies) were separated into Cohort 1, scheduled to receive intravenous carfilzomib 20 mg/m2 for all treatment cycles, and Cohort 2, scheduled to receive 20 mg/m2 for cycle 1 and then 27 mg/m2 for all subsequent cycles. The primary end point was an overall response rate (≥ partial response) of 42.4% in Cohort 1 and 52.2% in Cohort 2. The clinical benefit response (overall response rate + minimal response) was 59.3% and 64.2% in Cohorts 1 and 2, respectively. Median duration of response was 13.1 months and not reached, and median time to progression was 8.3 months and not reached, respectively. The most common treatment-emergent adverse events were fatigue (62.0%) and nausea (48.8%). Single-agent carfilzomib elicited a low incidence of peripheral neuropathy—17.1% overall (1 grade 3; no grade 4)—in these pretreated bortezomib-naive patients. The results of the present study support the use of carfilzomib in R/R MM patients. This trial is registered at www.clinicaltrials.gov as NCT00530816.