Pharmacokinetic evaluation and therapeutic activity of bendamustine in B-cell lymphoid malignancies

Pharmacokinetics and safety of bendamustine in the BEABOVP regimen for the treatment of pediatric patients with Hodgkin lymphoma

PURPOSE

The Stanford V chemotherapy regimen has been used to treat Hodgkin lymphoma (HL) patients since 2002 with excellent cure rates; however, mechlorethamine is no longer available. Bendamustine, a drug structurally similar to alkylating agents and nitrogen mustard, is being substituted for mechlorethamine in combination therapy in a frontline trial for low- and intermediate-risk pediatric HL patients, forming a new backbone of BEABOVP (bendamustine, etoposide, doxorubicin, bleomycin, vincristine, vinblastine, and prednisone). This study evaluated the pharmacokinetics and tolerability of a 180 mg/m2 dose of bendamustine every 28 days to determine factors that may explain this variability.

METHODS

Bendamustine plasma concentrations were measured in 118 samples from 20 pediatric patients with low- and intermediate-risk HL who received a single-day dose of 180 mg/m2 of bendamustine. A pharmacokinetic model was fit to the data using nonlinear mixed-effects modeling.

RESULTS

Bendamustine concentration vs time demonstrated a trend toward decreasing clearance with increasing age (p = 0.074) and age explained 23% of the inter-individual variability in clearance. The median (range) AUC was 12,415 (8,539, 18,642) µg hr/L and the median (range) maximum concentration was 11,708 (8034, 15,741) µg/L. Bendamustine was well tolerated with no grade 3 toxicities resulting in treatment delays of more than 7 days.

CONCLUSIONS

A single-day dose of 180 mg/m2 of bendamustine every 28 days was safe and well tolerated in pediatric patients. While age accounted for 23% of inter-individual variability observed in bendamustine clearance, the differences did not affect the safety and tolerability of bendamustine in our patient population.

Novel Peptide-drug Conjugate Melflufen Efficiently Eradicates Bortezomib-resistant Multiple Myeloma Cells Including Tumor-initiating Myeloma Progenitor Cells

Introduction of the proteasome inhibitor bortezomib has dramatically improved clinical outcomes in multiple myeloma. However, most patients become refractory to bortezomib-based therapies. On the molecular level, development of resistance to bortezomib in myeloma cells is accompanied by complex metabolic changes resulting in increased protein folding capacity, and less dependency on the proteasome. In this study, we show that aminopeptidase B, encoded by the RNPEP gene, is upregulated in bortezomib-resistant myeloma cell lines, and in a murine in vivo model. Moreover, increased RNPEP expression is associated with shorter survival in multiple myeloma patients previously treated with bortezomib-containing regimens. Additionally, expression is increased in plasma cell precursors, a B-lymphoid compartment previously associated with myeloma stem cells. We hypothesized that increased aminopeptidase B expression in aggressive myeloma clones may be used therapeutically toward elimination of the cells via the use of a novel peptide-drug conjugate, melphalan flufenamide (melflufen). Melflufen, a substrate of aminopeptidase B, efficiently eliminates bortezomib-resistant myeloma cells in vitro and in vivo, and completely suppresses clonogenic myeloma growth in vitro at subphysiological concentrations. Thus, melflufen represents a novel treatment option that is able to eradicate drug-resistant myeloma clones characterized by elevated aminopeptidase B expression.

Phase 1 study of bendamustine in combination with clofarabine, etoposide, and dexamethasone in pediatric patients with relapsed or refractory hematologic malignancies

BACKGROUND

A phase 1 study was conducted to determine the maximum tolerated dose of bendamustine when given in combination with clofarabine, etoposide, and dexamethasone daily for 5 days in children and adolescents with relapsed or refractory hematologic malignancies.

METHODS

Patients younger than 22 years with second or greater relapsed or refractory acute leukemia or lymphoma after 2 or more prior regimens were eligible. With the rolling 6 design, participants received escalating doses of bendamustine (30, 40, or 60 mg/m² /d) in combination with clofarabine (40 mg/m² ), etoposide (100 mg/m² ), and dexamethasone (8 mg/m² ) daily for 5 days. Optional pharmacokinetic studies were performed in cycle 1 on day 1 and day 5.

RESULTS

Sixteen patients were enrolled. Six patients were treated at the dose level of 30 mg/m² /d, 6 were treated at the dose level of 40 mg/m² /d, and 4 were treated at the dose level of 60 mg/m² /d. The dose-limiting toxicity was prolonged myelosuppression. The combination was otherwise well tolerated. The recommended dose of bendamustine in this combination was 30 mg/m² /d for 5 days. Ten responses were observed after 1 cycle: 6 complete remissions, 1 durable minimal residual disease-negative complete remission without platelet recovery in a patient with early T-cell precursor leukemia, and 3 partial remissions. Six patients proceeded to transplantation. The event-free survival rate was 40.6% (95% confidence interval [CI], 17.5%-63.7%) at 1 year and 33.9% (95% CI, 11.9%-55.9%) at 3 years.

CONCLUSIONS

Bendamustine is well tolerated in combination with clofarabine, etoposide, and dexamethasone. The combination administered over 5 days is effective for multiple relapsed and refractory hematologic malignancies. This trial is registered with ClinicalTrials.gov (NCT01900509).

LAY SUMMARY

Improvements to the existing chemotherapy regimen are still needed for patients who relapse after targeted therapies and immunotherapies and for those who are not eligible for or have no access to such therapies. A regimen combining cyclophosphamide, clofarabine, and etoposide has been used in relapsed and refractory pediatric patients with hematologic malignancies. This study shows that substituting bendamustine for cyclophosphamide in combination with clofarabine and etoposide is safe and effective.

Bendamustine alone or with rituximab modifies expression of apoptosis-regulating genes and proteins of CLL cells, depending on IGVH mutational status

We studied whether bendamustine (BENDA) alone or with rituximab (RIT) modifies in vitro expression of apoptosis-involved genes and proteins of chronic lymphocytic leukemia (CLL) cells depending on IGVH mutational status. Circulating lymphocytes from 34 untreated patients (18 IGVH-MUT and 16 IGVH-UNMUT) were incubated with above drugs to evaluate proteins expression. Microarray analysis of 93 genes was performed in 14 patients. BENDA and BENDA + RIT increased expression of BAX and BBC3 in IGVH-MUT and IGVH-UNMUT groups, and significant differences in expression of above genes after BENDA + RIT were observed between both groups. Additionally, BENDA + RIT decreased NFκB and BCL-2 genes in IGVH-UNMUT patients and increased expression of P53, BAX and PUMA proteins in IGVH-MUT and UNMUT subjects. However, no significant differences were found between these groups. In conclusion, BENDA + RIT modified gene expression profile in CLL cells and affected expression of some apoptosis-regulating proteins in vitro. Expression of BAX and BBC3 depends on action of drugs and IGVH mutational status.

Bendamustine-associated infections-systematic review and meta-analysis of randomized controlled trials

Data in the literature are lacking regarding the infection-related adverse events of bendamustine-containing regimens. Therefore, we aimed to assess this risk. We conducted a systematic review and meta-analysis of all randomized controlled trials including bendamustine-containing regimens and those administered for any lymphoproliferative disorder or plasma cell dyscrasia compared with any other regimens. A comprehensive search was conducted until December 2015. Two reviewers appraised the quality of trials and extracted data. Primary outcomes were any infections, grade 3 to 4 infections; secondary outcomes were grade 3 to 4 neutropenia and grade 3 to 4 lymphopenia. Relative risks (RRs) with 95% confidence intervals (CIs) were estimated and pooled. A fixed-effect model was used to pool data unless there was significant heterogeneity, in which case a random-effects model was used. Nine trials published between 2006 and 2016 and randomizing 2620 patients were included. There was no statistically significant effect for bendamustine on the rate of any infection (RR 1.09 [95% CI, 0.87-1.36]) or on the rate of grade 3 to 4 infections (RR 1.04 [95% CI, 0.64-1.71]). There was no increase in the rate of grade 3 to 4 neutropenia in the bendamustine arm (RR 0.84 [95% CI, 0.63-1.12]). Our systematic review demonstrates no effect of bendamustine on the rate of infections when compared with either alkylating agents or fludarabine. Thus, bendamustine remains a safe therapeutic option.

Bendamustine associated immune suppression and infections during therapy of hematological malignancies

Bendamustine is being increasingly used in patients with indolent non-Hodgkin lymphoma, mantle cell lymphoma and chronic lymphocytic leukemia. This review summarizes available evidence regarding the effects of bendamustine on the immune system, examines its role in consequent infections as reported in randomized controlled trials, prospective observational investigations, retrospective studies and individual published case reports. Myelosuppression including lymphopenia occurs relatively frequently after therapy with bendamustine. It is mostly CD4 + T cell counts that are suppressed, yet when given in combination with rituximab, both T cell and B cell depletion have been recorded. In addition, hypogammaglobulinemia after bendamustine therapy has also been reported. Variable infection rates have been documented and these include different bacterial, viral and fungal infections. Finally, we also consider issues relating to the use of prophylactic antibiotics in patients receiving the drug.

Infections associated with bendamustine containing regimens in hematological patients: a retrospective multi-center study

A multi-center retrospective analysis of a cohort of patients in Israel treated with any bendamustine containing regimen between 2010-2014 was performed in order to determine the incidence and predictors for infection. The Kaplan Meier Model, employing log rank analysis, was used to assess time-to-infection. The Cox Proportional Hazards model was used to analyze multivariate effects of risk and 234 patients were included in the analysis. One hundred and nine (46.6%) developed at least one infection and 33.76% had severe infections. Seventy-six (41.5%) developed bacterial infection, nine (3.8%) fungal infection and 26 (11.5%) had viral infections. Factors significantly associated with time to infection on multivariable analysis were: bendamustine-combinations [hazard ratio (HR) = 0.589 (95% CI = 0.374-0.926), p = 0.022], Hb level [HR = 0.791 (95% CI = 0.716-0.875), p < 0.0001] and ischemic heart disease [HR = 1.828 (95% CI = 1.165-2.868), p = 0.009]. Infections were associated with a higher mortality and hospitalization rate.

An evaluation of the potential for drug-drug interactions between bendamustine and rituximab in indolent non-Hodgkin lymphoma and mantle cell lymphoma

PURPOSE

Bendamustine plus rituximab has been reported to be effective in treating lymphoid malignancies. This analysis investigated the potential for drug-drug interactions between the drugs in patients with indolent non-Hodgkin lymphoma or mantle cell lymphoma.

METHODS

Data were derived from a bendamustine-rituximab combination therapy study, a bendamustine monotherapy study, and published literature on rituximab monotherapy and combination therapy. Analysis of the potential for rituximab to affect bendamustine systemic exposure included comparing bendamustine concentration-time profile following monotherapy to that following combination therapy and comparing model-predicted Bayesian bendamustine clearance in the presence and absence of rituximab. Analysis of the potential for bendamustine to affect rituximab systemic exposure included plotting observed minimum, median, and maximum serum rituximab concentrations at the end of rituximab infusion (EOI) and 24 h and 7 days post-infusion in patients receiving combination therapy versus concentrations reported in literature following rituximab monotherapy.

RESULTS

The established population pharmacokinetic model following bendamustine monotherapy was evaluated to determine its applicability to combination therapy for the purpose of confirming lack of pharmacokinetic interaction. The model adequately described the bendamustine concentration-time profile following monotherapy and combination therapy in adults. There was no statistically significant difference in estimated bendamustine clearance either alone or in combination. Also, rituximab concentrations from EOI to 24 h and 7 days demonstrated a pattern of decline similar to that seen in rituximab studies without bendamustine, suggesting that bendamustine does not affect the rituximab clearance rate.

CONCLUSIONS

Neither bendamustine nor rituximab appears to affect systemic exposure of the other drug when coadministered.