Next generation risk assessment (NGRA): Bridging in vitro points-of-departure to human safety assessment using physiologically-based kinetic (PBK) modelling - A case study of doxorubicin with dose metrics considerations

Using the chemical doxorubicin (DOX), the objective of the present study was to evaluate the impact of dose metrics selection in the new approach method of integrating physiologically-based kinetic (PBK) modelling and relevant human cell-based assays to inform a priori the point of departure for human health risk. We reviewed the literature on the clinical consequences of DOX treatment to identify dosing scenarios with no or mild cardiotoxicity observed. Key concentrations of DOX that induced cardiomyocyte toxicity in vitro were derived from studies of our own and others. A human population-based PBK model of DOX was developed and verified against pharmacokinetic data. The model was then used to predict plasma and extracellular and intracellular heart concentrations of DOX under selected clinical settings and compared with in vitro outcomes, based on several dose metrics: C_max (maximum concentration) or AUC (area under concentration-time curve) in free or total form of DOX. We found when using in vitro assays to predict cardiotoxicity for DOX, AUC is a better indicator. Our study illustrates that when appropriate dose metrics are used, it is possible to combine PBK modelling with in vitro-derived toxicity information to define margins of safety and predict low-risk human exposure levels.

Efficacy of bortezomib as first-line treatment for patients with multiple myeloma

Recent years have seen a dramatic change in the approach towards diagnosing and treating Multiple Myeloma. Newer and more target specific approach to treatment has prolonged the survival for patients with multiple myeloma. The proteasome inhibitors make an important class of anti-myeloma drugs that disrupts the proteolytic machinery of the tumor cells preferentially, enhancing their susceptibility to apoptosis. Bortezomib, in particular has shown significant clinical efficacy in myeloma treatment. It is the most commonly used proteasome inhibitor and has been tested to be effective in prolonging the overall survival in several trials. Its combinations with cyclophosphamide and dexamethasone are the treatment of choice for standard risk patients following the mSMART guidelines. The success with its lower dosage in elderly and its proven efficacious subcutaneous usage makes Bortezomib a useful agent for maximizing patient compliance and minimizing therapy related toxicity and costs. This review discusses several trials where Bortezomib has been used as a single/combination agent for front-line treatment of multiple myeloma.

The response to second-line induction with bortezomib and dexamethasone is predictive of long-term outcomes prior to high-dose chemotherapy with autologous stem cell transplantation for multiple myeloma

OBJECTIVE

We retrospectively investigated the efficacy and predictive factors for the treatment outcomes of bortezomib plus dexamethasone (BD) as second-line induction therapy prior to high-dose chemotherapy supported by autologous stem cell transplantation (HDT/ASCT) in multiple myeloma (MM) patients.

METHODS

Sixty-six transplant eligible MM patients treated by the Kyoto Clinical Hematology Study Group between 2006 and 2011 were investigated. Conventional induction chemotherapy, including vincristine, doxorubicin and dexamethasone (VAD) and high-dose dexamethasone (HDD), was used as first-line induction therapy in all patients, seven (10.6%) of whom attained a very good partial response (VGPR). Of the 59 patients who did not attain VGPR with VAD or HDD, 33 were given BD as second-line induction therapy prior to HDT/ASCT.

RESULTS

Patients not treated with BD induction showed an overall response rate (ORR, i.e., better than partial response) of 85.3% after induction therapy, while the ORR of patients treated with BD induction improved from 42.4% after conventional induction therapy to 84.8% after BD. The overall survival (OS) and progression-free survival (PFS) of patients not treated with BD induction were not significantly influenced by the response to induction therapy. Among the patients treated with BD, failure in attaining VGPR prior to ASCT was associated with a significantly shorter PFS and it also tended to show a shorter OS, while the disease stage and achievement of a complete response after HDT/ASCT had no impact on OS or PFS.

CONCLUSION

The achievement of at least VGPR with second-line BD induction therapy is a prerequisite for attaining longer OS and PFS after HDT/ASCT.