Switching from body surface area-based to fixed dosing for the investigational proteasome inhibitor ixazomib: a population pharmacokinetic analysis

Opportunity Strikes for Reducing Cancer Drug Waste: Bortezomib as an Example of Vial Mis-Sizing in Oncology

Mis-sized packaging leads to millions of dollars in drug waste annually. Now is the time to act.

A comprehensive regulatory and industry review of modeling and simulation practices in oncology clinical drug development

Exposure-response (E-R) analyses are an integral component in the development of oncology products. Characterizing the relationship between drug exposure metrics and response allows the sponsor to use modeling and simulation to address both internal and external drug development questions (e.g., optimal dose, frequency of administration, dose adjustments for special populations). This white paper is the output of an industry-government collaboration among scientists with broad experience in E-R modeling as part of regulatory submissions. The goal of this white paper is to provide guidance on what the preferred methods for E-R analysis in oncology clinical drug development are and what metrics of exposure should be considered.

Population pharmacokinetic/pharmacodynamic joint modeling of ixazomib efficacy and safety using data from the pivotal phase III TOURMALINE‐MM1 study in multiple myeloma patients

Ixazomib is an oral proteasome inhibitor approved in combination with lenalidomide and dexamethasone for the treatment of relapsed/refractory multiple myeloma (MM). Approval in the United States, Europe, and additional countries was based on results from the phase III TOURMALINE‐MM1 (C16010) study. Here, joint population pharmacokinetic/pharmacodynamic time‐to‐event (TTE) and discrete time Markov models were developed to describe key safety (rash and diarrhea events, and platelet counts) and efficacy (myeloma protein [M‐protein] and progression‐free survival [PFS]) outcomes observed in TOURMALINE‐MM1. Models reliably described observed safety and efficacy results; prior immunomodulatory drug therapy and race were significant covariates for diarrhea and rash events, respectively, whereas M‐protein dynamics were sufficiently characterized using TTE models of relapse and dropout. Moreover, baseline M‐protein was identified as a significant covariate for observed PFS. The developed framework represents an integrated approach to describing safety and efficacy with MM therapy, enabling the simulation of prospective trials and potential alternate dosing regimens.

Frailty-adjusted therapy in Transplant Non-Eligible patients with newly diagnosed Multiple Myeloma (FiTNEss (UK-MRA Myeloma XIV Trial)): a study protocol for a randomised phase III trial

INTRODUCTION

Multiple myeloma is a bone marrow cancer, which predominantly affects older people. The incidence is increasing in an ageing population.Over the last 10 years, patient outcomes have improved. However, this is less apparent in older, less fit patients, who are ineligible for stem cell transplant. Research is required in this patient group, taking into account frailty and aiming to improve: treatment tolerability, clinical outcomes and quality of life.

METHODS AND ANALYSIS

Frailty-adjusted therapy in Transplant Non-Eligible patients with newly diagnosed Multiple Myeloma is a national, phase III, multicentre, randomised controlled trial comparing standard (reactive) and frailty-adjusted (adaptive) induction therapy delivery with ixazomib, lenalidomide and dexamethasone (IRD), and to compare maintenance lenalidomide to lenalidomide+ixazomib, in patients with newly diagnosed multiple myeloma not suitable for stem cell transplant. Overall, 740 participants will be registered into the trial to allow 720 and 478 to be randomised at induction and maintenance, respectively.All participants will receive IRD induction with the dosing strategy randomised (1:1) at trial entry. Patients randomised to the standard, reactive arm will commence at the full dose followed by toxicity dependent reactive modifications. Patients randomised to the adaptive arm will commence at a dose level determined by their International Myeloma Working Group frailty score. Following 12 cycles of induction treatment, participants alive and progression free will undergo a second (double-blind) randomisation on a 1:1 basis to maintenance treatment with lenalidomide+placebo versus lenalidomide+ixazomib until disease progression or intolerance.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the North East-Tyne & Wear South Research Ethics Committee (19/NE/0125) and capacity and capability confirmed by local research and development departments for each participating centre prior to opening to recruitment. Participants are required to provide written informed consent prior to trial registration. Trial results will be disseminated by conference presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

ISRCTN17973108, NCT03720041.

Oral ixazomib, lenalidomide, and dexamethasone for transplant-ineligible patients with newly diagnosed multiple myeloma

Addition of ixazomib to Rd in nontransplant NDMM patients resulted in a nonstatistically significant increase in PFS (HR, 0.830; P = .073).

Ixazomib-Rd is a feasible and tolerable all-oral triplet regimen in this setting, with a well-characterized and manageable safety profile.

Continuous lenalidomide-dexamethasone (Rd)-based regimens are among the standards of care in transplant-ineligible newly diagnosed multiple myeloma (NDMM) patients. The oral proteasome inhibitor ixazomib is suitable for continuous dosing, with predictable, manageable toxicities. In the double-blind, placebo-controlled TOURMALINE-MM2 trial, transplant-ineligible NDMM patients were randomized to ixazomib 4 mg (n = 351) or placebo (n = 354) plus Rd. After 18 cycles, dexamethasone was discontinued and treatment was continued using reduced-dose ixazomib (3 mg) and lenalidomide (10 mg) until progression/toxicity. The primary endpoint was progression-free survival (PFS). Median PFS was 35.3 vs 21.8 months with ixazomib-Rd vs placebo-Rd, respectively (hazard ratio [HR], 0.830; 95% confidence interval, 0.676-1.018; P = .073; median follow-up, 53.3 and 55.8 months). Complete (26% vs 14%; odds ratio [OR], 2.10; P < .001) and ≥ very good partial response (63% vs 48%; OR, 1.87; P < .001) rates were higher with ixazomib-Rd vs placebo-Rd. In a prespecified high-risk cytogenetics subgroup, median PFS was 23.8 vs 18.0 months (HR, 0.690; P = .019). Overall, treatment-emergent adverse events (TEAEs) were mostly grade 1/2. With ixazomib-Rd vs placebo-Rd, 88% vs 81% of patients experienced grade ≥3 TEAEs, 66% vs 62% serious TEAEs, and 35% vs 27% TEAEs resulting in regimen discontinuation; 8% vs 6% died on study. Addition of ixazomib to Rd was tolerable with no new safety signals and led to a clinically meaningful PFS benefit of 13.5 months. Ixazomib-Rd is a feasible option for certain patients who can benefit from an all-oral triplet combination. This trial was registered at www.clinicaltrials.gov as #NCT01850524.

Pre-Clinical Evaluation of the Proteasome Inhibitor Ixazomib against Bortezomib-Resistant Leukemia Cells and Primary Acute Leukemia Cells

At present, 20-30% of children with acute leukemia still relapse from current chemotherapy protocols, underscoring the unmet need for new treatment options, such as proteasome inhibition. Ixazomib (IXA) is an orally available proteasome inhibitor, with an improved safety profile compared to Bortezomib (BTZ). The mechanism of action (proteasome subunit inhibition, apoptosis induction) and growth inhibitory potential of IXA vs. BTZ were tested in vitro in human (BTZ-resistant) leukemia cell lines. Ex vivo activity of IXA vs. BTZ was analyzed in 15 acute lymphoblastic leukemia (ALL) and 9 acute myeloid leukemia (AML) primary pediatric patient samples. BTZ demonstrated more potent inhibitory effects on constitutive β5 and immunoproteasome β5i proteasome subunit activity; however, IXA more potently inhibited β1i subunit than BTZ (70% vs. 29% at 2.5 nM). In ALL/AML cell lines, IXA conveyed 50% growth inhibition at low nanomolar concentrations, but was ~10-fold less potent than BTZ. BTZ-resistant cells (150-160 fold) displayed similar (100-fold) cross-resistance to IXA. Finally, IXA and BTZ exhibited anti-leukemic effects for primary ex vivo ALL and AML cells; mean LC50 (nM) for IXA: 24 ± 11 and 30 ± 8, respectively, and mean LC50 for BTZ: 4.5 ± 1 and 11 ± 4, respectively. IXA has overlapping mechanisms of action with BTZ and showed anti-leukemic activity in primary leukemic cells, encouraging further pre-clinical in vivo evaluation.

A phase 0 analysis of ixazomib in patients with glioblastoma

Improving overall survival in recurrent glioblastoma remains a challenge, and drugs acting by unique mechanisms are urgently required. Ixazomib is an orally-administered proteasome inhibitor used in combination with lenalidomide and dexamethasone to treat patients with multiple myeloma who have received at least one prior therapy. However, ixazomib's ability to reach brain tumors has not been studied during its development. The aim of the present study (ClinicalTrials.gov, NCT02630030) was to establish and quantify ixazomib's presence in glioblastoma. The present study investigated 3 patients with recurrent glioblastoma after administration of oral ixazomib citrate (MLN 9708) at a fixed 4.0 mg dose within a 3-hpreoperative window. A total of 2 blood samples were taken from each patient at the time of incision, tumor sampling and closure. Brain tumor samples were collected during tumor resection. These samples were then used to measure the plasma and brain tumor tissue concentration of the biologically-active form of ixazomib (MLN 2238). Patient 1 had plasma concentrations of ixazomib averaging 26.2, 21.8 and 15.3 ng/ml at incision, tumor sampling and closure, respectively. The brain tumor tissue concentration was 7.88 ng/g. Patient 2 had the same interval and brain tumor tissue measurements of 19.0, 18.0 and 8.93 ng/ml, and 2.03 ng/g. Patient 3 had plasma concentration interval measurements of 25.6, 36.2 and 28.7 ng/ml. Multiple brain tumor tissue samples were taken in patient 3, with an average tissue ixazomib concentration of 3.37 ng/g. Ixazomib was found at plasma concentrations commensurate with its previously established pharmacokinetic profile without clinically relevant drug-related adverse events. Ixazomib reaches glioblastoma tissues at measurable concentrations at the time of tumor resection, confirming target tissue delivery. This justifies the phase I study of ixazomib in recurrent glioblastoma currently in development.

The proteasome as a druggable target with multiple therapeutic potentialities: Cutting and non-cutting edges

Ubiquitin Proteasome System (UPS) is an adaptable and finely tuned system that sustains proteostasis network under a large variety of physiopathological conditions. Its dysregulation is often associated with the onset and progression of human diseases; hence, UPS modulation has emerged as a promising new avenue for the development of treatments of several relevant pathologies, such as cancer and neurodegeneration. The clinical interest in proteasome inhibition has considerably increased after the FDA approval in 2003 of bortezomib for relapsed/refractory multiple myeloma, which is now used in the front-line setting. Thereafter, two other proteasome inhibitors (carfilzomib and ixazomib), designed to overcome resistance to bortezomib, have been approved for treatment-experienced patients, and a variety of novel inhibitors are currently under preclinical and clinical investigation not only for haematological malignancies but also for solid tumours. However, since UPS collapse leads to toxic misfolded proteins accumulation, proteasome is attracting even more interest as a target for the care of neurodegenerative diseases, which are sustained by UPS impairment. Thus, conceptually, proteasome activation represents an innovative and largely unexplored target for drug development. According to a multidisciplinary approach, spanning from chemistry, biochemistry, molecular biology to pharmacology, this review will summarize the most recent available literature regarding different aspects of proteasome biology, focusing on structure, function and regulation of proteasome in physiological and pathological processes, mostly cancer and neurodegenerative diseases, connecting biochemical features and clinical studies of proteasome targeting drugs.

Population Pharmacokinetics of Brigatinib in Healthy Volunteers and Patients With Cancer

Background and objectives

Brigatinib is an oral tyrosine kinase inhibitor approved in multiple countries for the treatment of patients with anaplastic lymphoma kinase-positive metastatic non-small cell lung cancer who have progressed on or are intolerant to crizotinib. We report a population pharmacokinetic model-based analysis for brigatinib.

Methods

Plasma concentration–time data were collected from 442 participants (105 healthy volunteers and 337 patients with cancer) who received single or multiple doses of oral brigatinib in one of five trials. Data were analyzed using non-linear mixed-effects modeling (NONMEM software version 7.3).

Results

Brigatinib plasma concentrations were best described by a three-compartment model with a transit compartment input (number of transit compartments = 2.35; mean transit time = 0.9 h). The final model included albumin as a covariate on apparent clearance. None of the additional covariates examined, including sex, age, race, body weight, mild or moderate renal impairment, total bilirubin, aspartate aminotransferase, and alanine aminotransferase, were found to meaningfully explain variability in apparent clearance, suggesting that no dose adjustment is required based on these covariates.

Conclusions

Results from these population pharmacokinetic analyses informed the prescribing guidance for patients with mild or moderate renal impairment in the US Prescribing Information and the European Summary of Product Characteristics for brigatinib.

Electronic supplementary material

The online version of this article (10.1007/s40262-020-00929-4) contains supplementary material, which is available to authorized users.

Population Pharmacokinetics of Brentuximab Vedotin in Adult and Pediatric Patients With Relapsed/Refractory Hematologic Malignancies: Model-Informed Hypothesis Generation for Pediatric Dosing Regimens

Prior pharmacokinetic (PK) analyses of the antibody‐drug conjugate (ADC) brentuximab vedotin (1.8 mg/kg every 3 weeks) in pediatric patients with relapsed/refractory hematologic malignancies found that patients aged <12 years exhibited decreased ADC area under the curve (AUC) compared with those aged ≥12 years. This population PK (POPPK) analysis used data from pediatric (NCT01492088) and adult (NCT00430846) studies of brentuximab vedotin to quantify body size effects on ADC exposure. Data were collected from 84 patients with a median age of 25.7 years (range, 7.7‐87.3 years), 34 of whom (40.5%) were aged <18 years; median patient weight was 67 kg (range, 21‐154 kg), and median body surface area was 1.8 m² (range, 0.87‐2.81 m²). ADC PK was described by a linear 3‐compartment model with zero‐order input and first‐order elimination. POPPK modeling indicated that dosing brentuximab vedotin at 1.8 mg/kg every 3 weeks or 1.2 mg/kg every 2 weeks resulted in lower ADC AUC values in small/moderate‐sized pediatric patients (<28 kg and 28‐49 kg, respectively) compared with large pediatric/adult patients (50‐100 kg). Dosing at 71.5 mg/m² every 3 weeks and 47.7 mg/m² every 2 weeks was predicted to achieve comparable AUC values across all body weight ranges and a similar AUC to that in the 50‐ to 100‐kg group at the standard doses of 1.8 mg/kg every 3 weeks and 1.2 mg/kg every 2 weeks, respectively. These results have generated a hypothesis to support evaluation of brentuximab vedotin at 48 mg/m² every 2 weeks in combination with adriamycin, vinblastine, and dacarbazine chemotherapy in an ongoing pediatric trial in frontline Hodgkin lymphoma (NCT02979522).

Pharmacodynamics and pharmacokinetics of proteasome inhibitors for the treatment of multiple myeloma

Introduction: Multiple myeloma (MM) is the second most commonly diagnosed hematologic malignancy and has an increasing incidence and prevalence globally, and proteasome inhibitors (PIs) form the backbone of some of our most effective regimens for all phases of this disease in fit and frail patients. Areas covered: Strong understanding of the proteasome complex is increasingly important as the rapid development of new PIs and innovative myeloma therapies complicate the use of old and new combination regimens. We focus herein on the pharmacodynamics and pharmacokinetics of the approved PIs and others in development, including their safety and efficacy in corresponding clinical studies. Expert opinion: Advancements such as the first oral PI, ixazomib, with a more convenient route of administration and improved toxicity profile led to an improved quality of life, patient compliance, and all-oral combination regimens which are efficacious for long-term management of standard and high-risk MM. Novel pan-PIs, such as marizomib, hold the promise of superior clinical activity due to irreversible targeting of all multicatalytic proteinase complex subunits. Development of clinically validated biomarkers of PI sensitivity/resistance is required to inform utilization of the most optimal and effective, rationally targeted PI treatments for all MM patients.

Clinical Pharmacology of Ixazomib: The First Oral Proteasome Inhibitor

Ixazomib, the first oral proteasome inhibitor, is approved in combination with lenalidomide and dexamethasone for the treatment of patients with multiple myeloma (MM) who have received at least one prior therapy. Ixazomib is a selective, potent, and reversible inhibitor of the 20S proteasome, and preferentially binds to and inhibits the β5 chymotrypsin-like proteolytic site. Ixazomib absorption is rapid, with a median time to reach maximum plasma concentration of approximately 1 h post-dose. Ixazomib pharmacokinetics (PK) are adequately described by a three-compartment model (terminal half-life of 9.5 days) with first-order linear absorption (oral bioavailability of 58%). Plasma exposures of ixazomib increase in a dose-proportional manner. A high-fat meal decreases both the rate and extent of ixazomib absorption, supporting administration on an empty stomach. Population PK analyses demonstrated that no dose adjustment is required based on age, body size/weight, race, sex, mild-to-moderate renal impairment, or mild hepatic impairment. Results from dedicated studies indicate that a reduced starting dose (from 4 to 3 mg) is appropriate for patients with severe renal impairment, end-stage renal disease requiring dialysis, or moderate-to-severe hepatic impairment. Non-cytochrome P450 (CYP)-mediated metabolism appears to be the major clearance mechanism for ixazomib. Drug-drug interaction studies have shown no meaningful effects of strong inhibitors of CYP3A on ixazomib PK; however, the strong inducer rifampin caused a clinically relevant reduction in ixazomib exposure, supporting the recommendation to avoid concomitant administration of ixazomib with strong CYP3A inducers. Exposure-response analyses of data from the phase III TOURMALINE-MM1 registrational study demonstrate a favorable benefit-risk profile for the approved dose and regimen of weekly ixazomib 4 mg on days 1, 8, and 15 of each 28-day cycle.

Power Determination During Drug Development: Is Optimizing the Sample Size Based on Exposure-Response Analyses Underutilized?

The use of model-based drug development (MBDD) has been demonstrated to improve the efficiency of clinical trial design. However, MBDD complexity can limit its use, particularly early in clinical development. In this tutorial, a simple and generalizable exposure-response analysis approach to determine the power for dose-ranging studies is presented and described. We identified situations in which higher power and sample size reduction is achieved by utilizing the exposure-response powering methodology compared with conventional power calculations.

Model-Informed Drug Development for Ixazomib, an Oral Proteasome Inhibitor

Model-informed drug development (MIDD) was central to the development of the oral proteasome inhibitor ixazomib, facilitating internal decisions (switch from body surface area (BSA)-based to fixed dosing, inclusive phase III trials, portfolio prioritization of ixazomib-based combinations, phase III dose for maintenance treatment), regulatory review (model-informed QT analysis, benefit-risk of 4 mg dose), and product labeling (absolute bioavailability and intrinsic/extrinsic factors). This review discusses the impact of MIDD in enabling patient-centric therapeutic optimization during the development of ixazomib.

Target Validation and Identification of Novel Boronate Inhibitors of the Plasmodium falciparum Proteasome

The Plasmodium proteasome represents a potential antimalarial drug target for compounds with activity against multiple life cycle stages. We screened a library of human proteasome inhibitors (peptidyl boronic acids) and compared activities against purified P. falciparum and human 20S proteasomes. We chose four hits that potently inhibit parasite growth and show a range of selectivities for inhibition of the growth of P. falciparum compared with human cell lines. P. falciparum was selected for resistance in vitro to the clinically used proteasome inhibitor, bortezomib, and whole genome sequencing was applied to identify mutations in the proteasome β5 subunit. Active site profiling revealed inhibitor features that enable retention of potent activity against the bortezomib-resistant line. Substrate profiling reveals P. falciparum 20S proteasome active site preferences that will inform attempts to design more selective inhibitors. This work provides a starting point for the identification of antimalarial drug leads that selectively target the P. falciparum proteasome.

Biotransformation of [14C]-ixazomib in patients with advanced solid tumors: characterization of metabolite profiles in plasma, urine, and feces

PURPOSE

This metabolite profiling and identification analysis (part of a phase I absorption, distribution, metabolism, and excretion study) aimed to define biotransformation pathways and evaluate associated inter-individual variability in four patients with advanced solid tumors who received [¹⁴C]-ixazomib.

METHODS

After administration of a single 4.1-mg oral dose of [¹⁴C]-ixazomib (total radioactivity [TRA] ~ 500 nCi), plasma (at selected timepoints), urine, and fecal samples were collected before dosing and continuously over 0-168-h postdose, followed by intermittent collections on days 14, 21, 28, and 35. TRA analysis and metabolite profiling were performed using accelerator mass spectrometry. Radiolabeled metabolites were identified using liquid chromatography/tandem mass spectrometry.

RESULTS

Metabolite profiles were similar in plasma, urine, and feces samples across the four patients analyzed. All metabolites identified were de-boronated. In AUC_0-816 h time-proportional pooled plasma, ixazomib (54.2% of plasma TRA) and metabolites M1 (18.9%), M3 (10.6%), and M2 (7.91%), were the primary components identified. M1 was the major metabolite, contributing to 31.1% of the 76.2% of the total dose excreted in urine and feces over 0-35-day postdose. As none of the identified metabolites had a boronic acid moiety, they are unlikely to be pharmacologically active.

CONCLUSIONS

Hydrolytic metabolism in conjunction with oxidative deboronation appears to be the principal process in the in vivo biotransformation pathways of ixazomib. The inference of formation-rate-limited clearance of ixazomib metabolites and the inferred lack of pharmacologic activity of identified circulating metabolites provides justification for use of parent drug concentrations/systemic exposure in clinical pharmacology analyses.

Next-generation proteasome inhibitors for cancer therapy

Over 2 decades ago, the proteasome was considered a risky or even untenable therapeutic target. Today, proteasome inhibitors are a mainstay in the treatment of multiple myeloma (MM) and have sales in excess of 3 billion US dollars annually. More importantly, the availability of proteasome inhibitors has greatly improved the survival and quality of life for patients with MM. Despite the remarkable success of proteasome inhibitor therapies to date, the potential for improvement remains, and the development and optimal use of proteasome inhibitors as anticancer agents continues to be an active area of research. In this review, we briefly discuss the features and limitations of the 3 proteasome inhibitor drugs currently used in the clinic and provide an update on current efforts to develop next-generation proteasome inhibitors with the potential to overcome the limitations of existing proteasome inhibitor drugs.

Dose and Schedule Selection of the Oral Proteasome Inhibitor Ixazomib in Relapsed/Refractory Multiple Myeloma: Clinical and Model-Based Analyses

Background

The oral proteasome inhibitor ixazomib has been approved by regulatory authorities around the world, including in the United States and the European Union, for the treatment of patients with multiple myeloma (MM) who have received at least one prior therapy, based on the pivotal phase III TOURMALINE-MM1 study.

Objective

The objective of this study was to quantitatively characterize the benefit–risk profile of ixazomib in relapsed/refractory MM in support of the approved dose and schedule.

Methods

We report early-phase study data and exposure–response analyses of TOURMALINE-MM1 data that support the selection of the recommended ixazomib dose and schedule.

Results

Single-agent ixazomib studies showed a favorable efficacy/safety profile with weekly versus twice-weekly dosing; a phase I/II study of ixazomib in combination with lenalidomide and dexamethasone (IRd) identified a weekly ixazomib dose that offered an acceptable efficacy/safety profile. In IRd exposure–response analyses from TOURMALINE-MM1, ixazomib systemic exposure was not a significant predictor of progression-free survival or probability of response. Significant associations were observed between ixazomib exposure and the probability of grade ≥3 anemia and thrombocytopenia, and grade ≥2 diarrhea, fatigue, nausea, peripheral neuropathy, and rash. Additionally, higher ixazomib exposure was associated with lower lenalidomide relative dose intensity.

Conclusions

These analyses support a favorable benefit–risk profile for weekly ixazomib 4.0 mg on days 1, 8, and 15 of 28-day cycles, which was selected for the phase III TOURMALINE registration program.

Trial Registration Numbers

ClinicalTrials.gov NCT00932698, NCT00963820, NCT01217957, NCT01564537

Electronic supplementary material

The online version of this article (doi:10.1007/s11523-017-0524-3) contains supplementary material, which is available to authorized users.

Twice-weekly ixazomib in combination with lenalidomide-dexamethasone in patients with newly diagnosed multiple myeloma

Weekly ixazomib with lenalidomide-dexamethasone (Rd) is feasible and has shown activity in newly diagnosed multiple myeloma (NDMM) patients. This phase 1/2 study (NCT01383928) evaluated the recommended phase 2 dose (RP2D), pharmacokinetics, safety and efficacy of twice-weekly ixazomib plus Rd in NDMM; 64 patients were enrolled across both phases. Patients received twice-weekly oral ixazomib 3·0 or 3·7 mg plus lenalidomide 25 mg and dexamethasone 20 mg (10 mg in cycles 9-16) for up to sixteen 21-day cycles, followed by maintenance with twice-weekly ixazomib alone. No dose-limiting toxicities were reported in cycle 1; the RP2D was 3·0 mg based on overall tolerability across multiple cycles. In 62 evaluable patients, the confirmed overall response rate was 94% (68% ≥very good partial response; 24% complete response). Median progression-free survival was 24·9 months. Responses (median duration 36·9 months for patients receiving the RP2D) deepened during treatment. Grade 3 drug-related adverse events (AEs) occurred in 64% of patients, including: rash, 13%; peripheral neuropathy, 8%; hyperglycaemia, 8%. There were no grade 4 drug-related AEs. Thirteen patients discontinued due to AEs. Twice-weekly ixazomib-Rd offers substantial activity with promising long-term outcomes in NDMM patients but may be associated with greater toxicity compared with weekly ixazomib-Rd in this setting.

Population Pharmacokinetic Analysis of Ixazomib, an Oral Proteasome Inhibitor, Including Data from the Phase III TOURMALINE-MM1 Study to Inform Labelling

Ixazomib is an oral proteasome inhibitor, approved in USA, Canada, Australia and Europe in combination with lenalidomide and dexamethasone, for the treatment of patients with multiple myeloma who have received at least one prior therapy. We report a population pharmacokinetic model-based analysis for ixazomib that was pivotal in describing the clinical pharmacokinetics of ixazomib, to inform product labelling. Plasma concentration–time data were collected from 755 patients who received oral or intravenous ixazomib in once- or twice-weekly schedules in ten trials, including the global phase III TOURMALINE-MM1 study. Data were analysed using nonlinear mixed-effects modelling (NONMEM software version 7.2, ICON Development Solutions, Hanover, MD, USA). Ixazomib plasma concentrations from intravenous and oral studies were described by a three-compartment model with linear distribution and elimination kinetics, including first-order linear absorption with a lag time describing the oral dose data. Body surface area on the volume of the second peripheral compartment was the only covariate included in the final model. None of the additional covariates tested including body surface area (1.2–2.7 m²), sex, age (23–91 years), race, mild/moderate renal impairment and mild hepatic impairment were found to impact systemic clearance, suggesting that no dose adjustment is required based on these covariates. The geometric mean terminal disposition phase half-life was 9.5 days, steady-state volume of distribution was 543 L and systemic clearance was 1.86 L/h. The absolute bioavailability of an oral dose was estimated to be 58%.

[Pharmacological characteristics and clinical study results of the oral proteasome inhibitor ixazomib (NINLARO® capsules; 2.3 mg, 3 mg, and 4 mg)]

Ixazomib (Ninlaro^® capsule) is an oral small molecule 20S proteasome inhibitor created by Millennium Pharmaceuticals, Inc (Takeda Oncology Company). Ubiquitin proteasome system is a major regulatory system for maintaining protein homeostasis, and an important mechanism for degrading proteins, such as those involved in proliferation regulation, cell cycle regulation and apoptosis, in cells. Ixazomib selectively and reversibly binds to the β5 subunit of the 20S proteasome, inhibits its chymotrypsin-like activity, and thereby accumulates ubiquitinated proteins. It induces ER stress and apoptosis of myeloma cells. The phase 3, randomized, double-blind, multicenter global study (TOURMALINE-MM1) in patients with relapsed and/or refractory multiple myeloma, who have received 1 to 3 prior lines of therapy, showed that addition of ixazomib to lenalidomide-dexamethasone (ixazomib-Rd) demonstrated significant improvement in progression-free survival (hazard ratio = 0.742, P = 0.012) versus placebo-Rd (20.6 vs. 14.7 months in the median) (data cut-off as of October 30, 2014). Ixazomib has been approved by the United States Food and Drug Administration in November 2015, and the European Medicines Agency in November 2016 for the treatment of multiple myeloma (MM) patients who have received at least one prior therapy. In Japan, ixazomib was approved for the treatment of relapsed and/or refractory MM in March, 2017. It is expected to demonstrate that the oral proteasome inhibitor ixazomib is an effective and convenient treatment option in clinical practice.

The combination of MLN2238 (ixazomib) with interferon-alpha results in enhanced cell death in melanoma

The ubiquitin-proteasome signaling pathway is critical for cell cycle regulation and neoplastic growth. Proteasome inhibition can activate apoptotic pathways. Bortezomib, a selective proteasome inhibitor, has anti-melanoma activity. MLN2238 (ixazomib), an oral proteasome inhibitor, has improved pharmacotherapeutic parameters compared to bortezomib. Interferon-alpha (IFN-α), an immune boosting agent, is FDA-approved for treatment of melanoma. In this study in vitro and in vivo evaluation of the antitumor potential of ixazomib and combination treatments with ixazomib and IFN-α were performed. Apoptosis induced by ixazomib was first observed at 12 hours and was maximal at 48 hours with similar levels of cell death compared to bortezomib. IFN-α alone had little effect on cell viability in vitro. However, the combination of ixazomib with IFN-α significantly enhanced ixazomib's ability to induce apoptotic cell death in BRAF V600E mutant and BRAF wild-type human melanoma tumor cells. The combination of ixazomib and IFN-α also enhanced inhibition of cell proliferation in BRAF V600E mutant melanoma tumor cells; however, this was not seen in BRAF wild-type cells. Ixazomib-induced apoptosis was associated with processing of the pro-apoptotic proteins procaspase-3, -7, -8, and -9, and cleavage of poly-ADP-ribose polymerase (PARP). In an in vivo xenograft model of human melanoma, combination treatment with IFN-α-2b and ixazomib demonstrated a significant reduction in tumor volume when compared to vehicle (p = 0.005) and single therapy ixazomib (p = 0.017) and IFN-α-2b (p = 0.036). These pre-clinical results support further evaluation of combination treatment with ixazomib and IFN-α for the treatment of advanced BRAF V600E mutant melanoma.

Clinical pharmacokinetics of oral drugs in the treatment of multiple myeloma

Treatment of myeloma is a long-term treatment mainly based on all-oral combinations of drugs. Because oral drugs have a more complex pharmacokinetics compared with IV treatments, an appropriate knowledge of the factors that may alter their systemic exposure is of particular clinical relevance. Both drug-drug interactions, food-effect, and dose-adaptation in renal and hepatic impairment may influence the systemic drug levels with a potential impact on drug efficacy or safety. Moreover, a better control of drug exposure may improve the side effect profiles of these treatments with a favourable impact on patient compliance. Furthermore, as long-term treatments, these drugs may also alter the systemic exposure of coadministered medications in these rather old patients. The aim of this review was to identify the factors modifying the systemic exposure of oral drugs used in myeloma by focusing on the pharmacokinetic drug-drug interactions and the effects of renal and hepatic impairment and of food impact.

New developments in the management of relapsed/refractory multiple myeloma - the role of ixazomib

Ixazomib is the first oral proteasome inhibitor to be approved, in combination with lenalidomide and dexamethasone, for the treatment of patients with multiple myeloma who have received at least one prior therapy. Approval was on the basis of results from the phase 3, double-blind, placebo-controlled TOURMALINE-MM1 study, which demonstrated a 35% improvement in progression-free survival with the all-oral combination of ixazomib plus lenalidomide-dexamethasone versus lenalidomide-dexamethasone alone (median: 20.6 vs 14.7 months; hazard ratio: 0.74, p=0.012; median follow-up 14.7 months). The addition of ixazomib to the lenalidomide-dexamethasone regimen was associated with limited additional toxicity and had no adverse impact on patient-reported quality of life. Common grade ≥3 adverse events with ixazomib include gastrointestinal adverse events, rash, and thrombocytopenia. Here, we review the efficacy, safety, pharmacokinetics, and patient-reported quality of life data seen with ixazomib, and discuss the role of this oral agent in the treatment of patients with relapsed/refractory multiple myeloma, including in patients with high-risk cytogenetic abnormalities and those with multiple prior therapies.

Effects of Strong CYP3A Inhibition and Induction on the Pharmacokinetics of Ixazomib, an Oral Proteasome Inhibitor: Results of Drug-Drug Interaction Studies in Patients With Advanced Solid Tumors or Lymphoma and a Physiologically Based Pharmacokinetic Analysis

At clinically relevant ixazomib concentrations, in vitro studies demonstrated that no specific cytochrome P450 (CYP) enzyme predominantly contributes to ixazomib metabolism. However, at higher than clinical concentrations, ixazomib was metabolized by multiple CYP isoforms, with the estimated relative contribution being highest for CYP3A at 42%. This multiarm phase 1 study (Clinicaltrials.gov identifier: NCT01454076) investigated the effect of the strong CYP3A inhibitors ketoconazole and clarithromycin and the strong CYP3A inducer rifampin on the pharmacokinetics of ixazomib. Eighty-eight patients were enrolled across the 3 drug-drug interaction studies; the ixazomib toxicity profile was consistent with previous studies. Ketoconazole and clarithromycin had no clinically meaningful effects on the pharmacokinetics of ixazomib. The geometric least-squares mean area under the plasma concentration-time curve from 0 to 264 hours postdose ratio (90%CI) with vs without ketoconazole coadministration was 1.09 (0.91-1.31) and was 1.11 (0.86-1.43) with vs without clarithromycin coadministration. Reduced plasma exposures of ixazomib were observed following coadministration with rifampin. Ixazomib area under the plasma concentration-time curve from time 0 to the time of the last quantifiable concentration was reduced by 74% (geometric least-squares mean ratio of 0.26 [90%CI 0.18-0.37]), and maximum observed plasma concentration was reduced by 54% (geometric least-squares mean ratio of 0.46 [90%CI 0.29-0.73]) in the presence of rifampin. The clinical drug-drug interaction study results were reconciled well by a physiologically based pharmacokinetic model that incorporated a minor contribution of CYP3A to overall ixazomib clearance and quantitatively considered the strength of induction of CYP3A and intestinal P-glycoprotein by rifampin. On the basis of these study results, the ixazomib prescribing information recommends that patients should avoid concomitant administration of strong CYP3A inducers with ixazomib.

A Phase 1 Study to Assess the Relative Bioavailability of Two Capsule Formulations of Ixazomib, an Oral Proteasome Inhibitor, in Patients With Advanced Solid Tumors or Lymphoma

The oral proteasome inhibitor ixazomib is approved in multiple countries in combination with lenalidomide and dexamethasone for the treatment of patients with multiple myeloma who have received at least 1 prior therapy. Two oral capsule formulations of ixazomib have been used during clinical development. This randomized, 2-period, 2-sequence crossover study (Clinicaltrials.gov identifier NCT01454076) assessed the relative bioavailability of capsule B in reference to capsule A in adult patients with advanced solid tumors or lymphoma. The study was conducted in 2 parts. In cycle 1 (pharmacokinetic cycle), patients received a 4-mg dose of ixazomib as capsule A or capsule B on day 1, followed by a 4-mg dose of the alternate capsule formulation on day 15. Pharmacokinetic samples were collected over 216 hours postdose. After the pharmacokinetic cycle, patients could continue in the study and receive ixazomib (capsule B only) on days 1, 8, and 15 of each 28-day cycle. Twenty patients were enrolled; of these, 14 were included in the pharmacokinetic-evaluable population. Systemic exposures of ixazomib were similar after administration of capsule A or capsule B. The geometric least-squares mean ratios (capsule B versus capsule A) were 1.16 for C_max (90% confidence interval [CI], 0.84-1.61) and 1.04 for AUC_0-216 (90%CI, 0.91-1.18). The most frequently reported grade 3 drug-related adverse events were fatigue (15%) and nausea (10%); there were no grade 4 drug-related adverse events. These results support the combined analysis of data from studies that used either formulation of ixazomib during development.

Safety of ixazomib for the treatment of multiple myeloma

INTRODUCTION

Despite a major positive impact of proteasome inhibitors (PI), such as bortezomib and carfilzomib, on the survival of patients with multiple myeloma (MM) over the last few years, their use in clinical practice is limited by the development of drug resistance, significant side-effects or constraining administration schedules. Ixazomib is the first, and for now the only, oral PI, which was approved by the US Food and Drug Administration in 2015 and by the European Medicines Agency in 2016. Areas covered: In this review, we provide an overview of the preclinical and early-phase studies of ixazomib used as single-agent and in combination. Furthermore, we discuss the results of a recently published pivotal trial, which evaluated the safety profile and clinical benefit of the combination of ixazomib, lenalidomide and dexamethasone versus lenalidomide and dexamethasone alone in 722 patients with relapsed/refractory MM. Expert opinion: Ixazomib combines the comfort of oral administration, substantial clinical efficacy and a good safety profile with manageable side-effects, which mainly comprise low-grade hematological, digestive or cutaneous events, and the agent will therefore play an active part in long-term treatment strategies, both as single agent and as part of combination regimens. Ongoing phase III trials are currently defining its place in first-line, maintenance and relapse settings.

Randomized, double-blind, placebo-controlled phase III study of ixazomib plus lenalidomide-dexamethasone in patients with relapsed/refractory multiple myeloma: China Continuation study

Background

The China Continuation study was a separate regional expansion of the global, double-blind, placebo-controlled, randomized phase III TOURMALINE-MM1 study of ixazomib plus lenalidomide–dexamethasone (Rd) in patients with relapsed/refractory multiple myeloma (RRMM) following one to three prior therapies.

Methods

Patients were randomized (1:1) to receive ixazomib 4.0 mg or placebo on days 1, 8, and 15, plus lenalidomide 25 mg on days 1–21 and dexamethasone 40 mg on days 1, 8, 15, and 22, in 28-day cycles. Randomization was stratified according to number of prior therapies, disease stage, and prior proteasome inhibitor exposure. The primary endpoint was progression-free survival (PFS). In total, 115 Chinese patients were randomized (57 ixazomib-Rd, 58 placebo-Rd).

Results

At the preplanned final analysis for PFS, after median PFS follow-up of 7.4 and 6.9 months, respectively, PFS was improved with ixazomib-Rd versus placebo-Rd (median 6.7 vs 4.0 months; HR 0.598; p = 0.035). At the preplanned final analysis of overall survival (OS), after median follow-up of 20.2 and 19.1 months, respectively, OS was improved with ixazomib-Rd versus placebo-Rd (median 25.8 vs 15.8 months; HR 0.419; p = 0.001). On the ixazomib-Rd and placebo-Rd arms, respectively, 38 (67%) and 43 (74%) patients reported grade ≥3 adverse events (AEs), 19 (33%) and 18 (31%) reported serious AEs, and 4 (7%) and 5 (9%) died on-study. The most frequent grade 3/4 AEs were thrombocytopenia (18%/7% vs 14%/5%), neutropenia (19%/5% vs 19%/2%), and anemia (12%/0 vs 26%/2%).

Conclusions

This study demonstrated that PFS and OS were significantly improved with ixazomib-Rd versus placebo-Rd, with limited additional toxicity, in patients with RRMM.

Trial registration

ClinicalTrials.gov, NCT01564537

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-017-0501-4) contains supplementary material, which is available to authorized users.

The potential of ixazomib, a second-generation proteasome inhibitor, in the treatment of multiple myeloma

The therapeutic armamentarium for multiple myeloma has recently benefited from the addition of several new agents (including second-generation proteasome inhibitors, monoclonal antibodies and histone deacetylase inhibitors). This review will focus on ixazomib, an orally bioavailable second-generation proteasome inhibitor. Specifically, we will review the preclinical data, clinical trial experience, potential indications as well as unanswered questions pertaining to this new agent in multiple myeloma.

Novel Proteasome Inhibitors and Histone Deacetylase Inhibitors: Progress in Myeloma Therapeutics

The unfolded protein response is responsible for the detection of misfolded proteins and the coordination of their disposal and is necessary to maintain the cellular homoeostasis. Multiple myeloma cells secrete large amounts of immunoglobulins, proteins that need to be correctly folded by the chaperone system. If this process fails, the misfolded proteins have to be eliminated by the two main garbage-disposal systems of the cell: proteasome and aggresome. The blockade of either of these systems will result in accumulation of immunoglobulins and other toxic proteins in the cytoplasm and cell death. The simultaneous inhibition of the proteasome, by proteasome inhibitors (PIs) and the aggresome, by histone deacetylase inhibitors (HDACi) results in a synergistic increase in cytotoxicity in myeloma cell lines. This review provides an overview of mechanisms of action of second-generation PIs and HDACi in multiple myeloma (MM), the clinical results currently observed with these agents and assesses the potential therapeutic impact of the different agents in the two classes. The second-generation PIs offer benefits in terms of increased efficacy, reduced neurotoxicity as off-target effect and may overcome resistance to bortezomib because of their different chemical structure, mechanism of action and biological properties. HDACi with anti-myeloma activity in clinical development discussed in this review include vorinostat, panobinostat and selective HDAC6 inhibitor, ricolinostat.

Phase 1 study of ixazomib alone or combined with lenalidomide-dexamethasone in Japanese patients with relapsed/refractory multiple myeloma

We report the first clinical investigation conducted in Japan to confirm the safety, tolerability, and pharmacokinetics of ixazomib alone and combined with lenalidomide-dexamethasone (Rd) in Japanese patients with relapsed/refractory multiple myeloma. Adult patients with measurable disease and ≥2 prior lines of therapy received oral ixazomib 4.0 mg on days 1, 8, 15 alone or combined with lenalidomide 25 mg on days 1-21 and dexamethasone 40 mg on days 1, 8, 15, 22 in 28-day cycles. Fourteen patients who had received a median of seven prior therapies were enrolled (seven per cohort). One of six evaluable patients in each cohort experienced dose-limiting toxicities [diarrhea, nausea, hypokalemia, hypertension, thrombocytopenia, hyponatremia (ixazomib cohort); thrombocytopenia, and neutropenia (ixazomib + Rd cohort)]. The most common drug-related adverse events were neutropenia, thrombocytopenia, leukopenia, and lymphopenia. Drug-related grade ≥3 adverse events occurring in ≥3 patients per cohort were (ixazomib/ixazomib + Rd cohort, n): neutropenia (4/2), thrombocytopenia (3/2), and lymphopenia (5/2). Ixazomib was rapidly absorbed with a median T _max of approximately 1-2-h post-dose, and had a geometric mean terminal half-life of 5-6 days. Of 13 response-evaluable patients, one achieved a partial response (duration ∼38 weeks; ixazomib cohort) and seven had stable disease.

Oral ixazomib maintenance therapy in multiple myeloma

Continuous therapy has proven to be an effective therapeutic strategy to improve the outcome of both young and elderly multiple myeloma patients. Remarkably, lenalidomide and bortezomib showed to play a crucial role in this setting due to their safety profile allowing long-term exposure. Ixazomib, the first oral proteasome inhibitor to be evaluated in multiple myeloma, exerts substantial anti-myeloma activity as a single agent and particularly in combination with immunomodulatory drugs and it may be an attractive option for maintenance therapy. Here we address the issue of maintenance therapy as part of a therapeutic approach of multiple myeloma patients focusing on the potential role of ixazomib.

A pharmacokinetics and safety phase 1/1b study of oral ixazomib in patients with multiple myeloma and severe renal impairment or end-stage renal disease requiring haemodialysis

Renal impairment (RI) is a major complication of multiple myeloma (MM). This study aimed to characterize the single-dose pharmacokinetics (PK) of the oral proteasome inhibitor, ixazomib, in cancer patients with normal renal function [creatinine clearance (CrCl) ≥90 ml/min; n = 20), severe RI (CrCl <30 ml/min; n = 14), or end-stage renal disease requiring haemodialysis (ESRD; n = 7). PK and adverse events (AEs) were assessed after a single 3 mg dose of ixazomib. Ixazomib was highly bound to plasma proteins (~99%) in all renal function groups. Unbound and total systemic exposures of ixazomib were 38% and 39% higher, respectively, in severe RI/ESRD patients versus patients with normal renal function. Total ixazomib concentrations were similar in pre- and post-dialyser samples collected from ESRD patients; therefore, ixazomib can be administered without regard to haemodialysis timing. Except for anaemia, the incidence of the most common AEs was generally similar across groups, but grade 3 and 4 AEs were more frequent in the severe RI/ESRD groups versus the normal group (79%/57% vs. 45%), as were serious AEs (43%/43% vs. 15%). The PK and safety results support a reduced ixazomib dose of 3 mg in patients with severe RI/ESRD.

Pharmacokinetics of ixazomib, an oral proteasome inhibitor, in solid tumour patients with moderate or severe hepatic impairment

Aim

The aim of the present study was to characterize the pharmacokinetics of the oral proteasome inhibitor, ixazomib, in patients with solid tumours and moderate or severe hepatic impairment, to provide posology recommendations.

Methods

Eligible adults with advanced malignancies for which no further effective therapy was available received a single dose of ixazomib on day 1 of the pharmacokinetic cycle; patients with normal hepatic function, moderate hepatic impairment or severe hepatic impairment received 4 mg, 2.3 mg or 1.5 mg, respectively. Blood samples for single‐dose pharmacokinetic characterization were collected over 336 h postdose. After sampling, patients could continue to receive ixazomib on days 1, 8 and 15 in 28‐day cycles.

Results

Of 48 enrolled patients (13, 15 and 20 in the normal, moderate and severe groups, respectively), 43 were pharmacokinetics‐evaluable. Ixazomib was rapidly absorbed (median time to reach peak concentration was 0.95–1.5 h) and highly bound to plasma proteins, with a similar mean fraction bound (~99%) across the three groups. In patients with moderate/severe hepatic impairment (combined group), the geometric least squares mean ratios (90% confidence interval) for unbound and total dose‐normalized area under the plasma concentration vs. time curve from time zero to the time of the last quantifiable concentration in reference to the normal hepatic function group were 1.27 (0.75, 2.16) and 1.20 (0.79, 1.82), respectively. Seven (15%) of the 48 patients experienced a grade 3 drug‐related adverse event; there were no drug‐related grade 4 adverse events.

Conclusions

In patients with moderate/severe hepatic impairment, unbound and total systemic exposures of ixazomib were 27% and 20% higher, respectively, vs. normal hepatic function. A reduced ixazomib starting dose of 3 mg is recommended for patients with moderate or severe hepatic impairment.

Exposure-safety-efficacy analysis of single-agent ixazomib, an oral proteasome inhibitor, in relapsed/refractory multiple myeloma: dose selection for a phase 3 maintenance study

Background Ixazomib is the first oral, small molecule proteasome inhibitor to reach phase 3 trials. The current analysis characterized the exposure-safety and exposure-efficacy relationships of ixazomib in patients with relapsed/refractory multiple myeloma (MM) with a purpose of recommending an approach to ixazomib dosing for maintenance therapy. Methods Logistic regression was used to investigate relationships between ixazomib plasma exposure (area under the curve/day; derived from individual apparent clearance values from a published population pharmacokinetic analysis) and safety/efficacy outcomes (hematologic [grade ≥ 3 vs ≤ 2] or non-hematologic [grade ≥ 2 vs ≤ 1] adverse events [AEs], and clinical benefit [≥stable disease vs progressive disease]) using phase 1 data in relapsed/refractory MM (NCT00963820; N = 44). Results Significant relationships to ixazomib exposure were observed for five AEs (neutropenia, thrombocytopenia, rash, fatigue, and diarrhea) and clinical benefit (p < 0.05). Dose–response relationships indicated a favorable benefit/risk ratio at 3 mg and 4 mg weekly, which are below the maximum tolerated dose of 5.5 mg. At 3 mg, the model predicted that: 37 % of patients will achieve clinical benefit; incidence of grade ≥ 3 neutropenia and thrombocytopenia will be 10 % and 23 %, respectively; and incidence of grade ≥ 2 rash, fatigue, and diarrhea will be 8 %, 19 %, and 19 %, respectively. Conclusions Based on the findings, patients in the phase 3 maintenance trial will initiate ixazomib at a once-weekly dose of 3 mg, increasing to 4 mg if acceptable tolerability after 4 cycles, to provide maximum clinical benefit balanced with adequate tolerability.

The Effect of a High-Fat Meal on the Pharmacokinetics of Ixazomib, an Oral Proteasome Inhibitor, in Patients With Advanced Solid Tumors or Lymphoma

Ixazomib is the first oral proteasome inhibitor to be investigated in the clinic. This clinical study assessed whether the pharmacokinetics of ixazomib would be altered if administered after a high‐calorie, high‐fat meal. In a 2‐period, 2‐sequence, crossover study design, adult patients with advanced solid tumors or lymphoma received a 4‐mg oral dose of ixazomib as immediate‐release capsules on day 1 without food (fasted, administered following an overnight fast) or with food (fed, following consumption of a high‐calorie, high‐fat meal), followed by another dose on day 15 in the alternate food intake condition (fasted to fed or fed to fasted). Twenty‐four patients were enrolled; of these, 15 were included in the pharmacokinetic‐evaluable population. Administration of ixazomib after a high‐fat meal reduced both the rate and extent of absorption of ixazomib. Under fed conditions, the median time to peak plasma concentration (T_max) of ixazomib was delayed by approximately 3 hours compared with administration in the fasted state (1.02 hours vs 4.0 hours), and there was a 28% reduction in total systemic exposure (area under the curve, AUC) and a 69% reduction in peak plasma concentration (C_max). Together, the results support the administration of ixazomib on an empty stomach, at least 1 hour before or at least 2 hours after food. These recommendations are reflected in the United States Prescribing Information for ixazomib (clinicaltrials.gov identifier NCT01454076).

Selective Toxicity of Investigational Ixazomib for Human Leukemia Cells Expressing Mutant Cytoplasmic NPM1: Role of Reactive Oxygen Species

PURPOSE

This study was performed to determine whether the investigational proteasome inhibitor ixazomib demonstrated selective antineoplastic activity against acute myelogenous leukemia cells expressing a mutated nucleophosmin-1 gene and to gain a better understanding of its mechanisms of action.

EXPERIMENTAL DESIGN

The cytotoxic effects of ixazomib treatment were analyzed in human acute myelogenous leukemia (AML) cell lines and primary AML samples expressing wild-type or mutated NPM1 (NPMc(+)). The potential roles of oxidative stress in mediating cytotoxic activity were determined using flow cytometry, enzyme-based assays, and Western blots.

RESULTS

Apoptosis induced by ixazomib was abrogated by knockdown of NPM1/NPMc(+)expression using an inducible shRNA construct and enhanced by NPMc(+)overexpression. Cytotoxicity was associated with superoxide generation and was reduced by the addition of the antioxidant N-acetylcysteine. AML cells expressing NPMc(+)had significantly reduced levels of intracellular glutathione and NADPH associated with reduced antioxidant responses to drug treatment. Treatment of 3 patients with relapsed NPMc(+)AML resulted in an antileukemic effect in 1 patient as demonstrated by a marked reduction of leukemic blasts in the peripheral blood. Efficacy was associated with superoxide generation, reduced glutathione levels, and reduced mRNA and protein expression of antioxidant effectors in responding cells.

CONCLUSIONS

In this study, a direct association was observed between NPMc(+)expression in AML, reduced antioxidant responses, and enhanced sensitivity to an oral proteasome inhibitor that induces oxidative stress. These data suggest that intracellular determinants of antioxidant responses may be good predictors of therapeutic response to ixazomib.

Pharmacokinetics and safety of ixazomib plus lenalidomide-dexamethasone in Asian patients with relapsed/refractory myeloma: a phase 1 study

BACKGROUND

The oral proteasome inhibitor ixazomib is under phase 3 clinical investigation in multiple myeloma (MM) in combination with lenalidomide-dexamethasone. This study was conducted to investigate the pharmacokinetic and safety profiles of ixazomib, administered with lenalidomide-dexamethasone, in East Asian patients with relapsed/refractory MM.

METHODS

Adult patients with measurable disease who had received 1-3 prior lines of therapy received oral ixazomib on days 1, 8, and 15, lenalidomide (25 mg) on days 1-21, and dexamethasone (40 mg) on days 1, 8, 15, and 22, in 28-day cycles. Primary objectives were to characterize ixazomib plasma pharmacokinetics, determine the recommended phase 2/3 dose, and evaluate safety and tolerability.

RESULTS

Forty-three patients were enrolled. No dose-limiting toxicities were reported for the first six patients receiving ixazomib (4.0 mg), confirming this as the recommended phase 2/3 dose. Ixazomib was rapidly absorbed with a median T max of 1.5 h on day 1 and 2.0 h on day 15 of cycle 1 and had a geometric mean terminal half-life of 6.1 days. Twenty-one (49%) patients had at least one drug-related grade ≥3 adverse event (AE); the most common were neutropenia (19%), diarrhea (14%), and thrombocytopenia (12%). Twenty-eight of 43 (65%) response-evaluable patients had at least a partial response. The recommended phase 2/3 dose for ixazomib was determined to be 4.0 mg.

CONCLUSIONS

The all-oral combination of ixazomib plus lenalidomide-dexamethasone appeared active and well tolerated at 4.0 mg. Consequently, East Asian patients enrolled in phase 3 studies are receiving the same ixazomib dose as patients in other regions.

TRIAL REGISTRATION

This study is registered at NCT01645930.

Integrated nonclinical and clinical risk assessment of the investigational proteasome inhibitor ixazomib on the QTc interval in cancer patients

BACKGROUND

Ixazomib is the first oral, proteasome inhibitor to reach phase III trials. Here, we present an integrated nonclinical and clinical assessment of ixazomib's effect on QTc intervals.

METHODS

Nonclinical studies assessed (1) the in vitro binding of ixazomib to the hERG channel and (2) its effect on QT/QTc in dogs (N = 4) via telemetry. Pharmacokinetic-matched triplicate electrocardiograms were collected in four clinical phase I studies of intravenous (0.125-3.11 mg/m(2), N = 125, solid tumors/lymphoma) or oral (0.24-3.95 mg/m(2), N = 120, multiple myeloma) ixazomib. The relationship between ixazomib plasma concentration and heart rate (HR)-corrected QT using Fridericia (QTcF) or population (QTcP) methods was analyzed using linear mixed-effects models with fixed effects for day and time.

RESULTS

In vitro binding potency for ixazomib to the hERG channel was weak (K i 24.9 μM; IC50 59.6 μM), and nonclinical telemetry studies showed no QT/QTc prolongation at doses up to 4.2 mg/m(2). In cancer patients, ixazomib, when evaluated at doses yielding various plasma concentrations (with 26 % of data greater than mean C max for the 4 mg phase 3 dose), had no meaningful effect on QTc based on model-predicted mean change in QTcF/QTcP from baseline. There was no relationship between ixazomib concentration and RR, suggesting no effect on HR.

CONCLUSIONS

Ixazomib has no clinically meaningful effects on QTc or HR. Integrating preclinical data and concentration-QTc modeling of phase 1 data may obviate the need for a dedicated QTc study in oncology. A framework for QT assessment in oncology drug development is proposed.

Ixazomib for the treatment of multiple myeloma

INTRODUCTION

Proteasome inhibition is a mainstay in the treatment of multiple myeloma (MM). Bortezomib, the first proteasome inhibitor (PI) approved for MM therapy, has shown efficacy in relapsed/refractory patients and in the front-line setting. Among second-generation PIs, MLN9708 ( ixazomib ) is the first oral compound to be evaluated in MM treatment and has shown improvement in pharmacokinetic and pharmacodynamic parameters compared with bortezomib with a similar efficacy in the control of myeloma growth and in the prevention of bone loss.

AREAS COVERED

In this review, the authors discuss the rationale for use of PIs. They then summarize the clinical development of ixazomib in MM, from initial Phase I to Phase II studies as a monotherapy and in combination with other chemotherapeutics.

EXPERT OPINION

Preliminary data of Phase I/II trials showed that ixazomib had a good safety profile and exerted anti-myeloma activity as a single agent in relapsed/refractory patients. Furthermore, ixazomib also had efficacy in patients who were refractory to bortezomib. Its use in combination with lenalidomide and dexamethasone was shown to be an effective and well-tolerated regimen in up-front treatment leading to minimal residual disease negativity in a significant number of patients. Results of Phase III trials, evaluating ixazomib in induction or maintenance therapy, are awaited.