Nilotinib preclinical pharmacokinetics and practical application toward clinical projections of oral absorption and systemic availability

Gastroretentive fibrous dosage forms for prolonged delivery of sparingly-soluble tyrosine kinase inhibitors. Part 4: Experimental validation of the models of drug concentration in blood

In this final part, the models of drug concentration in blood developed in Part 3 are validated on dogs. Both slow-release gastroretentive fibrous and immediate-release particulate dosage forms containing 200 mg nilotinib were tested. After administering, the fibrous dosage form expanded linearly with time in the stomach, to about 1.5 times the initial radius by 4 h. The expanded dosage form fractured after 10 h, and then passed into the intestines. The drug concentration in blood exhibited a broad peak with a maximum of 0.51 μg/ml and a width at half-height of 10.2 h. By contrast, after administering the immediate-release capsule the drug concentration in blood exhibited a sharp peak with a maximum of 0.68 μg/ml and a width at half-height of just 3.6 h. The experimental data validate the theoretical models reasonably. The gastroretentive fibrous dosage forms designed in this study enable a steady drug concentration in blood for increasing the efficacy and mitigating side effects of drug therapies.

Enabling superior drug loading in lipid-based formulations with lipophilic salts for a brick dust molecule: Exploration of lipophilic counterions and in vitro-in vivo evaluation

Lipid-based formulations (LbFs) are an extensively used approach for oral delivery of poorly soluble drug compounds in the form of lipid suspension and lipid solution. However, the high target dose and inadequate lipid solubility limit the potential of brick dust molecules to be formulated as LbFs. Thus, the complexation of such molecules with a lipophilic counterion can be a plausible approach to improve the solubility in lipid-based solutions via reducing drug crystallinity and polar surface area. The study aimed to enhance drug loading in lipid solution for Nilotinib (Nil) through complexation or salt formation with different lipophilic counterions. We synthesized different lipophilic salts/ complexes via metathesis reactions and confirmed their formation by 1H NMR and FTIR. Docusate-based lipophilic salt showed improved solubility in medium-chain triglycerides (∼7 to 7.5-fold) and long-chain triglycerides (∼30 to 35-fold) based lipids compared to unformulated crystalline Nil. The increased lipid solubility could be attributed to the reduction in drug crystallinity which was further confirmed by the PXRD and DSC. Prototype LbFs were prepared to evaluate drug loading and their physicochemical characteristics. The findings suggested that structural features of counterion including chain length and lipophilicity affect the drug loading in LbF. In addition, physical stability testing of formulations was performed, inferring that aliphatic sulfate-based LbFs were stable with no sign of drug precipitation or salt disproportionation. An in vitro lipolysis-permeation study revealed that the primary driver of absorptive flux is the solubilization of the drug and reduced amount of lipid. Further, the in vivo characterization was conducted to measure the influence of increased drug load on oral bioavailability. Overall, the results revealed enhanced absorption of lipophilic salt-based LbF over unformulated crystalline Nil and conventional LbF (drug load equivalent to equilibrium solubility) which supports the idea that lipophilic salt-based LbF enhances drug loading, and supersaturation-mediated drug solubilization, unlocking the full potential of LbF.

Clinical pharmacokinetics and drug-drug interactions of tyrosine-kinase inhibitors in chronic myeloid leukemia: A clinical perspective

In the past decade, numerous tyrosine kinase inhibitors (TKIs) have been introduced in the treatment of chronic myeloid leukemia. Given the significant interpatient variability in TKIs pharmacokinetics, potential drug-drug interactions (DDIs) can greatly impact patient therapy. This review aims to discuss the pharmacokinetic characteristics of TKIs, specifically focusing on their absorption, distribution, metabolism, and excretion profiles. Additionally, it provides a comprehensive overview of the utilization of TKIs in special populations such as the elderly, children, and patients with liver or kidney dysfunction. We also highlight known or suspected DDIs between TKIs and other drugs, highlighting various clinically relevant interactions. Moreover, specific recommendations are provided to guide haemato-oncologists, oncologists, and clinical pharmacists in managing DDIs during TKI treatment in daily clinical practice.

Targeting a xenobiotic transporter to ameliorate vincristine-induced sensory neuropathy

Vincristine is a widely used chemotherapeutic drug for the treatment of multiple malignant diseases that causes a dose-limiting peripheral neurotoxicity. There is no clinically effective preventative treatment for vincristine-induced sensory peripheral neurotoxicity (VIPN), and mechanistic details of this side effect remain poorly understood. We hypothesized that VIPN is dependent on transporter-mediated vincristine accumulation in dorsal root ganglion neurons. Using a xenobiotic transporter screen, we identified OATP1B3 as a neuronal transporter regulating the uptake of vincristine. In addition, genetic or pharmacological inhibition of the murine orthologue transporter OATP1B2 protected mice from various hallmarks of VIPN - including mechanical allodynia, thermal hyperalgesia, and changes in digital maximal action potential amplitudes and neuronal morphology - without negatively affecting plasma levels or antitumor effects of vincristine. Finally, we identified α-tocopherol from an untargeted metabolomics analysis as a circulating endogenous biomarker of neuronal OATP1B2 function, and it could serve as a companion diagnostic to guide dose selection of OATP1B-type transport modulators given in combination with vincristine to prevent VIPN. Collectively, our findings shed light on the fundamental basis of VIPN and provide a rationale for the clinical development of transporter inhibitors to prevent this debilitating side effect.

Platform combining statistical modeling and patient-derived organoids to facilitate personalized treatment of colorectal carcinoma

BACKGROUND

We propose a new approach for designing personalized treatment for colorectal cancer (CRC) patients, by combining ex vivo organoid efficacy testing with mathematical modeling of the results.

METHODS

The validated phenotypic approach called Therapeutically Guided Multidrug Optimization (TGMO) was used to identify four low-dose synergistic optimized drug combinations (ODC) in 3D human CRC models of cells that are either sensitive or resistant to first-line CRC chemotherapy (FOLFOXIRI). Our findings were obtained using second order linear regression and adaptive lasso.

RESULTS

The activity of all ODCs was validated on patient-derived organoids (PDO) from cases with either primary or metastatic CRC. The CRC material was molecularly characterized using whole-exome sequencing and RNAseq. In PDO from patients with liver metastases (stage IV) identified as CMS4/CRIS-A, our ODCs consisting of regorafenib [1 mM], vemurafenib [11 mM], palbociclib [1 mM] and lapatinib [0.5 mM] inhibited cell viability up to 88%, which significantly outperforms FOLFOXIRI administered at clinical doses. Furthermore, we identified patient-specific TGMO-based ODCs that outperform the efficacy of the current chemotherapy standard of care, FOLFOXIRI.

CONCLUSIONS

Our approach allows the optimization of patient-tailored synergistic multi-drug combinations within a clinically relevant timeframe.

Serum and lymph pharmacokinetics of nilotinib delivered by yeast glucan particles per os

Nilotinib is a selective tyrosine-kinase inhibitor approved for the treatment of chronic myeloid leukemia. It is poorly soluble in aqueous media and has a low oral bioavailability. Nilotinib encapsulation into yeast glucan particles (GPs) was investigated in this work as a means of increasing bioavailability. The amorphization of nilotinib in GPs resulted in an increased dissolution rate, which was confirmed by in vitro experiments using biorelevant dissolution media. Simultaneously, GPs containing nilotinib were effectively taken up by macrophages, which was quantified in vitro on cell cultures. The overall oral bioavailability in a rat model was approximately 39 % for nilotinib delivered in a reference formulation (Tasigna) and was almost doubled when delivered in GPs. The contribution of glucan particles to the lymphatic transport of nilotinib was quantified. When delivered by GPs, cumulative nilotinib absorption via the lymphatic system increased by a factor of 10.8 compared to the reference, but still represented arelative bioavailability of only 1.12 %. The cumulative uptake of GPs in the lymph was found to be 0.54 mg after a single dose of 50 mg. Yeast glucan particles can therefore serve as a drug delivery vehicle with a dual function: dissolution rate enhancement by amorphization, and, to asmaller extent, lymphatic delivery due to macrophage uptake.

Dynamic Changes in Gastrointestinal Fluid Characteristics after Food Ingestion Are Important for Quantitatively Predicting the In Vivo Performance of Oral Solid Dosage Forms in Humans in the Fed State

The aim of this study was to develop a simulation model to predict the in vivo performance of solid oral dosage forms in humans in the fed state. We focused on investigating the effect of dynamic changes in gastrointestinal (GI) fluid characteristics in the fed state on the in vivo performance of solid dosage forms. We used six solid dosage forms containing weak base drugs as model formulations, two with positive food effects in humans, two with negative food effects, and two which are not affected by food ingestion. These model drug formulations were used to perform biorelevant dissolution tests in the stomach and small intestine under both prandial states. The in vitro properties of the drug products obtained from these tests were then coupled with in silico models (fasted or fed) to predict food effects in humans. We successfully incorporated the dynamic changes in GI fluid characteristics and their effects on the in vivo dissolution of drugs into the prediction model for the fed state. This newly designed physiologically based biopharmaceutics modeling approach provided the precise and quantitative prediction of food effects (i.e., changes in C_max and AUC after food ingestion) in humans while considering the dynamic changes in fluid characteristics in the fed state.

Applications, Challenges, and Outlook for PBPK Modeling and Simulation: A Regulatory, Industrial and Academic Perspective

Several regulatory guidances on the use of physiologically based pharmacokinetic (PBPK) analyses and physiologically based biopharmaceutics model(s) (PBBM(s)) have been issued. Workshops are routinely held, demonstrating substantial interest in applying these modeling approaches to address scientific questions in drug development. PBPK models and PBBMs have remarkably contributed to model-informed drug development (MIDD) such as anticipating clinical PK outcomes affected by extrinsic and intrinsic factors in general and specific populations. In this review, we proposed practical considerations for a "base" PBPK model construction and development, summarized current status, challenges including model validation and gaps in system models, and future perspectives in PBPK evaluation to assess a) drug metabolizing enzyme(s)- or drug transporter(s)- mediated drug-drug interactions b) dosing regimen prediction, sampling timepoint selection and dose validation in pediatric patients from newborns to adolescents, c) drug exposure in patients with renal and/or and hepatic organ impairment, d) maternal-fetal drug disposition during pregnancy, and e) pH-mediated drug-drug interactions in patients treated with proton pump inhibitors/acid-reducing agents (PPIs/ARAs) intended for gastric protection. Since PBPK can simulate outcomes in clinical studies with enrollment challenges or ethical issues, the impact of PBPK models on waivers and how to strengthen study waiver is discussed.

Optimization and Pharmacokinetic Evaluation of Synergistic Fenbendazole and Rapamycin Co-Encapsulated in Methoxy Poly(Ethylene Glycol)-b-Poly(Caprolactone) Polymeric Micelles

Purpose

We aimed to develop a nanocarrier formulation incorporating fenbendazole (FEN) and rapamycin (RAPA) with strong efficacy against A549 cancer cells. As FEN and RAPA are poorly soluble in water, it is difficult to apply them clinically in vivo. Therefore, we attempted to resolve this problem by encapsulating these drugs in polymeric micelles.

Methods

We evaluated drug synergy using the combination index (CI) values of various molar ratios of FEN and RAPA. We formed and tested micelles composed of different polymers. Moreover, we conducted cytotoxicity, stability, release, pharmacokinetic, and biodistribution studies to investigate the antitumor effects of FEN/RAPA-loaded mPEG-b-PCL micelles.

Results

We selected mPEG-b-PCL-containing FEN and RAPA at a molar ratio of 1:2 because these particles were consistent in size and had high encapsulation efficiency (EE, %) and drug loading (DL, %) capacity. The in vitro cytotoxicity was assessed for various FEN, RAPA, and combined FEN/RAPA formulations. After long-term exposures, both the solutions and the micelles had similar efficacy against A549 cancer cells. The in vivo pharmacokinetic study revealed that FEN/RAPA-loaded mPEG-b-PCL micelles had a relatively higher area under the plasma concentration–time curve from 0 to 2 h (AUC_{0–2 h}) and 0 to 8 h (AUC_{0–8 h}) and plasma concentration at time zero (C_o) than that of the FEN/RAPA solution. The in vivo biodistribution assay revealed that the IV injection of FEN/RAPA-loaded mPEG-b-PCL micelles resulted in lower pulmonary FEN concentration than the IV injection of the FEN/RAPA solution.

Conclusion

When FEN and RAPA had a 1:2 molar ratio, they showed synergism. Additionally, using data from in vitro cytotoxicity, synergism between a 1:2 molar ratio of FEN and RAPA was observed in the micelle formulation. The FEN/RAPA-loaded mPEG-b-PCL micelle had enhanced bioavailability than the FEN/RAPA solution.

Recent Developments in the Use of Kinase Inhibitors for Management of Viral Infections

Kinases are a group of therapeutic targets involved in the progression of numerous diseases, including cancer, rheumatoid arthritis, Alzheimer's disease, and viral infections. The majority of approved antiviral agents are inhibitors of virus-specific targets that are encoded by individual viruses. These inhibitors are narrow-spectrum agents that can cause resistance development. Viruses are dependent on host cellular proteins, including kinases, for progression of their life-cycle. Thus, targeting kinases is an important therapeutic approach to discovering broad-spectrum antiviral agents. As there are a large number of FDA approved kinase inhibitors for various indications, their repurposing for viral infections is an attractive and time-sparing strategy. Many kinase inhibitors, including baricitinib, ruxolitinib, imatinib, tofacitinib, pacritinib, zanubrutinib, and ibrutinib, are under clinical investigation for COVID-19. Herein, we discuss FDA approved kinase inhibitors, along with a repertoire of clinical/preclinical stage kinase inhibitors that possess antiviral activity or are useful in the management of viral infections.

Repurposing of Kinase Inhibitors for Treatment of COVID-19

The outbreak of COVID-19, the pandemic disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spurred an intense search for treatments by the scientific community. In the absence of a vaccine, the goal is to target the viral life cycle and alleviate the lung-damaging symptoms of infection, which can be life-threatening. There are numerous protein kinases associated with these processes that can be inhibited by FDA-approved drugs, the repurposing of which presents an alluring option as they have been thoroughly vetted for safety and are more readily available for treatment of patients and testing in clinical trials. Here, we characterize more than 30 approved kinase inhibitors in terms of their antiviral potential, due to their measured potency against key kinases required for viral entry, metabolism, or reproduction. We also highlight inhibitors with potential to reverse pulmonary insufficiency because of their anti-inflammatory activity, cytokine suppression, or antifibrotic activity. Certain agents are projected to be dual-purpose drugs in terms of antiviral activity and alleviation of disease symptoms, however drug combination is also an option for inhibitors with optimal pharmacokinetic properties that allow safe and efficacious co-administration with other drugs, such as antiviral agents, IL-6 blocking agents, or other kinase inhibitors.

Solute Carrier Transportome in Chemotherapy-Induced Adverse Drug Reactions

Members of the solute carrier (SLC) family of transporters are responsible for the cellular influx of a broad range of endogenous compounds and xenobiotics. These proteins are highly expressed in the gastrointestinal tract and eliminating organs such as the liver and kidney, and are considered to be of particular importance in governing drug absorption and elimination. Many of the same transporters are also expressed in a wide variety of organs targeted by clinically important anticancer drugs, directly affect cellular sensitivity to these agents, and indirectly influence treatment-related side effects. Furthermore, targeted intervention strategies involving the use of transport inhibitors have been recently developed, and have provided promising lead candidates for combinatorial therapies associated with decreased toxicity. Gaining a better understanding of the complex interplay between transporter-mediated on-target and off-target drug disposition will help guide the further development of these novel treatment strategies to prevent drug accumulation in toxicity-associated organs, and improve the safety of currently available treatment modalities. In this report, we provide an update on this rapidly emerging field with particular emphasis on anticancer drugs belonging to the classes of taxanes, platinum derivatives, nucleoside analogs, and anthracyclines.

New Insights into Using Lipid Based Suspensions for 'Brick Dust' Molecules: Case Study of Nilotinib

PURPOSE

Lipid suspensions have been shown to be a suitable bio-enabling formulation approach for highly lipophilic or 'grease ball' drug molecules, but studies on 'brick dust' drugs are lacking. This study explored the utility of lipid suspensions for enhancing oral bioavailability of the rather hydrophobic drug nilotinib in vivo in rats.

METHODS

Four lipid suspensions were developed containing long chain triglycerides, medium chain triglyceride, long chain monoglycerides and medium chain monoglycerides and in vivo bioavailability was compared to an aqueous suspension. Additionally, in vitro lipolysis and wettability tests were conducted.

RESULTS

Nilotinib lipid suspensions did not show a bioavailability increase compared to an aqueous suspension. The bioavailability was lower for triglyceride suspensions, relative to both monoglyceride and an aqueous suspension. The long chain monoglyceride displayed a significantly higher bioavailability relative to triglycerides. In vitro lipolysis results suggested entrapment of nilotinib crystals within poorly dispersible triglycerides, leading to slower nilotinib release and absorption. This was further supported by higher wettability of nilotinib by lipids.

CONCLUSION

Monoglycerides improved oral bioavailability of nilotinib in rats, relative to triglycerides. For 'brick dust' drugs formulated as lipid suspensions, poorly dispersible formulations may delay the release of drug crystals from the formulation leading to reduced absorption. Graphical Abstract An aqueous and four lipid suspensions have been evaluated in in vitro and in vivo to gain insights into the potential benefits and limitations of lipid suspensions.

Preclinical pharmacokinetic evaluation to facilitate repurposing of tyrosine kinase inhibitors nilotinib and imatinib as antiviral agents

Background

Several tyrosine kinase inhibitors (TKIs) developed as anti-cancer drugs, also have anti-viral activity due to their ability to disrupt productive replication and dissemination in infected cells. Consequently, such drugs are attractive candidates for “repurposing” as anti-viral agents. However, clinical evaluation of therapeutics against infectious agents associated with high mortality, but low or infrequent incidence, is often unfeasible. The United States Food and Drug Administration formulated the “Animal Rule” to facilitate use of validated animal models for conducting anti-viral efficacy studies.

Methods

To enable such efficacy studies of two clinically approved TKIs, nilotinib, and imatinib, we first conducted comprehensive pharmacokinetic (PK) studies in relevant rodent and non-rodent animal models. PK of these agents following intravenous and oral dosing were evaluated in C57BL/6 mice, prairie dogs, guinea pigs and Cynomolgus monkeys. Plasma samples were analyzed using an LC-MS/MS method. Secondarily, we evaluated the utility of allometry-based inter-species scaling derived from previously published data to predict the PK parameters, systemic clearance (CL) and the steady state volume of distribution (Vss) of these two drugs in prairie dogs, an animal model not tested thus far.

Results

Marked inter-species variability in PK parameters and resulting oral bioavailability was observed. In general, elimination half-lives of these agents in mice and guinea pigs were much shorter (1–3 h) relative to those in larger species such as prairie dogs and monkeys. The longer nilotinib elimination half-life in prairie dogs (i.v., 6.5 h and oral, 7.5 h), facilitated multiple dosing PK and safety assessment. The allometry-based predicted values of the Vss and CL were within 2.0 and 2.5-fold, respectively, of the observed values.

Conclusions

Our results suggest that prairie dogs and monkeys may be suitable rodent and non-rodent species to perform further efficacy testing of these TKIs against orthopoxvirus infections. The use of rodent models such as C57BL/6 mice and guinea pigs for assessing pre-clinical anti-viral efficacy of these two TKIs may be limited due to short elimination and/or low oral bioavailability. Allometry-based correlations, derived from existing literature data, may provide initial estimates, which may serve as a useful guide for pre-clinical PK studies in untested animal models.

Clinical Pharmacokinetic and Pharmacodynamic Overview of Nilotinib, a Selective Tyrosine Kinase Inhibitor

Nilotinib, an oral inhibitor of the tyrosine kinase activity of Abelson protein, is approved for the treatment of patients with newly diagnosed chronic myeloid leukemia (CML) in chronic phase and patients with CML in chronic phase or accelerated phase resistant or intolerant to prior therapies. This review describes the pharmacokinetic and pharmacodynamic data of nilotinib in patients with CML and in healthy volunteers. Nilotinib is rapidly absorbed, with a peak serum concentration approximately 3 hours after dosing. The area under the plasma drug concentration-time curve over 24 hours and the peak serum concentration of nilotinib were dose proportional from 50-400 mg once daily. The metabolism of nilotinib is primarily via hepatic cytochrome P450 (CYP) 3A4 according to in vitro studies. In the clinical setting, exposure to nilotinib was significantly reduced by the induction of CYP3A4 with rifampicin and significantly increased by the inhibition of CYP3A with ketoconazole. Additionally, nilotinib is a competitive inhibitor of CYP3A4/5, CYP2C8, CYP2C9, CYP2D6, and uridine diphosphate glucuronosyltransferase 1A1. The bioavailability of nilotinib is increased by up to 82% when given with a high-fat meal compared with fasted state. There is a positive correlation between the occurrences of all-grade total bilirubin elevations and the steady-state nilotinib trough concentrations. Fredericia method corrected QT interval change from baseline was observed to have a correlation with nilotinib exposure. No significant relationship between nilotinib exposure and major molecular response at 12 months was seen at therapeutic doses of nilotinib 300-400 mg, probably due to the narrow range of the doses investigated.

Absolute Oral Bioavailability of Creatine Monohydrate in Rats: Debunking a Myth

Creatine is an ergogenic compound used by athletes to enhance performance. Supplementation with creatine monohydrate (CM) has been suggested for musculoskeletal and neurological disorders. Until now, little is known about its pharmacokinetic profile. Our objective was to determine the oral bioavailability of CM and the influence of dose on oral absorption. Rats were dosed orally with low dose (10 mg/kg) or high dose (70 mg/kg) 13C-labeled CM. Blood samples were removed at various time points. Muscle and brain tissue were collected at the conclusion of the study. Plasma and tissue levels of 13C-labeled creatine were determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Physiologically based pharmacokinetic (PBPK) models of CM were built using GastroPlus™. These models were used to predict the plasma concentration-time profiles of creatine hydrochloride (CHCL), which has improved aqueous solubility compared to CM. Absolute oral bioavailability for low dose CM was 53% while high dose CM was only 16%. The simulated Cmax of 70 mg/kg CHCL was around 35 μg/mL compared to 14 μg/mL for CM with a predicted oral bioavailability of 66% with CHCL compared to 17% with CM. Our results suggest that the oral bioavailability of CM is less than complete and subject to dose and that further examination of improved dosage formulations of creatine is warranted.

OATP1B2 deficiency protects against paclitaxel-induced neurotoxicity

Paclitaxel is among the most widely used anticancer drugs and is known to cause a dose-limiting peripheral neurotoxicity, the initiating mechanisms of which remain unknown. Here, we identified the murine solute carrier organic anion-transporting polypeptide B2 (OATP1B2) as a mediator of paclitaxel-induced neurotoxicity. Additionally, using established tests to assess acute and chronic paclitaxel-induced neurotoxicity, we found that genetic or pharmacologic knockout of OATP1B2 protected mice from mechanically induced allodynia, thermal hyperalgesia, and changes in digital maximal action potential amplitudes. The function of this transport system was inhibited by the tyrosine kinase inhibitor nilotinib through a noncompetitive mechanism, without compromising the anticancer properties of paclitaxel. Collectively, our findings reveal a pathway that explains the fundamental basis of paclitaxel-induced neurotoxicity, with potential implications for its therapeutic management.

Identification of OAT1/OAT3 as Contributors to Cisplatin Toxicity

Cisplatin is among the most widely used anticancer drugs and known to cause a dose‐limiting nephrotoxicity, which is partially dependent on the renal uptake carrier OCT2. We here report a previously unrecognized, OCT2‐independent pathway of cisplatin‐induced renal injury that is mediated by the organic anion transporters OAT1 and OAT3. Using transporter‐deficient mouse models, we found that this mechanism regulates renal uptake of a mercapturic acid metabolite of cisplatin that acts as a precursor of a potent nephrotoxin. The function of these two transport systems can be simultaneously inhibited by the tyrosine kinase inhibitor nilotinib through noncompetitive mechanisms, without compromising the anticancer properties of cisplatin. Collectively, our findings reveal a novel pathway that explains the fundamental basis of cisplatin‐induced nephrotoxicity, with potential implications for its therapeutic management.

The Role of New Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia

Imatinib mesylate was the first tyrosine kinase inhibitor (TKI) approved for the management of chronic myeloid leukemia. Imatinib produces acceptable responses in approximately 60% of patients, with approximately 20% discontinuing therapy because of intolerance and approximately 20% developing drug resistance. The advent of newer TKIs, such as nilotinib, dasatinib, bosutinib, and ponatinib, has provided multiple options for patients. These agents are more potent, have unique adverse effect profiles, and are more likely to achieve relevant milestones, such as early molecular responses (3-6 months) and optimal molecular responses (12 months). The acquisition of BCR-ABL kinase domain mutations is also reportedly lower with these drugs. Thus far, none of the randomized phase III clinical trials have shown a clinically significant survival difference between frontline imatinib versus newer TKIs. Cost and safety issues with the newer TKIs, such as vascular disease with nilotinib and ponatinib and pulmonary hypertension with dasatinib, have dampened the enthusiasm of using these drugs as frontline options. While the utility of new TKIs in the setting of imatinib failure or intolerance is clear, their use as frontline agents should factor in the age of the patient, additional comorbidities, risk stratification (Sokal score), and cost. Combination therapies and newer agents with potential to eradicate quiescent chronic myeloid leukemia stem cells offers future hope.

Effective Concentration of a Multikinase Inhibitor within Bone Marrow Correlates with In Vitro Cell Killing in Therapy-Resistant Chronic Myeloid Leukemia

Leukemia cells escape BCR-ABL-targeted therapy by developing mutations, such as T315I, in the p210(BCR-ABL) fusion protein in Philadelphia chromosome-positive chronic myeloid leukemia (CML). Although most effort has been focused on development of new tyrosine kinase inhibitors, enrichment of these small-molecule inhibitors in the tumor tissue can also have a profound impact on treatment outcomes. Here, we report that a 2-hour exposure of the T315I-mutant CML cells to 10 μmol/L of the multikinase inhibitor TG101209 suppressed BCR-ABL-independent signaling and caused cell-cycle arrest at G2-M. Further increase in drug concentration to 17.5 μmol/L blocked phosphorylation of the mutant BCR-ABL kinase and its downstream JAK2 and STAT5. The effective dosage to overcome therapy resistance identified in an in vitro setting serves as a guidance to develop the proper drug formulation for in vivo efficacy. A targeted formulation was developed to achieve sustained bone marrow TG101209 concentration at or above 17.5 μmol/L for effective killing of CML cells in vivo Potent inhibition of leukemia cell growth and extended survival were observed in two murine models of CML treated with 40 mg/kg intravenously administered targeted TG101209, but not with the untargeted drug at the same dosage. Our finding provides a unique approach to develop treatments for therapy-resistant CML. Mol Cancer Ther; 15(5); 899-910. ©2016 AACR.

CBP/catenin antagonist safely eliminates drug-resistant leukemia-initiating cells

CBP and p300 are highly homologous transcriptional coactivators with unique, non-redundant roles that bind a wide array of proteins, including catenins – β and γ. ICG-001 is a small molecule inhibitor that specifically inhibits the CBP/catenin interaction. Importantly, ICG-001 does not inhibit the p300/catenin interaction. We demonstrate that specifically inhibiting the interaction between CBP and catenin with ICG-001, results in the differentiation of quiescent drug resistant chronic myelogenous leukemia initiating cells (CML-LICs), thereby sensitizing them to BCR-ABL tyrosine kinase inhibitors, e.g. Imatinib. Using ICG-001 in a NOD/SCID/IL2Rγ^−/− mouse model of engrafted human chronic myelogenous leukemia, we now demonstrate the complete elimination of engrafted leukemia after only one course of combined chemotherapy. Combination-treated animals live as long as their non-engrafted littermates. Results from these studies demonstrate that specifically antagonizing the CBP/catenin interaction with ICG-001 can eliminate drug resistant CML-LICs without deleterious effects to the normal endogenous hematopoietic stem cell population.

Preclinical pharmacokinetics of TPN729MA, a novel PDE5 inhibitor, and prediction of its human pharmacokinetics using a PBPK model

AIM

TPN729MA is a novel selective PDE5 inhibitor currently under clinical development in China for the treatment of erectile dysfunction. In this study we characterized its preclinical pharmacokinetics (PK) and predict its human PK using a physiologically based pharmacokinetic (PBPK) model.

METHODS

The preclinical PK of TPN729MA was studied in rats and dogs. Human clearance (CL) values for TPN729MA were predicted from various allometric methods and from intrinsic CL determined in human liver microsomes. Human PK and plasma concentration versus time profiles of TPN729MA were predicted by using a PBPK model in GastroPlus. Considering the uncertainties in the prediction, a preliminary human study was conducted in 3 healthy male volunteers with an oral dose of 25 mg.

RESULTS

After a single intravenous administration of TPN729MA at a dose of 1 mg/kg in rats and 3 mg/kg in dogs, the plasma CL was 69.7 mL·min(-1)·kg(-1) in rats and 26.3 mL·min(-1)·kg(-1) in dogs, and the steady-state volumes of distribution (V(ss)) were 7.35 L/kg in rats and 6.48 L/kg in dogs. The oral bioavailability of TPN729MA was 10% in rats and above 34% in dogs. Profiles of predicted plasma concentration versus time were similar to those observed in humans at 25 mg, and the predicted T(max), C(max) and AUC values were within 2-fold of the observed values.

CONCLUSION

TPN729MA demonstrates good preclinical PK. This compound is a valuable candidate for further clinical development. This study shows the benefits of using a PBPK model to predict PK in humans.

Matrix effects in nilotinib formulations with pH-responsive polymer produced by carbon dioxide-mediated precipitation

Factors determining the pH-controlled dissolution kinetics of nilotinib formulations with the pH-titrable polymer hydroxypropyl methylcellulose phthalate, obtained by carbon dioxide-mediated precipitation, were mechanistically examined in acid and neutral environment. The matrix effect, modulating the drug dissolution, was characterized with a battery of physicochemical methodologies, including ToF-SIMS for surface composition, SAXS/WAXS and modulated DSC for crystallization characterization, and simultaneous UV-imaging and Raman spectroscopy for monitoring the dissolution process in detail. The hybrid particle formulations investigated consisted of amorphous nilotinib embedded in a polymer matrix in single continuous phase, displaying extended retained amorphicity also under wet conditions. It was demonstrated by Raman and FTIR spectroscopy that the efficient drug dispersion and amorphization in the polymer matrix were mediated by hydrogen bonding between the drug and the phthalate groups on the polymer. Simultaneous Raman and UV-imaging studies of the effect of drug load on the swelling and dissolution of the polymer matrix revealed that high nilotinib load prevented matrix swelling on passage from acid to neutral pH, thereby preventing re-precipitation and re-crystallization of incorporated nilotinib. These findings provide a mechanistic foundation of formulation development of nilotinib and other protein kinase inhibitors, which are now witnessing an intense therapeutic and industrial attention due to the difficulty in formulating these compounds so that efficient oral bioavailability is reached.

Human in vivo regional intestinal permeability: importance for pharmaceutical drug development

Both the development and regulation of pharmaceutical dosage forms have undergone significant improvements and development over the past 25 years, due primarily to the extensive application of the biopharmaceutical classification system (BCS). The Biopharmaceutics Drug Disposition Classification System, which was published in 2005, has also been a useful resource for predicting the influence of transporters in several pharmacokinetic processes. However, there remains a need for the pharmaceutical industry to develop reliable in vitro/in vivo correlations and in silico methods for predicting the rate and extent of complex gastrointestinal (GI) absorption, the bioavailability, and the plasma concentration-time curves for orally administered drug products. Accordingly, a more rational approach is required, one in which high quality in vitro or in silico characterizations of active pharmaceutical ingredients and formulations are integrated into physiologically based in silico biopharmaceutics models to capture the full complexity of GI drug absorption. The need for better understanding of the in vivo GI process has recently become evident after an unsuccessful attempt to predict the GI absorption of BCS class II and IV drugs. Reliable data on the in vivo permeability of the human intestine (Peff) from various intestinal regions is recognized as one of the key biopharmaceutical requirements when developing in silico GI biopharmaceutics models with improved predictive accuracy. The Peff values for human jejunum and ileum, based on historical open, single-pass, perfusion studies are presented in this review. The main objective of this review is to summarize and discuss the relevance and current status of these human in vivo regional intestinal permeability values.