N-(4-Methyl-3-((4-(pyridin-3-yl)pyrimidin-2-yl)amino)phenyl)-4-((4-methylpiperazin-1-yl)methyl)benzamide

Imatinib is one of the most used therapeutic agents to treat leukemia, which specifically inhibits the activity of tyrosine kinases. This polytopic molecule has been structurally characterized only in the form of its piperazin-1-ium salt (mesylate, picrate, citrate, fumarate or malonate). Herein we present the crystal structure of the freebase Imatinib which precipitated from a 1:10 mixture with arginine. The molecule realizes an extended conformation and forms infinite H-bonded chains through its amide, amine and pyrimidine groups.

Property Map Collective Variable as a Useful Tool for a Force Field Correction

The accuracy of biomolecular simulations depends on the accuracy of an empirical molecular mechanics potential known as a force field: a set of parameters and expressions to estimate the potential from atomic coordinates. Accurate parametrization of force fields for small organic molecules is a challenge due to their high diversity. One of the possible approaches is to apply a correction to the existing force fields. Here, we propose an approach to estimate the density functional theory (DFT)-derived force field correction which is calculated during the run of molecular dynamics without significantly affecting its speed. Using the formula known as a property map collective variable, we approximate the force field correction by a weighted average of this force field correction calculated only for a small series of reference structures. To validate this method, we used seven AMBER force fields, and we show how it is possible to convert one force field to behave like the other one. We also present the force field correction for the important anticancer drug Imatinib as a use case example. Our method appears to be suitable for adjusting the force field for general drug-like molecules. We provide a pipeline that generates the correction; this pipeline is available at https://pmcvff-correction.cerit-sc.cz/.

Current evidence on the efficacy and safety of generic imatinib in CML and the impact of generics on health care costs

Since the introduction of imatinib, the management of chronic myeloid leukemia (CML) has changed considerably. Tyrosine kinase inhibitors (TKIs) are the mainstay of CML treatment; however, the high financial burden of TKIs can be problematic for both the patients and health care systems. After the emergence of generics, reimbursement policies of many countries have changed, and generics offered an alternative treatment option for CML patients. There are many papers published on the use of generics in CML patients with conflicting results regarding both efficacy and safety. In this paper, we systematically reviewed the current literature on generic imatinib use in CML, and 36 papers were evaluated. Both in vitro and in vivo studies of generic imatinib showed comparable results with branded imatinib in terms of bioequivalence and bioavailability. In most studies, generics were comparable with the original molecule in terms of efficacy and safety, both in newly diagnosed patients and after switching from Gleevec. Some generic studies showed contradictory findings regarding efficacy and toxicity, and these differences can be attributed to some factors including the use of different generics in different countries. Both in hypothetical models and in real life, introduction of generic imatinib caused significant reduction in health care costs. In conclusion, generics are not inferior to original imatinib in terms of efficacy with an acceptable toxicity profile. Notwithstanding the generally favorable efficacy and safety of generics worldwide to date, we most probably still need more time to draw firmer conclusions on the longer-term outcomes of generics.

Intermolecular Interactions in Crystal Structures of Imatinib-Containing Compounds

Imatinib, one of the most used therapeutic agents to treat leukemia, is an inhibitor that specifically blocks the activity of tyrosine kinases. The molecule of imatinib is flexible and contains several functional groups able to take part in H-bonding and hydrophobic interactions. Analysis of molecular conformations for this drug was carried out using density functional theory calculations of rotation potentials along single bonds and by analyzing crystal structures of imatinib-containing compounds taken from the Cambridge Structural Database and the Protein Data Bank. Rotation along the N-C bond in the region of the amide group was found to be the reason for two relatively stable molecular conformations, an extended and a folded one. The role of various types of intermolecular interactions in stabilization of the particular molecular conformation was studied in terms of (i) the likelihood of H-bond formation, and (ii) their contribution to the Voronoi molecular surface. It is shown that experimentally observed hydrogen bonds are in accord with the likelihood of their formation. The number of H-bonds in ligand-receptor complexes surpasses that in imatinib salts due to the large number of donors and acceptors of H-bonding within the binding pocket of tyrosine kinases. Contribution of hydrophilic intermolecular interactions to the Voronoi molecular surface is similar for both conformations, while π...π stacking is more typical for the folded conformation of imatinib.

Molecular Mobility and Stability Studies of Amorphous Imatinib Mesylate

The proposed study examined the characterization and stability of solid-state amorphous imatinib mesylate (IM) after 15 months under controlled relative humidity (60 ± 5%) and temperature (25 ± 2 °C) conditions. After 2 weeks, and 1, 3, 6, and 15 months, the samples were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray powder diffractometry (XRPD), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). Additionally, the amorphous form of imatinib mesylate was obtained via supercooling of the melt in a DSC apparatus, and aged at various temperatures (3, 15, 25 and 30 °C) and time periods (1–16 h). Glass transition and enthalpy relaxation were used to calculate molecular-relaxation-time parameters. The Kohlrausch–Williams–Watts (KWW) equation was applied to fit the experimental enthalpy-relaxation data. The mean molecular-relaxation-time constant (τ) increased with decreasing ageing temperature. The results showed a high stability of amorphous imatinib mesylate adequate to enable its use in solid dosage form.

Generic Imatinib in Chronic Myeloid Leukemia Treatment: Long-Term Follow-up

BACKGROUND

Similar to the application of other generic drugs, the use of generic imatinib in the treatment of chronic myeloid leukemia (CML) leads to significant cost savings, but it also raises issues related to efficacy, safety, and quality. This study assessed the long-term outcome of CML patients after administration of generic imatinib.

PATIENTS AND METHODS

The cohort of 83 patients was divided into 2 groups depending on whether generic imatinib was applied in the front-line setting or after switching from original imatinib. The groups were compared regarding rates of optimal treatment response, adverse events, and survival.

RESULTS

In the first group, at the time of switching, rates of complete cytogenetic response experienced, and major molecular response were 95% and 87.5% of patients in the front-line generic imatinib group and the group that switched from original to generic imatinib, respectively. After 24 months of treatment with generic imatinib, the rates of sustained, lost, and experienced major molecular response were 72.5%, 15%, and 12.5%, respectively. In the group treated with front-line generic imatinib at 6 months, 67.4% experienced complete cytogenetic response, while for major molecular response at 12 and 24 months, it was 58.1% and 69.8%, respectively. Estimated 5-year overall survival in the group treated with front-line generic imatinib was 86.1%, while 10-year overall survival in the group treated with second-line generic imatinib was 93.8%.

CONCLUSION

Results of this study with long-term follow-up are further evidence that generic imatinib is at least noninferior to original imatinib regarding efficacy and survival, both when provided initially and as a subsequent replacement for original imatinib.

Generic formulations of imatinib for treatment of Philadelphia chromosome-positive leukemia in pediatric patients

Since the patent for imatinib has expired, the role of generic imatinib (GI) in the management of Philadelphia chromosome-positive (Ph+) leukemia in pediatric patients has had ongoing discussion. Some studies in adults demonstrated that equivalent doses of GI and branded imatinib (BI) result in comparable plasma concentrations and clinical efficacy. However, other studies found that GI users are more likely to stop imatinib, with intolerance and decreased persistence as the main causes. Economic factors also heavily influence GI selection. This article aims to review the present knowledge to support further discussion on the role of GI in the management of pediatric Ph+ leukemia.

Effects of Temperature and Solvent on the Solid-State Transformations of Pranlukast During Mechanical Milling

Four solid forms of pranlukast (PRS) were obtained during mechanical milling including neat milling (NM) and solvent-drop milling (SDM), which were characterized by various analytical techniques. The effect of milling conditions including 3 milling temperatures and 6 assist solvents on the solid-state transformations of commercial PRS (PRS HH) was systemically investigated. Milling temperature significantly influenced the NM process. A low milling temperature (5°C) led to a complete amorphization of PRS HH, whereas higher milling temperatures (15°C and 30°C) only induced a partial amorphization. The milling at 5°C was proven to be a progressive amorphization process, and the amorphous material showed an increasing stability with prolonged milling time. Amorphous PRS can stay stable under low temperature and relative humidity conditions and showed significantly higher solubilities and faster dissolution rates in both water and pH 6.8 phosphate buffer solution. A total of 6 solvents were used in the SDM experiments. N,N-dimethylformamide and dimethyl sulfoxide should be avoided in the manufacturing process of PRS because corresponding solvates of PRS can be easily generated by SDM of PRS HH with short milling time and small amount of solvents.

The Efficacy of Generic Imatinib as First- and Second-line Therapy: 3-Year Follow-up of Patients With Chronic Myeloid Leukemia

INTRODUCTION

Generics of imatinib mesylate, the first tyrosine kinase inhibitor targeting the BCR-ABL1 fusion protein, have recently been approved in many countries as the alternative, low-cost forms for the treatment of patients with chronic myeloid leukemia (CML). The aim of this study was to evaluate the long-term clinical outcomes of patients with CML receiving first-line and second-line generic imatinib in Bosnia and Herzegovina.

PATIENTS AND METHODS

This was a multicenter retrospective cohort study of patients (n = 41) treated with generic imatinib in Bosnia between September 1, 2013 and August 5, 2016. Patients were categorized into 2 study groups: Group 1 (n = 27) included newly diagnosed patients with CML receiving front-line generic imatinib, and Group 2 (n = 14) consisted of patients who started with front-line Glivec and were mandated to switch to the second-line generic imatinib.

RESULTS

The median follow-up for Group 1 (first-line generic imatinib) and Group 2 (second-line generic imatinib) was 16 and 36 months, respectively. At 36 months, the overall survival for patients in Group 1 was 85%, and the achievement of complete cytogenetic response was 81%. At 24 months, the major molecular response rate was 48%. Overall, 52% of patients switched from first-line generic imatinib to nilotinib owing to treatment failure and side-effects. In Group 2, 93% of patients sustained cytogenetic and molecular response at 3 years after the switch from branded to generic imatinib.

CONCLUSION

Our results lead us to conclude that generic imatinib as second-line therapy does not have deleterious effects on patient outcomes. However, first-line generic imatinib showed suboptimal efficacy compared with branded imatinib.

Thermal stability and decompositions kinetics under non-isothermal conditions of imatinib mesylate α form

The thermal decomposition and kinetic parameters of synthetized imatinib mesylate α form α form were determined by thermogravimetry (TGA/DTG) under non-isothermal conditions. The experiments were performed at a 25-940°C temperature range at five different heating rates: 2.5Kmin(-1), 5Kmin(-1), 10Kmin(-1), 15Kmin(-1) and 20Kmin(-1) per minute in a nitrogen atmosphere. Imatinib mesylate α form presents one-step mass loss during the degradation process. The thermal stability of the examined material, the melting temperature (Tonset=220.6°C) and ΔH fusion=-95.74Jg(-1) at a heating rate of 10°Cmin(-1) was established. The values of activation energies have been estimated using Kissinger, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods.

A New, More Stable Polymorphic Form of Otilonium Bromide: Solubility, Crystal Structure, and Phase Transformation

A new polymorphic form of otilonium bromide is presented (Form I), and a thorough analysis of its crystal and molecular structure is performed. The compound suffers a temperature-driven first-order phase transition at about 396 K, which transforms it into the polymorph reported by Dapporto P and Sega A (Acta Cryst. 1986;C42:474-478) (Form II). Through thermal analysis and solubility experiments the relative stability of both crystal modifications were determined, confirming that at room temperature this new Form I is the more stable one, Form II existing just in a metastable state.

Polymorphs of Theophylline Characterized by DNP Enhanced Solid-State NMR

We show how dynamic nuclear polarization (DNP) enhanced solid-state NMR spectroscopy can be used to characterize polymorphs and solvates of organic solids. We applied DNP to three polymorphs and one hydrated form of the asthma drug molecule theophylline. For some forms of theophylline, sample grinding and impregnation with the radical-containing solution, which are necessary to prepare the samples for DNP, were found to induce polymorphic transitions or desolvation between some forms. We present protocols for sample preparation for solid-state magic-angle spinning (MAS) DNP experiments that avoid the polymorphic phase transitions in theophylline. These protocols include cryogrinding, grinding under inert atmosphere, and the appropriate choice of the impregnating liquid. By applying these procedures, we subsequently demonstrate that two-dimensional correlation experiments, such as (1)H-(13)C and (1)H-(15)N HETCOR or (13)C-(13)C INADEQUATE, can be obtained at natural isotopic abundance in reasonable times, thus enabling more advanced structural characterization of polymorphs.

Variability in bioavailability of small molecular tyrosine kinase inhibitors

Small molecular tyrosine kinase inhibitors (smTKIs) are in the centre of the very quickly expanding area of personalized chemotherapy and oral applicability thereof. The number of drugs in this class is rapidly growing, with twenty current approvals by both the European Medicines Agency (EMA) and the Food and Drug Administration (FDA). The drugs are, however, generally characterized by a poor oral, and thus variable, bioavailability. This results in significant variation in plasma levels and exposure. The cause is a complex interplay of factors, including poor aqueous solubility, issued permeability, membrane transport and enzymatic metabolism. Additionally, food and drug-drug interactions can play a significant role. The issues related with an impaired bioavailability generally receive little attention. To the best of our knowledge, this article is the first to provide an overview of the factors that determine the bioavailability of the smTKIs.

Clinical efficacy of generic imatinib

Background

Generic imatinib has recently been approved for chronic myeloid leukemia in Canada and the European Union (EU). There are anecdotal concerns of reduced efficacy related to generic vs. brand name imatinib.

Methods

MEDLINE and EMBASE were searched. Generic imatinib product monographs approved by Health Canada and the European Medicines Agency (EMA) were reviewed. Medical information of Novartis, Teva and Apotex were contacted.

Results

Several issues have been raised. First, generic imatinib approved outside Canada and the European Union has been associated with reduced efficacy in small case reports and contradictory findings with two case series. However, the clinical bioequivalence of these generic products has not been clearly established. Secondly, use of generic imatinib in other populations has been questioned. However, imatinib absorption is not significantly different in pediatric chronic myeloid leukemia or patients with gastrointestinal tumours compared to adults with chronic myeloid leukemia. Although reduced absorption was reported after gastric bypass and gastrectomy, imatinib absorption occurs mostly in the ileum, duodenum, colon and jejunum. Change in gastric acidity has also been shown to not affecting imatinib absorption. Finally, beta-crystal form of brand name imatinib is more stable than the alpha-crystal form of generic imatinib at room temperature. However, the EMA found both crystal forms to be highly soluble and polymorphism would not significantly influence the performance of generic imatinib.

Conclusion

Overall, anecdotal concerns appear to be unfounded for generic imatinib approved in Canada and the EU. There is no evidence that these generic imatinib products are less effective than brand name imatinib.