. Jul 21;13(8):. doi: 10./pharmaceutics

Direct Powder Extrusion 3D Printing of Praziquantel to Overcome Neglected Disease Formulation Challenges in Paediatric Populations

Janine Boniatti

Janine Boniatti

1IMT Mines Albi-Carmaux, CNRS UMR , Centre RAPSODEE, Campus Jarlard, Université de Toulouse, CEDEX 09, Albi, France; 2Oswaldo Cruz Foundation, Rua Sizenando Nabuco, 100 CEP 22.775-903, Rio de Janeiro -900, Brazil; (L.B.d.F.); (A.L.V.); (F.C.A.) Find articles by Janine Boniatti 1,2,*, Patricija Januskaite

Patricija Januskaite

3Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK; (P.J.); (C.T.) Find articles by Patricija Januskaite 3, Laís B da Fonseca

Laís B da Fonseca

2Oswaldo Cruz Foundation, Rua Sizenando Nabuco, 100 CEP 22.775-903, Rio de Janeiro -900, Brazil; (L.B.d.F.); (A.L.V.); (F.C.A.) Find articles by Laís B da Fonseca 2, Alessandra L Viçosa

Alessandra L Viçosa

2Oswaldo Cruz Foundation, Rua Sizenando Nabuco, 100 CEP 22.775-903, Rio de Janeiro -900, Brazil; (L.B.d.F.); (A.L.V.); (F.C.A.) Find articles by Alessandra L Viçosa 2, Fábio C Amendoeira

Fábio C Amendoeira

2Oswaldo Cruz Foundation, Rua Sizenando Nabuco, 100 CEP 22.775-903, Rio de Janeiro -900, Brazil; (L.B.d.F.); (A.L.V.); (F.C.A.) Find articles by Fábio C Amendoeira 2, Catherine Tuleu

Catherine Tuleu

3Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK; (P.J.); (C.T.) Find articles by Catherine Tuleu 3, Abdul W Basit

Abdul W Basit

3Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK; (P.J.); (C.T.) 4FabRx Ltd., 3 Romney Road, Ashford, Kent TN24 0RW, UK Find articles by Abdul W Basit 3,4,*, Alvaro Goyanes

Alvaro Goyanes

3Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK; (P.J.); (C.T.) 4FabRx Ltd., 3 Romney Road, Ashford, Kent TN24 0RW, UK 5I+D Farma Group (GI-), Departamento de Farmacología, Farmacia y Tecnología Farmaceutica, Universidade de Santiago de Compostela, Santiago de Compostela, Spain Find articles by Alvaro Goyanes 3,4,5,*, Maria-Inês Ré

Maria-Inês Ré

1IMT Mines Albi-Carmaux, CNRS UMR , Centre RAPSODEE, Campus Jarlard, Université de Toulouse, CEDEX 09, Albi, France; 2Oswaldo Cruz Foundation, Rua Sizenando Nabuco, 100 CEP 22.775-903, Rio de Janeiro -900, Brazil; (L.B.d.F.); (A.L.V.); (F.C.A.) Find articles by Maria-Inês Ré 1,2 Editor: Juan José Torrado

1IMT Mines Albi-Carmaux, CNRS UMR , Centre RAPSODEE, Campus Jarlard, Université de Toulouse, CEDEX 09, Albi, France; 2Oswaldo Cruz Foundation, Rua Sizenando Nabuco, 100 CEP 22.775-903, Rio de Janeiro -900, Brazil; (L.B.d.F.); (A.L.V.); (F.C.A.) 3Department of Pharmaceutics, UCL School of Pharmacy, University College London, 29-39 Brunswick Square, London WC1N 1AX, UK; (P.J.); (C.T.) 4FabRx Ltd., 3 Romney Road, Ashford, Kent TN24 0RW, UK 5I+D Farma Group (GI-), Departamento de Farmacología, Farmacia y Tecnología Farmaceutica, Universidade de Santiago de Compostela, Santiago de Compostela, Spain

Roles

Juan José Torrado: Academic Editor

Received Jun 29; Accepted Jul 18; Collection date Aug.

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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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Abstract

For the last 40 years, praziquantel has been the standard treatment for schistosomiasis, a neglected parasitic disease affecting more than 250 million people worldwide. However, there is no suitable paediatric formulation on the market, leading to off-label use and the splitting of commercial tablets for adults. In this study, we use a recently available technology, direct powder extrusion (DPE) three-dimensional printing (3DP), to prepare paediatric Printlets' (3D printed tablets) of amorphous solid dispersions of praziquantel with Kollidon® VA 64 and surfactants (Span' 20 or Kolliphor® SLS). Printlets were successfully printed from both pellets and powders obtained from extrudates by hot melt extrusion (HME). In vitro dissolution studies showed a greater than four-fold increase in praziquantel release, due to the formation of amorphous solid dispersions. In vitro palatability data indicated that the printlets were in the range of praziquantel tolerability, highlighting the taste masking capabilities of this technology without the need for additional taste masking excipients. This work has demonstrated the possibility of 3D printing tablets using pellets or powder forms obtained by HME, avoiding the use of filaments in fused deposition modelling 3DP. Moreover, the main formulation hurdles of praziquantel, such as low drug solubility, inadequate taste, and high and variable dose requirements, can be overcome using this technology.

Keywords: 3D printing, 3D printed drug products, printing pharmaceuticals and medicines, personalized therapeutics, oral drug delivery systems and technologies, taste masking, translational pharmaceutics, material extrusion additive manufacturing, M3DIMAKER printer, pediatric treatments

1. Introduction

Schistosomiasis is considered one of the most prominent neglected diseases in public health, affecting around 250 million people in more than 70 countries worldwide [1,2,3,4]. Even more alarming is the number of school-aged children (5'14 years old) requiring treatment, which has been estimated to be around 25 million [2,5,6]. The disorder, caused by parasitic worms, is responsible for the highest morbidity and mortality rates in developing countries [7]. To this day, approximately 90% of cases are found in Africa and South America, specifically Brazil, reaching 8'10 million cases of Schistosoma mansoni [2,7,8].

Praziquantel (PZQ) has been the standard treatment for over 40 years, and is included on the WHO Model List of Essential Drugs [9,10]. It is also used in preventive chemotherapy due to its efficiency, low cost, and promising safety results [10,11]. Although school-aged children have been the primary target to treat the disease, together with toddlers and children under six years of age, there is currently no suitable formulation available for paediatric patients on the market [3,4].

The current treatment for children is based on the off-label use of PZQ, and the dose adjustment is carried out by splitting commercial tablets for adults [3,4,12]. However, such an approach is dangerous, as dosing errors lead to potential toxic side effects or lack of treatment effect [9]. In conjunction, PZQ has an unpleasant taste and the splitting of tablets favours taste bud exposure to the bitter drug, leading to the rejection of the medication and, consequently, to therapeutic ineffectiveness [9]. Palatability is a determining factor in dosage form acceptability and patient adherence to treatment, especially for paediatric oral formulations [13].

The development of a suitable PZQ formulation for children is challenging since: (a) it exhibits a low water solubility (0.02 mg/mL'class II of the Biopharmaceutics Classification System (BCS)) [14], (b) a variable dose dependent on the patient's weight is needed to achieve a standard 40 mg/kg dose to treat preschool-aged children [3], and (c) it requires the use of an effective taste masking technology.

Various approaches have been evaluated to overcome the aforementioned obstacles, one being the transformation of the drug solid state structure from crystalline to amorphous [15,16,17,18]. The use of an amorphous form of the drug requires its physical stabilisation in the formulation, which can be achieved by the formation of amorphous solid dispersions (ASDs). The principle of an ASD is based on the dispersion of drug in an amorphous carrier, generally a polymer, generating a homogeneous mixture of reduced molecular mobility [19]. In addition to solubility enhancement properties, the dispersion of the drug within the polymer matrix could be expected to contribute towards taste masking. Solid dispersions of paracetamol and Eudragit® E have already been studied and demonstrated successful taste masking of the drug [20,21]. The combination of both properties (solubility improvement and taste masking) is an important requirement for paediatric patients. This patient group presents a great diversity in terms of anatomy and physiological and psychological responses when compared to adults, and as a result, varied therapeutic responses. Although the palatability of a drug is not the only factor that affects the acceptance of a drug, for unpalatable drugs, it is commonly listed as the first cause of non-adherence to treatment, especially in children [13,22,23].

ASDs can be prepared using different technologies, one being hot melt extrusion (HME), a process in which a material is melted or softened under an elevated temperature and pressure, and is forced through a die by rotating screws [24]. HME has been recently used to obtain filaments for the preparation of personalised medicines using three-dimensional (3D) printing [25]. Three-dimensional printing (3DP) is an innovative additive manufacturing technique, capable of converting 3D computer models into real objects by the sequential deposition of material in a layer by layer manner [26,27,28,29,30,31,32,33,34,35,36]. Currently, the most evaluated 3DP technique in the pharmaceutical area is fused deposition modelling (FDM), as a result of the low printer cost, the good quality of the final product, and the direct use of filaments obtained by HME [37]. Many HME'FDM studies have shown the potential opportunities of preparing medicines with different drugs [38], designs [39], and release profiles [35,40,41], even for paediatric formulations [42].

One of the technical limitations of the FDM 3DP process is the high dependency on the physical and mechanical properties of the filaments for printing feasibility [26,43], and the difficulty of filament preparation [44], especially when high drug loads are required. Recently, direct powder extrusion (DPE), a new 3DP technology that does not require the preparation of filaments using HME and allows the direct extrusion of drug and excipient mixtures in the powder form, was reported [26,45]. This technique has allowed the production of 35 wt% itraconazole tablets via a single step process, with improved solubility characteristics through itraconazole amorphisation during printing [26].

The aim of this study was to use an innovative technology, DPE 3DP, to overcome the main challenges of formulating PZQ for paediatric patients: low drug solubility, unacceptable taste, and requirement for a range of relatively high drug doses, by preparing PZQ ASDs as paediatric Printlets' (3D printed tablets). The suitability of different powdered materials to directly feed the 3D printer was investigated. The powdered materials tested were physical mixtures of crystalline drug and polymer, and for the first time, pellets and powder forms obtained from ASD'HME extrudates. The characteristics of the resulting printlets were evaluated, with special focus on drug dissolution profiles, taste masking effectiveness, and physical stability.

2. Materials and Methods

2.1. Materials

Racemic praziquantel (MW 312.4 g/mol) (PZQ) was kindly provided by Farmanginhos/Fiocruz from Brazil. Kollidon® VA 64 (MW 45,000'70,000 g/mol) (KOL) and Kolliphor® SLS Fine (SLS) were donated by BASF Chemical Company, Ludwigshafen, Germany, and Span' 20 (Span) by Croda International, Snaith, UK. Acetonitrile HPLC/Spectro and Methyl Alcohol HPLC/Spectro came from Tedia Company, Fairfield, USA. For the analysis, distilled and purified water (conductivity of 18.2 MΩ.cm at 23 °C) was obtained by the purification system Milli-Q (classic Purelab DI, MK2) (Elga, High Wycombe, UK). Sodium chloride and potassium phosphate monobasic were obtained from Merck (Darmstadt, Germany), praziquantel reference standard was purchased from USP (Rockville, MD, USA) and sodium phosphate dibasic from Sigma-Aldrich (St. Louis, MO, USA).

2.2. Methods

2.2.1. Preparation of the Powdered Materials

Powdered materials with different compositions were tested in the DPE 3D printer (Table 1): physical mixtures (PM) of crystalline PZQ and polymer, pellets (P) produced in a twin-screw extruder by HME and powder obtained by milling the pellets (M).

Table 1.

Formulation Code Composition (wt%) Printing Parameters PZQ KOL SLS Span Printing Temperature (°C) Flow Rate (%) Feed Rate (%) Physical mixtures (PM) PM 50 50 50 - - 145'170 100'140 100 PM 35 35 65 - - 145'170 100'140 100 PM 35 SLS 35 60 5 - 140'200 100'140 100 Pellets (P) and milled powder (M) obtained from HME extrudates produced in a twin-screw extruder P 50 50 50 - - 140 90 100 M 50 50 50 - - 135 75 100 M 35 Span 35 60 - 5 130 75 100 M 35 SLS 35 60 5 - 130 75 100

The physical mixtures (PM 50, PM 35, and PM 35 SLS) were prepared in a Turbula® T2F mixer (96 rpm, 8 min). HME extrudates were prepared using a Thermo-Fisher pharma 16 Extruder (Thermo scientific', Karlsruhe, Germany), in a co-rotating twin-screw configuration with eight heating zones, two mixing zones, and a screw diameter (D) of 16 mm and L/D ratio equal to 40 (L being the length of the barrel). The heating zones of the extrusion were determined for each of the formulations according to their specific characteristics, ranging from 50 to 180 °C. The HME extrudates were cut into pellets of 1 mm in length. Part of the binary formulation was used as pellets (P 50), and part was milled (M 50). The two ternary formulations (M 35 Span, M 35 SLS) were milled. The milling process was carried out using a Quadro Comil H5 High Energy Mill (Fitzpatrick®, Waterloo, ON, Canada) with a mill speed of rpm and a 610 µm size sieve. The samples were protected from light and kept in a desiccator for conservation.

The three formulations of PZQ processed by HME contained 35 or 50 wt% PZQ, in the presence/absence of surfactants. The addition of the surfactants (Span or SLS) in the formulations was to increase the dissolution of the solid dispersions produced by HME. This investigation was conducted for the formulation containing 35 wt% of PZQ. The surfactant Span (liquid) was added using a peristaltic pump (Thermo Scientific', Dreieich, Germany) directly into the extruder, while the surfactant SLS (solid) was directly added to the PZQ and polymer during physical mixture preparation. The respective placebo formulations were produced (M Placebo Span and M Placebo SLS) to check the printer's cleanliness by contaminating the batches with PZQ prior to printing.

2.2.2. DPE 3D Printing

The prepared mixtures, pellets or milled extrudates, were then added to the hopper of a M3DIMAKER' pharmaceutical 3D printer (FabRx Ltd., London, UK) with a direct powder extruder nozzle as previously reported [26]. AutoCAD (Autodesk Inc., San Rafael, CA, USA) was used to design the templates of the printlets, which were then exported as a stereolithography (.stl) file into the 3D printer software (Repetier host V 2.1.3, Willich, Germany). The selected 3D geometry was a cylindrical printlet (10 mm diameter × 3.6 mm height). The printer settings in the Repetier Host software were as follows: feed steps/mm, infill 100%, high resolution with brim, without raft, speed while extruding (20 mm/s), speed while travelling (90 mm/s), number of shells (2), and layer height (0.20 mm). The flow rate, extruder temperature, and feed rate were adjusted for each formulation (Table 1).

The 3D printer used (FabRx Ltd., Kent, UK) was specifically designed with a direct single-screw powder extruder and a nozzle diameter of 0.8 mm. Its design is based on a single-screw HME with rotation speed (and hence extrusion) controlled by the 3D printer software (Repetier-Host V 2.1.3, Willich, Germany). Furthermore, the extruder nozzle moves in three dimensions to create the objects in a layer-by-layer fashion (Figure 1).

After printing each formulation, the extruder was removed from the printing platform and the screw and barrel were dismounted and washed to avoid cross-contamination between different formulations.

2.2.3. Printlet Characterisation

Dimensions

The physical dimensions of the printlets were measured using a digital Vernier calliper and a Sartorius Entris 124-1S analytical balance to determine the mass of each printlet.

Optical Microscopy

Images were obtained using a Leica EZ4 HD® microscope (Leica, Wetzlar, Germany) with an integrated high-definition digital camera, set to 8× magnification. The images were then edited with the Leica LAS EZ software program. For calibration purposes, an image (obtained under the same conditions) of a standard slide containing a straight 1 cm segment, with 100 divisions, was employed.

Scanning Electronic Microscopy (SEM)

SEM printlet images were obtained using a scanning electron microscope HITACHI TM Plus (Hitachi, Tokyo, Japan) with an acceleration voltage of 15 kV. Samples were fixed on a support using a double-sided adhesive and covered with platinum using a high-resolution SEM coated spray Polaron SC (Quorom Technologies, Lewes, UK).

X-ray Powder Diffraction (XRPD) Analysis

Discs of 20 mm diameter × 2 mm height from the same printlet formulations were 3D printed and analysed. A Philips X'Pert Panalytical X-ray diffractometer (Malvern Panalytical, Malvern, UK) using CuKα radiation, 40 mA of current, and 45 kV of voltage was used. The recording spectral range was set at 7'50° with a measuring step (angular deviation between 2 consecutive points) of 0.° and an acquisition time of 100 s per point. In addition, each disc was rotated in its sample holder (1 revolution/s) during the results acquisition. Disc printing was performed only for feeding with HME-extrudate powder. X-ray powder diffraction (XRPD) analysis was performed for the ground raw and extruded materials using the same method.

Differential Scanning Calorimetry (DSC)

The analysis was performed using a DSC Q200 with the base module and modulated DSC (mDSC) (TA instruments, New Castle, DE, USA). An RCS90 cooling system was used to precisely control the cooling rate. Nitrogen (N2) was used as the purging gas at 50 mL/min, and the analysis was carried out in non-hermetic aluminium pans. Indium standards were used for enthalpy and temperature calibration, and an empty aluminium pan was used as a blank control. As for mDSC, sapphire was used to calibrate the instrument for specific heat capacity (Cp) measurements. Samples were heated at a rate of 2 °C/min from 10 to 180 °C, with a modulation period of 40 s and an amplitude of 0.2 °C. Two samples of each printlet (average weight of each sample: 2'6 mg) were analysed: one taken from the border and the other taken from the core.

Raman Microscopy

Raman mapping was performed at room temperature (25 °C) using a Raman 300R Alpha confocal microscope (WITec GmbH, Ulm, Germany), equipped with a laser at a wavelength of 532 nm. Samples were analysed by a 50× objective on the surface and deep mapping (8 × 8 μm KOL, 5 × 5 μm PZQ, and 10 × 10 μm and 10 × 20 μm P and M printlets, respectively) was applied to predict drug and polymer distributions.

Determination of Drug Loading

One printlet of each formulation was placed in a volumetric flask with 60:40 acetonitrile: water mixture (50 mL) under ultrasound for 5 min until complete dissolution (n = 2). Samples of the solutions were then filtered through a 0.22 μm PTFE filter (Millipore Ltd., Dublin, Ireland) and the concentration of drug was determined by external standardisation. Quantification was carried out using a fresh standard stock solution prepared each time before starting the analysis. The standard solution of PZQ was prepared by dissolving 9 mg of PZQ in mobile phase to obtain a final concentration of 0.18 mg/mL. Each sample solution was prepared and analysed in duplicate. The results were expressed as a % of PZQ recovery.

PZQ was determined in the printlets by a high-performance liquid chromatography (HPLC) system (Shimadzu Scientific Instruments, Kyoto, Japan) comprising a diode array UV detector (SPD-10A VP), a pump (LC-10AD VP), an autosampler (SIL-20A VP), and an interface (SCL-10A VP) for the acquisition of data through a software (Ez Start).

The validated HPLC assay involved the injection of 10 µL samples through a Protosil C18 column at room temperature (25 °C) (150 × 4.60 mm'5 µm) (Phenomenex, Bologna, Italy) in an isocratic mode with mobile phase consisting of methanol and water (60:40 v/v) at a flow rate of 1.5 mL/min. A wavelength of 210 nm was used for detection. The retention time of PZQ was found to be approximately 3 min and the run time was set at 10 min.

In Vitro Drug Release Studies

The drug release profiles of the printlets were monitored using a USP-II paddle apparatus (DT 60) (ERWEKA, Heusenstamm, Germany). Paddle stirrers at a speed of 50 rpm and temperature of 37 ± 0.5 °C were used in each test. The printlets were placed at the bottom of a 900 mL vessel of 0.1M HCl media (without surfactant). During the dissolution test, 5 mL samples were taken and filtered through 0.22 µm PTFE filters, and the drug concentration was determined by HPLC (method described in Section 2.2.3 (Determination of Drug Loading)). Tests were conducted in triplicate. Data are reported throughout as mean ± standard deviation.

Assessment of Taste Masking Efficiency Using a Novel Biorelevant Buccal Dissolution Test

The in vitro method described by Keeley et al. [46] was used to predict the taste of PZQ released from the milled extrudates and printlets in a simulated buccal environment.

The simulated salivary fluid (SSF) (Sodium chloride'8 g/L; Potassium phosphate monobasic'0.19 g/L; Sodium phosphate dibasic'2.38 g/L; pH 7.4) [47] kept under magnetic stirring at 37 °C ± 1 °C, was pumped through the 'buccal dissolution column' using a peristaltic pump at a rate of 1 mL/min, corresponding to an average adult normal total simulated saliva flow range. The other two adjacent parts were composed of wire mesh discs, placed either side of the column. After inserting the sample in the centre of the column lumen, from the top, aliquots were collected at 60, 120, 180, 240, 300, 360, 420, 480, 540, and 600 s, filtered through a 0.22 um membrane, and PZQ analysed by HPLC. Tests were conducted in triplicate. Data are reported throughout as mean ± standard deviation using Microsoft Excel (Microsoft Corp., Redmond, WA, USA) software (version MSO).

The PZQ taste-concentration profile was previously determined with the rat brief-access taste aversion (BATA) model [48]. It was found that the half maximal inhibitory concentration (IC50) was 0.06 mg/mL, and the taste threshold was 0.03 mg/mL. The classification proposed by Mohamed-Ahmed et al. [48] was used to classify levels of PZQ released at different time points as fully tolerated, well tolerated, tolerated, aversive/untolerated, or highly aversive/highly untolerated, and predict taste masking efficiency of the different formulations.

Stability Study

The samples were stored in a Memmert HPP260eco climatic chamber (Memmert, Schwabach, Germany) at 25 °C and 60% relative humidity (RH) for a period of 3 months. The printlets were packaged in amber glass bottles, while the printed discs were stored in transparent glass bottles protected by aluminium. All bottles were closed with plastic screw caps. They were monitored by DSC (printlets) and XRPD (discs) analysis over the period of storage.

3. Results

3.1. Physical Printlet Characteristics

PZQ printlets with different compositions were investigated in the present work to find the best solution for a PZQ formulation to treat schistosomiasis in children. The work was designed to obtain PZQ printlets and to demonstrate the feasibility of producing medications with personalised doses in printlets of 10 mm diameter and 3.6 mm height. The pictures of the best formulations are shown in Figure 2.

The physical mixture of PZQ and KOL (PM 50) was directly added to the hopper of the 3D printer extruder, but the feeding material hampered the printing process and led to unsatisfactory final products (pictures not shown). Varying mass feed rates and screw speed parameters were tested, but none produced printlets with a satisfactory visual quality or enough extruded material. The poor flow of the mixture and electrostatic forces caused high variation in the feeding during printing, making it impossible to produce a continuous and homogeneous flow of material through the screw.

A similar and unsatisfactory behaviour was verified when another physical mixture of PZQ (PM 35 SLS) was directly added to the hopper of the 3D printer extruder. These results showed that, for 3DP with direct powdered material feeding, powder characteristics capable of providing fluidity and homogeneity are essential to a regular flow through the extruder [49]. Without adding additional excipients to improve the flow properties of physical mixtures, it was not possible to obtain good quality printlets from both PZQ formulations.

For the third tested formulation (PM 35 Span), printing was not possible since the mixture could not be prepared with the same conditions used for HME extrusion (addition of the liquid surfactant directly into the extruder).

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Alternative processed materials were directly fed into the 3D printer: pellets obtained by HME, and powders obtained from the milled pellets. The main objective of printing using pellets was to facilitate the overall process and overcome the need for milling. Although it was possible to print with pellets, the flow into the printer was inconsistent, most likely due to the size (~1 mm) and the lack of homogeneity in the materials' particulate morphology. The printing of the printlets using the sample P 50 was possible, however, for a limited number of printlets, since the cleaning of the screw was necessary after each unit produced. For this reason, only DSC analysis was performed for this sample to verify the thermal behaviour after printing and during the stability testing period.

In contrast, milled materials provided a continuous flow, and the printing process was notably improved. However, it was evidenced that the feed rate was impacted by the drug load in the system. The samples in the milled form with a load of 35 wt% PZQ (M 35) showed greater ease of continuous printing compared to the sample containing 50 wt% PZQ (M 50). As a result, even the M 50 formulation presented limitations in the printlet reproducibility. Due to this, SEM and palatability analyses were not performed. Even with these limitations, the characterisations present in this work are an important step as they demonstrate the possibility of printing with high drug load materials obtained by HME.

The images obtained by optical microscopy of PZQ printlets are shown in Figure 2. The variation in printlet colour is related to the differing composition of each one. After the HME process, both tested formulations containing surfactant (M 35 Span and M 35 SLS) had a yellow appearance, with the most intense coloration for the one containing SLS. This is most likely because the surfactant interacts with other formulation components (polymer and drug), resulting in a colour change. This feature was constant for the respective printlets produced with the M 35 Span and M 35 SLS formulations. Interactions (chemical and/or physical) between API and excipients can affect characteristics such as stability, chemical nature, and bioavailability of the API, resulting in efficacy and safety impacts [50,51]. Further studies, such as forced degradation, should be conducted in addition to other spectroscopic techniques (e.g., Fourier-transform infrared spectroscopy, UV-Vis) [52] to better understand the colour differences between the formulations. Another characteristic that can be identified in the optical microscopy images is the greater opacity of the printlet containing 50 wt% PZQ (M 50) compared to the others having only a 35 wt% drug load. When comparing the M 35 Span and M 35 SLS printlets to the respective placebos, the absence of PZQ configures even more transparency. Nonetheless, all printlets presented a good physical appearance, with a smooth surface and shiny finish.

SEM cross-section images of two PZQ printlets (M 35 Span and M 35 SLS) are shown in Figure 3. They display a dense and homogeneous inner matrix, in which some small holes can be observed. These were most likely formed from air bubbles entrapped during the printing process. The images also provide a clear view of the consistent layers formed by the deposition of material during printing.

The printlet dimensions and weight are reported in Table 2. P 50 and M 50 printlets showed a higher mass variation (0.270 and 0.298 mg, respectively), presumably due to the difference in flow rate (75 and 90%, respectively), as a slower flow rate results in less material deposition. PZQ drug loading was determined only for the M 50 printlets based on the number of units available, and was close to the theoretical load value (48.4%), showing that the dose is approximately 150 mg.

Table 2.

Measured Characteristics of Printlets Printlet Formulation Weight (g) Diameter (mm) Height (mm) P 50 * 0.270 ± 0.02 9.720 ± 0.22 3.579 ± 0.05 M 50 * 0.298 ± 0.01 9.810 ± 0.16 3.554 ± 0.14 M 35 Span ** 0.297 ± 0.02 9.982 ± 0.25 3.507 ± 0.09 M 35 SLS ** 0.290 ± 0.04 9.841 ± 0.22 3.591 ± 0.11

Formulations M 35 with surfactants (Span and SLS) showed a homogeneous flow during the printer feeding process and good uniformity was achieved with regard to physical dimensions (Table 2). PZQ content values of milled extrudates before printing were 34.84% (M 35 Span) and 33.25% (M 35 SLS). After printing, the results remained similar for both formulations (35.02 and 33.54%, respectively), and with that, the dosages of the printlets were found to be around 100 mg. One of the most discussed applications of 3DP for medicine manufacture is the easy adjustment of dose via the manipulation of the size, structure, or shape of the solid dosage form. The adjustment of the dose by changing the size of 3D printed formulations was already demonstrated in the first clinical study of printlets prepared in a hospital for children [53].

As an initial stage in developing a paediatric pharmaceutical formulation, characteristics such as pharmacokinetics and pharmacodynamics, potential routes of administration, toxicity relationship, and taste preferences should be evaluated [54].

In general, it can be argued that from birth to approximately 16/18 years, individuals are considered paediatric patients [55]. However, when analysing this heterogenous age group, it is easy to see significant differences in the physiological development of the body and the need for personalised medicine development for the different stages of childhood [54]. The 3DP approach can therefore produce different designs, resulting in new dosage forms with specific and unique pharmacokinetic characteristics.

Placebo printlets were also analysed for drug content to check for any possible contamination of printer parts. For all placebo printlets, the presence of PZQ was not identified, thus indicating that cleaning the printer between each batch was effective, with no drug contamination throughout.

3.2. Physicochemical Characterisations

DSC, XRPD, and Raman mapping were used to characterise the solid state of the printlets. DSC thermograms confirmed the crystalline nature of the pure drug by the presence of a sharp melting endotherm at ~140 °C, and the amorphous state of the polymer KOL (Figure 4), as reported previously in the literature [56,57,58,59]. Although an endothermic event was observed in the HME powdered material and mainly after milling (data not shown), its low intensity allows us to conclude that P 50 and M 50 powdered materials were predominantly amorphous before printing due to the melting process in HME. These physical characteristics were maintained after printing for both formulations, where the P 50 remained amorphous while the DSC thermogram of the M 50 printlet shows an endothermic peak visualised in the range of 120'122 °C with ΔHfusion 2.15 J/g. However, the crystallinity is similar to that evidenced in the material before printing and cannot be attributed to the presence of the crystalline PZQ (Tm ~ 136 °C) or one of the polymorphs of PZQ, B, or C, for which the melting temperatures described in the literature are different (around 106 and 112 °C, respectively) [58,59,60]. The endothermic event shown in Figure 4 can be related to the effect of the polymer on lowering the melting temperature of the drug in the mixture. Figure 4 also shows the homogeneity of the printlets, with no differences in their characteristics measured in the core and on the border.

Although M 50 printlets presented a mixture of crystalline and amorphous material, it was identified that over three months of storage under controlled conditions (25 °C, 60% RH), the endothermic signal and the enthalpy of fusion detected after production remained unchanged (data not shown), evidencing no change in the solid state exposed to the storage conditions.

Figure 5 displays the DSC thermograms for printlets containing 35 wt% PZQ with surfactants (Span or SLS). The amorphous nature of M 35 Span and M 35 SLS materials subjected to HME before printing was confirmed, with no evidence of crystalline PZQ due to the absence of a melting event and the presence of a single glass transition (TgM35SPAN33 °C and ΔCp0.37 J/g.; TgM35SLS25 °C and ΔCp0.36 J/g., respectively). The amorphous pattern after printing (M 35 Span and M 35 SLS printlets) remained unchanged (t0), and no evolution was detected by DSC analysis after three months of storage at 25 °C, 60% RH (t3).

XRPD diffractograms of all raw, powdered, and printed materials are grouped in Figure 6. The crystalline nature of the raw PZQ and SLS are confirmed by the sharp peaks, in line with the data already described in the literature for the commercial racemic molecule [14,60]. Likewise, the polymer (KOL) also presents a characteristic halo of amorphous material. The amorphous nature of powdered materials and their respective printlets (M 35 Span) previously found in the DSC analysis are also confirmed by XRPD diffractograms. However, the M 35 SLS printlet was the only material presenting some diffraction signals, indicating the presence of crystalline material. It could be verified during this study that these signals are also identified in absence of the drug in the placebo formulation (Figure 6), being related to some structural change in the surfactant (SLS), which was not further investigated here. Unlike the DSC results, the printlet M 50 showed no signs of diffraction, indicating that the sample may be amorphous or the drug in crystalline state is in a proportion under the detection limits of the XRPD technology.

Raman microscopy was performed to provide information about the distribution of PZQ in the printlets. Figure 7 shows Raman spectra for PZQ and KOL and their respective characteristic signals (, , , cm'1, and 749, 862, , cm'1, respectively). The results showed the presence of PZQ in the M 35 SLS and M 50 printlets (, , , and cm'1), but it is not possible to detect Raman characteristic peaks of the surfactant (SLS), most likely due to the small proportion used (5 wt%) (Figure 7).

3D images obtained from the integration of PZQ and KOL peaks revealed each material's distribution in the analysis area (Figure 8a,b). It is possible to visualise the graphs with different colour intensities that reflect the distribution of PZQ in the printlet. Areas that appear light yellow indicate high absorbance (high concentration of drug), and areas with a darker colour (black) indicate a lower concentration of drug present due to the low absorbance [61]. Thus, these colour variations can map the homogeneity and concentration of the dispersed drug on the screened printlet area. The even distribution of yellow and orange peaks confirms the good distribution level of the PZQ within the polymer matrix, a critical quality attribute for the physical stability of amorphous solid dispersions.

For the M 35 SLS printlet, several analyses were performed, with two different lasers (532 and 785 nm), different integration times, and different laser intensities. In all these analyses, the fluorescence phenomena remained important for the perimeter of Raman images. Therefore, it was impossible to obtain a spectrum on this sample, certainly due to the darker printlet colour.

3.3. Dissolution Profiles

The dissolution profiles of M 50, M 35 Span, and M 35 SLS printlets show a greater than four-fold increase in drug release after 2 h compared to PZQ alone (Figure 9). It is important to mention that all printlets were printed directly with powdered materials obtained from HME extrudates without the addition of other excipients that could improve properties such as flowability, dissolution, disintegration, and taste masking. This proves that 3DP can be a highly valuable technology for producing personalised pharmaceutical dosage forms to improve physical and sensory properties necessary for a large variety of medicines. The combination of HME and 3DP techniques could be useful to overcome challenges in the formulation development of BCS class II drugs with low solubility, which represent more than 70% of new drug candidates in the pipeline [62].

It is known from the drug-polymer composition-temperature previously determined by the authors (data not shown) that, at room temperature, 35 wt% PZQ in KOL corresponds to a supersaturated amorphous binary system. Considering that the highest concentration of PZQ (50 wt%) would be sensitive to recrystallisation, in the present study, M 35 Span and M 35 SLS printlets were chosen to be evaluated for taste masking performance using an in vitro biorelevant buccal dissolution method described previously by Keeley et al. [46].

M 35 Span and M 35 SLS milled materials before printing released more than 0.2 mg/mL of PZQ in the artificial saliva in the first minute of the experiment (Figure 10a). Münster et al. [63] found that the half maximal inhibitory concentration (IC50) for a PZQ taste response was 0.06 mg/mL when tested with the rat BATA model. The dashed lines indicate the PZQ taste tolerability thresholds they found and are classified as tolerable (0.05 mg/mL) and well tolerable (0.03 mg/mL). Therefore, when ingesting a drug in the particulate form, i.e., a powder formulation for dispersion, the bitter and unpleasant taste of PZQ is likely to be present in the mouth immediately upon administration, at a level triggering aversion. The 3D printed formulations exhibited a significantly lower drug release, even after 600 s, than the M 35 Span and M 35 SLS HME milled extrudates before printing (Figure 10a), demonstrating that the 3DP step was key for successful taste masking. As shown in Figure 10b, both printlets (M 35 Span and M 35 SLS) were below the threshold of good tolerability of the PZQ and even further below the PZQ IC50 (0.06 mg/mL), indicating that the formulations provided efficient taste masking without the use of additional taste masking excipients.

The bespoke flowthrough oral dissolution apparatus was used in a previous study to evaluate chlorphenamine maleate, a bitter BCS class I drug, incorporated in sugar spheres and coated with different technologies and polymer coatings [46]. In this study, the system could discriminate the taste masking capabilities of the formulations, using taste thresholds generated with the rat BATA model and confirmed with human taste thresholds.

In the case of PZQ, this in vitro taste assessment is a very useful tool to screen formulations and evaluate printlets in early-stage formulation development. The method is simple to execute, relatively inexpensive, and can guide development decisions so that animal experimentation can be reduced as only one taste profiling of the drug is needed. However, although the preliminary results of the printlets are encouraging, there is still the possibility of improving the final formulation with additional excipients to further favour taste masking.

4. Conclusions

For the first time, 3D printed tablets containing 35 and 50 wt% praziquantel (PZQ) were successfully produced by direct powder extrusion (DPE) 3DP from HME extrudates (in pellet and powder form), reducing the dependence on the strict mechanical properties of HME filaments for FDM 3DP.

Printlets with adequate dimensional characteristics and two different doses (~150 and 100 mg) were produced. In vitro dissolution studies showed a greater than four-fold increase in PZQ from the printlets when compared to pure PZQ, most likely due to the predominantly amorphous solid state of PZQ after printing. In addition to the improved performance in the dissolution studies, in vitro taste masking results revealed that the formulations would be within acceptable taste thresholds (tolerated and well tolerated), with enhanced features for paediatric patients.

Most of the paediatric users of PZQ are found in developing countries, with a large variation in the children's weight due to the poor dietary conditions, showing a wide range of physiological and pharmacokinetic characteristics within a heterogeneous age group. Due to the absence of an appropriate paediatric formulation, treatment of schistosomiasis patients involves the breaking or crushing of a standard adult tablet to achieve the required dose of 40 mg/kg [64,65,66].

The printlets in this work were developed with a focus on paediatric patients, and although the drug loading still requires optimisation, promising results with amorphous systems have been obtained in taste masking and possible dose reduction compared to what is currently available [63,67]. The results from this work demonstrate the unique potential of 3DP in customising PZQ medicines from amorphous systems, specifically for paediatric patients.

Acknowledgments

The authors would like to thank Sylvie Del Confetto, Veronique Nallet, and Vinicius Marin Boniatti for technical support in the DSC, XRD, and editions of printer figures, respectively, and the Gala® platform for providing technical facilities for the extrusion processes and Raman analysis.

Author Contributions

J.B., M.-I.R., A.G., C.T.: conceptualisation and data curation; J.B.: experimental analysis; J.B., M.-I.R., A.G.: writing'original draft preparation; J.B., M.-I.R., A.G., C.T., P.J.: writing'review and editing; L.B.d.F., F.C.A., A.L.V., A.W.B.: review and editing; M.-I.R., A.G., A.W.B.: supervision. All authors have read and agreed to the published version of the manuscript.

Funding

The authors would like to thank the Oswaldo Cruz Foundation (Fiocruz) (Innovation Program-VPPIS-001-FIO-18-41), Université de Toulouse, and IMT Mines Albi'Rapsodee Center for their financial support. This research was partially funded by the Engineering and Physical Sciences Research Council (EPSRC) UK grant number EP/S/1.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Conflicts of Interest

A.G. and A.W.B. are founders of FabRx Ltd., and as indicated in the Author Contribution section they took part in the design of the study; in the data curation, manuscript writing and editing, supervision, and in the decision to publish the results. Other authors have no conflict of interest.

Footnotes

Publisher's Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

• 1.Karunamoorthi K., Almalki M.J., Ghailan K.Y. Schistosomiasis: A neglected tropical disease of poverty: A call for intersectoral mitigation strategies for better health. J. Health Res. Rev. ;5:1. doi: 10./jhrr.jhrr_92_17. [DOI] [Google Scholar]
• 2.Mondiale O., La Santé D. Schistosomiasis: Number of people treated worldwide in Schistosomiase: Nombre de personnes traitées dans le monde en . Wkly. Epidemiol. Rec. ;30:25'31. [Google Scholar]
• 3.Coulibaly J.T., Panic G., Silué K.D., Kovač J., Hattendorf J., Keiser J. Efficacy and safety of praziquantel in preschool-aged and school-aged children infected with Schistosoma mansoni: A randomised controlled, parallel-group, dose-ranging, phase 2 trial. Lancet Glob. Health. ;5:e688'e698. doi: 10./S-109X(17)-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 4.Hoekstra P.T., Partal M.C., Van Lieshout L., Corstjens P.L.A.M., Tsonaka R., Assaré R.K., Silué K.D., Meité A., N'Goran E.K., N'Gbesso Y.K., et al. Efficacy of single versus four repeated doses of praziquantel against Schistosoma mansoni infection in school-aged children from Côte d'Ivoire based on Kato-Katz and POC-CCA: An open-label, randomised controlled trial (RePST) PLoS Negl. Trop. Dis. ;14:e. doi: 10./journal.pntd.. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 5.Osakunor D.N.M., Woolhouse M., Mutapi F. Paediatric schistosomiasis: What we know and what we need to know. PLoS Negl. Trop. Dis. ;12:e. doi: 10./journal.pntd.. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 6.Pediatric Praziquantel Consortium Schistosomiasis in Children: A Major Public Health Problem. [(accessed on 19 May )]; Available online: https://www.pediatricpraziquantelconsortium.org/
• 7.Eyayu T., Zeleke A.J., Worku L. Current status and future prospects of protein vaccine candidates against Schistosoma mansoni infection. Parasite Epidemiol. Control. ;11:e. doi: 10./j.parepi..e. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 8.Cruz J.I.N., Salazar G.D.O., La Corte R. Retrocesso do Programa de Controle da Esquistossomose no estado de maior prevalência da doença no Brasil. Rev. Pan Amaz. Saúde. ;11:1'9. doi: 10./s-. [DOI] [Google Scholar]
• 9.Meyer T., Sekljic H., Fuchs S., Bothe H., Schollmeyer D., Miculka C. Taste, A New Incentive to Switch to (R)-Praziquantel in Schistosomiasis Treatment. PLoS Negl. Trop. Dis. ;3:e357. doi: 10./journal.pntd.. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 10.Da Silva J.C.S., Bernardes M.V.A.D.S., de Melo F.L., Sá M.P., Carvalho B.M. Praziquantel versus praziquantel associated with immunomodulators in mice infected with schistosoma mansoni: A systematic review and meta-analysis. Acta Trop. ;204:. doi: 10./j.actatropica... [DOI] [PubMed] [Google Scholar]
• 11.Navaratnam A., Sousa-Figueiredo J., Stothard R., Kabatereine N., Fenwick A., Mutumba-Nakalembe M. Efficacy of praziquantel syrup versus crushed praziquantel tablets in the treatment of intestinal schistosomiasis in Ugandan preschool children, with observation on compliance and safety. Trans. R. Soc. Trop. Med. Hyg. ;106:400'407. doi: 10./j.trstmh..03.013. [DOI] [PubMed] [Google Scholar]
• 12.Winzenburg G., Desset-Brèthes S. Industry perspective on palatability testing in children'Two case studies. Int. J. Pharm. ;435:139'142. doi: 10./j.ijpharm..05.057. [DOI] [PubMed] [Google Scholar]
• 13.European Medicines Agency (EMA) Guideline on Pharmaceutical Development of Medicines for Paediatric Use; UK, ; pp. 1'24, [Online] [(accessed on 10 March )]; Available online: https://www.ema.europa.eu/en/documents/scientific-guideline/guideline-pharmaceutical-development-medicines-paediatric-use_en.pdf.
• 14.Borrego-Sánchez A., Carazo E., Albertini B., Passerini N., Perissutti B., Cerezo P., Viseras C., Hernández-Laguna A., Aguzzi C., Sainz-Díaz C.I. Conformational polymorphic changes in the crystal structure of the chiral antiparasitic drug praziquantel and interactions with calcium carbonate. Eur. J. Pharm. Biopharm. ;132:180'191. doi: 10./j.ejpb..09.028. [DOI] [PubMed] [Google Scholar]
• 15.Malaquias L.F., Schulte H.L., Chaker J.A., Karan K., Durig T., Marreto R., Gratieri T., Gelfuso G., Cunha-Filho M. Hot Melt Extrudates Formulated Using Design Space: One Simple Process for Both Palatability and Dissolution Rate Improvement. J. Pharm. Sci. ;107:286'296. doi: 10./j.xphs..08.014. [DOI] [PubMed] [Google Scholar]
• 16.Tian Y., Jacobs E., Jones D.S., McCoy C.P., Wu H., Andrews G.P. The design and development of high drug loading amorphous solid dispersion for hot-melt extrusion platform. Int. J. Pharm. ;586:. doi: 10./j.ijpharm... [DOI] [PubMed] [Google Scholar]
• 17.Zhao M., You D., Yin J., Sun W., Yin T., Gou J., Zhang Y., Wang Y., He H., Tang X. Quaternary enteric solid dispersion prepared by hot-melt extrusion to mask the bitter taste and enhance drug stability. Int. J. Pharm. ;597:. doi: 10./j.ijpharm... [DOI] [PubMed] [Google Scholar]
• 18.Pandi P., Bulusu R., Kommineni N., Khan W., Singh M. Amorphous solid dispersions: An update for preparation, characterization, mechanism on bioavailability, stability, regulatory considerations and marketed products. Int. J. Pharm. ;586:. doi: 10./j.ijpharm... [DOI] [PMC free article] [PubMed] [Google Scholar]
• 19.Kanaujia P., Poovizhi P., Ng W., Tan R. Amorphous formulations for dissolution and bioavailability enhancement of poorly soluble APIs. Powder Technol. ;285:2'15. doi: 10./j.powtec..05.012. [DOI] [Google Scholar]
• 20.Al-Kasmi B., Alsirawan M.H.D.B., Paradkar A., Nattouf A.-H., El-Zein H. Aqueous and pH dependent coacervation method for taste masking of paracetamol via amorphous solid dispersion formation. Sci. Rep. ;11:1'11. doi: 10./s-021--6. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 21.Maniruzzaman M., Boateng J., Chowdhry B.Z., Snowden M., Douroumis D. A review on the taste masking of bitter APIs: Hot-melt extrusion (HME) evaluation. Drug Dev. Ind. Pharm. ;40:145'156. doi: 10./... [DOI] [PubMed] [Google Scholar]
• 22.Januskaite P., Xu X., Ranmal S.R., Gaisford S., Basit A.W., Tuleu C., Goyanes A. I Spy with My Little Eye: A Paediatric Visual Preferences Survey of 3D Printed Tablets. Pharmaceutics. ;12:. doi: 10./pharmaceutics. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 23.Nordenmalm S., Kimland E., Ligas F., Lehmann B., Claverol J., Nafria B., Tötterman A.M., Pelle B. Children's views on taking medicines and participating in clinical trials. Arch. Dis. Child. ;104:900'905. doi: 10./archdischild--. [DOI] [PubMed] [Google Scholar]
• 24.Lyons J.G., Hallinan M., Kennedy J.E., Devine D.M., Geever L.M., Blackie P., Higginbotham C.L. Preparation of monolithic matrices for oral drug delivery using a supercritical fluid assisted hot melt extrusion process. Int. J. Pharm. ;329:62'71. doi: 10./j.ijpharm..08.028. [DOI] [PubMed] [Google Scholar]
• 25.Zhang J., Feng X., Patil H., Tiwari R.V., Repka M.A. Coupling 3D printing with hot-melt extrusion to produce controlled-release tablets. Int. J. Pharm. ;519:186'197. doi: 10./j.ijpharm..12.049. [DOI] [PubMed] [Google Scholar]
• 26.Goyanes A., Allahham N., Trenfield S.J., Stoyanov E., Gaisford S., Basit A.W. Direct powder extrusion 3D printing: Fabrication of drug products using a novel single-step process. Int. J. Pharm. ;567:. doi: 10./j.ijpharm... [DOI] [PubMed] [Google Scholar]
• 27.Capel A.J., Rimington R.P., Lewis M.P., Christie S.D.R. 3D printing for chemical, pharmaceutical and biological applications. Nat. Rev. Chem. ;2:422'436. doi: 10./s-018--y. [DOI] [Google Scholar]
• 28.Goyanes A., Fernández-Ferreiro A., Majeed A., Gomez-Lado N., Awad A., Luaces-Rodríguez A., Gaisford S., Aguiar P., Basit A.W. PET/CT imaging of 3D printed devices in the gastrointestinal tract of rodents. Int. J. Pharm. ;536:158'164. doi: 10./j.ijpharm..11.055. [DOI] [PubMed] [Google Scholar]
• 29.Elbadawi M., McCoubrey L.E., Gavins F.K., Ong J.J., Goyanes A., Gaisford S., Basit A.W. Harnessing artificial intelligence for the next generation of 3D printed medicines. Adv. Drug Deliv. Rev. ;175:. doi: 10./j.addr..05.015. [DOI] [PubMed] [Google Scholar]
• 30.Awad A., Fina F., Goyanes A., Gaisford S., Basit A.W. Advances in powder bed fusion 3D printing in drug delivery and healthcare. Adv. Drug Deliv. Rev. ;174:406'424. doi: 10./j.addr..04.025. [DOI] [PubMed] [Google Scholar]
• 31.Seoane-Viaño I., Trenfield S.J., Basit A.W., Goyanes A. Translating 3D printed pharmaceuticals: From hype to real-world clinical applications. Adv. Drug Deliv. Rev. ;174:553'575. doi: 10./j.addr..05.003. [DOI] [PubMed] [Google Scholar]
• 32.Awad A., Yao A., Trenfield S.J., Goyanes A., Gaisford S., Basit A.W. 3D Printed Tablets (Printlets) with Braille and Moon Patterns for Visually Impaired Patients. Pharmaceutics. ;12:172. doi: 10./pharmaceutics. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 33.Vithani K., Goyanes A., Jannin V., Basit A.W., Gaisford S., Boyd B.J. A Proof of Concept for 3D Printing of Solid Lipid-Based Formulations of Poorly Water-Soluble Drugs to Control Formulation Dispersion Kinetics. Pharm. Res. ;36:102. doi: 10./s-019--y. [DOI] [PubMed] [Google Scholar]
• 34.Seoane-Viaño I., Gómez-Lado N., Lázare-Iglesias H., García-Otero X., Antúnez-López J.R., Ruibal Á., Varela-Correa J.J., Aguiar P., Basit A.W., Otero-Espinar F.J., et al. 3D Printed Tacrolimus Rectal Formulations Ameliorate Colitis in an Experimental Animal Model of Inflammatory Bowel Disease. Biomedicines. ;8:563. doi: 10./biomedicines. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 35.Fina F., Goyanes A., Rowland M., Gaisford S., Basit A.W. 3D Printing of Tunable Zero-Order Release Printlets. Polymers. ;12:. doi: 10./polym. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 36.Elbadawi M., McCoubrey L.E., Gavins F.K., Ong J.J., Goyanes A., Gaisford S., Basit A.W. Disrupting 3D printing of medicines with machine learning. Trends Pharmacol. Sci. doi: 10./j.tips..06.002. [DOI] [PubMed] [Google Scholar]
• 37.Mathew E., Pitzanti G., Larrañeta E., Lamprou D.A. 3D Printing of Pharmaceuticals and Drug Delivery Devices. Pharmaceutics. ;12:266. doi: 10./pharmaceutics. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 38.Goyanes A., Fina F., Martorana A., Sedough D., Gaisford S., Basit A.W. Development of modified release 3D printed tablets (printlets) with pharmaceutical excipients using additive manufacturing. Int. J. Pharm. ;527:21'30. doi: 10./j.ijpharm..05.021. [DOI] [PubMed] [Google Scholar]
• 39.Tabriz A.G., Nandi U., Hurt A.P., Hui H.-W., Karki S., Gong Y., Kumar S., Douroumis D. 3D printed bilayer tablet with dual controlled drug release for tuberculosis treatment. Int. J. Pharm. ;593:. doi: 10./j.ijpharm... [DOI] [PubMed] [Google Scholar]
• 40.Skowyra J., Pietrzak K., Alhnan M.A. Fabrication of extended-release patient-tailored prednisolone tablets via fused deposition modelling (FDM) 3D printing. Eur. J. Pharm. Sci. ;68:11'17. doi: 10./j.ejps..11.009. [DOI] [PubMed] [Google Scholar]
• 41.Gioumouxouzis C.I., Katsamenis O.L., Bouropoulos N., Fatouros D.G. 3D printed oral solid dosage forms containing hydrochlorothiazide for controlled drug delivery. J. Drug Deliv. Sci. Technol. ;40:164'171. doi: 10./j.jddst..06.008. [DOI] [Google Scholar]
• 42.Palekar S., Nukala P.K., Mishra S.M., Kipping T., Patel K. Application of 3D printing technology and quality by design approach for development of age-appropriate pediatric formulation of baclofen. Int. J. Pharm. ;556:106'116. doi: 10./j.ijpharm..11.062. [DOI] [PubMed] [Google Scholar]
• 43.Melocchi A., Briatico-Vangosa F., Uboldi M., Parietti F., Turchi M., von Zeppelin D., Maroni A., Zema L., Gazzaniga A., Zidan A. Quality considerations on the pharmaceutical applications of fused deposition modeling 3D printing. Int. J. Pharm. ;592:. doi: 10./j.ijpharm... [DOI] [PubMed] [Google Scholar]
• 44.Elbadawi M., Castro B.M., Gavins F.K., Ong J.J., Gaisford S., Pérez G., Basit A.W., Cabalar P., Goyanes A. M3DISEEN: A novel machine learning approach for predicting the 3D printability of medicines. Int. J. Pharm. ;590:. doi: 10./j.ijpharm... [DOI] [PubMed] [Google Scholar]
• 45.Ong J.J., Awad A., Martorana A., Gaisford S., Stoyanov E., Basit A.W., Goyanes A. 3D printed opioid medicines with alcohol-resistant and abuse-deterrent properties. Int. J. Pharm. ;579:. doi: 10./j.ijpharm... [DOI] [PubMed] [Google Scholar]
• 46.Keeley A., Teo M., Ali Z., Frost J., Ghimire M., Rajabi-Siahboomi A., Orlu M., Tuleu C. In Vitro Dissolution Model Can Predict the in Vivo Taste Masking Performance of Coated Multiparticulates. Mol. Pharm. ;16:'. doi: 10./acs.molpharmaceut.9b. [DOI] [PubMed] [Google Scholar]
• 47.Marques M.R.C., Loebenberg R., Almukainzi M. Simulated Biological Fluids with Possible Application in Dissolution Testing. Dissolut. Technol. ;18:15'28. doi: 10./DTP15. [DOI] [Google Scholar]
• 48.Mohamed-Ahmed A.H., Soto J., Ernest T., Tuleu C. Non-human tools for the evaluation of bitter taste in the design and development of medicines: A systematic review. Drug Discov. Today. ;21:'. doi: 10./j.drudis..05.014. [DOI] [PubMed] [Google Scholar]
• 49.Spath S., Seitz H. Influence of grain size and grain-size distribution on workability of granules with 3D printing. Int. J. Adv. Manuf. Technol. ;70:135'144. doi: 10./s-013--8. [DOI] [Google Scholar]
• 50.Bharate S.S., Bharate S.B., Bajaj A.N. Interactions and incompatibilities of pharmaceutical excipients with active pharmaceutical ingredients: A comprehensive review. J. Excipients Food Chem. ;1:3'26. [Google Scholar]
• 51.Rowe R.C., Sheskey P.J., Owen S.C. Handbook of Pharmaceutical Excipients. 5th ed. Pharmaceutical Press; London, UK: . [Google Scholar]
• 52.Schlindwein W., Bezerra M., Almeida J., Berghaus A., Owen M., Muirhead G. In-Line UV-Vis Spectroscopy as a Fast-Working Process Analytical Technology (PAT) during Early Phase Product Development Using Hot Melt Extrusion (HME) Pharmaceutics. ;10:166. doi: 10./pharmaceutics. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 53.Goyanes A., Madla C.M., Umerji A., Piñeiro G.D., Montero J.M.G., Diaz M.J.L., Barcia M.G., Taherali F., Sánchez-Pintos P., Couce M.-L., et al. Automated therapy preparation of isoleucine formulations using 3D printing for the treatment of MSUD: First single-centre, prospective, crossover study in patients. Int. J. Pharm. ;567:. doi: 10./j.ijpharm... [DOI] [PubMed] [Google Scholar]
• 54.Ivanovska V., Rademaker C.M., Van Dijk L., Mantel-Teeuwisse A.K. Pediatric Drug Formulations: A Review of Challenges and Progress. Pediatrics. ;134:361'372. doi: 10./peds.-. [DOI] [PubMed] [Google Scholar]
• 55.Gerrard S.E., Walsh J., Bowers N., Salunke S., Hershenson S. Innovations in Pediatric Drug Formulations and Administration Technologies for Low Resource Settings. Pharmaceutics. ;11:518. doi: 10./pharmaceutics. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 56.Pawar J.N., Shete R.T., Gangurde A.B., Moravkar K., Javeer S.D., Jaiswar D.R., Amin P. Development of amorphous dispersions of artemether with hydrophilic polymers via spray drying: Physicochemical and in silico studies. Asian J. Pharm. Sci. ;11:385'395. doi: 10./j.ajps..08.012. [DOI] [Google Scholar]
• 57.Gupta S.S., Meena A., Parikh T., Serajuddin A.T.M. Investigation of thermal and viscoelastic properties of polymers relevant to hot melt extrusion'I: Polyvinylpyrrolidone and related polymers. J. Excip. Food Chem. ;5:32'45. [Google Scholar]
• 58.Zanolla D., Perissutti B., Vioglio P.C., Chierotti M.R., Gigli L., Demitri N., Passerini N., Albertini B., Franceschinis E., Keiser J., et al. Exploring mechanochemical parameters using a DoE approach: Crystal structure solution from synchrotron XRPD and characterization of a new praziquantel polymorph. Eur. J. Pharm. Sci. ;140:. doi: 10./j.ejps... [DOI] [PubMed] [Google Scholar]
• 59.Zanolla D., Hasa D., Arhangelskis M., Schneider-Rauber G., Chierotti M.R., Keiser J., Voinovich D., Jones W., Perissutti B. Mechanochemical Formation of Racemic Praziquantel Hemihydrate with Improved Biopharmaceutical Properties. Pharmaceutics. ;12:289. doi: 10./pharmaceutics. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 60.Zanolla D., Perissutti B., Passerini N., Chierotti M.R., Hasa D., Voinovich D., Gigli L., Demitri N., Geremia S., Keiser J., et al. A new soluble and bioactive polymorph of praziquantel. Eur. J. Pharm. Biopharm. ;127:19'28. doi: 10./j.ejpb..01.018. [DOI] [PubMed] [Google Scholar]
• 61.De Lima Á.A.N. Ph.D. Thesis. Universidade Federal de Pernambuco; Recife, Brazil: . Avaliação dos Aspectos Físico-Químicos do Antichagásico Benznidazol, Diferentes Sistemas Carreadores e Formas Farmacêuticas, Através de Técnicas Analíticas e de Imagens Avaliação dos Aspectos Físico-Químicos do Antichagásico Benznidazol, Diferentes sis. [Google Scholar]
• 62.Mendonsa N., Almutairy B., Kallakunta V.R., Sarabu S., Thipsay P., Bandari S., Repka M.A. Manufacturing strategies to develop amorphous solid dispersions: An overview. J. Drug Deliv. Sci. Technol. ;55:. doi: 10./j.jddst... [DOI] [PMC free article] [PubMed] [Google Scholar]
• 63.Münster M., Ahmed A.M., Immohr L.I., Schoch C., Schmidt C., Tuleu C., Breitkreutz J. Comparative in vitro and in vivo taste assessment of liquid praziquantel formulations. Int. J. Pharm. ;529:310'318. doi: 10./j.ijpharm..06.084. [DOI] [PubMed] [Google Scholar]
• 64.World Health Organization 'Report of A Meeting to Review the Results of Studies on the Treatment of Schistosomiasis in Preschool-Age Children'. [(accessed on 10 May )]; Available online: https://apps.who.int/iris/bitstream/handle///_eng.pdf?sequence=1.
• 65.Olliaro P.L., Coulibaly J.T., Garba A., Halleux C., Keiser J., King C., Mutapi F., N'Goran E.K., Raso G., Scherrer A.U., et al. Efficacy and safety of single-dose 40 mg/kg oral praziquantel in the treatment of schistosomiasis in preschool-age versus school-age children: An individual participant data meta-analysis. PLoS Negl. Trop. Dis. ;14:e. doi: 10./journal.pntd.. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 66.Coulibaly J.T., Panić G., Yapi R.B., Kovac J., Barda B., N'Gbesso Y.K., Hattendorf J., Keiser J. Efficacy and safety of ascending doses of praziquantel against Schistosoma haematobium infection in preschool-aged and school-aged children: A single-blind randomised controlled trial. BMC Med. ;16:81. doi: 10./s-018--y. [DOI] [PMC free article] [PubMed] [Google Scholar]
• 67.Boniatti J. Taste evaluation of three different commercial tablets for paediatric patients for neglected tropical diseases; Proceedings of the 11th European Paediatric Formulation Initiative (EUPFI); Malmo, Sweden. 10'12 September . [Google Scholar]

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Open AccessArticle

Mechanochemical Synthesis of Praziquantel Hemihydrate in the Presence of Five Solvents with Different Water Miscibility '

Department of Chemical and Pharmaceutical Sciences, University of Trieste, Piazzale Europa 1, Trieste, Italy * Author to whom correspondence should be addressed. ' In the loving memory of Guglielmo Zingone. Crystals , 14(4), 374; https://doi.org/10./cryst Submission received: 25 March / Revised: 12 April / Accepted: 14 April / Published: 16 April (This article belongs to the Special Issue Structural Studies in Drug Discovery and Development: From the Lead to the Pharmaceutical Form)

Abstract

: In this study, we report the mechanochemical synthesis of praziquantel hemihydrate in the presence of five solvents with different water miscibility. The commercially available praziquantel Form A (a racemic anhydrate structure) was ground in the presence of several water'solvent mixtures using two grinding procedures (i.e., direct liquid-assisted grinding and neat grinding plus liquid-assisted grinding). Five organic solvents (i.e., acetic acid, 2-pyrrolidone, ethanol, ethyl acetate and hexane) were chosen considering their different miscibility with water and their capability to form solvates with praziquantel (documented for acetic acid and 2-pyrrolidone). The results suggested that the use of a second solvent has a detrimental effect on the formation of the hemihydrate. The inclusion of water in the solid is even worse in the case of water-miscible solvents, probably due to the favored interactions between the liquids. In fact, hexane is the only solvent permitting the mechanochemical crystallization of praziquantel hemihydrate to a limited extent. Importantly, interconversion studies between the hydrate/monosolvate/anhydrous forms revealed a preferential inclusion of solvents over water in the crystal lattice when using acetic acid or 2-pyrrolidone and complete dehydration of the hemihydrate and conversion in the most thermodynamically stable polymorph A of praziquantel with ethanol, ethyl acetate and hexane. Graphical Abstract

1. Introduction

In many steps of chemical and pharmaceutical industrial processing, substances could be exposed to water or other solvents during solvent-based preparation techniques (e.g., classical solution crystallization, coacervation, lyophilization, spray-drying, wet granulation) or by contact with environmental humidity during storage. Sometimes, these solvents remain 'entrapped' in the crystal structure, causing the formation of hydrated/solvated forms of the solid substance. Drug solvents generally have different crystal structures than the anhydrous form and, therefore, different physicochemical properties such as solubility, dissolution rate and physical and chemical stability. These aspects may affect not only technological properties such as industrial processability but also'and more importantly'the bioavailability of the drug, determining marked differences in the absorbed amount of the active pharmaceutical ingredient (API) [1]. Differently from hydrates, the inclusion of solvated API in a drug product must be pondered in light of the ICH guideline Q3C on residual solvents in pharmaceuticals, in consideration of possible toxicity issues [2]. In addition, since in the pharmaceutical industry, both water and solvents are used in different steps of the production processes [3], hydrate'solvate interconversions are likely to happen.In this context, in a previous study, the API theophylline was successfully used as a model drug to investigate the mechanochemical competitive solvate formation in the presence of two solvate/hydrate-forming miscible liquids (i.e., water (H2O) and 2-pyrrolidone (2-pyr)) [4]. The drug is known to convert into a monohydrate in the presence of H2O, whereas it gives a monosolvate or a sesquisolvate in the presence of 2-pyr. Different solid/liquid ratios and several H2O/2-pyr mixtures have been used to understand the hydrate/solvate competitive formation. The results suggested that H2O and 2-pyr, when used simultaneously, reduced their efficiency in being incorporated into the crystal structure: due to their mutual miscibility, more liquid than the solid-to-solvent stoichiometric ratio was required to obtain a pure specific solvated phase. Interconversion experiments between hydrate/monosolvate/sesquisolvate suggested a preferential inclusion of 2-pyr over H2O in the crystal structure.Based on the above-mentioned study, in this work, the experimental research was extended to another API, that is praziquantel (PZQ), the recommended drug against all species of schistosomiasis [5,6,7,8,9,10,11], included in the WHO (World Health Organization) Model List of Essential Drugs for the treatment of both adults and children [12,13]. This API, commercially available in racemic anhydrous solid dosage forms (trade name Biltricide® (Bayer Vital, Leverkusen, Germany)) [14], has been demonstrated to be prone to solid-state transformations (especially through mechanochemistry).To date, the literature provides seven PZQ anhydrous polymorphic forms (including the commercial Form A) [15,16,17,18], six hydrates [7,19,20,21,22,23], three solvates [18,24] and forty-eight cocrystals, including one cocrystal monohydrate and six cocrystal solvates [25,26,27,28,29,30,31,32,33,34,35,36], demonstrating a very high propensity to solid-state transformation and interaction with water/solvents [37]. Moreover, the industrial production of PZQ tablets often involves the use of solvents during its crystallization and wet granulation before tablet production [38,39], and consequently, hydrates or solvates of PZQ could unexpectedly arise. In this context, one hemihydrate (i.e., PZQ-HH) and two monosolvates of PZQ (i.e., PZQ-2-pyr and PZQ-AA) are reported in the Cambridge Structural Database (CSD) [40] and indexed as WUHQAU, DAJCAW and DAJCEA, respectively. Figure 1 indicates the chemical structure of commercial PZQ Form A and the crystal structures of the above-mentioned hemihydrate PZQ-HH and two solvates (PZQ-AA and PZQ-2-pyr).Considering these multicomponent solvates, PZQ-2-pyr and PZQ-AA are obtained through direct grinding of anhydrous PZQ Form A with an equimolar ratio of each solvent [24]. On the other hand, PZQ-HH can only be obtained starting from Form A via a two-step process, using initially neat grinding (NG) (for the formation of a mainly amorphous intermediate) and, subsequently, liquid-assisted grinding (LAG) in H2O. Alternatively, single-step LAG of PZQ Form B in H2O results in the hemihydrate, possibly related to the structural similarity between PZQ-HH and anhydrous Form B [21,37]. As for the physical stability, mechanical treatment at 25 Hz for 200 min without interruptions was almost ineffective on both solvates, while PZQ-HH gave PZQ Form B after 1 h, probably due to the similarity of their crystal structures [21].The racemic PZQ-HH is a very promising PZQ multicomponent crystal, as both its aqueous solubility and intrinsic dissolution rate (IDR) are largely superior to those of the commercially available PZQ Form A, counteracting the general rule that an anhydrous form is usually more soluble in H2O than the hydrated form [41]. Further, PZQ-HH maintains an unaltered antischistosomal activity level and physical state for three months at room temperature. As all these promising features could suggest a possible future industrial production of this solid, it is highly recommended to study, in detail, PZQ-HH and obtain provisional information on its possible transition in other solid forms because of the presence of common solvents.Additionally, compared to the significant number of publications exploring mechanochemistry as a suitable technique for cocrystal formation, studies about the mechanochemical synthesis of solvates are still limited [24,42,43,44,45,46]; the solvate outcome is often regarded as an undesired by-product rather than its main goal, and in most cases, the investigation is carried out by using only one solvent [47,48,49].Therefore, focusing this experimental research on PZQ-HH and using mechanochemistry as a fast-screening technique, PZQ was ground in the presence of several H2O'solvent mixtures with two different grinding procedures: (i) direct LAG of PZQ for 60 min (hereinafter referred as to Di-LAG); (ii) previous NG of anhydrous PZQ for 30 min followed by 1 h LAG (hereinafter referred as to NG+LAG).Five different solvents (i.e., acetic acid (AA), 2-pyrrolidone (2-pyr), ethanol (EtOH), ethyl acetate (EA) and hexane (HXN)) were tested considering their capability to form solvates with PZQ and their miscibility in H2O. Four of these (AA, 2-pyr, EtOH, EA) were selected from previous works on the mechanochemical formation of PZQ solvates and the formation of PZQ solid dispersions with PVP [24,50], while HXN was chosen for its well-known immiscibility with H2O [51]. The miscibility of the five solvents in H2O is reported in Section 2.2.2.Going into details, solvents were chosen based on this rationale:

• Two solvents able to form solvates with PZQ, one miscible and one less miscible, such as AA and 2-pyr, respectively;
• Two solvents not forming PZQ solvate, one miscible and one slightly miscible, i.e., EtOH and EA, respectively;
• One solvent that does not form PZQ solvate and is immiscible, such as HXN.

As for 2-pyr and AA, since both are miscible in H2O, the main objective was to understand if they compete with H2O for inclusion in the PZQ crystal lattice. Further, it was also intended to check if in the PZQ case, as seen in the theophylline example, when using H2O'solvent mixed liquids, a largely superior amount than the stoichiometric quantity was needed to form a pure multicomponent phase. EtOH, EA and HXN, with H2O miscibility in descending order, were also tested to further investigate the competitive effect between H2O and the second solvent on PZQ-HH formation in relation to their miscibility. Furthermore, we wanted to establish if the copresence of a second liquid during the grinding of PZQ with H2O could accelerate PZQ-HH formation, bypassing the NG limiting step.Moreover, following our previous experimental work on theophylline [4], interconversion experiments were also conducted by grinding preformed PZQ-HH in the presence of the above-mentioned five solvents for 60 min at 25 Hz.

2. Materials and Methods

2.1. Materials

Commercially available PZQ Form A (racemic anhydrate form), (RS)-2-(Cyclohexylcarbonyl)-1,2,3,6,7,11b-hexahydro-4-H-pyrazino[2,1-a]-isoquinolin-4-one], of Ph. Eur. grade was kindly donated by Fatro S.p.a. (Bologna, Italy). Acetic acid (AA) and 2-pyrrolidone (2-pyr) were provided from Carlo Erba (Rodano-Milan, Italy), while ethanol (EtOH) and ethyl acetate (EA) were purchased from Honeywell Riedel-de Haën (St. Louis, MO, USA). HPLC-grade hexane (HXN) was provided by Sigma-Aldrich Ltd. (Milan, Italy).All the actives and chemicals were used without further purification. Water (H2O) was freshly distilled.

2.2. Sample Preparation

2.2.1. Milling Experiments

Milling experiments were performed in Retsch MM400 vibrational mills (Retsch, Haan, Germany) equipped with two 25 mL stainless steel jars and one 10 mm Ø bead, respectively. The milling frequency was kept fixed at 25 Hz. For each mechanochemical experiment, the amount of commercially available PZQ Form A was kept fixed at 400 mg. AA, 2-pyr, EtOH, EA and HXN were the five selected solvents used with H2O for the research purpose.Each experiment was developed by adding to the drug an equimolar amount of liquid, either as pure H2O, one of the five selected solvents, or in the form of seven H2O'solvent mixtures. Specifically, eight different molar fractions of each of the two solvents were added directly to the milling jars using Eppendorf Research plus micropipettes (Eppendorf, Hamburg, Germany) (Table 1).For each of the five sets of experiments, two different grinding procedures were carried out: (i) direct LAG for 60 min of PZQ in the presence of H2O'solvent mixture (Di-LAG); (ii) NG for 30 min of anhydrous PZQ followed by 1 h LAG with H2O'solvent mixture (NG+LAG).The mechanochemical products were stored in a desiccator at room temperature and characterized the day after preparation by powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) (see Section 2.3.1 and Section 2.3.2).

2.2.2. Solvent Properties

As previously mentioned, five different solvents were chosen considering both their ability to form PZQ solvates and their miscibility with H2O, to evaluate the effect of each solvent on PZQ-HH formation (possible H2O'solvent competitivity). These two characteristics are summarized in Table 2.In this research, other solvent properties (such as interfacial tension, boiling temperature, API dissolution rate in solvents, density, viscosity, etc.) were not considered because, in our previous work, we noticed that there was no direct correlation between the experimental results and the characteristics of the solvent considered [4]. The same was applied for H2O activity [4], which cannot be calculated in this survey because the H2O activity equation cannot be applied in the case of using H2O-immiscible solvents.

2.2.3. Mechanochemical Interconversion Experiments

Preformed PZQ-HH was also used as a starting material in a series of mechanochemical interconversion experiments based on the experimental work on theophylline [4]. PZQ-HH was prepared mechanochemically, following the procedure reported by Zanolla and coauthors [21].The interconversion milling experiments were performed by adding the amount of liquid needed to give a PZQ/solvent 1:1 molar ratio, considering the amount of H2O in the crystalline lattice of preformed PZQ-HH. The transformation of the selected molar ratios into practical volumes was performed by considering the density of the liquids at 25° C [51]. Table 3 summarizes the micromolar amount of each solvent used for the five sets of experiments.The process conditions (e.g., milling time and frequency, number and size of milling media) were kept fixed.

2.3. Sample Characterization

As mentioned in the introduction, all ground products were characterized through PXRD and DSC by comparison with anhydrous PZQ Form A, B, PZQ-AA and PZQ-2-pyr monosolvates (in the case of using AA and 2-pyr as second solvents) and PZQ-HH.

2.3.1. Powder X-ray Diffraction (PXRD)

PXRD analyses were carried out by a Bruker D2 Phaser benchtop diffractometer (Bruker, Manheim, Germany) using the Bragg'Brentano geometry and Cu-Kα radiation (λ = 1. Å) with a 300 W low-power X-ray generator (30 kV at 10 mA). All the measurements were conducted in a 2θ range of 3'40° with a step size of 0.02° and a scan speed of 0.6°/s.Each sample was prepared by gently pressing approximately 200 mg of ground product into the cavity of a steel sample holder equipped with a cylindrical polyvinylidene fluoride (PVDF) reducer.

2.3.2. Differential Scanning Calorimetry (DSC)

For DSC analysis, each sample weighing 2'4 mg was introduced into an aluminum sealed and pierced 40 μL crucible and analyzed by a Mettler Toledo DSC 3 Star System (Milan, Italy) with a heating program of 30'160 °C (10 °C/min) under a nitrogen atmosphere (50 mL/min flow rate).

3. Results

The results of the experimental work are presented below and organized in different sections as a function of the type of H2O'second solvent mixture. For the sake of simplicity, the PXRD and DSC results are only presented for the first set of experiments considered (H2O-AA mixture); in the case of the other four sets, the results are reported as qualitative tables, to make more immediate and intuitive the comparison with Form A, B, PZQ-2-pyr and PZQ-HH. PXRD and DSC analyses of these sets are reported in the Supporting Information (SI) File. Also, the Di-LAG results for all five H2O'second solvent mixtures are reported in the SI file (Figures S1'S10), as the copresence of a second liquid during grinding, rather than promoting PZQ-HH formation, always gave origin to PZQ Form A, confirming NG as a mandatory preliminary step for the synthesis of the hemihydrate. Thus, only NG+LAG results will be presented below.

3.1. Grinding Tests in the Presence of H2O-AA Mixture

Figure 2 and Figure 3 show the PXRD and DSC results of the tests of the H2O-AA mixture in the NG+LAG procedure.In this set of experiments, PZQ-HH appeared in only one case, e.g., when PZQ was ground in the presence of pure H2O, whereas the presence of even small amounts of AA (i.e., H2O/AA molar fractions of 1.80:0.20) avoided the formation of the hemihydrate, suggesting a strong competitive effect between the two miscible liquids.The formation of PZQ-HH was attested by PXRD from the characteristic peaks at 6°, 16° and 18'19° 2θ (see the bottom pattern in Figure 2) and from the typical dehydration at about 70'75 °C in DSC (bottom curve in Figure 3).Considering the formation of PZQ-AA monosolvate, we observed the complete conversion of anhydrous PZQ in PZQ-AA up to a H2O/AA molar fraction of 0.66:1.34, even though at lower AA molar fractions (i.e., H2O/AA 1:1), the amount of AA was sufficient to form the monosolvate as a pure phase. On the one hand, from the PXRD results (Figure 2), it is possible to note that the intensity of the characteristic peaks of the monosolvate at 6.3°, 9.3°, 15.6°, 17.8°, 22.7° and 23.16° 2 progressively decreases as the molar fraction of AA in the H2O-AA mixture decreases. On the other hand, starting from a 1:1 H2O/AA molar fraction, characteristic peaks of anhydrous Form A (at 4°, 6'7°, 8° e 12'13° 2θ) appear and become more intense as the quantity of H2O increases, up to the appearance of PZQ-HH at 2:0 of H2O/AA. Noteworthy is the fact that the formation of PZQ-AA was observed up to a H2O/AA molar fraction of 1.50:0.50, while proportions of 1.80:0.20 gave anhydrous Form A, even though a small amount of AA is still present and theoretically able to form the monosolvate.The DSC results (Figure 3) were consistent with the PXRD analyses: the typical desolvation band of PZQ-AA at 70'75 °C, visible in the case of grinding PZQ with pure AA, gradually becomes less intense and defined'moving at lower temperatures'with a decreased AA molar fraction. From H2O/AA proportions of 1:1, it is possible to note the copresence of the melting peak of Form A, as also attested from PXRD results. The PZQ-AA desolvation band disappears in the presence of a H2O/AA molar ratio of 1.80:0.20, which, instead, shows the melting peak of Form A. The DSC curve shown at the bottom of Figure 3 corresponds to the PZQ-HH thermogram (H2O/AA molar fraction of 2:0). In this thermogram, its typical dehydration range at about 75 °C is visible, followed by the melting of Form A, shifted at lower temperatures due to the particle size reduction during grinding [57].Despite the similarity between PZQ-HH and polymorph B of PZQ, in such a set of grindings, rather than observing the formation of Form B, the only outcome was Form A, as evident from the PXRD and DSC analyses.

3.2. Grinding Tests in the Presence of H2O-2-pyr Mixture

Figure 4 qualitatively summarizes the results obtained from grinding tests in the presence of H2O-2-pyr mixtures. The PXRD and DSC results are reported in the SI File (Figures S11 and S12). Grinding PZQ with 2-pyr as an individual solvent caused the formation of PZQ-2-pyr monosolvate with a decreasing yield as the 2-pyr molar fraction in the aqueous mixture decreased. In parallel, a progressive increase in the signals both in PXRD and DSC (Figures S12 and S13) corresponding to anhydrous Form A was noticed. As noticed in the previous H2O-AA case, the formation of PZQ-2-pyr monosolvate was detected up to a 0.50:0.50 H2O/2-pyr molar ratio; after that extent, only PZQ Form A was observed or PZQ-HH, when H2O was used as an individual solvent.Again, in no case was the formation of anhydrous polymorph B observed.

3.3. Grinding Tests in the Presence of H2O-EtOH Mixture

According to the previous experimental work of Zanolla and coauthors [24], EtOH does not produce any PZQ solvate when used through LAG, but it has a well-known high miscibility with H2O (see Table 2 in Section 2.2.2).As in the previous H2O-AA and H2O-2-pyr cases, the formation of PZQ-HH was observed in the case of using pure H2O (e.g., molar fractions of H2O/EtOH of 1:0), and even H2O/EtOH molar fractions of 0.90:0.10 did not give rise to PZQ-HH, confirming a strong competitive effect between the miscible liquids.The outcomes after grinding with all H2O/EtOH molar fractions were the same: the only product recovered was the starting solid, PZQ Form A, and no traces of Form B emerged. The results are reported in Figure 5 as a qualitative table, whereas PXRD patterns and DSC curves are reported in the SI File (Figures S13 and S14).

3.4. Grinding Tests in the Presence of H2O-EA Mixtures

According to solubility properties (see Section 2.2.2), the polar aprotic EA is slightly miscible in H2O, so one would expect an increased formation of PZQ-HH, even at H2O/EA molar fractions different from 1:0 (e.g., 0.90:0.10, 0.75:0.25, 0.67:0.33). However, as shown in Figure 6 (see Figures S15 and S16 in the SI file for PXRD and DSC results), the results obtained were identical to those previously described for EtOH: the formation of PZQ-HH was observed only when PZQ was ground in the presence of pure H2O, whereas all the liquid mixtures gave anhydrous Form A.

3.5. Grinding Tests in the Presence of H2O-HXN Mixtures

Non-polar HXN, which is completely H2O-immiscible, was demonstrated to be the only solvent able to produce PZQ-HH with two liquid mixtures: 0.90:0.10 H2O/HXN and, as usual, pure H2O. For all other H2O/HXN molar fractions, starting PZQ Form A was the unique recovered solid phase, and no traces of other PZQ polymorphs were detected. PXRD and DSC results are reported in Figures S17 and S18 in the SI file, while a qualitative representation is shown in Figure 7.

3.6. Mechanochemical Interconversion Experiments

This set of experiments was conducted by grinding preformed PZQ-HH in the presence of the above-mentioned five solvents as individual liquids (see Figure 8 for qualitative results and Figures S19 and S20 for PXRD and DSC results). The objectives of this set of experiments could be divided into two categories depending on the type of second solvent used. Specifically, in the case of using AA and 2-pyr, which form PZQ solvates, we wanted to understand if PZQ-HH is stable after grinding or if it preferentially switches into the two solvates, while for the remaining three (not able to form PZQ solvates), the aim was to understand the outcome of an LAG process in the presence of EtOH, EA or HXN. Turning to the results, it is noteworthy that PZQ-HH never persists. On the one hand, with AA and 2-pyr, PZQ-HH converts into the respective monosolvate (with traces of PZQ Form A); on the other hand, EtOH, EA and HXN cause the complete dehydration of PZQ-HH, which converts into the most thermodynamically stable polymorph A of PZQ. Even in this set of experiments, no traces of polymorph B emerged.

4. Discussion

PZQ-HH, a white crystalline powder, has peculiar beneficial properties in comparison to commercially available PZQ Form A (e.g., double solubility and IDR, unaltered in vitro anthelmintic activity, absence of harmful organic solvents) [21]. This study, conducted by mechanochemistry, investigated the influence of five commonly used solvents in addition to H2O (as H2O is often mixed with other solvents in many industrial processes) on the formation of the hydrated crystal.For this aim, the anthelmintic drug PZQ, in its commercially available Form A, was ground in the presence of several H2O'solvent mixtures, through Di-LAG and NG+LAG procedures. Five organic solvents (AA, 2-pyr, EtOH, EA, HXN) were chosen considering their different miscibility with H2O and their capability to form solvates with PZQ. In our previous work, carried out on a different API, we noticed a detrimental effect of the addition of H2O'miscible liquid on the inclusion of H2O in the crystal lattice [4].Interconversion studies between the hydrate/monosolvate/anhydrous forms were also conducted, as PZQ-HH and PZQ solvates have different documented stability upon grinding [21,24].The adopted mechanochemical approach has proven to be an efficient and sustainable technique for solid form screening, as it allows rapid and reproducible information with a very limited number of samples and almost no solvents [46,58], thus demonstrating its superiority over classical solution crystallization or slurry. The PZQ-HH case is one of those examples in which mechanochemistry allows access to a compound that cannot be obtained from solution-based routes. In fact, PZQ-HH, rather than being crystallizable from solution/suspension in H2O from Form A, as usually happens for crystal hydrates, is crystallizable only via a mechanochemically activated form or starting from Form B.The experimental findings here reported confirm and even exalt the conclusions of previous work. PZQ-HH formation is not only reduced but completely prevented in the presence of a second solvent. In some way, the exaltation of this phenomenon is expected, since PZQ-HH has a lower stoichiometry compared to that of theophylline (i.e., hemihydrate for PZQ instead of monohydrate for theophylline). The use of a second solvent has a detrimental effect on the formation of PZQ-HH, and if the solvent is miscible, as in the case of theophylline, this effect is enhanced due to existing interactions between the two miscible liquids, which can be favored with respect to those of singular liquids with the solid. In fact, HXN is the only solvent permitting the mechanochemical crystallization of PZQ-HH to a limited extent. This means that, to obtain a specific pure hydrated phase, more liquid than the pure solid-to-solvent stoichiometric ratio is required. Also, pointing the attention to the opposite site, i.e., the formation of PZQ solvates, in the case of H2O-miscible AA or 2-pyr as second solvents, once again the formation of the two PZQ monosolvates is observed only at solvent molar ratios equal to or greater than 0.5, as for theophylline [4]. Therefore, the use of these two solvents in the presence of H2O reduces their incorporation efficiency in the crystal lattice, and a higher amount than the stoichiometric ratio is necessary to form the two specific solvates as pure phases.It is known from the literature that 2-pyr molecules form energetically favorable heterocomplexes with H2O. The interaction between these two molecules is clearly favored through the formation of hydrogen bonds, which can lead to complex fluid structures. In aqueous-dominated H2O-2-pyr mixtures, the presence of H2O molecules exerts a strong effect on fluid structures, reducing the 2-pyr dimer population to an efficient development of liquid heterostructures [59]. This strong interaction between the two liquids can give a reason for the significant change in the amount of solvent needed to produce pure PZQ-2-pyr solvate. As for AA, it is also well known that AA and H2O have strong interactions, so the separation of the H2O-AA binary solution to obtain pure AA is very difficult. Indeed, AA forms different kinds of association molecules with H2O depending on the composition of the H2O-AA binary mixtures. AA and H2O molecules mainly form a ring-opening association molecule in an aqueous solution, and cyclic AA dimers cannot exist in this environment. Increasing the AA molar fraction, H2O molecules are bound to AA molecules, sacrificing H2O-H2O (or AA'AA at higher molar fractions) interactions and consequently PZQ-H2O (or PZQ-AA) interaction and incorporation [60,61].However, the miscibility of the second solvent cannot be stated as the only factor lowering the efficiency of PZQ-HH formation, as the presence of a second solvent is per se deleterious, probably due to different mechanochemical dynamics inside the jars, resulting in a reduced probability of contact between H2O and solid PZQ upon grinding.As a logical consequence, in none of the samples analyzed in this survey with two contemporaneous solvents is PZQ-HH obtained by Di-LAG. Starting from PZQ Form A, PZQ-HH is formed in the presence of H2O as an individual solvent exclusively via a two-step process, passing through the NG limiting step (which generates an almost amorphous intermediate phase). Therefore, rather than promoting the formation of the PZQ-HH in a one-step procedure, the presence of a second solvent is detrimental even for its formation in the two-step process. Unlike the case of theophylline, where for some liquid compositions, mixed phases have been recovered (i.e., the monosolvate or the sesquisolvate together with the monohydrate), in this research, neither AA nor 2-pyr monosolvate was ever recovered together with the hemihydrate. When a second phase in addition to PZQ monosolvate was retrieved, this was traces of PZQ Form A. These results are in line with the physical stability of the hemihydrate compared to that of solvates and to the superior stability of the solvates upon grinding [21,24].Interconversion grinding experiments confirmed that the solvated forms prevail over the hemihydrate, as the preformed hydrate converts in the presence of AA or 2-pyr into their respective monosolvates. When preformed PZQ-HH was ground in the presence of EtOH, EA and HXN, a complete dehydration of PZQ-HH and a conversion in the most thermodynamically stable polymorph A of PZQ were observed. This means that grinding PZQ-HH, rather than giving rise to PZQ Form B as reported in the literature [21], promotes the formation of Form A in the presence of solvent mixtures. This is a key point, as in the presence of solvent mixes, the system goes to the most stable phase (Form A), counteracting the structural similarity of PZQ-HH and PZQ Form B crystals. Despite the large number of samples processed, in no case did we collect an anhydrous polymorph of PZQ different from commercial Form A, and neither new PZQ solid forms nor mixed solvates (i.e., solids incorporating two solvents in the same crystal lattice) have been obtained. Moreover, no evidence of PZQ monohydrate [23] has ever been found in this experimental research.These relevant data confirm that PZQ exclusively converts into anhydrous polymorphs in the absence of solvents. Indeed, the presence of binary solvent mixtures always produces the starting Form A or (if feasible, i.e., for AA and 2-pyr) PZQ crystal solvates. The overview of the outcome at the end of each mechanochemical process is summarized in Table 4.

5. Conclusions

Racemic praziquantel hemihydrate is a very promising multicomponent crystal, as it presents beneficial properties in comparison to the commercially available racemic anhydrous Form A (e.g., double solubility and intrinsic dissolution rate, unaltered in vitro anthelmintic activity, absence of harmful organic solvents). In this study, conducted by mechanochemistry, we investigated the influence of adding five commonly used solvents to water on the formation of the hydrated crystal. Specifically, anhydrous praziquantel Form A was ground in the presence of several water'solvent mixtures using two grinding procedures (i.e., direct liquid-assisted grinding and neat grinding plus liquid-assisted grinding). Five organic solvents (i.e., acetic acid, 2-pyrrolidone, ethanol, ethyl acetate and hexane) were chosen considering their different miscibility with water and their capability to form solvates with praziquantel (documented for acetic acid and 2-pyrrolidone).The results suggested that the use of a second solvent has a detrimental effect on the formation of the hemihydrate and, if the solvent is miscible, this effect is enhanced due to the existing interactions between the two miscible solvents. In fact, hexane is the only solvent allowing the crystallization of the hydrated form in a limited content. Also, pointing the attention to the formation of praziquantel solvates, their formation was observed only at solvent molar ratios equal to or greater than 0.5, thus demonstrating that the use of these two solvents in the presence of water reduces their incorporation efficiency in the crystal lattice. This means that, to obtain a specific pure hemihydrated or solvated phase, more liquid than the pure solid-to-solvent stoichiometric ratio is required.Moreover, interconversion experiments, conducted between the hydrate/monosolvate/anhydrous forms, revealed a preferential inclusion of solvents over water in the crystal lattice when using acetic acid or 2-pyrrolidone. Conversely, with ethanol, ethyl acetate and hexane, a complete dehydration of the hemihydrate occurred together with a conversion in the most thermodynamically stable polymorph A of praziquantel.Surprisingly, we never assisted in the formation of anhydrous praziquantel polymorph B in the presence of solvent mixes. The grinding outcome in most cases was the most thermodynamically stable Form A, counteracting the structural similarity of PZQ-HH and PZQ Form B crystals.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10./cryst/s1, Figure S1. PXRD results of the tests in the presence of H2O-AA, Di-LAG. Green and grey dotted lines highlight PZQ-AA and PZQ reflections, respectively; Figure S2. DSC results of the tests in the presence of H2O-AA, Di-LAG; Figure S3. PXRD results of the tests in the presence of H2O-2-pyr, Di-LAG. Green and grey dotted lines highlight PZQ-2-pyr and PZQ reflections, respectively; Figure S4. DSC results of the tests in the presence of H2O-2-pyr, Di-LAG; Figure S5. PXRD results of the tests in the presence of H2O-EtOH, Di-LAG; Figure S6. DSC results of the tests in the presence of H2O-EtOH, Di-LAG; Figure S7. PXRD results of the tests in the presence of H2O-EA, Di-LAG; Figure S8. DSC results of the tests in the presence of H2O-EA, Di-LAG; Figure S9. PXRD results of the tests in the presence of H2O-HXN, Di-LAG; Figure S10. DSC results of the tests in the presence of H2O-HXN, Di-LAG; Figure S11. PXRD results of the tests in the presence of H2O-2-pyr, NG+LAG procedure. Green, blue and grey dotted lines highlight PZQ-2-pyr, PZQ-HH and PZQ reflections, respectively; Figure S12. DSC results of the tests in the presence of H2O-2-pyr, NG+LAG procedure; Figure S13. PXRD results of the tests in the presence of H2O-EtOH, NG+LAG procedure. Blue and grey dotted lines highlight PZQ-HH and PZQ reflections, respectively; Figure S14. DSC results of the tests in the presence of H2O-EtOH, NG+LAG procedure; Figure S15. PXRD results of the tests in the presence of H2O-EA, NG+LAG procedure. Blue and grey dotted lines highlight PZQ-HH and PZQ reflections, respectively; Figure S16. DSC results of the tests in the presence of H2O-EA, NG+LAG procedure; Figure S17. PXRD results of the tests in the presence of H2O-HXN, NG+LAG procedure. Blue and grey dotted lines highlight PZQ-HH and PZQ reflections, respectively; Figure S18. DSC results of the tests in the presence of H2O-HXN, NG+LAG procedure; Figure S19. PXRD results of the five interconversion experiments starting from preformed PZQ-HH; Figure S20. DSC results of the five interconversion experiments starting from preformed PZQ-HH.

Author Contributions

Conceptualization, I.D. and B.P.; methodology, I.D.; resources, D.V.; writing'original draft preparation, I.D.; writing'review and editing, I.D., D.V. and B.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.

Acknowledgments

The authors thank Carlo Albino D'Auria for his kind cooperation.

Conflicts of Interest

The authors declare no conflicts of interest.

References

1. Griesser, U.J. The Importance of Solvates. In Polymorphism; Wiley: Hoboken, NJ, USA, ; pp. 211'233. [Google Scholar]
2. ICH Q3C (R8) Residual Solvents'Scientific Guideline|European Medicines Agency. Available online: https://www.ema.europa.eu/en/ich-q3c-r8-residual-solvents-scientific-guideline (accessed on 29 February ).
3. Papadakis, E.; Tula, A.K.; Gani, R. Solvent selection methodology for pharmaceutical processes: Solvent swap. Chem. Eng. Res. Des. , 115, 443'461. [Google Scholar] [CrossRef]
4. D'Abbrunzo, I.; Spadaro, M.; Arhangelskis, M.; Zingone, G.; Hasa, D.; Perissutti, B. Competitive Mechanochemical Solvate Formation of Theophylline in the Presence of Miscible Liquid Mixtures. Cryst. Growth Des. , 23, '. [Google Scholar] [CrossRef]
5. Cioli, D.; Pica-Mattoccia, L.; Basso, A.; Guidi, A. Schistosomiasis Control: Praziquantel Forever? Mol. Biochem. Parasitol. , 195, 23'29. [Google Scholar] [CrossRef] [PubMed]
6. Cioli, D.; Pica-Mattoccia, L. Praziquantel. Parasitol. Res. , 90, S3'S9. [Google Scholar] [CrossRef]
7. Cedillo-Cruz, A.; Aguilar, M.I.; Flores-Alamo, M.; Palomares-Alonso, F.; Jung-Cook, H. A Straightforward and Efficient Synthesis of Praziquantel Enantiomers and Their 4'-Hydroxy Derivatives. Tetrahedron Asymmetry , 25, 133'140. [Google Scholar] [CrossRef]
8. Meister, I.; Ingram-Sieber, K.; Cowan, N.; Todd, M.; Robertson, M.N.; Meli, C.; Patra, M.; Gasser, G.; Keiser, J. Activity of Praziquantel Enantiomers and Main Metabolites against Schistosoma Mansoni. Antimicrob. Agents Chemother. , 58, '. [Google Scholar] [CrossRef] [PubMed]
9. Kovač, J.; Vargas, M.; Keiser, J. In Vitro and in Vivo Activity of R- and S- Praziquantel Enantiomers and the Main Human Metabolite Trans-4-Hydroxy-Praziquantel against Schistosoma Haematobium. Parasit. Vectors , 10, 365. [Google Scholar] [CrossRef] [PubMed]
10. Bagchus, W.M.; Bezuidenhout, D.; Harrison-Moench, E.; Kourany-Lefoll, E.; Wolna, P.; Yalkinoglu, O. Relative Bioavailability of Orally Dispersible Tablet Formulations of Levo- and Racemic Praziquantel: Two Phase I Studies. Clin. Transl. Sci. , 12, 66'76. [Google Scholar] [CrossRef] [PubMed]
11. Shu-Hua, X.; Catto, B.A. Comparative in Vitro and in Vivo Activity of Racemic Praziquantel and Its Levorotated Isomer on Schistosoma Mansoni. J. Infect. Dis. , 159, 589'592. [Google Scholar] [CrossRef]
12. WHO Model List of Essential Medicines'22nd List. . Available online: https://www.who.int/publications/i/item/WHO-MHP-HPS-EML-.02 (accessed on 18 September ).
13. WHO Model List of Essential Medicines for Children'8th List. . Available online: https://www.who.int/publications/i/item/WHO-MHP-HPS-EML-.03 (accessed on 18 September ).
14. FDA Biltricide (Praziquantel) Tablets Label. Available online: https://www.accessdata.fda.gov/drugsatfda_docs/label//s012lbl.pdf (accessed on 4 November ).
15. Zanolla, D.; Perissutti, B.; Passerini, N.; Chierotti, M.R.; Hasa, D.; Voinovich, D.; Gigli, L.; Demitri, N.; Geremia, S.; Keiser, J.; et al. A New Soluble and Bioactive Polymorph of Praziquantel. Eur. J. Pharm. Biopharm. , 127, 19'28. [Google Scholar] [CrossRef] [PubMed]
16. Zanolla, D.; Perissutti, B.; Vioglio, P.C.; Chierotti, M.R.; Gigli, L.; Demitri, N.; Passerini, N.; Albertini, B.; Franceschinis, E.; Keiser, J.; et al. Exploring Mechanochemical Parameters Using a DoE Approach: Crystal Structure Solution from Synchrotron XRPD and Characterization of a New Praziquantel Polymorph. Eur. J. Pharm. Sci. , 140, . [Google Scholar] [CrossRef] [PubMed]
17. Saikia, B.; Seidel-Morgenstern, A.; Lorenz, H. Role of Mechanochemistry in Solid Form Selection and Identification of the Drug Praziquantel. Cryst. Growth Des. , 21, '. [Google Scholar] [CrossRef]
18. de Moraes, M.G.F.; Barreto, A.G., Jr.; Secchi, A.R.; de Souza, M.B., Jr.; Lage, P.L.D.C.; Myerson, A.S. Polymorphism of Praziquantel: Role of Cooling Crystallization in Access to Solid Forms and Discovery of New Polymorphs. Cryst. Growth Des. , 23, '. [Google Scholar] [CrossRef]
19. Meyer, T.; Sekljic, H.; Fuchs, S.; Bothe, H.; Schollmeyer, D.; Miculka, C. Taste, A New Incentive to Switch to (R)-Praziquantel in Schistosomiasis Treatment. PLoS Negl. Trop. Dis. , 3, e357. [Google Scholar] [CrossRef] [PubMed]
20. Liu, Y.; Wang, X.; Wang, J.-K.; Ching, C.B. Investigation of the Phase Diagrams of Chiral Praziquantel. Chirality , 18, 259'264. [Google Scholar] [CrossRef] [PubMed]
21. Zanolla, D.; Hasa, D.; Arhangelskis, M.; Schneider-Rauber, G.; Chierotti, M.R.; Keiser, J.; Voinovich, D.; Jones, W.; Perissutti, B. Mechanochemical Formation of Racemic Praziquantel Hemihydrate with Improved Biopharmaceutical Properties. Pharmaceutics , 12, 289. [Google Scholar] [CrossRef] [PubMed]
22. MacEachern, L.; Kermanshahi-Pour, A.; Mirmehrabi, M. Transformation under Pressure: Discovery of a Novel Crystalline Form of Anthelmintic Drug Praziquantel Using High-Pressure Supercritical Carbon Dioxide. Int. J. Pharm. , 619, . [Google Scholar] [CrossRef] [PubMed]
23. Salazar-Rojas, D.; Maggio, R.M.; Kaufman, T.S. Preparation and Characterization of a New Solid Form of Praziquantel, an Essential Anthelmintic Drug. Praziquantel Racemic Monohydrate. Eur. J. Pharm. Sci. , 146, . [Google Scholar] [CrossRef] [PubMed]
24. Zanolla, D.; Gigli, L.; Hasa, D.; Chierotti, M.R.; Arhangelskis, M.; Demitri, N.; Jones, W.; Voinovich, D.; Perissutti, B. Mechanochemical Synthesis and Physicochemical Characterization of Previously Unreported Praziquantel Solvates with 2-Pyrrolidone and Acetic Acid. Pharmaceutics , 13, . [Google Scholar] [CrossRef] [PubMed]
25. D'Abbrunzo, I.; Bianco, E.; Gigli, L.; Demitri, N.; Birolo, R.; Chierotti, M.R.; Škorić, I.; Keiser, J.; Häberli, C.; Voinovich, D.; et al. Praziquantel Meets Niclosamide: A Dual-Drug Antiparasitic Cocrystal. Int. J. Pharm. , 644, . [Google Scholar] [CrossRef] [PubMed]
26. Espinosa-Lara, J.C.; Guzman-Villanueva, D.; Arenas-García, J.I.; Herrera-Ruiz, D.; Rivera-Islas, J.; Román-Bravo, P.; Morales-Rojas, H.; Höpfl, H. Cocrystals of Active Pharmaceutical Ingredients'Praziquantel in Combination with Oxalic, Malonic, Succinic, Maleic, Fumaric, Glutaric, Adipic, and Pimelic Acids. Cryst. Growth Des. , 13, 169'185. [Google Scholar] [CrossRef]
27. Cappuccino, C.; Spoletti, E.; Renni, F.; Muntoni, E.; Keiser, J.; Voinovich, D.; Perissutti, B.; Lusi, M. Co-Crystalline Solid Solution Affords a High-Soluble and Fast-Absorbing Form of Praziquantel. Mol. Pharm. , 20, '. [Google Scholar] [CrossRef] [PubMed]
28. Liu, Q.; Yang, D.; Chen, T.; Zhang, B.; Xing, C.; Zhang, L.; Lu, Y.; Du, G. Insights into the Solubility and Structural Features of Four Praziquantel Cocrystals. Cryst. Growth Des. , 21, '. [Google Scholar] [CrossRef]
29. Yang, D.; Cao, J.; Heng, T.; Xing, C.; Yang, S.; Zhang, L.; Lu, Y.; Du, G. Theoretical Calculation and Structural Analysis of the Cocrystals of Three Flavonols with Praziquantel. Cryst. Growth Des. , 21, '. [Google Scholar] [CrossRef]
30. Cugovčan, M.; Jablan, J.; Lovrić, J.; Cinčić, D.; Galić, N.; Jug, M. Biopharmaceutical Characterization of Praziquantel Cocrystals and Cyclodextrin Complexes Prepared by Grinding. J. Pharm. Biomed. Anal. , 137, 42'53. [Google Scholar] [CrossRef]
31. Devogelaer, J.J.; Charpentier, M.D.; Tijink, A.; Dupray, V.; Coquerel, G.; Johnston, K.; Meekes, H.; Tinnemans, P.; Vlieg, E.; Ter Horst, J.H.; et al. Cocrystals of Praziquantel: Discovery by Network-Based Link Prediction. Cryst. Growth Des. , 21, '. [Google Scholar] [CrossRef] [PubMed]
32. Rodrigues, S.G.; Chaves, I.d.S.; Melo, N.F.S.; Jesus, M.B.; Fraceto, L.F.; Fernandes, S.A.; Paula, E.; de Freitas, M.P.; Pinto, L.d.M.A. Computational Analysis and Physico-Chemical Characterization of an Inclusion Compound between Praziquantel and Methyl-β-Cyclodextrin for Use as an Alternative in the Treatment of Schistosomiasis. J. Incl. Phenom. Macrocycl. Chem. , 70, 19'28. [Google Scholar] [CrossRef]
33. Rodríguez-Ruiz, C.; Salas-Zúñiga, R.; Obdulia Sánchez-Guadarrama, M.; Delgado-Díaz, A.; Herrera-Ruiz, D.; Morales-Rojas, H.; Höpfl, H. Structural, Physicochemical, and Biopharmaceutical Properties of Cocrystals with RS- and R-Praziquantel'Generation and Prolongation of the Supersaturation State in the Presence of Cellulosic Polymers. Cryst. Growth Des. , 22, '. [Google Scholar] [CrossRef]
34. Yang, S.; Liu, Q.; Ji, W.; An, Q.; Song, J.; Xing, C.; Yang, D.; Zhang, L.; Lu, Y.; Du, G. Cocrystals of Praziquantel with Phenolic Acids: Discovery, Characterization, and Evaluation. Molecules , 27, . [Google Scholar] [CrossRef] [PubMed]
35. Rapeenun, P.; Gerard, C.J.J.; Cartigny, Y.; Tinnemans, P.; De Gelder, R.; Flood, A.E.; Ter Horst, J.H. Searching for Conglomerate Cocrystals of the Racemic Compound Praziquantel. Cryst. Growth Des. , 24, 490. [Google Scholar] [CrossRef]
36. Garrido, C.C.; Vandooren, M.; Robeyns, K.; Debecker, D.P.; Luis, P.; Leyssens, T. Combining a Drug and a Nutraceutical: A New Cocrystal of Praziquantel and Curcumin. Crystals , 14, 181. [Google Scholar] [CrossRef]
37. D'Abbrunzo, I.; Procida, G.; Perissutti, B. Praziquantel Fifty Years on: A Comprehensive Overview of Its Solid State. Pharmaceutics , 16, 27. [Google Scholar] [CrossRef]
38. Tabasum, F.; Sowmyalatha, T.; Omar, M.; Raja Reddy, R. Design of Experiment (Doe) of a New Formulation of Praziquantel by Using Microcrystalline Depolymerized Cellulose. IJAMSCR , 11, 463'470. [Google Scholar] [CrossRef]
39. WHO Part 6. . Available online: https://extranet.who.int/prequal/sites/default/files/whopar_files/NT004part6v1.pdf (accessed on 9 April ).
40. Groom, C.R.; Bruno, I.J.; Lightfoot, M.P.; Ward, S.C. The Cambridge Structural Database. Acta Crystallogr. B Struct. Sci. Cryst. Eng. Mater. , 72, 171'179. [Google Scholar] [CrossRef] [PubMed]
41. Jurczak, E.; Mazurek, A.H.; Szeleszczuk, Ł.; Pisklak, D.M.; Zielińska-Pisklak, M. Pharmaceutical Hydrates Analysis'Overview of Methods and Recent Advances. Pharmaceutics , 12, 959. [Google Scholar] [CrossRef]
42. Bērziņš, A.; Skarbulis, E.; Rekis, T.; Actiņš, A. On the Formation of Droperidol Solvates: Characterization of Structure and Properties. Cryst. Growth Des. , 14, '. [Google Scholar] [CrossRef]
43. Caira, M.R.; Nassimbeni, L.R.; Toda, F.; Vujovic, D. Inclusion of Aminobenzonitrile Isomers by a Diol Host Compound: Structure and Selectivity. J. Am. Chem. Soc. , 122, '. [Google Scholar] [CrossRef]
44. Friščić, T.; Halasz, I.; Strobridge, F.C.; Dinnebier, R.E.; Stein, R.S.; Fábián, L.; Curfs, C. A Rational Approach to Screen for Hydrated Forms of the Pharmaceutical Derivative Magnesium Naproxen Using Liquid-Assisted Grinding. CrystEngComm , 13, . [Google Scholar] [CrossRef]
45. Karki, S.; Friščić, T.; Jones, W.; Motherwell, W.D.S. Screening for Pharmaceutical Cocrystal Hydrates via Neat and Liquid-Assisted Grinding. Mol. Pharm. , 4, 347'354. [Google Scholar] [CrossRef] [PubMed]
46. Hasa, D.; Pastore, M.; Arhangelskis, M.; Gabriele, B.; Cruz-Cabeza, A.J.; Rauber, G.S.; Bond, A.D.; Jones, W. On the Kinetics of Solvate Formation through Mechanochemistry. CrystEngComm , 21, '. [Google Scholar] [CrossRef]
47. Bingham, A.L.; Hughes, D.S.; Hursthouse, M.B.; Lancaster, R.W.; Tavener, S.; Threlfall, T.L. Over One Hundred Solvates of Sulfathiazole. Chem. Comumn. , 7, 603'604. [Google Scholar] [CrossRef]
48. Campeta, A.M.; Chekal, B.P.; Abramov, Y.A.; Meenan, P.A.; Henson, M.J.; Shi, B.; Singer, R.A.; Horspool, K.R. Development of a Targeted Polymorph Screening Approach for a Complex Polymorphic and Highly Solvating API. J. Pharm. Sci. , 99, '. [Google Scholar] [CrossRef] [PubMed]
49. Tan, D.; Loots, L.; Friščić, T. Towards Medicinal Mechanochemistry: Evolution of Milling from Pharmaceutical Solid Form Screening to the Synthesis of Active Pharmaceutical Ingredients (APIs). Chem. Commun. , 52, '. [Google Scholar] [CrossRef] [PubMed]
50. Costa, E.D.; Priotti, J.; Orlandi, S.; Leonardi, D.; Lamas, M.C.; Nunes, T.G.; Diogo, H.P.; Salomon, C.J.; Ferreira, M.J. Unexpected Solvent Impact in the Crystallinity of Praziquantel/Poly(Vinylpyrrolidone) Formulations. A Solubility, DSC and Solid-State NMR Study. Int. J. Pharm. , 511, 983'993. [Google Scholar] [CrossRef] [PubMed]
51. Lide, D.R. Handbook of Organic Solvents; Routledge: London, UK; CRC Press: Boca Raton, FL, USA, . [Google Scholar]
52. Altshuller, A.P.; Everson, H.E. The Solubility of Ethyl Acetate in Water. J. Am. Chem. Soc. , 75, . [Google Scholar] [CrossRef]
53. Carl Roth GmbH. Safety Data Sheet: 2-Pyrrolidone. Available online: https://www.carlroth.com/medias/SDB--GB-EN.pdf?context=bWFzdGVyfHNlY3VyaXR5RGF0YXNoZWV0c3wyNDk5ODB8YXBwbGljYXRpb24vcGRmfHNlY3VyaXR5RGF0YXNoZWV0cy9oMmYvaDVmLzkwNzQ1MTQ1NTkwMDYucGRmfDhhZjU0NWVjZGFhMThlNTY2NmFiMGY2OGQxNThiYTU5MDBiMTc2NzU5NjU2YjllYWUwMWE0NjE4OGY2NzE1MzY (accessed on 29 February ).
54. McNaught, A.D.; Wilkinson, A. The IUPAC Compendium of Chemical Terminology, 2nd ed.; Gold, V., Ed.; International Union of Pure and Applied Chemistry (IUPAC): Research Triangle Park, NC, USA, . [Google Scholar]
55. Carl Roth GmbH. Safety Data Sheet: N-Hexane. Available online: https://www.carlroth.com/medias/SDB-CP47-IE-EN.pdf?context=bWFzdGVyfHNlY3VyaXR5RGF0YXNoZWV0c3wzMDYwMTN8YXBwbGljYXRpb24vcGRmfHNlY3VyaXR5RGF0YXNoZWV0cy9oNjYvaDE2LzkwNjAzNzY4MDU0MDYucGRmfGU3NjdjNGYxZjI0ZTNjMDhjNTU4NGRiYjZkMTc3MWNmNjRlNmQxNWFmYWZjZmMyMTMwNTA3NjU2ODJhNjQ5OGU (accessed on 29 February ).
56. Riddick, J.A.; Bunger, W.B.; Sakano, T.K. Organic Solvents: Physical Properties and Methods of Purification, 4th ed.; U.S. Department of Energy, Office of Scientific and Technical Information: Oak Ridge, TN, USA, . [CrossRef]
57. Hasa, D.; Voinovich, D.; Perissutti, B.; Grassi, G.; Fiorentino, S.; Farra, R.; Abrami, M.; Colombo, I.; Grassi, M. Reduction of Melting Temperature and Enthalpy of Drug Crystals: Theoretical Aspects. Eur. J. Pharm. Sci. , 50, 17'28. [Google Scholar] [CrossRef] [PubMed]
58. Hasa, D.; Jones, W. Screening for New Pharmaceutical Solid Forms Using Mechanochemistry: A Practical Guide. Adv. Drug Deliv. Rev. , 117, 147'161. [Google Scholar] [CrossRef] [PubMed]
59. Dávila, M.J.; Alcalde, R.; Aparicio, S. Pyrrolidone Derivatives in Water Solution: An Experimental and Theoretical Perspective. Ind. Eng. Chem. Res. , 48, '. [Google Scholar] [CrossRef]
60. Yang, B.; Li, Y.; Gong, N.; Cao, X.; Wang, S.; Sun, C. Study of Molecular Association in Acetic Acid-Water Binary Solution by Raman Spectroscopy. Spectrochim. Acta A Mol. Biomol. Spectrosc. , 213, 463'466. [Google Scholar] [CrossRef] [PubMed]
61. Bag, S.; Pezzotti, S.; Das Mahanta, D.; Schulke, S.; Schwaab, G.; Havenith, M. From Local Hydration Motifs in Aqueous Acetic Acid Solutions to Macroscopic Mixing Thermodynamics: A Quantitative Connection from THz-Calorimetry. J. Phys. Chem. B , 127, '. [Google Scholar] [CrossRef] [PubMed]

Figure 1. Crystal structures of commercial PZQ Form A (racemic form, bottom centre) compared to PZQ hemihydrate (PZQ-HH, top) and racemic PZQ acetic acid monosolvate (PZQ-AA, bottom left) and racemic PZQ 2-pyrrolidone monosolvate (PZQ-2-pyr, bottom right). Figure 2. PXRD results of the tests in the presence of H2O-AA mixture. Green, blue and grey dotted lines highlight PZQ-AA, PZQ-HH and PZQ reflections, respectively. Figure 3. DSC results of the tests conducted in the presence of H2O-AA mixture. Figure 4. Solid phases recovered from each molar fraction of H2O-2-pyr mixtures. Green circles stand for solid phase present and red circles for solid phase absent. Figure 5. Solid phases recovered from each molar fraction of H2O-EtOH mixtures. Green circles stand for solid phase present and red circles for solid phase absent. Figure 6. Solid phases recovered from each molar fraction of H2O-EA mixtures. Green circles stand for solid phase present and red circles for solid phase absent. Figure 7. Solid phases recovered from each molar fraction of H2O-HXN mixtures. Green circles stand for solid phase present and red circles for solid phase absent. Figure 8. Solid phases recovered from the interconversion milling experiments. Green circles stand for solid phase present and red circles for solid phase absent. Table 1. Composition of the liquid added during grinding experiments to 400 mg of PZQ Form A (solid). Solvent Molar Fractions H2O00.250.330.500.670.750.90 *1Second Solvent **10.750.670.500.330.250.10 *0 Table 2. Ability to form PZQ solvates and miscibility values in H2O of the five screened solvents. SolventsAA 2-pyrEtOHEAHXNKnown PZQ solvates
[18,21,22,23,24,31]YesYesNoNoNoMiscibility with H2O [51,52,53,54,55,56]Miscible
g/LMiscible
>65 g/L Miscible
100 g/LSlightly miscible
0.8 g/LImmiscible
<0.1 g/L Table 3. Overview of the mechanochemical interconversion experiments. Starting Solid
(PZQ-HH)AA 2-pyrEtOHEAHXN411.5 mg73 μL 98 μL75 μL125 μL167 μL Table 4. Nature of praziquantel polymorphs obtained in the presence of different solvent mixtures. Initial PolymorphMethod/TechniqueCondition/DurationOutcomePZQ Form ALAG with H2ONG+LAGPZQ-HHPZQ Form ALAG with H2ODi-LAGPZQ Form APZQ Form A Slurry [21]7 daysPZQ Form APZQ Form BSlurry [21]3 daysPZQ-HHPZQ-HHNG [21]60 minPZQ Form BPZQ Form ALAG with H2O-EtOHNG+LAG
or Di-LAGPZQ Form APZQ Form ALAG with H2O-EANG+LAG
or Di-LAGPZQ Form APZQ Form ALAG with
0.9 H2O'0.1 HXNNG+LAGPZQ-HHPZQ Form ALAG with H2O-HXNNG+LAG
or Di-LAGPZQ Form APZQ Form ALAG with H2O-AA ('0.5AA)NG+LAG
or Di-LAGPZQ-AAPZQ Form ALAG with H2O-2-pyr ('0.5AA)NG+LAG
or Di-LAGPZQ-2-pyrPZQ Form ALAG with H2O-AA (<0.5AA)NG+LAG
or Di-LAGPZQ Form APZQ Form ALAG with H2O-2-pyr (<0.5AA)NG+LAG
or Di-LAGPZQ Form APZQ-HHLAG with AADi-LAGPZQ-AAPZQ Form ALAG with 2-pyr Di-LAGPZQ-2-pyrPZQ Form ALAG with EtOH or EA or HXNDi-LAGPZQ Form A Disclaimer/Publisher's Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
© by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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D'Abbrunzo, I.; Voinovich, D.; Perissutti, B. Mechanochemical Synthesis of Praziquantel Hemihydrate in the Presence of Five Solvents with Different Water Miscibility. Crystals , 14, 374. https://doi.org/10./cryst

AMA Style

D'Abbrunzo I, Voinovich D, Perissutti B. Mechanochemical Synthesis of Praziquantel Hemihydrate in the Presence of Five Solvents with Different Water Miscibility. Crystals. ; 14(4):374. https://doi.org/10./cryst

Chicago/Turabian Style

D'Abbrunzo, Ilenia, Dario Voinovich, and Beatrice Perissutti. . "Mechanochemical Synthesis of Praziquantel Hemihydrate in the Presence of Five Solvents with Different Water Miscibility" Crystals 14, no. 4: 374. https://doi.org/10./cryst

APA Style

D'Abbrunzo, I., Voinovich, D., & Perissutti, B. (). Mechanochemical Synthesis of Praziquantel Hemihydrate in the Presence of Five Solvents with Different Water Miscibility. Crystals, 14(4), 374. https://doi.org/10./cryst

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