Development of Continuous Additive-Controlled MSMPR Crystallization by DoE-Based Batch Experiments.

Additive-controlled crystallization is a promising method to improve crystal morphology and produce solid drug particles with the desired technological and pharmacological properties. However, its adaptation to continuous operation is a hardly researched area. Accordingly, in this work, we aimed to come up with a methodology that provides the systematic and fast development of a continuous three-stage MSMPR cascade crystallizer. For that, a cooling crystallization of famotidine (FMT) from water, in the presence of a formulation additive, poly(vinylpyrrolidone) (PVP-K12), was developed. Process parameters with a significant impact on product quality and quantity were examined in batch mode through a 24-1 fractional factorial design for the implementation of additive-controlled continuous crystallization. These batch experiments represented one residence time of the continuous system. Based on the statistical analysis, the residence time (RT) had the highest effect on yield, while the polymer amount was critical from the product polymorphism, crystal size, and flowability points of view. The values of critical process parameters in continuous operation were fixed according to the batch results. Two continuous cooling crystallization experiments were carried out, one with 1.25 w/wFMT% PVP-K12 and one with no additive. A mixture of FMT polymorphs (Form A and Form B) crystallized without the additive through five residence times (>6.5 h) with 70.8% overall yield. On the other hand, the additive-controlled continuous experiment resulted pure and homogeneous Form A product with excellent flowability. The system could be operated for >6.5 h without clogging with a 71.1% overall yield and a 4-fold improvement in productivity compared to its batch equivalent.

Explainable deep recurrent neural networks for the batch analysis of a pharmaceutical tableting process in the spirit of Pharma 4.0.

Due to the continuously increasing Cost of Goods Sold, the pharmaceutical industry has faced several challenges, and the Right First-Time principle with data-driven decision-making has become more pressing to sustain competitiveness. Thus, in this work, three different types of artificial neural network (ANN) models were developed, compared, and interpreted by analyzing an open-access dataset from a real pharmaceutical tableting production process. First, the multilayer perceptron (MLP) model was used to describe the total waste based on 20 raw material properties and 25 statistical descriptors of the time series data collected throughout the tableting (e.g., tableting speed and compression force). Then using 10 process time series data in addition to the raw material properties, the cumulative waste, during manufacturing was also predicted by long short-term memory (LSTM) and bidirectional LSTM (biLSTM) recurrent neural networks (RNN). The LSTM network was used to forecast the waste production profile to allow preventive actions. The results showed that RNNs were able to predict the waste trajectory, the best model resulting in 1096 and 2174 tablets training and testing root mean squared errors, respectively. For a better understanding of the process, and the models and to help the decision-support systems and control strategies, interpretation methods were implemented for all ANNs, which increased the process understanding by identifying the most influential material attributes and process parameters. The presented methodology is applicable to various critical quality attributes in several fields of pharmaceutics and therefore is a useful tool for realizing the Pharma 4.0 concept.

Improvement of drug processability in a connected continuous crystallizer system using formulation additive.

Continuous crystallization in the presence of polymer additives is a promising method to omit some drug formulation steps by improving the technological and also pharmacological properties of crystalline active ingredients. Accordingly, this study focuses on developing an additive-assisted continuous crystallization process using polyvinylpyrrolidone in a connected ultrasonicated plug flow crystallizer and an overflow mixed suspension mixed product removal (MSMPR) crystallizer system. We aimed to improve the flowability characteristics of small, columnar primary plug flow crystallizer-produced acetylsalicylic acid crystals as a model drug by promoting their agglomeration in MSMPR crystallizer with polyvinylpyrrolidone. The impact of the cooling antisolvent crystallization process parameters (temperature, polymer amount, total flow rate) on product quality and quantity was investigated. Finally, a spatially segmented antisolvent dosing method was also evaluated. The developed technology enabled the manufacture of purified, constant quality products in a short startup period, even with an 85% yield. We found that a higher polymer amount (7.5-14%) could facilitate agglomeration resulting in "good" flowability without altering the favorable dissolution characteristics of the primary particles.

Soft sensor for content prediction in an integrated continuous pharmaceutical formulation line based on the residence time distribution of unit operations.

In this study, a concentration predicting soft sensor was achieved based on the Residence Time Distribution (RTD) of an integrated, three-step pharmaceutical formulation line. The RTD was investigated with color-based tracer experiments using image analysis. Twin-screw wet granulation (TSWG) was directly coupled with a horizontal fluid bed dryer and an oscillating mill. Based on integrated measurement, we proved that it is also possible to couple the unit operations in silico. Three surrogate tracers were produced with a coloring agent to investigate the separated unit operations and the solid and liquid inputs of the TSWG. The soft sensor's prediction was compared to validating experiments of a 0.05 mg/g (15% of the nominal) concentration change with High-Performance Liquid Chromatography (HPLC) reference measurements of the active ingredient proving the adequacy of the soft sensor (RMSE < 4%).

Applications of machine vision in pharmaceutical technology: A review.

The goal of this paper is to give an introduction to analysis of images acquired by a digital camera with visible illumination and to review its applications as a Process Analytical Technology (PAT) which has great potential in pharmaceutical manufacturing. By utilizing in-line analytical techniques, it is possible to monitor the quality of all the material leaving a processing unit and to create models capable to predict product quality attributes, which are otherwise measured by cumbersome off-line techniques. The rapidly developing machine vision has proven its versatility in numerous applications and it has great potential as an in-line analytical tool. The ongoing conversion of the pharmaceutical industry from batch to continuous manufacturing accelerated the development of digital image analysis methods in the last decade. Among numerous other benefits, continuous technologies, equipped with digital image analysis, enable detecting disturbances in the material flow, and analyzing the products comprehensively. The purpose of this work is to give an insight into the currently available image analysis methods in the characterization of powders, crystallization, granulation, milling, mixing, tableting, film coating, in vitro dissolution testing, and residence time distribution measurements by highlighting some of the most relevant examples of application.

Process Design of Continuous Powder Blending Using Residence Time Distribution and Feeding Models.

The present paper reports a thorough continuous powder blending process design of acetylsalicylic acid (ASA) and microcrystalline cellulose (MCC) based on the Process Analytical Technology (PAT) guideline. A NIR-based method was applied using multivariate data analysis to achieve in-line process monitoring. The process dynamics were described with residence time distribution (RTD) models to achieve deep process understanding. The RTD was determined using the active pharmaceutical ingredient (API) as a tracer with multiple designs of experiment (DoE) studies to determine the effect of critical process parameters (CPPs) on the process dynamics. To achieve quality control through material diversion from feeding data, soft sensor-based process control tools were designed using the RTD model. The operation block model of the system was designed to select feasible experimental setups using the RTD model, and feeder characterizations as digital twins, therefore visualizing the output of theoretical setups. The concept significantly reduces the material and instrumental costs of process design and implementation.

Raman-based dynamic feeding strategies using real-time glucose concentration monitoring system during adalimumab producing CHO cell cultivation.

The use of Process Analytical Technology tools coupled with chemometrics has been shown great potential for better understanding and control of mammalian cell cultivations through real-time process monitoring. In-line Raman spectroscopy was utilized to determine the glucose concentration of the complex bioreactor culture medium ensuring real-time information for our process control system. This work demonstrates a simple and fast method to achieve a robust partial least squares calibration model under laboratory conditions in an early phase of the development utilizing shake flask and bioreactor cultures. Two types of dynamic feeding strategies were accomplished where the multi-component feed medium additions were controlled manually and automatically based on the Raman monitored glucose concentration. The impact of these dynamic feedings was also investigated and compared to the traditional bolus feeding strategy on cellular metabolism, cell growth, productivity, and binding activity of the antibody product. Both manual and automated dynamic feeding strategies were successfully applied to maintain the glucose concentration within a narrower and lower concentration range. Thus, besides glucose, the glutamate was also limited at low level leading to reduced production of inhibitory metabolites, such as lactate and ammonia. Consequently, these feeding control strategies enabled to provide beneficial cultivation environment for the cells. In both experiments, higher cell growth and prolonged viable cell cultivation were achieved which in turn led to increased antibody product concentration compared to the reference bolus feeding cultivation.

Revisit of solubility of oxytetracycline polymorphs. An old story in the light of new results.

In the literature the therapeutic nonequivalence of oxytetracycline hydrochloride (OTCH) capsules and tablets was attributed to the different aqueous solubility of polymorphs without their comprehensive study. Our aim was to reveal the effects of polymorphism on equilibrium solubility, dissolution kinetics and the supersaturation of two OTCH polymorphs (stable Form A and metastable Form B).The equilibrium solubility was measured in biorelevant pH range 4-7.4 by the standardized saturation shake-flask method. We also studied the solubility in SGF at pH 1.2 and the effect of the pH change from 1.2 to 5.0 on solubility. The dissolution was studied using real-time concentration monitoring with an ATR probe attached to a UV spectrophotometer (µDISS Profiler). A wide spectrum of solid phase analysis methods (SEM, IR, XRPD, Raman) was applied for characterization of polymorphs and to identify which form is present at the equilibrium solubility. Identical equilibrium solubility values were obtained at the same pHs in region 4.0-7.4 using the two polymorphs as starting materials. The XRPD analysis of the isolated solid phases proved that both polymorphic forms were converted to dihydrate form. In situ monitoring of the dissolution at pH 5.0 showed immediate dissolution, no difference in supersaturation, and short equilibration time for both forms indicating the immediate conversion. In SGF (pH 1.2) Form B dissolved better than Form A and showed significantly different dissolution kinetic and stability. A long-lasting, false chain-citation stating that Form B dissolves 28x better in water than Form A, was cut by the present study (i) revealing that the cited data was measured in IPA not in water, and (ii) proving that only the intrinsic solubility of OTC dihydrate can be measured in water due to conversion of polymorphs under the experimental conditions of solubility measurement. However this conversion is inhibited below pH 1.5, so the differences in solubility and dissolution kinetic found at pH 1.2 may contribute to the interpretation of the different serum-levels reported at solid formulations.

End-to-end continuous manufacturing of conventional compressed tablets: From flow synthesis to tableting through integrated crystallization and filtration.

An end-to-end continuous pharmaceutical manufacturing process was developed for the production of conventional direct compressed tablets on a proof-of-concept level for the first time. The output reaction mixture of the flow synthesis of acetylsalicylic acid was crystallized continuously in a mixed suspension mixed product removal crystallizer. The crystallizer was directly connected to a continuous filtration carousel device, thus the crystallization, filtration and drying of acetylsalicylic acid (ASA) was carried out in an integrated 2-step process. Steady state was reached during longer operations and the interaction of process parameters was evaluated in a series of experiments. The filtered crystals were ready for further processing in a following continuous blending and tableting experiment due to the good flowability of the material. The ASA collected during the crystallization-filtration experiments was fed into a continuous twin-screw blender along with microcrystalline cellulose as tableting excipient. After continuous blending Near-Infrared spectroscopy was applied to in-line analyze the drug content of the powder mixture. A belt conveyor carried the mixture towards an eccentric lab-scale tablet press, which continuously produced 500 mg ASA-loaded compressed tablets of 100 mg dose strength. Thus, starting from raw materials, the final drug product was obtained by continuous manufacturing steps with appropriate quality.

Videometric mass flow control: A new method for real-time measurement and feedback control of powder micro-feeding based on image analysis.

The present paper reports the first monitoring and control of ultra-low dose powder feeding using a camera image-based mass flow measurement system. Caffeine was fed via a single-screw microfeeder as a model active pharmaceutical ingredient (API). The mass, mass flow and sizes of the particles were successfully monitored in real-time by the developed videometric system consisting of a high-speed process camera coupled with an image analysis software. The system was also tested in feedback control mode to automatically reach the desired mass flow values by adjusting the feeder speed based on the mass flow measured by the image analysis system. Based on these features, the developed videometric system can serve as a multi-purpose PAT-tool and can provide valuable real-time information about the process which is indispensable for modern continuous pharmaceutical manufacturing.

Prediction of Bioequivalence and Food Effect Using Flux- and Solubility-Based Methods.

In this work, two different approaches have been developed to predict the food effect and the bioequivalence of marketed itraconazole (ITRA) formulations. Kinetic solubility and simultaneous dissolution-permeation tests of three (ITRA) formulations (Sporanox capsules and solution and SUBA-ITRA capsules) were carried out in simulated fasted and fed states. Fraction of dose absorbed ratios estimating food effect and bioequivalence were calculated based on these results and were compared to the in vivo study results published by Medicines Agencies. The comparison demonstrated that kinetic solubility and flux values could be used as input parameters for biopharmaceutics modeling and simulations to estimate food effect and bioequivalence. Both prediction methods were able to determine a slightly negative food effect in the case of the Sporanox solution and also a pronounced positive food effect for the Sporanox capsule. Superior bioavailability was predicted when the Sporanox solution was compared to the Sporanox capsule (in agreement with in vivo data).

Inline noninvasive Raman monitoring and feedback control of glucose concentration during ethanol fermentation.

Raman spectroscopy as a process analytical technology tool was implemented for the monitoring and control of ethanol fermentation carried out with Saccharomyces cerevisiae. The need for the optimization of bioprocesses such as ethanol production, to increase product yield, enhanced the development of control strategies. The control system developed by the authors utilized noninvasive Raman measurements to avoid possible sterilization problems. Real-time data analysis was applied using partial least squares regression (PLS) method. With the aid of spectral pretreatment and multivariate data analysis, the monitoring of glucose and ethanol concentration was successful during yeast fermentation with the prediction error of 4.42 g/L for glucose and 2.40 g/L for ethanol. By Raman spectroscopy-based feedback control, the glucose concentration was maintained at 100 g/L by the automatic feeding of concentrated glucose solution. The control of glucose concentration during fed-batch fermentation resulted in increased ethanol production. Ethanol yield of 86% was achieved compared to the batch fermentation when 75% yield was obtained. The results show that the use of Raman spectroscopy for the monitoring and control of yeast fermentation is a promising way to enhance process understanding and achieve consistently high production yield.

Real-time feedback control of twin-screw wet granulation based on image analysis.

The present paper reports the first dynamic image analysis-based feedback control of continuous twin-screw wet granulation process. Granulation of the blend of lactose and starch was selected as a model process. The size and size distribution of the obtained particles were successfully monitored by a process camera coupled with an image analysis software developed by the authors. The validation of the developed system showed that the particle size analysis tool can determine the size of the granules with an error of less than 5 µm. The next step was to implement real-time feedback control of the process by controlling the liquid feeding rate of the pump through a PC, based on the real-time determined particle size results. After the establishment of the feedback control, the system could correct different real-life disturbances, creating a Process Analytically Controlled Technology (PACT), which guarantees the real-time monitoring and controlling of the quality of the granules. In the event of changes or bad tendencies in the particle size, the system can automatically compensate the effect of disturbances, ensuring proper product quality. This kind of quality assurance approach is especially important in the case of continuous pharmaceutical technologies.

On-line prediction of the glucose concentration of CHO cell cultivations by NIR and Raman spectroscopy: Comparative scalability test with a shake flask model system.

In this study, near-infrared (NIR) and Raman spectroscopy were compared in parallel to predict the glucose concentration of Chinese hamster ovary cell cultivations. A shake flask model system was used to quickly generate spectra similar to bioreactor cultivations therefore accelerating the development of a working model prior to actual cultivations. Automated variable selection and several pre-processing methods were tested iteratively during model development using spectra from six shake flask cultivations. The target was to achieve the lowest error of prediction for the glucose concentration in two independent shake flasks. The best model was then used to test the scalability of the two techniques by predicting spectra of a 10l and a 100l scale bioreactor cultivation. The NIR spectroscopy based model could follow the trend of the glucose concentration but it was not sufficiently accurate for bioreactor monitoring. On the other hand, the Raman spectroscopy based model predicted the concentration of glucose in both cultivation scales sufficiently accurately with an error around 4mM (0.72g/l), that is satisfactory for the on-line bioreactor monitoring purposes of the biopharma industry. Therefore, the shake flask model system was proven to be suitable for scalable spectroscopic model development.

Oral bioavailability enhancement of flubendazole by developing nanofibrous solid dosage forms.

The bioavailability of the anthelminthic flubendazole was remarkably enhanced in comparison with the pure crystalline drug by developing completely amorphous electrospun nanofibres with a matrix consisting of hydroxypropyl-ß-cyclodextrin and polyvinylpyrrolidone. The thus produced formulations can potentially be active against macrofilariae parasites causing tropical diseases, for example, river blindness and elephantiasis, which affect altogether more than a hundred million people worldwide. The bioavailability enhancement was based on the considerably improved dissolution. The release of a dose of 40 mg could be achieved within 15 min. Accordingly, administration of the nanofibrous system ensured an increased plasma concentration profile in rats in contrast to the practically non-absorbable crystalline flubendazole. Furthermore, easy-to-grind fibers could be developed, which enabled compression of easily administrable immediate release tablets.

Quantification and handling of nonlinearity in Raman micro-spectrometry of pharmaceuticals.

This work demonstrates how nonlinearity in Raman spectrometry of pharmaceuticals can be handled and accurate quantification can be achieved by applying certain chemometric methods including variable selection. Such approach proved to be successful even if the component spectra are very similar or spectral intensities of the constituents are strongly different. The relevant examples are: blends of two crystalline forms of carvedilol ("CRYST-PM" blend) and a three-component pharmaceutical model system ("PHARM-TM" blend). The widely used classical least squares regression (CLS) and partial least squares regression (PLS) quantification methods provided relatively poor root mean squared error of prediction (RMSEP) values: approximately 2-4% and 4-10% for CRYST-PM and PHARM-TM respectively. The residual plots of these models indicated the nonlinearity of the preprocessed data sets. More accurate quantitative results could be achieved with properly applied variable selection methods. It was observed that variable selection methods discarded the most intensive bands while less intensive ones were retained as the most informative spectral ranges. As a result not only the accuracy of concentration determination was enhanced, but the linearity of models was improved as well. This indicated that nonlinearity occurred especially at the intensive spectral bands. Other methods developed for handling nonlinearity were also capable of adapting to the spectral nature of both data sets. The RMSEP could be decreased this way to 1% in CRYST-PM and 3-6% in PHARM-TM. Raman maps with accurate real concentrations could be prepared this way. All quantitative models were compared by the non-parametric sum of ranking differences (SRD) method, which also proved that models based on variable selection or nonlinear methods provide better quantification.

Effect of ultrasound-assisted crystallization in the diastereomeric salt resolution of tetramisole enantiomers in ternary system with O,O'-dibenzoyl-(2R,3R)-tartaric acid.

The diastereomeric salt resolution of racemic tetramisole was studied using ultrasound irradiation. We examined the effect of power and duration of ultrasonic irradiation on the properties of the crystalline phase formed by ultrasound-assisted crystallization and the result of the whole optical resolution. The results were compared with reference experiment without using ultrasound. The US time (5-30min) caused higher enantiomeric excess. Although yield was lower continuously high resolving efficiency could have been reached through ultrasound. We had the best results with 4.3W ultrasound power when resolvability was even higher than the best of reference. Furthermore, we accomplished a deep and thorough examination of the salts that possibly could form in this resolution. One of the four diastereomeric salts, which have been identified by powder X-ray diffraction, FTIR-spectroscopy, and differential scanning calorimetry (DSC) in the ternary system of the two tetramisole enantiomers and the resolving agent, namely the bis[(S)-tetramisole]-dibenzoyl-(R,R)-tartrate salt have been proven the key compound in the resolution process, and presented the highest melting point of 166°C (dec.) among the four salts. The originally expected diastereomeric bitartrate salts with 1:1M base:acid ratio [(S)-tetramisole-dibenzoyl-(R,R)-hydrogen-tartrate salt and (R)-tetramisole-dibenzoyl-(R,R)-hydrogen-tartrate salt] and their 'racemic' co-crystal [(RS)-tetramisole-dibenzoyl-(R,R)-hydrogen-tartrate salt] showed somewhat lower melting points (152, 145, and 150°C, respectively) and their crystallization was also prevented by application of ultrasound. Based on the melting points and enthalpies of fusion measured by DSC, all the binary and ternary phase diagrams have been newly established and calculated in the system with help of classical modelling equations of liquidus curves.

Comparison of spray drying, electroblowing and electrospinning for preparation of Eudragit E and itraconazole solid dispersions.

Three solvent based methods: spray drying (SD), electrospinning (ES) and air-assisted electrospinning (electroblowing; EB) were used to prepare solid dispersions of itraconazole and Eudragit E. Samples with the same API/polymer ratios were prepared in order to make the three technologies comparable. The structure and morphology of solid dispersions were identified by scanning electron microscopy and solid phase analytical methods such as, X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and Raman chemical mapping. Moreover, the residual organic solvents of the solid products were determined by static headspace-gas chromatography/mass spectroscopy measurements and the wettability of samples was characterized by contact angle measurement. The pharmaceutical performance of the three dispersion type, evaluated by dissolution tests, proved to be very similar. According to XRPD and DSC analyses, made after the production, all the solid dispersions were free of any API crystal clusters but about 10 wt% drug crystallinity was observed after three months of storage in the case of the SD samples in contrast to the samples produced by ES and EB in which the polymer matrix preserved the API in amorphous state.

High speed electrospinning for scaled-up production of amorphous solid dispersion of itraconazole.

High speed electrospinning (HSES), compatible with pharmaceutical industry, was used to demonstrate the viability of the preparation of drug-loaded polymer nanofibers with radically higher productivity than the known single-needle electrospinning (SNES) setup. Poorly water-soluble itraconazole (ITRA) was formulated with PVPVA64 matrix polymer using four different solvent-based methods such as HSES, SNES, spray drying (SD) and film casting (FC). The formulations were assessed in terms of improvement in the dissolution rate of ITRA (using a "tapped basket" dissolution configuration) and analysed by SEM, DSC and XRPD. Despite the significantly increased productivity of HSES, the obtained morphology was very similar to the SNES nanofibrous material. ITRA transformed into an amorphous form, according to the DSC and XRPD results, in most cases except the FC samples. The limited dissolution of crystalline ITRA could be highly improved: fast dissolution occurred (>90% within 10min) in the cases of both (the scaled-up and the single-needle) types of electrospun fibers, while the improvement in the dissolution rate of the spray-dried microspheres was significantly lower. Production of amorphous solid dispersions (ASDs) with the HSES system proved to be flexibly scalable and easy to integrate into a continuous pharmaceutical manufacturing line, which opens new routes for the development of industrially relevant nanopharmaceuticals.

Predicting final product properties of melt extruded solid dispersions from process parameters using Raman spectrometry.

Raman spectrometry was utilized to estimate degraded drug percentage, residual drug crystallinity and glass-transition temperature in the case of melt-extruded pharmaceutical products. Tight correlation was shown between the results obtained by confocal Raman mapping and transmission Raman spectrometry, a PAT-compatible potential in-line analytical tool. Immediate-release spironolactone-Eudragit E solid dispersions were the model system, owing to the achievable amorphization and the heat-sensitivity of the drug compound. The deep investigation of the relationship between process parameters, residual drug crystallinity and degradation was performed using statistical tools and a factorial experimental design defining 54 different circumstances for the preparation of solid dispersions. From the examined factors, drug content (10, 20 and 30%), temperature (110, 130 and 150°C) and residence time (2.75, 11.00 and 24.75min) were found to have significant and considerable effect. By forming physically stable homogeneous dispersions, the originally very slow dissolution of the lipophilic and poorly water-soluble spironolactone was reasonably improved, making 3minute release possible in acidic medium.