Enhancing crystalline properties of a cardiovascular active pharmaceutical ingredient using a process analytical technology based crystallization feedback control strategy

Investigation into polymorphism within ethenzamide-ethylmalonic acid cocrystal using Raman and terahertz vibrational spectroscopy

Two cocrystal polymorphs of ethenzamide (ETZ) and ethylmalonic acid (EMA) were synthesized by solvent evaporation. Crystal structure analysis revealed that the main amide - carboxyl heterosynthon in ETZ-EMA cocrystal Form I and Form II are the same, but the crystal structure of these two polymorphs are different. Terahertz (THz) and Raman vibrational spectroscopy were used to characterize ETZ, EMA, ETZ-EMA cocrystal polymorph Form I and Form II respectively. The experimental results showed that ETZ, EMA, ETZ-EMA cocrystal Form I and ETZ-EMA cocrystal Form II exhibited completely different characteristic peaks. Both THz and Raman vibrational spectroscopy can be used to distinguish ETZ-EMA cocrystal Form I from Form II. Furthermore, the investigation of phase transition induced by temperature and solid-state grinding was also performed. In the temperature phase transition experiments, when the powder sample was heated to a temperature range of 80-82 °C, the metastable ETZ-EMA cocrystal Form I transformed into the more stable ETZ-EMA cocrystal Form II. Solid-state grinding analysis revealed that the results of the ETZ-EMA cocrystal polymorph synthesis in grinding experiments depended on the polarity of the solvents used. Grinding without solvent or with high polarity solvents tended to result in the stable ETZ-EMA cocrystal Form II. Moreover, the metastable ETZ-EMA cocrystal Form I would transform into Form II after further grinding process. These results demonstrate that THz and Raman vibrational spectroscopy have high sensitivity and accuracy in the detection of both cocrystal synthesis and cocrystal polymorph phase transitions.

The fingerprints of nifedipine/isonicotinamide cocrystal polymorph studied by terahertz time-domain spectroscopy

Cocrystal is constructed to improve physicochemical properties of active pharmaceutical ingredient and prevent polymorphism via intermolecular interactions. However, recent examples on cocrystal polymorphs display significantly different properties. Even though some analytical techniques have been used to characterize the cocrystal polymorphic system, it remains unclear how intermolecular interactions drive and stabilize the structure. In this work, we study the cocrystal polymorphs of nifedipine (NFD) and isonicotinamide (INA) using terahertz (THz) spectroscopy. Form I and form II of NFD-INA cocrystals show spectral fingerprints in THz region. Temperature-dependent THz spectra display distinguished frequency shifts of each fingerprint. Combined with solid-state density functional theory (DFT) calculations, the experimental fingerprints and their distinct responses to temperature are elucidated by specific collective vibrational modes. The vibrations of hydrogen bonding between dihydropyridine ring of NFD and INA are generally distributed below 1.5 THz, which play important roles in stabilizing cocrystal and preventing the oxidation of NFD. The rotations of methyl group in NFD are widely distributed in the range of 1.5-4.0 THz, which helps the steric recognition. The results demonstrate that THz spectroscopy is a sensitive tool to discriminate cocrystal polymorphs. It has the potential to be used as a non-invasive technique for pharmaceutical screening.

Impurity incorporation in solution crystallization: diagnosis, prevention, and control

This work highlights recent advances in the diagnosis, prevention, and control of impurity incorporation during solution crystallization.

Computational pharmaceutics - A new paradigm of drug delivery

In recent decades pharmaceutics and drug delivery have become increasingly critical in the pharmaceutical industry due to longer time, higher cost, and less productivity of new molecular entities (NMEs). However, current formulation development still relies on traditional trial-and-error experiments, which are time-consuming, costly, and unpredictable. With the exponential growth of computing capability and algorithms, in recent ten years, a new discipline named "computational pharmaceutics" integrates with big data, artificial intelligence, and multi-scale modeling techniques into pharmaceutics, which offered great potential to shift the paradigm of drug delivery. Computational pharmaceutics can provide multi-scale lenses to pharmaceutical scientists, revealing physical, chemical, mathematical, and data-driven details ranging across pre-formulation studies, formulation screening, in vivo prediction in the human body, and precision medicine in the clinic. The present paper provides a comprehensive and detailed review in all areas of computational pharmaceutics and "Pharma 4.0", including artificial intelligence and machine learning algorithms, molecular modeling, mathematical modeling, process simulation, and physiologically based pharmacokinetic (PBPK) modeling. We not only summarized the theories and progress of these technologies but also discussed the regulatory requirements, current challenges, and future perspectives in the area, such as talent training and a culture change in the future pharmaceutical industry.

Application of PAT-Based Feedback Control Approaches in Pharmaceutical Crystallization

Crystallization is one of the important unit operations for the separation and purification of solid products in the chemical, pharmaceutical, and pesticide industries, especially for realizing high-end, high-value solid products. The precise control of the solution crystallization process determines the polymorph, crystal shape, size, and size distribution of the crystal product, which is of great significance to improve product quality and production efficiency. In order to develop the crystallization process in a scientific method that is based on process parameters and data, process analysis technology (PAT) has become an important enabling platform. In this paper, we review the development of PAT in the field of crystallization in recent years. Based on the current research status of drug crystallization process control, the monitoring methods and control strategies of feedback control in the crystallization process were systematically summarized. The focus is on the application of model-free feedback control strategies based on the solution and solid information collected by various online monitoring equipment in product engineering, including improving particle size distribution, achieving polymorphic control, and improving purity. In this paper, the challenges of feedback control strategy in the crystallization process are also discussed, and the development trend of the feedback control strategy has been prospected.

A perspective on Quality-by-Control (QbC) in pharmaceutical continuous manufacturing

The Quality-by-Design (QbD) guidance issued by the US Food and Drug Administration (FDA) has catalyzed the modernization of pharmaceutical manufacturing practices including the adoption of continuous manufacturing. Active process control was highlighted recently as a means to improve the QbD implementation. This advance has since been evolving into the concept of Quality-by-Control (QbC). In this study, the concept of QbC is discussed, including a definition of QbC, a review of the recent developments towards the QbC, and a perspective on the challenges of QbC implementation in continuous manufacturing. The QbC concept is demonstrated using a rotary tablet press, integrated into a pilot scale continuous direct compaction process. The results conclusively showed that active process control, based on product and process knowledge and advanced model-based techniques, including data reconciliation, model predictive control (MPC), and risk analysis, is indispensable to comprehensive QbC implementation, and ensures robustness and efficiency.

Preventing Crystal Agglomeration of Pharmaceutical Crystals Using Temperature Cycling and a Novel Membrane Crystallization Procedure for Seed Crystal Generation

In this work, a novel membrane crystallization system was used to crystallize micro-sized seeds of piroxicam monohydrate by reverse antisolvent addition. Membrane crystallization seeds were compared with seeds produced by conventional antisolvent addition and polymorphic transformation of a fine powdered sample of piroxicam form I in water. The membrane crystallization process allowed for a consistent production of pure monohydrate crystals with narrow size distribution and without significant agglomeration. The seeds were grown in 350 g of 20:80 w/w acetone-water mixture. Different seeding loads were tested and temperature cycling was applied in order to avoid agglomeration of the growing crystals during the process. Focused beam reflectance measurement (FBRM); and particle vision and measurement (PVM) were used to monitor crystal growth; nucleation and agglomeration during the seeded experiments. Furthermore; Raman spectroscopy was used to monitor solute concentration and estimate the overall yield of the process. Membrane crystallization was proved to be the most convenient and consistent method to produce seeds of highly agglomerating compounds; which can be grown via cooling crystallization and temperature cycling.

Investigation of the Evolution of Crystal Size and Shape during Temperature Cycling and in the Presence of a Polymeric Additive Using Combined Process Analytical Technologies

Crystal size and shape can be manipulated to enhance the qualities of the final product. In this work the steady-state shape and size of succinic acid crystals, with and without a polymeric additive (Pluronic P123) at 350 mL, scale is reported. The effect of the amplitude of cycles as well as the heating/cooling rates is described, and convergent cycling (direct nucleation control) is compared to static cycling. The results show that the shape of succinic acid crystals changes from plate- to diamond-like after multiple cycling steps, and that the time required for this morphology change to occur is strongly related to the type of cycling. Addition of the polymer is shown to affect both the final shape of the crystals and the time needed to reach size and shape steady-state conditions. It is shown how this phenomenon can be used to improve the design of the crystallization step in order to achieve more efficient downstream operations and, in general, to help optimize the whole manufacturing process.

Resolution and Sensitivity of Inline Focused Beam Reflectance Measurement During Wet Granulation in Pharmaceutically Relevant Particle Size Ranges

Real-time process monitoring using a process analytical technology for granule size distribution can enable quality-by-design in drug product manufacturing. In this study, the resolution and sensitivity of chord length distribution (CLD) measured inline inside a high shear granulator using focused beam reflectance measurement (FBRM) C35 probe was investigated using different particle size grades of microcrystalline cellulose (MCC). In addition, the impact of water and impeller tip speed on the measurement accuracy as well as correlation with offline particle sizing techniques (FBRM, laser diffraction [Malvern Mastersizer^®], microscopy [Sympatec QicPic^®], and nested sieve analysis) was studied. Inline FBRM resolved size differences between different MCC grades, and the data correlated well with offline analyses. Impeller tip speed changed the number density of inline CLD measurements while addition of water reduced the CLD of dry MCC, likely due to deagglomeration of primary particles. In summary, inline FBRM CLD measurement in high shear granulator provides adequate resolution and reproducible measurements in the pharmaceutically relevant size range both in the presence and in the absence of water. Therefore, inline FBRM can be a valuable tool for the monitoring of high shear wet granulation.

A perspective on the growth-only zone, the secondary nucleation threshold and crystal size distribution in solution crystallisation

The metastable zone between the solubility curve and the crystallisation curve can be divided into two regions, separated by the secondary nucleation threshold.

Crystallisation and physicochemical property characterisation of conformationally-locked co-crystals of fenamic acid derivatives

Co-crystals of fenamic acid and its highly polymorphic derivatives with 4,4′-bipyridine are prepared using various crystallisation techniques and have been shown to afford single polymorphic forms for each of the co-crystals.

Multivariate PAT solutions for biopharmaceutical cultivation: current progress and limitations

Increasingly elaborate and voluminous datasets are generated by the (bio)pharmaceutical industry and are a major challenge for application of PAT and QbD principles. Multivariate data analysis (MVDA) is required to delineate relevant process information from large multi-factorial and multi-collinear datasets. Here the key role of MVDA for industrial (bio)process data is discussed, with a focus on progress and limitations of MVDA as a PAT solution for biopharmaceutical cultivation processes. MVDA based models were proven useful and should be routinely implemented for bioprocesses. It is concluded that although the highest level of PAT with process control within its design space in real-time during manufacturing is not reached yet, MVDA will be central to reach this ultimate objective for cell cultivations.