Bottom-up production of injectable itraconazole suspensions using membrane technology

Bottom-up production of active pharmaceutical ingredient (API) crystal suspensions offers advantages in surface property control and operational ease over top-down methods. However, downstream separation and concentration pose challenges. This proof-of-concept study explores membrane diafiltration as a comprehensive solution for downstream processing of API crystal suspensions produced via anti-solvent crystallization. It involves switching the residual solvent (N-methyl-2-pyrrolidone, NMP) with water, adjusting the excipient (d-α-Tocopherol polyethylene glycol 1000 succinate, TPGS) quantity, and enhancing API loading (solid concentration) in itraconazole crystal suspensions. NMP concentration was decreased from 9 wt% to below 0.05 wt% (in compliance with European Medicine Agency guidelines), while the TPGS concentration was decreased from 0.475 wt% to 0.07 wt%. This reduced the TPGS-to-itraconazole ratio from 1:2 to less than 1:50 and raised the itraconazole loading from 1 wt% to 35.6 wt%. Importantly, these changes did not adversely affect the itraconazole crystal stability in suspension. This study presents membrane diafiltration as a one-step solution to address downstream challenges in bottom-up API crystal suspension production. These findings contribute to optimizing pharmaceutical manufacturing processes and hold promise for advancing the development of long-acting API crystal suspensions via bottom-up production techniques at a commercial scale.

Tailoring the use of excipients in bottom-up production of naproxen crystal suspensions via membrane technology

Long-acting crystal suspensions of active pharmaceutical ingredients (API) mostly comprised of an API, a suspension media (water) and excipients and provide sustained API release over time. Excipients are crucial for controlling particle size and to achieve the stability of the API crystals in suspension. A bottom-up process was designed to produce long-acting crystal suspensions whilst investigating the excipient requirements during the production process and the subsequent storage. PVP K30 emerged as the most effective excipient for generating stable naproxen crystals with the desired size of 1 to 15 μm, using ethanol as solvent and water as anti-solvent. Calculations, performed based on the crystal properties and assuming complete PVP K30 adsorption on the crystal surface, revealed lower PVP K30 requirements during storage compared to initial crystal generation. Consequently, a membrane-based diafiltration process was used to determine and fine-tune PVP K30 concentration in the suspension post-crystallization. A seven-stage diafiltration process removed 98 % of the PVP K30 present in the suspension thereby reducing the PVP-to-naproxen ratio from 1:2 to 1:39 without impacting the stability of naproxen crystals in suspension. This work provides insights into the excipient requirements at various production stages and introduce the membrane-based diafiltration for precise excipient control after crystallization.

Development of long-acting injectable suspensions by continuous antisolvent crystallization: An integrated bottom-up process

Our present work elucidated the operational feasibility of direct generation and stabilization of long-acting injectable (LAI) suspensions of a practically insoluble drug, itraconazole (ITZ), by combining continuous liquid antisolvent crystallization with downstream processing (i.e., centrifugal filtration and reconstitution). A novel microchannel reactor-based bottom-up crystallization setup was assembled and optimized for the continuous production of micro-suspension. Based upon the solvent screening and solubility study, N-methyl pyrrolidone (NMP) was selected as the optimal solvent and an impinging jet Y-shaped microchannel reactor (MCR) was selected as the fluidic device to provide a reproducible homogenous mixing environment. Operating parameters such as solvent to antisolvent ratio (S/AS), total jet liquid flow rates (TFRs), ITZ feed solution concentration and the maturation time in spiral tubing were tailored to 1:9 v/v, 50 mL/min, 10 g/100 g solution, and 96 h, respectively. Vitamin E TPGS (0.5% w/w) was found to be the most suitable excipient to stabilize ITZ particles amongst 14 commonly used stabilizers screened. The effect of scaling up from 25 mL to 15 L was evaluated effectively with in situ monitoring of particle size distribution (PSD) and solid-state form. Thereafter, the suspension was subjected to centrifugal filtration to remove excess solvent and increase ITZ solid fraction. As an alternative, an even more concentrated wet pellet was reconstituted with an aqueous solution of 0.5% w/w Vitamin E TPGS as resuspending agent. The ITZ LAI suspension (of 300 mg/mL solid concentration) has the optimal PSD with a D10 of 1.1 ± 0.3 µm, a D50 of 3.53 ± 0.4 µm and a D90 of 6.5 ± 0.8 µm, corroborated by scanning electron microscopy (SEM), as remained stable after 548 days of storage at 25 °C. Finally, in vitro release methods using Dialyzer, dialysis membrane sac were investigated for evaluation of dissolution of ITZ LAI suspensions. The framework presented in this manuscript provides a useful guidance for development of LAI suspensions by an integrated bottom-up approach using ITZ as model API.

Twin Tandem Bicycle Pedal Motion - Using X-rays to Resolve Disorder Thermodynamic Parameters

During our research into polar crystals for organic electronic applications, we synthesized E,E-1-[2-(4-nitrophenyl)ethenyl]-4-[2-(2,4-dimethoxyphenyl)ethenyl]benzene, which has a polar crystal structure (space group Pc) and displays the typical bicycle pedal motion, as studied in detail by Harada and Ogawa [1], in one of its ethenylic links. A van `t Hoff plot of the logarithm of the population ratio versus 1/T, however, showed a kink instead of being a straight line, which led us to conclude that an unusual phase transition was occurring in this material [2]. In the mean time we have crystallized the same material in a second, centrosymmetric polymorph (space group P-1). There, the asymmetric unit consists of two complete molecules, and they display the same kind of bicycle pedal motion, but this time in all four different ethenylic linkers. Every one of these population differences increases with temperature, so that four van `t Hoff plots can be constructed for this structure. Two of these behave normally, the other two display a kink, just like the van `t Hoff plot of the pedaling ethenylic link in the other polymorph of this molecule. This is, to the best of our knowledge, the first instance of a structure where four different dynamic equilibria can be resolved simultaneously, and only the second example in which van `t Hoff plots for the thermodynamics of dynamic disorder are not linear, indicating an unusual type of phase transition linked only to the dynamics of the molecules in the crystal.

(E,E)-N1-(2,3,4,5,6-Pentafluorobenzylidene)-N4-(3,4,5-trimethoxybenzylidene)benzene-1,4-diamine

The title compound, C₂₃H₁₇F₅N₂O₃, forms a layered centrosymmetric crystal structure in which C—H⋯F inter­actions are responsible for the formation of planar ribbons along [110], meth­oxy–meth­oxy (C—H⋯O) inter­actions for the formation of layers parallel to [13], and OCH₃⋯π and C—F⋯π inter­actions for the stacking of these layers.

(E)-4-[2-(3,4,5-trimethoxyphenyl)ethenyl]nitrobenzene and its 'bridge-flipped' analogues

The solid-state structures of three push-pull acceptor-π-donor (A-π-D) systems differing only in the nature of the π-spacer have been determined. (E)-1-Nitro-4-[2-(3,4,5-trimethoxyphenyl)ethenyl]benzene, C(17)H(17)NO(5), (I), and its 'bridge-flipped' imine analogues, (E)-3,4,5-trimethoxy-N-(4-nitrobenzylidene)aniline, C(16)H(16)N(2)O(5), (II), and (E)-4-nitro-N-(3,4,5-trimethoxybenzylidene)aniline, C(16)H(16)N(2)O(5), (III), display different kinds of supramolecular networks, viz. corrugated planes, a herringbone pattern and a layered structure, respectively, all with zero overall dipole moments. Only (III) crystallizes in a noncentrosymmetric space group (P2(1)2(1)2(1)) and is, therefore, a potential material for second-harmonic generation (SHG).

4,4'-Bis[2-(3,5-dimeth-oxy-phen-yl)ethen-yl]biphen-yl

The title compound, C(32)H(30)O(4), crystallizes with three different conformers of the same mol-ecule in the asymmetric unit, which explains the unusually large unit cell volume. The supra-molecular structure is based on inter-actions involving the meth-oxy groups [C⋯O contacts between 3.090 (2) and 3.204 (2) Å, and C-H⋯O contacts between (normalized) 2.40 and 2.71 Å], π-π stacking of the electron-rich meth-oxy-substituted rings [centroid-centroid distances of 3.6454 (9)-3.738 (1) Å] and C-H⋯π contacts (normalized, 2.62-2.97Å).

Dynamic disorder in the crystal structure of an organic semiconductor: an unusual phase transition involving the heat capacity

(E,E)-1-[2-(4-Nitrophenyl)ethenyl]-4-[2-(2,4-dimethoxyphenyl)ethenyl]benzene was characterised by X-ray diffraction and shown to be dynamically disordered at room temperature. The structure was re-determined over a range of temperatures to infer the thermodynamic parameters related to this disorder. A phase transition of third order according to the Ehrenfest classification scheme was discovered. To the best of our knowledge, this is the first experimentally observed phase transition of formal third order. It can be explained by the involvement of long-range lattice vibrations.

2-(4-Formyl-2,6-dimeth-oxy-phenoxy)-acetic acid

In the title compound, C(11)H(12)O(6), the aldehyde group is disordered over two sites in a 0.79:0.21 ratio. The carb-oxy-lic acid chain is found in the [ap,ap] conformation due to two intramolecular O-H⋯O hydrogen bonds.

4-[(E)-2-(2,4,6-Trinitrophenyl)ethylidene]benzonitrile

In the crystal of the title compound, C₁₅H₈N₄O₆, the mol­ecules are organized in layers due to their linkage by weak C—H⋯N hydrogen bonds. The layers are themselves inter­connected by weak C—H⋯O hydrogen bonds and π–π inter­actions [centroid–centroid distances = 3.8690 (15) and 3.9017 (16) Å]. The dihedral angle between the rings is 31.9 (1)°.

3-(2-Formyl-phen-oxy)propanoic acid

In the structure of the title compound, C(10)H(10)O(4), the carboxyl group forms a catemer motif in the [100] direction instead of the expected dimeric structures. The carboxylic acid group is found in the syn conformation and the three-dimensional organization in the crystal is based on C-H⋯O and O-H⋯O interactions.

(E)-1-(2,4,6-Trimeth-oxy-phen-yl)pent-1-en-3-one

The title compound, C(14)H(18)O(4), was obtained unintentionally as the major product of an attempted synthesis of (E,E)-2,5-bis-[2-(2,4,6-trimeth-oxy-phen-yl)ethen-yl]pyrazine. The crystal packing features layers based on two weak C-H⋯O hydrogen bonds involving the O atom of the carbonyl group and two O(meth-oxy)⋯C(meth-oxy) inter-actions [3.109 (2) Å]. The sheets are inter-connected via meth-oxy-meth-oxy dimers and C-H⋯π inter-actions.

Synthesis and structures of substituted triphenyl(phenylimino)phosphoranes

Three substituted triphenyl(phenylimino)phosphoranes, namely (4-cyanophenylimino)triphenylphosphorane, C(25)H(19)N(2)P, (I), (4-nitrophenylimino)triphenylphosphorane, C(24)H(19)N(2)O(2)P, (II), and (3-nitrophenylimino)triphenylphosphorane, C(24)H(19)N(2)O(2)P, (III), were synthesized as precursors for the preparation of substituted diphenylcarbodiimides. All three compounds display a supramolecular arrangement in which the substituted benzene rings are organized in an antiparallel fashion. The nitro group on the ring participates in C-H...O and O...pi interactions, forming intermolecular dimers. Compound (III) shows disorder which involves the rotation of one of the phenyl rings of the triphenylphosphine group.