Cocrystallization: Cutting Edge Tool for Physicochemical Modulation of Active Pharmaceutical Ingredients

Development of direct compression Acetazolamide tablet with improved bioavailability in healthy human volunteers enabled by cocrystallization with p-Aminobenzoic acid

Pharmaceutical cocrystallization has been widely used to improve physicochemical properties of APIs. However, developing cocrystal formulation with proven clinical success remains scarce. Successful translation of a cocrystal to suitable dosage forms requires simultaneously improvement of several deficient physicochemical properties over the parent API, without deteriorating other properties critical for successful product development. In the present work, we report the successful development of a direct compression tablet product of acetazolamide (ACZ), using a 1:1 cocrystal of acetazolamide with p-aminobenzoic acid (ACZ-PABA). The ACZ-PABA tablet exhibits superior biopharmaceutical performance against the commercial tablet, DIAMOX® (250 mg), in healthy human volunteers, leading to more than 50 % reduction in the required dose.

Cocrystals of a coumarin derivative: an efficient approach towards anti-leishmanial cocrystals against MIL-resistant Leishmania tropica

Leishmaniasis is a neglected parasitic tropical disease with numerous clinical manifestations. One of the causative agents of cutaneous leishmaniasis (CL) is Leishmania tropica (L. tropica) known for causing ulcerative lesions on the skin. The adverse effects of the recommended available drugs, such as amphotericin B and pentavalent antimonial, and the emergence of drug resistance in parasites, mean the search for new safe and effective anti-leishmanial agents is crucial. Miltefosine (MIL) was the first recommended oral medication, but its use is now limited because of the rapid emergence of resistance. Pharmaceutical cocrystallization is an effective method to improve the physicochemical and biological properties of active pharmaceutical ingredients (APIs). Herein, we describe the cocrystallization of coumarin-3-carboxylic acid (CU, 1a; 2-oxobenzopyrane-3-carboxylic acid, C10H6O4) with five coformers [2-amino-3-bromopyridine (1b), 2-amino-5-(trifluoromethyl)-pyridine (1c), 2-amino-6-methylpyridine (1d), p-aminobenzoic acid (1e) and amitrole (1f)] in a 1:1 stoichiometric ratio via the neat grinding method. The cocrystals 2-6 obtained were characterized via single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis, as well as Fourier transform infrared spectroscopy. Non-covalent interactions, such as van der Waals, hydrogen bonding, C-H...π and π...π interactions contribute significantly towards the packing of a crystal structure and alter the physicochemical and biological activity of CU. In this research, newly synthesized cocrystals were evaluated for their anti-leishmanial activity against the MIL-resistant L. tropica and cytotoxicity against the 3T3 (normal fibroblast) cell line. Among the non-cytotoxic cocrystals synthesized (2-6), CU:1b (2, IC50 = 61.83 ± 0.59 µM), CU:1c (3, 125.7 ± 1.15 µM) and CU:1d (4, 48.71 ± 0.75 µM) appeared to be potent anti-leishmanial agents and showed several-fold more anti-leishmanial potential than the tested standard drug (MIL, IC50 = 169.55 ± 0.078 µM). The results indicate that cocrystals 2-4 are promising anti-leishmanial agents which require further exploration.

Tuning Caco-2 permeability by cocrystallization: Insights from molecular dynamics simulation

Emerging evidence suggests that intestinal permeability can be potentially enhanced through cocrystallization. However, a mechanism for this effect remains to be established. In this study, we first demonstrate the enhancement in intestinal permeability, evaluated by the Caco-2 cell permeability assay, of acetazolamide (ACZ) in the presence of a conformer, p-aminobenzoic acid (PABA), delivered in the form of a 1:1 cocrystal. The binding strength of ACZ and PABA with the Pgp efflux transporter, either alone or as a mixture, was calculated using molecular dynamics simulation. Results show that PABA weakens the binding of ACZ with Pgp, which leads to a lower efflux ratio and elevated permeability of ACZ. This work provides molecular-level insights into a potentially effective strategy to improve the intestinal permeability of drugs. If the same cocrystal also exhibits higher solubility, oral bioavailability of BCS IV drugs can likely be improved by forming a cocrystal with a Pgp inhibitor.

Modulating Pharmaceutical Properties of Berberine Chloride through Cocrystallization with Benzendiol Isomers

PURPOSE

To synthesize and characterize new cocrystals of berberine chloride (BCl) for potential pharmaceutical tablet formulation.

METHODS

Solutions of BCl with each of three selected cocrystal formers, catechol (CAT), resorcinol (RES), and hydroquinone (HYQ) were slowly evaporated at room temperature to obtain crystals. Crystal structures were solved using single crystal X-ray diffraction. Bulk powders were characterized by powder X-ray diffraction, thermogravimetric-differential scanning calorimetry, FTIR, dynamic moisture sorption, and dissolution (both intrinsic and powder).

RESULTS

Single crystal structures confirmed the formation of cocrystals with all three coformers, which revealed various intermolecular interactions that stabilized crystal lattices, including O-H···Cl- hydrogen bonds. All three cocrystals exhibited better stability against high humidity (up to 95% relative humidity) at 25 ℃ and higher intrinsic and powder dissolution rates than BCl.

CONCLUSION

The enhanced pharmaceutical properties of all three cocrystals, as compared to BCl, further contribute to the existing evidence that confirms the beneficial role of cocrystallization in facilitating drug development. These new cocrystals expand the structure landscape of BCl solid forms, which is important for future analysis to establish a reliable relationship between crystal structure and pharmaceutical properties.

5-fluorouracil-caffeic acid cocrystal delivery agent with long-term and synergistic high-performance antitumor effects

Aim: To explore how to transform cocrystals of the anticancer drug 5-fluorouracil (FL) with caffeic acid (CF; FL-CF-2H₂O) into a nanoformulation, a self-assembly strategy of cocrystal-loaded micelles is proposed. Methods: Nanomicelles were assembled to deliver cocrystal FL-CF-2H₂O with synergistic activity, and their in vitro/vivo properties were evaluated by combining theoretical and experimental methods. Result: More cocrystal was packed into the polymers due to the stronger interaction energy during micellar assembly, producing excellent cytotoxicity and pharmacokinetic behavior, especially synergistic abilities and long-term therapy. Conclusion: This case exemplifies the particular benefits of the self-assembly strategy of cocrystal-loaded micelles in keeping a delicate balance between long-term effects and high efficiency for FL, and offers a feasible technical scheme for cocrystal delivery agents for antitumor drugs.

Development of ezetimibe eutectic with improved biopharmaceutical and mechanical properties to design an optimized oral solid dosage formulation

Eutectics are multicomponent systems which are an alternative to the conventional techniques for modulating the biopharmaceutical properties of a pharmaceutical. Ezetimibe (ETZ) is a hypocholesterolemic agent with limited dissolution, poor water solubility, and subsequently demonstrates low oral bioavailability. Additionally, ETZ exhibits poor mechanical properties, leading to difficulties in developing dosage forms through direct compression. The present work highlights the applicability of eutectics in the simultaneous improvement of physicochemical along with mechanical properties of ETZ. A pharmaceutical eutectic of ETZ with succinimide (SUC) was prepared by mechanochemical grinding and thoroughly characterized using thermoanalytical, X-ray diffraction, and spectroscopic methods. Intrinsic dissolution rate and pharmacokinetic analysis were also performed for ezetimibe-succinimide (ETZ-SUC) eutectic in contrast to pure ETZ. The eutectic demonstrated ∼2-fold increase in the solubility and dissolution rate. In pharmacokinetic studies, the area under the curve (AUC) for ETZ-SUC eutectic (28.03 ± 2.22 ng*h/mL) was found to be higher than ETZ (8.98 ± 0.36 ng*h/mL), indicating improved oral bioavailability for eutectics. Also, it was observed that enhanced material functionality aids in designing directly compressed tablets, where the eutectic formulation showed an improved dissolution profile over the ETZ formulation. The study demonstrates that eutectic conglomerates could be utilized to develop ideal oral solid dosage formulations.

Mechanical Activation by Ball Milling as a Strategy to Prepare Highly Soluble Pharmaceutical Formulations in the Form of Co-Amorphous, Co-Crystals, or Polymorphs

Almost half of orally administered active pharmaceutical ingredients (APIs) have low solubility, which affects their bioavailability. In the last two decades, several alternatives have been proposed to modify the crystalline structure of APIs to improve their solubility; these strategies consist of inducing supramolecular structural changes in the active pharmaceutical ingredients, such as the amorphization and preparation of co-crystals or polymorphs. Since many APIs are thermosensitive, non-thermal emerging alternative techniques, such as mechanical activation by milling, have become increasingly common as a preparation method for drug formulations. This review summarizes the recent research in preparing pharmaceutical formulations (co-amorphous, co-crystals, and polymorphs) through ball milling to enhance the physicochemical properties of active pharmaceutical ingredients. This report includes detailed experimental milling conditions (instrumentation, temperature, time, solvent, etc.), as well as solubility, bioavailability, structural, and thermal stability data. The results and description of characterization techniques to determine the structural modifications resulting from transforming a pure crystalline API into a co-crystal, polymorph, or co-amorphous system are presented. Additionally, the characterization methodologies and results of intermolecular interactions induced by mechanical activation are discussed to explain the properties of the pharmaceutical formulations obtained after the ball milling process.

Investigating the Role of the Reduced Solubility of the Pirfenidone-Fumaric Acid Cocrystal in Sustaining the Release Rate from Its Tablet Dosage Form by Conducting Comparative Bioavailability Study in Healthy Human Volunteers

Pirfenidone (PFD) is the first pharmacological agent approved by the US Food and Drug Administration (FDA) in 2014 for the treatment of idiopathic pulmonary fibrosis (IPF). The recommended daily dosage of PFD in patients with IPF is very high (2403 mg/day) and must be mitigated through additives. In the present work, sustained-release (SR) formulations of the PFD-FA cocrystal of two different strengths such as 200 and 600 mg were prepared and its comparative bioavailability in healthy human volunteers was studied against the reference formulation PIRFENEX (200 mg). A single-dose pharmacokinetic study (200 mg IR vs 200 mg SR) demonstrated that the test formulation exhibited lower C_max and T_max in comparison to the reference formulation, which showed that the cocrystal behaved like an SR formulation. Further in the multiple-dose comparative bioavailability study (200 mg IR thrice daily vs 600 mg SR once daily), the test formulation was found bioequivalent to the reference formulation. In conclusion, the present study suggests that cocrystallization offers a promising strategy to reduce the solubility of PFD and opens the door for potential new dosage forms of this important pharmaceutical.

Crystal Structure, Solubility, and Pharmacokinetic Study on a Hesperetin Cocrystal with Piperine as Coformer

Hesperetin (HES) is a key biological active ingredient in citrus peels, and is one of the natural flavonoids that attract the attention of researchers due to its numerous therapeutic bioactivities that have been identified in vitro. As a bioenhancer, piperine (PIP) can effectively improve the absorption of insoluble drugs in vivo. In the present study, a cocrystal of HES and PIP was successfully obtained through solution crystallization. The single-crystal structure was illustrated and comprehensive characterization of the cocrystal was conducted. The cocrystal was formed by two drug molecules at a molar ratio of 1:1, which contained O–H–O hydrogen bonds between the carbonyl and ether oxygen of PIP and the phenolic hydroxyl group of HES. In addition, a solubility experiment was performed on powder cocrystal in simulated gastrointestinal fluid, and the result revealed that the cocrystal improves the dissolution behavior of HES compared with that of the pure substance. Furthermore, HES’s bioavailability in the cocrystal was six times higher than that of pristine drugs. These results may provide an efficient oral formulation for HES.

Energy framework and solubility: a new predictive model in the evaluation of the structure–property relationship of pharmaceutical solid forms

Crystal structures with lower interaction energy tend to present higher aqueous solubility.

Progress on cocrystallization of poorly soluble NME's in the last decade

Cocrystallization of pharmaceuticals has been an exciting field of interest to both academia and industries, demonstrated from its increasing growth rate of publications, patents, and marketed formulations.