Chapter 4 - Development of Preclinical Formulations for Toxicology Studies

Genistein is an isoflavone compound that has been proven to have anticancer activity and is capable of binding to estrogen β receptors with Selective Estrogen Receptor Modulators (SERMs) properties, and has a strong affinity to inhibit the development of cancer cells. This study is to determine the optimum conditions of the reaction in the synthesis process of compounds labeled ¹³¹I-genestein which can be potential for application of breast cancer diagnosis.

Synthesis of ¹³¹I-Genistein compound labeling using the Chloramine-T iodination method. This method uses several parameter optimizations, including: pH conditions, the amount of chloramine-T oxidizer and sodium metabisulfite reducing agent. The radiochemical purity of the ¹³¹I-Genistein compound was determined using thin layer chromatography TLC-SG F₂₅₄, and measured by SCA (Single Channel Analyzer). The radiochemical purity of labeled compounds must fulfill the requirements of the United States of Pharmacopeia.

Optimization of the synthesis conditions of the ¹³¹I-Genistein compound was obtained at pH 8, the amount of chloramine-T 0.225 mg, and the amount of Na-Metabisulfite 0.342 mg, with 30 min reaction time. This optimum condition produces radiochemical purity of 95.02 ± 0.76%.

Products labeled ¹³¹I-Genistein meet radiochemical purity requirements according to USP requirements. The labeled compound is expected to be able to be used to detect breast cancer through a binding mechanism with estrogen receptors β.

Intravenous (IV) route is preferred for rapid onset of action, avoiding first pass metabolism and achieving site specific delivery. Development of IV formulations for poorly water soluble drugs poses significant challenges. Formulation approaches like salt formation, co-solvents, surfactants and inclusion complexation using cyclodextrins are used for solubilisation. However, these approaches are not applicable universally and have limitations in extent of solubilisation, hypersensitivity, toxicity and application to only specific type of molecules. IV nanosuspension have been attracting attention as a viable strategy for development of IV formulations of poorly water-soluble drugs. Nanosuspension consists of nanocrystals of poorly water soluble drug suspended in aqueous media and stabilized using minimal concentration of stabilizers. Recent years have witnessed their potential in formulations for toxicological studies and clinical trials. However various challenges are associated with the translational development of IV nanosuspensions. Therefore, the objective of the current review is to provide a holistic view of formulation development and desired properties of IV nanosuspensions. It will also focus on advancements in characterization tools, manufacturing techniques and post-production processing. Challenges associated with translational development and regulatory aspects of IV nanosuspension will be addressed. Additionally, their role in preclinical evaluation and special applications like targeting will also be discussed with the help of case studies. The applications of IV nanosuspensions shall expand as their applications move from preclinical phase to commercialization.

This study reports the potential of different polymers and polymer incorporation methods to inhibit crystallisation and maintain supersaturation of amorphous indomethacin (IND) in aqueous suspensions during storage. Three different polymers (poly(vinyl pyrrolidone) (PVP), hydroxypropyl methylcellulose (HPMC) and Soluplus® (SP)) were used and included in the suspensions either as a solid dispersion (SD) with IND or dissolved in the suspension medium prior to the addition of amorphous IND. The total concentrations of both IND and the polymer in the suspensions were kept the same for both methods of polymer incorporation. All the polymers (with both incorporation methods) inhibited crystallisation of the amorphous IND. The SDs were better than the predissolved polymer solutions at inhibiting crystallisation. The SDs were also better at maintaining drug supersaturation. SP showed a higher IND crystallisation inhibition and supersaturation potential than the other polymers. However, this depended on the method of addition. IND in SD with SP did not crystallise, nor did the SD generate any drug supersaturation, whereas IND in the corresponding predissolved SP solution crystallised (into the recently characterised η polymorphic form of the drug) but also led to a more than 20-fold higher IND solution concentration than that observed for crystalline IND. The ranking of the polymers with respect to crystallisation inhibition potential in SDs was SP ≫ PVP > HPMC. Overall, this study showed that both polymer type and polymer incorporation method strongly impact amorphous form stability and drug supersaturation in aqueous suspensions.