Different solid state forms of an ester of an active pharmaceutical ingredient (API) or esterified active pharmaceutical ingredient (EAPI) may possess different properties that can provide a formulation, in which the EAPI is included, with specific advantages, for example, by facilitating better processing or handling characteristics, changing the dissolution profile in a favorable direction, or improving stability (polymorph as well as chemical stability) and shelf-life. These variations in the properties of different solid state forms may also translate to benefits to a final dosage form, for instance, by providing or contributing to improved bioavailability. Different solid state forms of an EAPI may also give rise to a variety of polymorphs or crystalline forms, which may in turn provide additional opportunities to assess variations in the properties and characteristics of a solid EAPI.
An important characteristic of EAPI is that it's dissolution or release rate does not change substantially over time. Changes in dissolution or release rate of EAPI over time can result in otherwise identical products except for the solid state form (e.g., having the same EAPI, formulations components and amounts thereof), but different pharmacokinetic properties which can change or alter the efficacy or safety of a drug product.
The stability of EAPI in pharmaceutical preparations (e.g., compositions and unit dosage forms) is also important. For example, if the EAPI changes physical form (e.g., crystal form or amount thereof) in a pharmaceutical composition or unit dosage form, this can also affect pharmacokinetic properties and therefore related safety and efficacy parameters.
To be useful, the solid state has to be stable. A number of examples of bulk drug substance and pharmaceutical compositions/dosage forms that have changed physical form are known in the literature and have resulted in substantial problems to patients receiving these drugs. A well known example is ritonavir which underwent a change in crystal form resulting in the product failing dissolution tests and being pulled off the market for a period of time (see Morissette et al. Proc Natl Acad Sci USA. 2003 Mar. 4; 100(5):2180-4). Other high profile cases include the recall of batches of Neupro (rotigotine) due to the appearance of a new polymorph in 2008, recall of 1.5 million tablets of warfarin in 2010 due to concerns over 2-propanol levels, which potentially could affect API crystallinity, and in 2010 the recall of 60 million tablets of Avalide over concerns in variability in the amounts of the less soluble polymorph of irbesartan in 2010. See Lee et al. Annu. Rev. Chem. Biomol. Eng. 2011, 2, 259-280.
Absorption of any prodrug such as an ester derivative of an API (EAPI) needs to be managed to provide adequate and sustained levels of the API derived from EAPI in vivo without adding any safety issues associated with the ester or its metabolite. Solubility, release, dissolution and partitioning of EAPI in a particular solvent is a function of lipophilicity and is related to solid state characteristics e.g., the physical form of the drug substance such as crystal form, solvation, whether or not amorphous material is present, etc. Therefore, the solid state physical form is one of the key properties with respect to ease of manufacturing, storage, and performance of the EAPI for enabling safe and effective levels of API.
Esters of (17-β)-Hydroxy-4-Androsten-3-one, which themselves are not thought to be biological active, are known to be transformed to the biologically active molecule ((17-β)-Hydroxy-4-Androsten-3-one in vivo (and other related metabolites like (17-β)-hydroxy-5α-androstan-3-one) and therefore can be used for treating patients in need of (17-β)-Hydroxy-4-Androsten-3-one treatment. However, inadequate solubility and/or release or dissolution or partitioning and/or physical stability of the solid state of the EAPI can result in poor bioavailability of (17-β)-Hydroxy-4-Androsten-3-one, a useful hormone for the treatment of several disease states such as male or female hypogonadism.
Several prodrug esters of (17-β)-Hydroxy-4-Androsten-3-one have been reported in the literature (Gooren L J Front Horm Res. 2009; 37:32-5). However, in addition to overcoming solubility challenges with (17-β)-Hydroxy-4-Androsten-3-one esters, adequate absorption and conversion rate into the parent drug remain an important design element in preparing and identifying solid state esters of (17-β)-Hydroxy-4-Androsten-3-one. Approaches to date have failed to disclose or adequately characterize specific solid state (17-β)-Hydroxy-4-Androsten-3-one esters (i.e., the tridecanoate, tetradecanoate esters, and others), compositions and dosage forms having these esters and methods of their use that would be particularly useful in overcoming poor solubility in biologically relevant media such as aqueous media for adequate release/dissolution of the (17-β)-Hydroxy-4-Androsten-3-one ester or in lipophilic additives such as fatty acids or fatty acid glycerides for adequate lipid/membrane/chylomicron partitioning.
Steroids including steroid esters, testosterone and testosterone esters are known to exhibit different solid state forms that have different properties including dissolution, bioavailability and absorption (See e.g., Ballard B E, Biles J, Steroids, 1964; 4: 273; Bouche R, Draguet-Brughmans M, J Pharm Belg, 1977; 32: 347; Carless et al. Journal of Pharmacy and Pharmacology Volume 20, Issue 8, pages 630-638, August 1968; Borka & Haleblian (1990) Acta Pharm. Jugosl. 40:71-94).
There is a need for stable and bioavailable solid state forms of esters (17-β)-Hydroxy-4-Androsten-3-one such as (17-β)-3-Oxoandrost-4-en-17-yl tridecanoate (or the corresponding tetradecanoate) that would be suitable for use in treatment of subjects in need of (17-β)-Hydroxy-4-Androsten-3-one.