Objectives In a short approach, we want to present the improvements that have recently been done in the world of new solid forms of known active pharmaceutical ingredients (APIs). The different strategies will be addressed, and successful examples will be given. Key findings This overview presents a possible step to overcome the 10-15 years of hard work involved in launching a new drug in the market: the use of new forms of well-known APIs, and improve their efficiency by enhancing their bioavailability and pharmacokinetics. It discusses some of the latest progresses. Summary We want to present, in a brief overview, what recently has been done to improve the discovery of innovative methods of using well-known APIs, and improve their efficiency. Multicomponent crystal forms have shown to be the most promising achievements to accomplish these aims, by altering API physicochemical properties, such as solubility, thermal stability, shelf life, dissolution rate and compressibility. API-ionic liquids (ILs) and their advantages will be briefly referred. An outline of what has recently been achieved in metal drug coordination and in drug storage and delivery using bio-inspired metal-organic frameworks (BioMOFs) will also be addressed. PreambleIn the last decade, several approaches to attain multicomponent pharmaceutical forms have been used and different kinds have been obtained. The most notorious cases are undoubtedly co-crystals and molecular salts [1] and their design, using crystal engineering principles, strategic and synthetic approaches have been the subject of different reviews.[2-5] Also, their characterization and implications for regulatory control and intellectual property protection have been presented and discussed. Here, we go one step forward and taking into account the recent definition of pharmaceutical co-crystal; from the published outcome of the Indo-US bilateral meeting in 2012 [6] and the FDA guidance draft for co-crystals, [7] which classifies co-crystals as 'dissociable API-excipient molecular complexes' where the co-former is the excipient, we call pharmaceutical companies' attention to the fact that following FDA rules, co-crystals can be treated as drug product intermediate, offering the potential of abbreviated new drug application rather than the full new drug application. This can be looked upon as not only a prompt process involving fewer risks, but also a less cost-effective process. Different steps have also been given to enhance drug properties through API metal coordination, generating metallodrugs and metallopharmaceuticals and more recently bio-inspired metal-organic frameworks (BioMOFs) for drug storage and controlled delivery. Here, we briefly present and discuss some of the recent published work, giving examples where the proposed routes proved to be beneficial.

No abstract

No abstract

The reactivity of the active pharmaceutical ingredient azelaic acid (AA) with carboxylic acid, alcohol, amine, and amide based co-formers was screened. Five new multicomponent crystal forms of AA were obtained by liquid assisted grinding and conventional solution methods. The obtained forms: (i) a co-crystal with 4,4′-bipyridine (AA:BIP, 1), (ii) an anhydrous and an hydrated molecular salt with piperazine (AA:PIP, 2 and 3), and (iii) two anhydrous molecular salts with morpholine (AA:MORPH, 4) and 1,4-diazobicyclo­[2.2.2]­octane (AA:DABCO, 5), were fully characterized by X-ray diffraction and solid-state (SS) NMR. In all new forms the carboxylic-carboxylic R 2 2(8) homosynthon present in AA is broken, and NH2···OCOOH or +NH2···OCOO- hydrogen bonds (HBs) become the fundamental pillars in the new supramolecular arrangements. The X-ray structure of 4 exhibits a static disorder in the hydrogen atoms engaged in an HB between two COOH moieties of AA. Density functional theory geometry optimization of the hydrogen positions followed by GIPAW-DFT calculations of 1H chemical shifts showed that such disordered atoms refer to O···H···O hydrogens, roughly equidistant from both proton acceptor and donor atoms. 1H SSNMR detected unusually strong HBs associated with such disordered hydrogens through the presence of 1H resonances shifted to very high frequencies (up to ca. 20.1 ppm). These results clearly show the advantageous use of both X-ray diffraction and SSNMR techniques for structural elucidation. We concluded that the hydrated piperazine salt 3 readily converted to 2 at ambient RH and that their thermal behavior is strongly determined by both the supramolecular arrangement and strength of HB network. Piperazine salt 2 presents an improved aqueous solubility bestowing a promising opportunity to avoid the use of alcoholic solutions in the final formulations.