by Giuliana Miglierini
Oral solid dosage (OSD) forms (i.e. capsules and tablets) historically represent the most easy and convenient way for the administration of medicines. Recent years saw an increasing role of new approaches to treatment based on the extensive use of biotechnology to prepare advanced therapies (i.e. cellular, gene and tissue-based medicinal products). These are usually administered by i.v. injections or infusions, and may pose many challenges to develop a suitable dosage form, as acknowledged for example by the use of new lipid nanoparticles for the formulation of the mRNA Covid-19 vaccines.
The most recent trends in the development of new dosage forms have been addressed by Felicity Thomas from the column of Pharmaceutical Technology.
The increasing complexity of formulations is due to the need to accommodate the peculiar characteristics of biological macro-molecules and cellular therapies, which are very different from traditional small-molecules. Bioavailability and solubility issues are very typical, for example, and ask for the identification of new strategies for the setting up of a suitable formulation. The sensitivity of many new generation active pharmaceutical ingredients (APIs) to environmental conditions (i.e. temperature, oxygen concentration, humidity, etc.) also poses many challenges. Another important target is represented by the need to improve the compliance to treatment, to be pursued through the ability of patients to self-administer also injectable medicines using, for example, specifically designed devices. The parenteral administration of medicines has become more acceptable to many patients, especially in the case of serious indications and when auto-injectors are available, indicates another PharmTech’s article.
According to the experts interviewed by Felicity Thomas, there is also room for the development of new oral solid dosage forms for the delivery of biological medicines, as well as for OSD forms specifically designed to address the needs of paediatric and geriatric patients.
Some examples of technological advancements
Productive plants based on the implementation of high containment measures (i.e. isolators and RABS) are widely available to enable the entire manufacturing process to occur under “sea led” conditions, thus allowing for the safer manipulation of high potency APIs and the prevention of cross-contamination. Process analytical technologies (PAT), digital systems and artificial intelligence (AI) can be used to improve the overall efficiency of the formulation process. This may also prove true for previously “undruggable” proteins, that thanks to the AI can now become “druggable” targets denoted by a very high potency (and a low stability, thus asking for specific formulation strategies).
Advances in material sciences and the availability of new nanotechnology can support the development of oral formulations characterised by improved efficacy and bioavailability. To this instance, the article mentions the example of new softgel capsules able to provide inherent enteric protection and extended-release formulation. Functional coating, non-glass alternatives for injectables, and new excipients may also play an important role in the development of new formulations, such as controlled-release products, multi-particulates, orally disintegrating tablets, intranasal dosage forms, fixed-dose combinations.
The ability to establish a robust interaction with the suppliers enables the development of “tailor-made” specifications for excipients, aimed to better reflect the critical material attributes of the drug substance. The ability to formulate personalised dosage forms may prove relevant from the perspective of the increasingly important paradigm of personalised medicine, as they may better respond to the genetic and/or epigenetic profile of each patient, especially in therapeutic areas such as oncology.
Not less important, advancements of processing techniques used to prepare the biological APIs (for example, the type of adeno-viral vectors used in gene therapy) are also critical; to this regard, current trends indicate the increasing relevance of continuous manufacturing processes for both the API and the dosage form.
Injectable medicines may benefit from advancements in the understanding of the role played by some excipients, such as polysorbates, and of the interactions between the process, the formulation and the packaging components. Traditional techniques such as spray drying and lyophilisation are also experiencing some advancements, leading to the formulation of a wider range of biomolecules at the solid or liquid states into capsules or tablets.
New models for manufacturing
API solubility often represents a main challenge for formulators, that can be faced using micronization or nano-milling techniques, or by playing with the differential solubility profile of the amorphous vs crystalline forms of the active ingredient (that often also impact on its efficacy and stability profile).
As for the manufacturing of OSD forms, 3D printing allows the development of new products comprehensive of several active ingredients characterised by different release/dissolution profiles. This technology is currently represented, mostly in the nutraceutical field, and may prove important to develop personalised dosage forms to be rapidly delivered to single patients. 3D printing also benefits from advancements in the field of extrusion technologies, directly impacting on the properties of the materials used to print the capsules and tablets.
Artificial intelligence is today of paramount importance in drug discovery, as it allows the rapid identification of the more promising candidate molecules. Smart medical products, such as digital pills embedding an ingestible sensor or printed with special coating inks, enable the real-time tracking of the patient’s compliance as well as the monitoring “from the inside” of many physiological parameters. This sort of technology may also be used to authenticate the medicinal product with high precision, as it may incorporate a bar code or a spectral image directly on the dosage form. Dosage flexibility may benefit from the use of mini-tablets, that can be used by children as well as by aged patients experiencing swallowing issues.
The peculiarities of the OTC sector
Over-the-counter (OTC) medicines present some distinctive peculiarities compared to prescription drugs. According to an article on PharmTech, since the mid-‘80s the OTC segment followed the dynamics characteristic of other fast-moving consumer packaged goods (FMCG) industries (e.g., foods, beverages, and personal care products), thus leading to a greater attention towards the form and sensory attributes of the dosage form.
The following switch of many prescription medicines to OTC, in the ‘90s, reduced the difference in dosage forms between the two categories of medicinal products. Today, the competition is often played on the ability to provide patients with enhanced delivery characteristics, for example in the form of chewable gels, effervescent tablets for hot and cold drinks, orally disintegrating tablets and confectionery-derived forms. The availability of rapid or sustained-released dosage forms and long-acting formulations, enabling the quick action or the daily uptake of the medicine, is another important element of choice. Taste-masking of API’s particles is a relevant characteristic, for example, to make more acceptable an OSD form to children; this is also true for chewable tablets and gels, a “confectionery pharmaceutical form” often used to formulate vitamins and supplements.