Development of a range of retinoid-based products and preliminary design of its manufacturing process

Treballs Finals de Grau d'Enginyeria Química, Facultat de Química, Universitat de Barcelona, Curs: 2024-2025, Tutora: Esther SantamaríaIn recent years, there has been a change in dermocosmetics towards a more integrated understanding of skin health, emphasizing the balance and internal well-being of the skin microbiome and the prevention of dermatological issues. Since their introduction in dermatology, retinoids have demonstrated their effectiveness in treating acne and the marks it leaves behind, such as post-inflammatory erythema and hyperpigmentation. Moreover, the biologically active forms of retinoids can influence the expression of genes related to cell differentiation and proliferation, thus improving the signs of skin aging This project focuses on the development of two products formulated with different retinoids:a retinal-based serum for the topical treatment of acne and post-acne marks, and a retinol-based cream to prevent and treat signs of skin aging. The development stages include product conceptualization, identification of quality factors, formulation in accordance with European regulations, and preliminary design of the manufacturing process, including detailed equipment selection, annual campaign scheduling, and design of the flow process and Gantt diagram. The formulation of both products consists of oil-in-water (O/W) emulsions, considering the serum a microemulsion, and the cream a macroemulsion. Both feature a combination of active ingredients that act synergistically: the serum includes retinaldehyde, zinc PCA, niacinamide, and a derivative of vitamin B6, while the cream contains a mixture of retinol, hyaluronic acid, and niacinamide. Production is set at 6,000 kg/year for the serum and 10,000 kg/year for the cream, following a batch process on a multiproduct plant with an overlapping production configuration enabling simultaneous processing of different operations and improving time efficienc

Preparation and handling of investigational medicinal products

Mestrado em Biomedicina FarmacêuticaDuo to all of the challenges related with the production and logistics of the investigational medicinal products, this project aims to make an overview about the development of an investigational medicinal product, and the main details that must be considered in the preparation, packaging, labelling and distribution of investigational medicinal products, in order to provide a quick reference tool in a professional and academic context. A review was made in the international literature to identify studies focusing on development and handling of investigational medicinal products, mainly through PubMed and Medline databases, although it has also resorted to guidelines, some books on the subject, and master and doctoral thesis. Only English language papers were selected. Whenever possible, it were selected the most recent articles. During the development of IMP, solubility, as well as bioavailability assessment and bioequivalence studies, are the most challenging steps in the early phase of preparation of IMPs. Concerning the IMP production, the critical aspects, such as comparators, blinding and package, will determine the success of the entire clinical trial. When the IMP is fully prepared, it enters in the different clinical trials phases, with the aim of providing a range of information, such as efficacy and safety. This whole process must meet a series of requirements previously established, and adequate trained staff, in order to minimize the costs associated with the development of the IMP, as well as accelerate its market entry. It is important to note some limitations in the review. Although there is a wide range of information on the preparation of investigational medicinal products, little information was found on the logistics. In a future work, it would be interesting to further explore the distribution of investigational medicinal products, addressing the main unsatisfactory results of audits, in a clinical trial environment, and find tools and procedures to prevent nonconformities.Face a todos os desafios relacionados com a produção e logística do medicamento experimental, este projeto tem como objetivo fornecer uma visão geral sobre o desenvolvimento de um medicamento experimental, assim como os principais detalhes que devem ser considerados na preparação, embalagem, rotulagem e distribuição de medicamentos experimentais, de forma a fornecer uma ferramenta de referência rápida em contexto profissional e académico. Foi realizada uma revisão na literatura internacional para identificar estudos com foco no desenvolvimento e distribuição de medicamentos experimentais, principalmente através de bases de dados como o PubMed e Medline, embora também se tenha recorrido a guidelines, e alguns livros e teses de mestrado e doutoramento sobre o objeto de estudo. Foram selecionados apenas artigos na língua inglesa. Sempre que possível, foram selecionados os artigos mais recentes. Durante o processo de desenvolvimento de um medicamento experimental, os estudos de solubilidade, assim como os de biodisponibilidade e bioequivalência, são os maiores desafios nas fases iniciais de desenvolvimento. Atendendo à produção do medicamento experimental, aspectos críticos, como os comparadores, os processos de blinding e embalamento, são determinantes para o sucesso de todo o ensaio clínico. Após a completa preparação do medicamento experimental, este é introduzido nas diferentes fases de ensaio clínico, com o objetivo de fornecer uma ampla informação, como a eficácia e a segurança. Todo este processo deve englobar uma série de requisitos previamente estabelecidos, assim como uma equipa devidamente treinada, de forma a minimizar os custos associados ao desenvolvimento do medicamento experimental, acelerando a sua entrada no mercado. É importante ressalvar que embora exista uma ampla gama de informação sobre a preparação de medicamentos experimentais, foi encontrada pouca informação sobre a logística, sendo fundamental, no futuro, explorar mais a temática da distribuição de medicamentos experimentais, abordando os principais resultados não satisfatórios das auditorias, no âmbito dos ensaios clínicos, e encontrar ferramentas e procedimentos para evitar as nãoconformidades

Developing Methods to Assess Enzyme Stability in Liquid Laundry Detergents

This thesis presents work focused on developing established protein analysis methods for use in studying enzyme inactivation in laundry detergent systems. In a multi-billion dollar per year industry, basic, labour intensive procedures still dominate commercial stability studies, with extensive storage tests and activity assays remaining the industry standard. These methods are both inefficient and provide little insight into inactivation processes, leading to a 'trial and error' approach to product development. This slows the introduction new formulations and enzyme variants to the market. Furthermore, a valuable opportunity is being missed, harnessing available resources in the detergent industry to advance both protein analysis technologies and understanding of protein denaturation processes. Transfer from these basic, low throughput methods to those favoured by other protein-focused industries has been hindered by sample complexity and the presence of high concentrations of the surfactant, LAS. In this work, two novel approaches to enzyme analysis in LAS-rich media will be presented. The first employing an analogous surfactant, SDS, which yields similar effects on protein stability but does not affect UV detection, and the second, exploiting the irreversible nature of detergent enzyme unfolding to enable manipulation of formulations to within instrument specifications. These approaches will allow for incorporation of ultra-high throughput screening methods, such as DSF, as well as techniques which provide further insight into protein unfolding processes, such as CD, to the available suite of analytical techniques. Thermal data arising from this work were compared with rates of degradation obtained through conventional storage tests. Empirical fittings suggest a linear relationship between Tm values and long-term storage stability, enabling the use of thermal analysis as a tool for prediction of degradation rates. Further work is required to refine these models, however, before expanding to more complex systems

Formulation and evaluation of captopril loaded polymethacrylate and hydroxypropyl methycellulose microcapsules

Angiotensin-converting enzyme (ACE) inhibitors are some of the most commonly prescribed medications for hypertension. They are cited in many papers as the treatment most often recommended by guidelines and favoured over other antihypertensive drugs as first-line agents especially when other high-risk conditions are present, such as diabetic nephropathy. The development of captopril (CPT) was amongst the earliest successes of the revolutionary concept of structure-based drug design. Due to its relatively poor pharmacokinetic profile or short half-life of about 1 hour, the formulation of sustained-release microcapsule dosage form is useful to improve patient compliance and to achieve predictable and optimized therapeutic plasma concentrations. Currently, CPT is mainly administered in tablet form. One of the difficulties of CPT formulation has been reported to be its instability in aqueous solutions. CPT is characterized by a lack of a strong chromophore and, therefore, not able to absorb at the more useful UV–Vis region of the spectrum. For this reason, an accurate, simple, reproducible, and sensitive HPLC-ECD method was developed and validated for the determination of CPT in dosage forms. The method was successfully applied for the determination of CPT in commercial and developed formulations. Possible drug-excipient and excipient-excipient interactions were investigated prior to formulating CPT microcapsules because successful formulation of a stable and effective solid dosage form depends on careful selection of excipients. Nuclear magnetic resonance spectroscopy, Fourier transform infra-red spectroscopy (FT-IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used for the identification and purity testing of CPT and excipients. The studies revealed no thermal changes during stress testing of binary and whole mixtures which indicate absence of solid state interactions. There were no shifts, appearance and disappearance in the endothermic or exothermic peaks and on the change of other associated enthalpy values on thermal curves obtained with DSC method. Characteristic peaks for common functional groups in the FT-IR were present in all the mixtures indicating the absence of incompatibility. The techniques used in this study can be said to have been efficient in the characterization and evaluation of the drug and excipients. The technique of microencapsulation by oil-in-oil was used to prepare CPT microcapsules. The effects of polymer molecular weight, homogenizing speed on the particle size, flow properties, morphology, surface properties and release characteristics of the prepared CPT microcapsules were examined. In order to decrease the complexity of the analysis and reduce cost response surface methodology using best polynomial equations was successfully used to quantify the effect of the formulation variables and develop an optimized formulation thereby minimizing the number of experimental trials. There was a burst effect during the first stage of dissolution. Scanning electron microscopy (SEM) results indicated that the initial burst effect observed in drug release could be attributed to dissolution of CPT crystals present at the surface or embedded in the superficial layer of the matrix. During the preparation of microcapsules, the drug might have been trapped near the surface of the microcapsules and or might have diffused quickly through the porous surface. The release kinetics of CPT from most formulations followed Fickian diffusion mechanism. SEM photographs showed that diffusion took place through pores at the surface of the microcapsules. The Kopcha model diffusion and erosion terms showed predominance of diffusion relative to swelling or erosion throughout the entire test period. Drug release mechanism was also confirmed by Makoid-Banakar and Korsmeyer-Peppas models exponents which further support diffusion release mechanism in most formulations. The models postulate that the total of drug release is a summation of a couple of mechanisms; burst release, relaxation induced controlled-release and diffusional release. Inspection of the 2D contour and 3D response surfaces allowed the determination of the geometrical nature of the surfaces and further providing results about the interaction of the different variables used in central composite design (CCD). The wide variation indicated that the factor combinations resulted in different drug release rates. Lagrange, canonical and mathematical modelling were used to determine the nature of the stationery point of the models. This represented the optimal variables or stationery points where there is interaction in the experimental space. It is difficult to understand the shape of a fitted response by mere inspection of the algebraic polynomial when there are many independent variables in the model. Canonical and Lagrange analyses facilitated the interpretation of the surface plots after a mathematical transformation of the original variables into new variables. In conclusion, these results suggest the potential application of Eudragit® / Methocel® microcapsules as suitable sustained-release drug delivery system for CPT

A self-emulsifying delivery system loaded with efavirenz: The case for flax-seed oil

The feasibility of incorporating efavirenz (EFV), an antiretroviral agent against HIV into a lipid-based self-emulsifying drug delivery system (SEDDS) containing vegetable oils was investigated. EFV has poor aqueous solubility and is classified under the Biopharmaceutical Classification System (BCS) as a class II compound with highly permeability, its aqueous solubility is less than 10 mg/ml and is defined as a practically insoluble compound with a consequent poor bioavailability of approximately 40%, and erratic dissolution behaviour. SEDDS formulations have been shown to improve the aqueous solubility and consequently the bioavailability of BCS II compounds such as EFV. EFV is a first line antiviral agent used in combination with other agents in antiretroviral therapy (ART). Among the number of NNRTIs approved for use in HIV treatment, EFV is one of the most commonly prescribed drug. Statistical methods and Design of Experiments (DoE) using Response Surface Methodology (RSM), specifically a Central Composite Design (CCD), were used to facilitate the development of a reversed-phase high performance liquid chromatographic (HPLC) method for the quantitation of EFV during formulation product and process development studies. A rapid, accurate, precise and sensitive HPLC method with ultraviolet (UV) detection was developed, optimised and validated for the in-vitro analysis of EFV in a total run time under 10 minutes for the elution of both EFV and loratidine which was used as the internal standard (IS). The method was then successfully applied to the determination of EFV in commercially available tablets. Excipient screening was undertaken using solubility studies and revealed that EFV had highest solubility in flaxseed oil in comparison to soybean, macadamia, grapeseed, sunflower and olive oils. The non-ionic Tween® 80 and Span® 20 were selected as surfactant and co-surfactant, respectively with ethanol co-solvent as they exhibited improved miscibility with co-solvent. Pre-formulation studies were undertaken to investigate the compatibility of the API with excipients and to identify a nano-emulsion region and other emulsion types using pseudoternary phase diagrams. The phase behaviour of crude cold pressed flaxseed oil with the selected non-ionic surfactants revealed an area within pseudo-ternary phase diagrams for different surfactant-mixtures formed gels/semisolid structures which can be exploited for other drug delivery strategies that require such properties. Fourier transform infrared spectroscopy (FT-IR), powder x-ray diffraction (XRD) and Raman spectroscopy were used to identify and assess the compatibility of EFV with chosen excipients. 2 A reduction in the peak intensity was observed for EFV when combined with each hydrophobic/lipid excipient evaluated revealing that there was a marked reduction in the crystallinity of the EFV. A decrease in crystallinity in comparison with the bulk API may indicate that EFV were amorphous or sequestered in a molecular dispersion and exhibited an increased solubility for the molecule. Flaxseed oil was used as the oil phase in studies for the optimization of surfactant mixtures undertaken using DoE, specifically a D-optimal mixtures design with the flaxseed oil content set at 10% m/m was performed. Solutions from the desired optimization function were produced based on desirability and five nanoemulsion formulations were produced and characterized in terms of in vitro release of efavirenz, drug loading capacity, Zeta Potential, droplet sizes and polydispersity index (PDI). Kinetically stable nanoemulsions containing 10% m/m flaxseed oil were successfully manufactured and assessed. Droplet sizes ranged between 156 and 225 nm, Zeta Potential between −24 and −41 mV and all formulations were found to be monodisperse with polydispersity indices ≤ 0.487. SEDDS formulations of EFV in nano-sized carriers were developed and optimised, in vitro drug release varied with varying amounts of ethanol in the formulation producing formulations that exhibited differently modulated drug in-vitro release profiles that may be further manipulated for better performance and therapeutic outcomes in terms of solubility and possibly bioavailability of EFV when delivered using SEDDS rather than using tablets which in turn may lead to better therapeutic outcomes for patients with HIV.Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 202

Development and assessment of sustained release stavudine loaded microparticles

Stavudine (D4T) has been used as first line treatment for HIV/AIDS and is part of highly active anti retroviral treatment (HAART). It is an affordable medicine and its use is beneficial in resource limited settings. However D4T exhibits dose dependent side effects that may lead to non-adherence in patients. This study was undertaken to formulate, develop and manufacture a dosage form that could reduce dose dependent side effects by decreasing the dose of D4T but still exhibit antiretroviral (ARV) activity. The use of sustained release (SR) formulations of D4T that ensure constant levels of the D4T in the body would not only optimize therapy but also reduce the incidence of side effects thereby increasing patient adherence. SR microparticles containing 30mg D4T were manufactured and loaded into size 3 hard gelatine capsules prior to analysis. The D4T microparticles were manufactured by microencapsulation using non-aqueous oil-in-oil solvent evaporation approach. D4T-excipient, excipient-excipient interactions and D4T purity were assessed using Infrared Spectroscopy (IR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Copolymers synthesized from acrylic and methacrylic acid esters viz., Eudragit® RSPO and S100 were used as rate retardant materials and the effect of microcrystalline cellulose (Avicel® PH102) on the microparticles was also investigated. Magnesium stearate was used as a droplet stabilizer and n-hexane was added to harden the microspheres formed in a liquid paraffin continuous phase. The microparticles were optimized using a Box Behnken design and Response Surface Methodology (RSM). The microparticles were characterized in terms of their flow properties and encapsulation efficiency (% EE), in addition to visualization of the surface morphology with Scanning Electron Microscopy. In vitro D4T release studies were performed using USP Apparatus III in media of different pH and the samples were analysed using a validated High Performance Liquid Chromatographic (HPLC) method with ultraviolet (UV) detection that had been developed and optimized using a Central Composite Design (CCD). The method was validated according to ICH guidelines. The IR spectra and DSC thermographs revealed that D4T exhibited thermal stability and there was no evidence of D4T-excipient and excipient-excipient interactions. The microparticles that were produced were white, free flowing and were obtained in a high yield with high encapsulation efficiency. Scanning Electron Microscopy studies revealed that the microparticles were spherical and porous in nature. In vitro D4T release extended to 12 hours and the mechanism of release was established using model dependent methods by fitting the data to a Zero order, First order, Higuchi and Hixson Crowell model. It was observed that the mechanism of D4T release was diffusion-controlled and that the data was best fitted to the Higuchi model with correlation coefficients > 0.9. The release mechanism was confirmed using the Korsmeyer-Peppas model that revealed that most of the formulations exhibited anomalous transport kinetics with the release exponent, n, ranging from 0.5<n<1.0. These data suggest that diffusion was not the only mechanism controlling D4T release and that swelling and/or polymer relaxation may contribute to the release. Model-independent analysis for comparison of dissolution profiles was undertaken and the f1 and f2 difference and similarity factor were calculated. The optimized formulation, Batch BB-018 was found to be similar to two batches (BB-005 and BB-016). The dissolution profiles were evaluated to establish which of the batches exhibited D4T release that was appropriate for SR dosage forms. In conclusion polymethacrylate copolymers were successfully used to produce SR D4T microparticles that have the potential to be used for a twice a day dosing of D4T

The influence of moisture content and temperature on storage stability of freeze-dried biologics

Moisture and temperature are both critical factors that affect the long term storage stability of Freeze-dried (FD) biologics. Both physical structure and biological activity can be affected by the conditions that the FD material is subject to over a prolonged storage period. This project aimed to investigate how these key factors affected the long term storage stability of FD biologics. The relationship between moisture content, cake structure and the physical/biological stability for model proteins/antigen standards during long term storage was investigated. Novel techniques and procedures were developed to measure the effects of moisture and storage temperature in FD material. Dynamic vapour sorption (DVS) instrumentation, in conjunction with a real time video imaging, was used to measured visible collapse/shrinkage of FD materials. DVS data used in conjunction with video images for a series of temperatures were analysed to provide stability maps. These provided critical moisture content levels that should not be exceeded in order to retain structural cake stability. In addition, other novel techniques were utilised to measure morphological or physical changes with regards to moisture and temperature. Mechanical properties of the FD materials was measured with a flat punch indenter, while inverse gas chromatography (IGC) was used to measure the cake specific surface area (SSA). Mechanical indention data showed that increasing moisture and storage temperature lead to a reduction of mechanical properties and specifically Young’s modulus. IGC was shown to be suitable alternative to measure SSA of FD biologics, providing comparable SSA values to standard volumetric gas adsorption techniques. Advantages of IGC included being able to show and measure changes to SSA of FD materials conditioned at different relative humidities. A series of long term stability trials were also conducted for high protein concentration formulations (IgG) with a range of 10 - 200 mg/mL to further investigate mechanisms of protein stabilisation in regards to optimum moisture and temperature. Higher concentration proteins had lower SSA’s with larger Young’s Modulus but suffered from longer reconstitution times. IgG stability during 12 month storage trials showed evidence for both vitrification and water replacement theories. The data also provided further evidence for the bell shaped distribution theory of optimum moisture content for some materials and that over-drying with a low moisture cycle might not necessarily be the best option for long term storage stability of IgG. High moisture contents of up to 5% w/w did not seem to have any impact on stability until storage above 45°C. With high concertation FD proteins above 50 mg/mL, there was low of risk of structural collapse with increasing moisture content compared to lower concentration materials. Water ingress into vials during their long term storage is of huge concern especially for all FD materials, but especially so for low mass products such as FD Influenza antigens. Comparison of different closure storage formats for FD antigens was explored and it was found that vials with vacuum-oven dried stoppers had less moisture ingress than vials with unprocessed stoppers (straight out of manufacturers packaging). Vials with vacuum-oven dried stoppers were shown to give comparable potency and moisture content ingress as glass ampoules for reference standard influenza antigens over a 1 year period from -20°C to 45°C. Thus not only can vials with vacuum oven dried stoppers reduce moisture ingress compared to unprocessed stopper vials, but can also result in retaining greater potency and stability during long term storage. In summary, this thesis via use of prolonged stability trials, expanded and further consolidated knowledge on current theories of mechanisms of stability in context to moisture content and temperature during long term storage for real world commercial FD biological standards. This thesis also promoted and endorsed the adoption of novel techniques or practices (such as vacuum oven drying stoppers) to provide further aid and insight in optimising the long term storage stability of FD biologics for future use in industry.Open Acces

The development of an orodispersible sildenafil citrate tablet intended for paediatric use

Sildenafil citrate (SC) is a phosphodiesterase-5 inhibitor that is used to treat pulmonary hypertension (PH) in paediatric patients. The purpose of these studies was to develop a formulation and manufacture an orodispersible tablet (ODT) that can be easily administered to neonates and children with PH. The advantages of ODT dosage forms include ease of administration, rapid dissolution of the API, SC. Furthermore the dosage form can be taken without water which is beneficial to patients without immediate access to potable fluids. A simple, rapid, accurate, precise and selective reversed-phase HPLC method was developed and validated in accordance with International Conference on Harmonization (ICH) guidelines and was successfully used for the analysis of SC as raw material and in SC containing pharmaceutical dosage forms. Preformulation studies were performed on SC, alone and in combination with potential excipients that could be used to make tablets. Investigations into potential interactions between SC and the excipients were performed using Differential Scanning Calorimetry (DSC) and Infrared Spectroscopy (IR). DSC results revealed that SC was compatible with all potential excipients except mannitol and magnesium stearate. However these interactions were not observed with IR and therefore it was concluded that the interactions were induced by the high temperatures that DSC operates at. Particle size and shape was also established by use of Scanning Electron Microscopy (SEM) and flow properties were monitored by calculating Carr’s Index (CI) and the Hausner Ratio (HR). Direct compression was used as the method of manufacture for SC tablets as this approach is simple and the most economic production approach. The powder blends were assessed for bulk and tapped density and the CI and HR were used to determine the flowability of the blends. The quality attributes of the resultant tablets that were monitored included uniformity of weight, friability, crushing strength, tensile strength, disintegration, wetting and in vitro dispersion times. Design of Experiments is an efficient statistical approach that has become a popular tool used in the pharmaceutical industry to optimize formulation compositions, as it allows for the investigation of several input factors at the same time whilst not using the tedious and traditional “ modification of one variable at a time” approach. A Central composite experimental design was chosen as the most appropriate means to optimize the formulation as it produces more accurate results as opposed to other experimental designs approaches as input factors are investigated at five different levels. Through the use of mathematical modelling, optimum concentrations of disintegrant(s) and an appropriate blending time were established. Analysis of the data from the experimental design and mathematical modelling studies reveal that no changes in disintegrant concentration or blending time altered the disintegration time of the formulation to any significant extent. This result is most likely due to the fact that the critical disintegrant concentration has been reached and increasing the disintegrant concentration further has no effect on disintegration time. It was also established that a change in the concentration of CMS and CRP altered the wetting time of the tablet significantly. Finally it was noted that there was a linear relationship between blending time and the uniformity of content of the tablets produced in these studies. The optimized product was a white tablet with a diameter of 7.31 mm with a thickness of 2.80mm.The dosage form had no visible cracks or evidence of picking or sticking. The tablet exhibits suitable friability and tensile strength while exhibiting a disintegration time of only 8s. Therefore an orodispersible tablet containing SC intended for paediatric use has been successfully developed, manufactured and optimized through the use of preformulation studies, appropriate quality control monitoring and mathematical modelling. These formulations require further optimization in respect of addition of flavours and or additional sweetening agents

Health technology assessment of pathogen reduction technologies applied to plasma for clinical use

Although existing clinical evidence shows that the transfusion of blood components is becoming increasingly safe, the risk of transmission of known and unknown pathogens, new pathogens or re-emerging pathogens still persists. Pathogen reduction technologies may offer a new approach to increase blood safety. The study is the output of collaboration between the Italian National Blood Centre and the Post-Graduate School of Health Economics and Management, Catholic University of the Sacred Heart, Rome, Italy. A large, multidisciplinary team was created and divided into six groups, each of which addressed one or more HTA domains.Plasma treated with amotosalen + UV light, riboflavin + UV light, methylene blue or a solvent/detergent process was compared to fresh-frozen plasma with regards to current use, technical features, effectiveness, safety, economic and organisational impact, and ethical, social and legal implications. The available evidence is not sufficient to state which of the techniques compared is superior in terms of efficacy, safety and cost-effectiveness. Evidence on efficacy is only available for the solvent/detergent method, which proved to be non-inferior to untreated fresh-frozen plasma in the treatment of a wide range of congenital and acquired bleeding disorders. With regards to safety, the solvent/detergent technique apparently has the most favourable risk-benefit profile. Further research is needed to provide a comprehensive overview of the cost-effectiveness profile of the different pathogen-reduction techniques. The wide heterogeneity of results and the lack of comparative evidence are reasons why more comparative studies need to be performed