Mamr,Drugs2014.12,1066-1101:doi:10.3390/md12021066 OPEN ACCESS marine drugs 1SSN1660-3397 www.mdpi.com/journal/marinedrugs Review Marketed Marine Natural Products in the Pharmaceutical and Cosmeceutical Industries:Tips for Success Ana Martins',Helena Vieira 2,Helena Gaspar3and Susana Santos3* BIOALVO,S.A.,Tec Labs Centro de Inovacao,Campus da FCUL,Campo Grande,Lisboa 1749-016. Portugal;E-Mails:ana.martins@bioalvo.com(A.M.),hmvieira@fc.ul.pt(H.V.) 2 Center for Biodiversity,Functional&Integrative Genomics(BioFIG)and Departamento de Operacional (DEIO),Faculdade de Cincias,Universidade de Lisboa Campo Grande.Lisboa 1749-016.Portugal Centro de Quimicae Bioquimica(CQB)and Departamento de Quimicae Bioquimica(DQB). Faculdade de Ciencias,Universidade de Lisboa.Campo Grande,Lisboa 1749-016.Portugal E-Mail:hmgaspar@fc.ul.pt *Author to whom correspondence should be addressed;E-Mail:smsantos@fc.ul.pt; Tel.:+351-217-500-948,Fax:+351-217-500-088. Received:2 December 2013:in revised form:14January 2014/Accepted:27 Jamuary 2014/ Published:17 February 2014 Abstract:The marine environment harbors a number of macro and micro organisms tha have developed unique metabolic abilities to ensure their survival in diverse and hostile habitats,resulting in the biosynthesis of an array of secondary metabolites with specific activities.Several of these metabolites are high-value commercial products for the pharmaceutical and cosmeceutical industries.The aim of this review is to outline the paths of marine natural products discovery and development,with a special focus on the compounds that successfully reached the market and particularly looking at the approaches tackled by the pharmaceutical and cosmetic companies that succeeded in marketing those products.The main challenges faced during marine bioactives discovery and developmen programs were analyzed and grouped in three categories:biodiversity (accessibility to marine resources and efficient screening),supply and technical (sustainable production of the bioactives and knowledge of the mechanism of action)and market (processes,costs. partnerships and marketing).Tips to surpass these challenges are given in order to improve the market entry succes rates of highly promising marine bioactives in the curren pipelines,highlighting what can be learned from the successful and unsuccessful stories
Mar. Drugs 2014, 12, 1066-1101; doi:10.3390/md12021066 marine drugs ISSN 1660-3397 www.mdpi.com/journal/marinedrugs Review Marketed Marine Natural Products in the Pharmaceutical and Cosmeceutical Industries: Tips for Success Ana Martins 1 , Helena Vieira 1,2, Helena Gaspar 3 and Susana Santos 3, * 1 BIOALVO, S.A., Tec Labs Centro de Inovação, Campus da FCUL, Campo Grande, Lisboa 1749-016, Portugal; E-Mails: ana.martins@bioalvo.com (A.M.); hmvieira@fc.ul.pt (H.V.) 2 Center for Biodiversity, Functional & Integrative Genomics (BioFIG) and Departamento de Estatística e Investigação Operacional (DEIO), Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa 1749-016, Portugal 3 Centro de Química e Bioquímica (CQB) and Departamento de Química e Bioquímica (DQB), Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Lisboa 1749-016, Portugal; E-Mail: hmgaspar@fc.ul.pt * Author to whom correspondence should be addressed; E-Mail: smsantos@fc.ul.pt; Tel.: +351-217-500-948; Fax: +351-217-500-088. Received: 2 December 2013; in revised form: 14 January 2014 / Accepted: 27 January 2014 / Published: 17 February 2014 Abstract: The marine environment harbors a number of macro and micro organisms that have developed unique metabolic abilities to ensure their survival in diverse and hostile habitats, resulting in the biosynthesis of an array of secondary metabolites with specific activities. Several of these metabolites are high-value commercial products for the pharmaceutical and cosmeceutical industries. The aim of this review is to outline the paths of marine natural products discovery and development, with a special focus on the compounds that successfully reached the market and particularly looking at the approaches tackled by the pharmaceutical and cosmetic companies that succeeded in marketing those products. The main challenges faced during marine bioactives discovery and development programs were analyzed and grouped in three categories: biodiversity (accessibility to marine resources and efficient screening), supply and technical (sustainable production of the bioactives and knowledge of the mechanism of action) and market (processes, costs, partnerships and marketing). Tips to surpass these challenges are given in order to improve the market entry success rates of highly promising marine bioactives in the current pipelines, highlighting what can be learned from the successful and unsuccessful stories OPEN ACCESS
Mar.Drugs 2014,12 1067 that can be applied to novel and/or ongoing marine natural products discovery and development programs Keywords:marine natural products;pharmaceuticals,cosmeceuticals;biodiscovery; challenges:success;market 1.Introduction Natural products(NP)are usually small molecules,with a molecular weight below 3000 Da,which are produced by a biological source such as plants.animals and microorganisms,but which occurrence may be limited to a particular taxonomic family,genus,species or even organism [1].They are often called secondary metabolites because,predominantly,they are not biosynthesized by the general metabolic pathways and have no primary function directly involved in the normal growth, development or reproduction of an organism.They are generally used by organisms to control ecological relationships that involve defense against predation,competition for space and food, interspecies communication for the purposes of mating.hunting or quorum signaling.among other functions.NP have long been a traditional source of medicines,and are still nowadays considered the most successful supply of potential drug leads with more than 1 million new chemical entities discovered so far [2.3].Historical examples of early identified natural compounds are undoubtedly the isolation of morphine from Papaver somniferum poppies,first reported in 1803,and the discovery in 1929 by Flemming of the first antibiotic penicillin from the fungus Penicillium notatum [3].Since then,numerous other NP have been isolated and identified with60%of the drugs currently on the market being of natural origin [4].These compounds are known to present several advantageous as compared with non-natural compounds such as high chemical diversity,biochemical specificity. binding efficiency and propensity to interact with biological targets,which make them favorable lead structures. Suitable natural sources for the discovery of new potentially bioactive molecules are numerous but marine environment,harboring a vast variety of organisms differing in their physiology and adaptation capacity,is becoming a top spot for the identification of new drug leads.From the over 33 animal phyla described to date,32 are represented in the aquatic environment,with 15 being exclusively marine [5.Despite the fact that oceans cover more than 70%of the earth's surface,the exploration of marine ecosystems has only began in the mid 1970's,with the emergence of modern snorkeling.the introduction of scuba in 1970and later,around 990,with the use of remotely operated vehicles(ROVs)[2].Due to technical limitations,exploitation of marine organisms started with the collection of large creatures such as red algae.sponges and soft corals,which were shown to produce a large variety of compounds with quite unique chemical structures [6].Invertebrates alone comprise approximately 60%of all marine animals and were described as the source of more than 11,000 new NP since 1990 9].With the continuous exploitation of the marine environment. attention turned to microorganisms such as marine cyanobacteria,marine fungi,and several other groups of marine bacteria due to their biological and habitat diversity,which resulted in the ability to produce metabolites with unmatched structures []Microorganisms constitute nowadays a prolific
Mar. Drugs 2014, 12 1067 that can be applied to novel and/or ongoing marine natural products discovery and development programs. Keywords: marine natural products; pharmaceuticals; cosmeceuticals; biodiscovery; challenges; success; market 1. Introduction Natural products (NP) are usually small molecules, with a molecular weight below 3000 Da, which are produced by a biological source such as plants, animals and microorganisms, but which occurrence may be limited to a particular taxonomic family, genus, species or even organism [1]. They are often called secondary metabolites because, predominantly, they are not biosynthesized by the general metabolic pathways and have no primary function directly involved in the normal growth, development or reproduction of an organism. They are generally used by organisms to control ecological relationships that involve defense against predation, competition for space and food, interspecies communication for the purposes of mating, hunting or quorum signaling, among other functions. NP have long been a traditional source of medicines, and are still nowadays considered the most successful supply of potential drug leads with more than 1 million new chemical entities discovered so far [2,3]. Historical examples of early identified natural compounds are undoubtedly the isolation of morphine from Papaver somniferum poppies, first reported in 1803, and the discovery in 1929 by Flemming of the first antibiotic penicillin from the fungus Penicillium notatum [3]. Since then, numerous other NP have been isolated and identified with 60% of the drugs currently on the market being of natural origin [4]. These compounds are known to present several advantageous as compared with non-natural compounds such as high chemical diversity, biochemical specificity, binding efficiency and propensity to interact with biological targets, which make them favorable lead structures. Suitable natural sources for the discovery of new potentially bioactive molecules are numerous, but marine environment, harboring a vast variety of organisms differing in their physiology and adaptation capacity, is becoming a top spot for the identification of new drug leads. From the over 33 animal phyla described to date, 32 are represented in the aquatic environment, with 15 being exclusively marine [5]. Despite the fact that oceans cover more than 70% of the earth‘s surface, the exploration of marine ecosystems has only began in the mid 1970‘s, with the emergence of modern snorkeling, the introduction of scuba in 1970 and later, around 1990, with the use of remotely operated vehicles (ROVs) [2]. Due to technical limitations, exploitation of marine organisms started with the collection of large creatures such as red algae, sponges and soft corals, which were shown to produce a large variety of compounds with quite unique chemical structures [6]. Invertebrates alone comprise approximately 60% of all marine animals and were described as the source of more than 11,000 new NP since 1990 [7–9]. With the continuous exploitation of the marine environment, attention turned to microorganisms such as marine cyanobacteria, marine fungi, and several other groups of marine bacteria due to their biological and habitat diversity, which resulted in the ability to produce metabolites with unmatched structures [10]. Microorganisms constitute nowadays a prolific
Mar.Drugs 2014.12 1068 source of structurally diverse bioactive metabolites and have vielded some of the most important active ingredients known today[11].Recently it was even realized that many compounds previously isolated from marine macroorganisms,such as sponges and tunicates,are in fact,metabolic products of associated microorganisms [12.13]. Due to their broad panel of bioactivities such as anti-tumor,anti-microtubule,anti-proliferative. photoprotective,antibiotic and anti-infective [14-19].marine natural products(MNP)are exceptionally interesting high-value ingredients for applications in the pharmaceutical industry and more and more companies are investing in this field.Following the same trend,cosmetics industry is progressively turning to the sea in the search for new ingredients.Traditionally,in the field of cosmetic industry cosmetics were defined as articles to be applied to human body for cleansing,beautifying,promoting attractiveness.or altering the appearance without affecting body structure or functions [201.However. more recently,the cosmetic industry introduced a special class of products.the cosmeceuticals,as a combination of cosmetics and pharmaceuticals,as bioactive ingredients are now combined with creams,lotions and ointments [21].Interestingly,an increasing number of suppliers of the cosmetic industry are being pushed to include extracts made from costal plants,seaweeds,algae and sea minerals into cosmeceutical ingredients.These extracts contain vitamins and minerals and they show ultraviolet and anti-oxidant protection and general anti-aging benefits [22-25].In fact,activities such as antioxidant,anti-wrinkle,anti-tyrosinase and anti-acne are among the most usual activities of marine cosmetic ingredients for skin health [21,26].Hence,an entire new paradigm of beauty care, combining cosmetics and pharmaceuticals properties into novel products with biologically active ingredients,will be the hallmark of the next decades The aim of this review is to outline the role of MNP in pharmaceutical and cosmeceutical industries,to identify the main bottlenecks found during the process of discovery and development. and to give an overview over the compounds that entered successfully in those markets.Tips for success will also be given so that more mne can reach the market 2.Marine Environment as an Unexploited Source for Bioactives Discovery The discovery and identification of the two nucleosides spongothymidine and spongouridine in the early 1950s from the Caribbean marine sponge Cryptotethia crypta paved the way of MNP as promising new chemical entities of potential therapeutic value [27].Since then,several other therapeutic agents have been obtained through isolation from natural sources.by chemical synthesis or a combination of both. In the most traditional process for bioactive discovery,a natural product is firstly extracted from the source,screened against a specific target,isolated by a bioassay-guided isolation procedure. fractionated and purified,yielding essentially a single biological active compound.Despite its widespread use,this traditional method of natural product bioactive discovery is slow,labor intensive barely efficient and provides no guarantee of success.Nowadays,NP discovery is on high demand for rapid screening.hit identification and hit-to-lead faster development processes.being mandatory to explore new approaches in order to compete successfully with other alternative drug discovery methods.In fact,rational drug design involving high throughput screening (HTS)technology in combination with combinatorial chemistry (CC)have reduced in the past decades the interest on NP
Mar. Drugs 2014, 12 1068 source of structurally diverse bioactive metabolites and have yielded some of the most important active ingredients known today [11]. Recently it was even realized that many compounds previously isolated from marine macroorganisms, such as sponges and tunicates, are in fact, metabolic products of associated microorganisms [12,13]. Due to their broad panel of bioactivities such as anti-tumor, anti-microtubule, anti-proliferative, photoprotective, antibiotic and anti-infective [14–19], marine natural products (MNP) are exceptionally interesting high-value ingredients for applications in the pharmaceutical industry and more and more companies are investing in this field. Following the same trend, cosmetics industry is progressively turning to the sea in the search for new ingredients. Traditionally, in the field of cosmetic industry cosmetics were defined as articles to be applied to human body for cleansing, beautifying, promoting attractiveness, or altering the appearance without affecting body structure or functions [20]. However, more recently, the cosmetic industry introduced a special class of products, the cosmeceuticals, as a combination of cosmetics and pharmaceuticals, as bioactive ingredients are now combined with creams, lotions and ointments [21]. Interestingly, an increasing number of suppliers of the cosmetic industry are being pushed to include extracts made from costal plants, seaweeds, algae and sea minerals into cosmeceutical ingredients. These extracts contain vitamins and minerals and they show ultraviolet and anti-oxidant protection and general anti-aging benefits [22–25]. In fact, activities such as antioxidant, anti-wrinkle, anti-tyrosinase and anti-acne are among the most usual activities of marine cosmetic ingredients for skin health [21,26]. Hence, an entire new paradigm of beauty care, combining cosmetics and pharmaceuticals properties into novel products with biologically active ingredients, will be the hallmark of the next decades. The aim of this review is to outline the role of MNP in pharmaceutical and cosmeceutical industries, to identify the main bottlenecks found during the process of discovery and development, and to give an overview over the compounds that entered successfully in those markets. Tips for success will also be given so that more MNP can reach the market. 2. Marine Environment as an Unexploited Source for Bioactives Discovery The discovery and identification of the two nucleosides spongothymidine and spongouridine in the early 1950s from the Caribbean marine sponge Cryptotethia crypta paved the way of MNP as promising new chemical entities of potential therapeutic value [27]. Since then, several other therapeutic agents have been obtained through isolation from natural sources, by chemical synthesis or a combination of both. In the most traditional process for bioactive discovery, a natural product is firstly extracted from the source, screened against a specific target, isolated by a bioassay-guided isolation procedure, fractionated and purified, yielding essentially a single biological active compound. Despite its widespread use, this traditional method of natural product bioactive discovery is slow, labor intensive, barely efficient and provides no guarantee of success. Nowadays, NP discovery is on high demand for rapid screening, hit identification and hit-to-lead faster development processes, being mandatory to explore new approaches in order to compete successfully with other alternative drug discovery methods. In fact, rational drug design involving high throughput screening (HTS) technology in combination with combinatorial chemistry (CC) have reduced in the past decades the interest on NP
Mar.Drugs 2014,12 1069 discovery [28].The two techniques together make the screening of synthetic compounds faster and cheaper as compared to traditional natural product discovery 9.Nevertheess,such rapid synthetic techniques have not led to successful development of bioactives.For instance,early CC libraries were composed of compounds with poor solubility,low purity and short chemical diversity and hence only a few useful hits were identified [28.29].So,some companies,driven by achievements on total or hemi-synthesis of NP [291.development of synthetic analogues or design of synthesizable pharmacophores of reduced complexity.brought back natural product discovery programs [30.31]. The development of refined analytical and spectroscopic methods.particularly high resolution nuclear magnetic resonance(NMR)and mass spectrometry (MS)has also contributed tremendously to put NP,and in particular MNP,back on the track of drug discovery [32].In fact,the many advances in spectroscopic methods.allowed the de novo structure determination of new chemical entities (NCEs) in very small concentrations [33]even in complex mixtures as crude extracts. An additional fact that helped to put MNP back on the agenda of drug discovery programs was the recent development of techniques that allow the access to a vast community of microbial sources unattainable until recently.Culture broths of new microorganisms are now very easy to obtain,through small scale,high-throughput cultivation methods that use nutrient deficient media,specific nutrients and long cultivation times [34].In addition,as more than 99%of the microorganisms is not readily cultivable,culture independent methods based on the total DNA of the bacterial community,can now detect a considerable fraction of the uncultivable organisms (in addition to those that can be cultured) enabling the access to these previously unreachable natural product resources.Metagenomics,in particular.enables direct access to the genomes of whole environmental uncultivable microorganisms by total environmental dna extraction 1351 and it has already proven to be a good alternative for exploiting uncultivable microorganisms for natural product discovery 36]. Ultimately,genome mining.which consists in the analyses of genome sequences for the identification of genes encoding proteins,is an additional recent approach which has allowed the discovery of numerous novel NP and also revealed gene clusters and novel pathways for the biosynthesis of several known natural compounds [37].The biosynthesis of polyketides,for example,has attracted most attention,since many commercial antibiotics derive from this pathway.Genome mining is of high importance on NP discovery as it opens up the possibility of expressing the gene clusters in a heterologous organism. obtaining the desired secondary metabolites [38].Furthermore,it has also allowed the development of combinatorial biosynthesis,which involves the genetic manipulation of the gene cluster involved in NP biosynthesis to obtain new molecules that would be difficult to synthesize using other methods [39]. All the progressive improvements in the past 50 years of exploration of the marine enviro pointed out earlier,have resulted in the isolation of approximately 20,000 structurally unique bioactive MNP [40].Just in 2012,1241 new compounds were reported which clearly identifies the marine environment as a rich source of bioactive molecules [Nevertheless,despite this enormous numbe of structurally unique bioactive MNP.to the date the global marine pharmaceutical pipeline includes only eight approved drugs,twelve NP(or derivatives thereof)in different clinical phases and a large number of marine chemicals in the preclinical phase [6,41,42].The global market for marine-derived drugs is forecasted to reach $8.6 B by 2016 [43]. In alignment with the pharmaceutical industry,the the sea in the search for new molecules.In fact,MNP are on high demand for skin care,as they
Mar. Drugs 2014, 12 1069 discovery [28]. The two techniques together make the screening of synthetic compounds faster and cheaper as compared to traditional natural product discovery [29]. Nevertheless, such rapid synthetic techniques have not led to successful development of bioactives. For instance, early CC libraries were composed of compounds with poor solubility, low purity and short chemical diversity and hence only a few useful hits were identified [28,29]. So, some companies, driven by achievements on total or hemi-synthesis of NP [29], development of synthetic analogues or design of synthesizable pharmacophores of reduced complexity, brought back natural product discovery programs [30,31]. The development of refined analytical and spectroscopic methods, particularly high resolution nuclear magnetic resonance (NMR) and mass spectrometry (MS) has also contributed tremendously to put NP, and in particular MNP, back on the track of drug discovery [32]. In fact, the many advances in spectroscopic methods, allowed the de novo structure determination of new chemical entities (NCEs) in very small concentrations [33] even in complex mixtures as crude extracts. An additional fact that helped to put MNP back on the agenda of drug discovery programs was the recent development of techniques that allow the access to a vast community of microbial sources unattainable until recently. Culture broths of new microorganisms are now very easy to obtain, through small scale, high-throughput cultivation methods that use nutrient deficient media, specific nutrients and long cultivation times [34]. In addition, as more than 99% of the microorganisms is not readily cultivable, culture independent methods based on the total DNA of the bacterial community, can now detect a considerable fraction of the uncultivable organisms (in addition to those that can be cultured) enabling the access to these previously unreachable natural product resources. Metagenomics, in particular, enables direct access to the genomes of whole environmental uncultivable microorganisms by total environmental DNA extraction [35] and it has already proven to be a good alternative for exploiting uncultivable microorganisms for natural product discovery [36]. Ultimately, genome mining, which consists in the analyses of genome sequences for the identification of genes encoding proteins, is an additional recent approach which has allowed the discovery of numerous novel NP and also revealed gene clusters and novel pathways for the biosynthesis of several known natural compounds [37]. The biosynthesis of polyketides, for example, has attracted most attention, since many commercial antibiotics derive from this pathway. Genome mining is of high importance on NP discovery as it opens up the possibility of expressing the gene clusters in a heterologous organism, obtaining the desired secondary metabolites [38]. Furthermore, it has also allowed the development of combinatorial biosynthesis, which involves the genetic manipulation of the gene cluster involved in NP biosynthesis to obtain new molecules that would be difficult to synthesize using other methods [39]. All the progressive improvements in the past 50 years of exploration of the marine environment, pointed out earlier, have resulted in the isolation of approximately 20,000 structurally unique bioactive MNP [40]. Just in 2012, 1241 new compounds were reported which clearly identifies the marine environment as a rich source of bioactive molecules [8]. Nevertheless, despite this enormous number of structurally unique bioactive MNP, to the date the global marine pharmaceutical pipeline includes only eight approved drugs, twelve NP (or derivatives thereof) in different clinical phases and a large number of marine chemicals in the preclinical phase [6,41,42]. The global market for marine-derived drugs is forecasted to reach $8.6 B by 2016 [43]. In alignment with the pharmaceutical industry, the cosmeceutical industry is increasingly turning to the sea in the search for new molecules. In fact, MNP are on high demand for skin care, as they
Mar.Drugs 2014.12 1070 are scientifically advanced and environmentally friendly,besides offering a variety of benefits. Seven types of cosmeceutical ingredients derived from marine resources have been identified so far and are currently commercialized [21].Driven by an aging population looking for innovative anti-aging solutions,the global cosmeceuticals in the US has reached $13.1 B in 2011 and is projected to grow almost twice the average rate of cosmetics sector [44] In conclusion.MNP constitute a strategic research area with enormous economic and social revenues,where scientists all over the world are interested.According to EuroOcean there are over 590 European marine projects funded by both FP6 and FP7 actions [45],which shows the engagement of academia and industry in bringing more marine bioactives into the market 3.Challenges Faced during Marine Natural Products Development For the purposes of this review,the major challenges faced by discovery and development programs of new bioactives from marine biological resources were grouped in three categories:biodiversity. supply and technical,and market.In the topic "biodiversity",a focus is addressed on challenges associated with secure access to marine resources,with the correct identification of the biological material and with the efficient screening of samples and compounds.The topic "supply and technical" covers the challenges associated with the actual process of isolation and sustainable production of the pure bioactive,and the understanding of its mechanism of action towards the desired target).Finally, in the topic "market challenges"considerations are made on the process and the costs of developing a nP bioactive 1461 3.1.Biodiversity Challenges It is widely accepted that we know more about the moon than we actually know about the sea The access to the ocean and to the deepest of its spots remains very difficult and further robotic and engineering technology is needed to fully evaluate the oceans available biodiversity.Because traditional medicinal knowledge associated with marine organisms is almost nonexistent,the search for biologically active compounds from marine sources has occurred via a random selection of organisms.Three different sampling approaches are commonly used:(i)exploring unexploited taxonomical groups or geographical sources,in order to maximize the chances of finding new molecules;(ii)exploring new taxa and/or regions of confirmed chemical diversity;or(iii)combining both of these strategies [47,48].In either case,substantial knowledge of bio-and chemo-diversity is required. Marine natural product studies were formerly conducted,randomly,in shallow coastal waters which left aside an enormous community of very promising organisms which lived in untapped but unreachable environments [49],e.g.,hydrothermal vents and sea mounts.Sampling in difficult access spots,deeper than 30 m,is not possible by scuba diving and is usually performed by trawling.This technique besides being unselective.often damages the samples and the benthic ecosystems,and hides valuable information about the environment of the organism [50].The ideal sampling of marine organisms in deep waters is by the use of sophisticated or ingenious equipment,such as manned submersibles and,more recently,ROVs [2].With this kind of equipment it is possible to observe the organism's habitat,and to foresee a possible bioactivity for its metabolites.For instance,if it is
Mar. Drugs 2014, 12 1070 are scientifically advanced and environmentally friendly, besides offering a variety of benefits. Seven types of cosmeceutical ingredients derived from marine resources have been identified so far, and are currently commercialized [21]. Driven by an aging population looking for innovative anti-aging solutions, the global cosmeceuticals in the US has reached $13.1 B in 2011 and is projected to grow almost twice the average rate of cosmetics sector [44]. In conclusion, MNP constitute a strategic research area with enormous economic and social revenues, where scientists all over the world are interested. According to EuroOcean there are over 590 European marine projects funded by both FP6 and FP7 actions [45], which shows the engagement of academia and industry in bringing more marine bioactives into the market. 3. Challenges Faced during Marine Natural Products Development For the purposes of this review, the major challenges faced by discovery and development programs of new bioactives from marine biological resources were grouped in three categories: biodiversity, supply and technical, and market. In the topic ―biodiversity‖, a focus is addressed on challenges associated with secure access to marine resources, with the correct identification of the biological material and with the efficient screening of samples and compounds. The topic ―supply and technical‖ covers the challenges associated with the actual process of isolation and sustainable production of the pure bioactive, and the understanding of its mechanism of action towards the desired target). Finally, in the topic ―market challenges‖ considerations are made on the process and the costs of developing a NP bioactive [46]. 3.1. Biodiversity Challenges It is widely accepted that we know more about the moon than we actually know about the sea. The access to the ocean and to the deepest of its spots remains very difficult and further robotic and engineering technology is needed to fully evaluate the oceans available biodiversity. Because traditional medicinal knowledge associated with marine organisms is almost nonexistent, the search for biologically active compounds from marine sources has occurred via a random selection of organisms. Three different sampling approaches are commonly used: (i) exploring unexploited taxonomical groups or geographical sources, in order to maximize the chances of finding new molecules; (ii) exploring new taxa and/or regions of confirmed chemical diversity; or (iii) combining both of these strategies [47,48]. In either case, substantial knowledge of bio- and chemo-diversity is required. Marine natural product studies were formerly conducted, randomly, in shallow coastal waters, which left aside an enormous community of very promising organisms which lived in untapped but unreachable environments [49], e.g., hydrothermal vents and sea mounts. Sampling in difficult access spots, deeper than 30 m, is not possible by scuba diving and is usually performed by trawling. This technique besides being unselective, often damages the samples and the benthic ecosystems, and hides valuable information about the environment of the organism [50]. The ideal sampling of marine organisms in deep waters is by the use of sophisticated or ingenious equipment, such as manned submersibles and, more recently, ROVs [2]. With this kind of equipment it is possible to observe the organism‘s habitat, and to foresee a possible bioactivity for its metabolites. For instance, if it is
Mar.Drugs 2014,12 1071 observed that a sponge lays alone in the habitat,and around it there is a clean area,most probably,its metabolites inhibit the growth of competing organisms [50].Unfortunately,these sampling facilities are very expensive and only a small number of laboratories have access to them,a drawback that is difficult to overcome,especially if we think that the majority of biological diversity is located in underdeveloped countries from the tropical and subtropical regions [51].This is just one of the reasons why international collaboration is so important in this research field.However,the access to biodiversity on natural resources is now under the host of the Convention on Biological Diversity (CBD).Unfortunately.the different levels of Nagova protocol implementation (which clarifies the scope of the CBD)in different regions,and the increasing difficulties to work under a still unclear regulatory framework on biodiversity access may push current industries out of the NP arena The lack of taxonomic knowledge for marine species,and the still large number of unidentified species and strains,is alsoa major blockage faced by marine natural products programs.The selection for pharmacological purposes.of macro or microorganisms.either terrestrial or marine.must be grounded on a correct taxonomic identification and classification.An incorrect classification of a species may compromise an entire drug discovery project,not only because it is impossible to reproduce the isolation in the event of a bioactive extract and/or metabolite.but also because it can mislead the dereplication process-the process by which the bioactives are identified.Approaches to classification of marine macroorganisms (algae and invertebrates)and microorganisms(fungi and bacteria)are quite different.For the majority of marine macroorganisms taxonomic knowledge is still insufficient to enable unambiguous species classification [52].Macroinvertebrates are especially challenging.not only due the fact that there are still many undescribed species.but also because many related species must be distinguished based on subtle morphological characteristics [531 Following the process of target identification and validation,the next step of a drug discovery process is the development of the screening assays.A variety of screening paradigms exist to identify hit molecules [54]being HTS the most widely used in the case of NP.The success key to apply HTS methodology to NP is constructing high quality libraries.Researchers at Pfizer proposed that the output from HTS is dependent on the interrelationships between the quality of the compound library. the target and the screening process [55].Ideally,the library itself should be composed by crud extracts.simplified extract fractions and pure compounds for a well-balanced natural product discovery program [56].Crude extract libraries are easier and cheaper to construct,have moderate overall size and a high degree of diversity,but have major disadvantages when compared with pure compounds libraries.Crude extracts are complex mixtures of several compounds that may have synergistic interaction.a fact that accounts for the disappearance of the bioactivity in purified fractions and,ultimately,in final pure compounds [57].On the other hand,false negative readouts may also be obtained.either because an active metabolite is present in a small percentage in the crude extract.or because of the interference of compounds such as tannins [56]that bind to other metabolites masking its activity.Due to these reasons.in a recent past this approach was discouraged in drug discovery programs [56].Screening pre-fractionated libraries is an effective strategy to avoid these problems [3]. Depending on the method used for pre-fractionation and on the number of compounds in the original crude extract,the resulting fractions can vary widely in complexity from a mixture of multiple compounds to a single major compound of%purity.Pre-fractionation can eliminate several undesired compounds and facilitate hit identification
Mar. Drugs 2014, 12 1071 observed that a sponge lays alone in the habitat, and around it there is a clean area, most probably, its metabolites inhibit the growth of competing organisms [50]. Unfortunately, these sampling facilities are very expensive and only a small number of laboratories have access to them, a drawback that is difficult to overcome, especially if we think that the majority of biological diversity is located in underdeveloped countries from the tropical and subtropical regions [51]. This is just one of the reasons why international collaboration is so important in this research field. However, the access to biodiversity on natural resources is now under the host of the Convention on Biological Diversity (CBD). Unfortunately, the different levels of Nagoya protocol implementation (which clarifies the scope of the CBD) in different regions, and the increasing difficulties to work under a still unclear regulatory framework on biodiversity access may push current industries out of the NP arena. The lack of taxonomic knowledge for marine species, and the still large number of unidentified species and strains, is also a major blockage faced by marine natural products programs. The selection, for pharmacological purposes, of macro or microorganisms, either terrestrial or marine, must be grounded on a correct taxonomic identification and classification. An incorrect classification of a species may compromise an entire drug discovery project, not only because it is impossible to reproduce the isolation in the event of a bioactive extract and/or metabolite, but also because it can mislead the dereplication process—the process by which the bioactives are identified. Approaches to classification of marine macroorganisms (algae and invertebrates) and microorganisms (fungi and bacteria) are quite different. For the majority of marine macroorganisms taxonomic knowledge is still insufficient to enable unambiguous species classification [52]. Macroinvertebrates are especially challenging, not only due the fact that there are still many undescribed species, but also because many related species must be distinguished based on subtle morphological characteristics [53]. Following the process of target identification and validation, the next step of a drug discovery process is the development of the screening assays. A variety of screening paradigms exist to identify hit molecules [54] being HTS the most widely used in the case of NP. The success key to apply HTS methodology to NP is constructing high quality libraries. Researchers at Pfizer proposed that the output from HTS is dependent on the interrelationships between the quality of the compound library, the target and the screening process [55]. Ideally, the library itself should be composed by crude extracts, simplified extract fractions and pure compounds for a well-balanced natural product discovery program [56]. Crude extract libraries are easier and cheaper to construct, have moderate overall size and a high degree of diversity, but have major disadvantages when compared with pure compounds libraries. Crude extracts are complex mixtures of several compounds that may have synergistic interaction, a fact that accounts for the disappearance of the bioactivity in purified fractions and, ultimately, in final pure compounds [57]. On the other hand, false negative readouts may also be obtained, either because an active metabolite is present in a small percentage in the crude extract, or because of the interference of compounds such as tannins [56] that bind to other metabolites masking its activity. Due to these reasons, in a recent past this approach was discouraged in drug discovery programs [56]. Screening pre-fractionated libraries is an effective strategy to avoid these problems [3]. Depending on the method used for pre-fractionation and on the number of compounds in the original crude extract, the resulting fractions can vary widely in complexity from a mixture of multiple compounds to a single major compound of >90% purity. Pre-fractionation can eliminate several undesired compounds and facilitate hit identification
Mar.Drugs 2014.12 1072 All in all,the association of modern HTS methods and robust NP libraries,representative of a wide biodiversity,is a powerful tool to streamline cosmeceutical and therapeutic lead discovery programs 3.2.Supply and Technical Challenges Several different problems are associated with supply and technical issues.The first one is related to the variability of the organism itself.For instance,taking the example of sponges,the high frequency of their bioactive metabolites is interpreted as chemical defense against environmental stress factors such as predation,overgrowth by fouling organisms or competition for space.The highest incidence of toxic or deterrent sponge metabolites is found in habitats such as coral reefs that are characterized by intense competition and feeding pressure.Because these environmental conditions are not static,it is likely that a resupply of the same organism does not provide the same metabolite.Also, in the case of marine invertebrates another challenge is the fact the microorganisms are sometimes the actual producers of the bioactives Once a particular natural product has been isolated and identified as a lead compound,the issue of its sustainable supply is faced.Most of the times,the compound of interest is present only in low amounts and/or can be very difficult to isolate [17].In the case of tissues of marine invertebrates, which present unique extraction-related problems due to their high water and salt content,this problem can be even more challenging.Whatever the use of the compound (drug cosmetic,rc.).several grams to hundreds of grams are required for preclinical development,multikilogram quantities are needed for clinical phases and tons for cosmetic uses. Mariculture(favoring by farming the growth of the organism in its natural milieu)and aquaculture (culture of the organism under artificial conditions)have been attempted in order to solve the problem of sustainable supply of macroorganisms.However,the unique and sometimesexclusive.conditions of the sea make cultivation or maintenance of the isolated samples very difficult and often impossible. For example,sponges and their microbiota are generally not suitable for cultivation,hence,the compound of interest may need to be extracted and purified from the specimens collected in the wild [47].These constraints lead to the loss of a major portion of the available marine biodiversity and represent a major bottleneck in the sustainable supply of the desired natural compound. This lack of sustainable supply of substances has stopped further development of several highly promising marine compounds,and attempts have been made to overcome this barrier by developing synthetic or hemisynthesic analogues,derivatives with more manageable properties.or by design of a pharmacophore of reduced complexity which can then be synthesized [301.However.it is worth noting.that these approaches embrace themselves their own challenges.Total synthesis is by no means an easy undertaking task,and chemistry still has a very long way to go before it can make any molecule in a practical manner.NP are complex and exquisite molecules possessing,almost always, one or several stereocenters,a fact that renders their synthesis hard to achieve,since enanteo or diastereoselective synthetic or purification processes are difficult to perform.Hemisynthesis may be.in some cases,a good solution for compound's supply.This process involves harvesting a biosynthetic intermediate from the natural source,rather than the lead itself,and converting it into the lead.This approach has two advantages.First,the intermediate may be more easily extracted in a higher yield than the final product itself.Second,it may allow the syntheses of analogues of the final product
Mar. Drugs 2014, 12 1072 All in all, the association of modern HTS methods and robust NP libraries, representative of a wide biodiversity, is a powerful tool to streamline cosmeceutical and therapeutic lead discovery programs. 3.2. Supply and Technical Challenges Several different problems are associated with supply and technical issues. The first one is related to the variability of the organism itself. For instance, taking the example of sponges, the high frequency of their bioactive metabolites is interpreted as chemical defense against environmental stress factors such as predation, overgrowth by fouling organisms or competition for space. The highest incidence of toxic or deterrent sponge metabolites is found in habitats such as coral reefs that are characterized by intense competition and feeding pressure. Because these environmental conditions are not static, it is likely that a resupply of the same organism does not provide the same metabolite. Also, in the case of marine invertebrates another challenge is the fact the microorganisms are sometimes the actual producers of the bioactives. Once a particular natural product has been isolated and identified as a lead compound, the issue of its sustainable supply is faced. Most of the times, the compound of interest is present only in low amounts and/or can be very difficult to isolate [17]. In the case of tissues of marine invertebrates, which present unique extraction-related problems due to their high water and salt content, this problem can be even more challenging. Whatever the use of the compound (drug, cosmetic, etc.), several grams to hundreds of grams are required for preclinical development, multikilogram quantities are needed for clinical phases and tons for cosmetic uses. Mariculture (favoring by farming the growth of the organism in its natural milieu) and aquaculture (culture of the organism under artificial conditions) have been attempted in order to solve the problem of sustainable supply of macroorganisms. However, the unique and sometimes exclusive, conditions of the sea make cultivation or maintenance of the isolated samples very difficult and often impossible. For example, sponges and their microbiota are generally not suitable for cultivation, hence, the compound of interest may need to be extracted and purified from the specimens collected in the wild [47]. These constraints lead to the loss of a major portion of the available marine biodiversity and represent a major bottleneck in the sustainable supply of the desired natural compound. This lack of sustainable supply of substances has stopped further development of several highly promising marine compounds, and attempts have been made to overcome this barrier by developing synthetic or hemisynthesic analogues, derivatives with more manageable properties, or by design of a pharmacophore of reduced complexity which can then be synthesized [30]. However, it is worth noting, that these approaches embrace themselves their own challenges. Total synthesis is by no means an easy undertaking task, and chemistry still has a very long way to go before it can make any molecule in a practical manner. NP are complex and exquisite molecules possessing, almost always, one or several stereocenters, a fact that renders their synthesis hard to achieve, since enanteo or diastereoselective synthetic or purification processes are difficult to perform. Hemisynthesis may be, in some cases, a good solution for compound‘s supply. This process involves harvesting a biosynthetic intermediate from the natural source, rather than the lead itself, and converting it into the lead. This approach has two advantages. First, the intermediate may be more easily extracted in a higher yield than the final product itself. Second, it may allow the syntheses of analogues of the final product
Mar.Drugs 2014,12 1073 Additionally,the synthesis or hemisynthesis of a bioactive natural compound must be supported by a correct identification of the compound isolated from the biological source.Despite the fact that modern methodologies of struetural elucidation are well advanced,errors can never be completely ruled out.In fact,there are numerous structural revisions reported in literature,even of recently elucidated NP.In average,per 5-year period,369 NP and 135 MNP are misassigned [58].The structural complexity of the isolated compounds and the small amount of samples,especially in the case of compounds from marine sources.can contribute to misassignments which can be divided in several categories:incorrect formula,constitution (planar connectivity),double bond configuration, absolute configuration,and one or several stereocenters assigned incorrectly [59]. To avoid"rediscovery of the known"more specialized and effective dereplication strategies need to be employed.With over 150,000 small molecules characterized from natural sources,previously known natural compounds are often re-isolated during bioassay-guided fractionation and that should be avoided [29].Hyphenated technics such as liquid chromatography with ultraviolet detection (LC-UV),liquid chromatography-mass spectrometry (LC-MS,LC-MS/MS)or LC-NMR are valuable toos for the dereplication process,especially if used early in the prefractionation step [60].Access to suitable databases is essential for the rapid dereplication of crude extracts in natural product research. Several commercial databases are available to implement the dereplication process,from which the most comprehensive ones are:Chemical abstracts,including NAPRALERT,Beilstein,AntiBase [61] (>40,000 natural compounds from micro-organisms and higher fungi),MarinLit (-24,000 marine compounds isolated from approximately 6000 species)[62]Chapman&Hall's Dictionary of Natural Products (~170.000 compounds from both marine and terrestrial organisms)63]and NAPROC-13 ('CNMR spectral information of over 6000 natural compounds)[641. When using pure natural compound libraries,virtual screening is also a possibility that must be stressed out.Virtual screening can be used for browsing databases in the quest for molecules fitting either an established pharmacophore model or a three dimensional structure of a macromolecular target.The advantages of this approach overinro sereening are obvious:higher capacity,no need for physically isolating the compounds,less time-consuming and expensive and theoretically interactions of all compounds to all structurally defined targets can be calculated and predicted Additionally early evaluation of absorption.distribution.metabolism.and excretion/toxicity in pharmacokinetics(ADMET)properties is also possible [65].But,because virtual screening is only a predictive tool,in the case of NP it is important the integration with traditional avenues,gathering information from bioassay guided fractionation,on-line analytical activity an optimization of drug lead discovery 65. Finally.upon the identification of a lead it is necessary to understand its mode of action against the specific target.This includes secondary testing in which molecular and cellular techniques are normally applied.This identification constitutes a major challenge but is becoming more and more compulsory in both pharmaceutical and cosmeceutical industries
Mar. Drugs 2014, 12 1073 Additionally, the synthesis or hemisynthesis of a bioactive natural compound must be supported by a correct identification of the compound isolated from the biological source. Despite the fact that modern methodologies of structural elucidation are well advanced, errors can never be completely ruled out. In fact, there are numerous structural revisions reported in literature, even of recently elucidated NP. In average, per 5-year period, 369 NP and 135 MNP are misassigned [58]. The structural complexity of the isolated compounds and the small amount of samples, especially in the case of compounds from marine sources, can contribute to misassignments which can be divided in several categories: incorrect formula, constitution (planar connectivity), double bond configuration, absolute configuration, and one or several stereocenters assigned incorrectly [59]. To avoid ―rediscovery of the known‖ more specialized and effective dereplication strategies need to be employed. With over 150,000 small molecules characterized from natural sources, previously known natural compounds are often re-isolated during bioassay-guided fractionation and that should be avoided [29]. Hyphenated technics such as liquid chromatography with ultraviolet detection (LC-UV), liquid chromatography-mass spectrometry (LC-MS, LC-MS/MS) or LC-NMR are valuable tools for the dereplication process, especially if used early in the prefractionation step [60]. Access to suitable databases is essential for the rapid dereplication of crude extracts in natural product research. Several commercial databases are available to implement the dereplication process, from which the most comprehensive ones are: Chemical abstracts, including NAPRALERT, Beilstein, AntiBase [61] (>40,000 natural compounds from micro-organisms and higher fungi), MarinLit (~24,000 marine compounds isolated from approximately 6000 species) [62], Chapman & Hall‘s Dictionary of Natural Products (~170,000 compounds from both marine and terrestrial organisms) [63] and NAPROC-13 ( 13CNMR spectral information of over 6000 natural compounds) [64]. When using pure natural compound libraries, virtual screening is also a possibility that must be stressed out. Virtual screening can be used for browsing databases in the quest for molecules fitting either an established pharmacophore model or a three dimensional structure of a macromolecular target. The advantages of this approach over in vitro screening are obvious: higher capacity, no need for physically isolating the compounds, less time-consuming and expensive and theoretically, interactions of all compounds to all structurally defined targets can be calculated and predicted. Additionally early evaluation of absorption, distribution, metabolism, and excretion/toxicity in pharmacokinetics (ADMET) properties is also possible [65]. But, because virtual screening is only a predictive tool, in the case of NP it is important the integration of in silico screening with traditional avenues, gathering information from bioassay guided fractionation, on-line analytical activity profiling, ethnopharmacological screening, if it is the case, and chemoinformatics, in order to achieve an optimization of drug lead discovery [65]. Finally, upon the identification of a lead it is necessary to understand its mode of action against the specific target. This includes secondary testing in which molecular and cellular techniques are normally applied. This identification constitutes a major challenge but is becoming more and more compulsory in both pharmaceutical and cosmeceutical industries
Mar.Drugs 2014,12 1074 3.3.Market Challenges Finally the commercial and market issues are very relevant and most of the times disregarded in the natural product development programs.Since the very early stages of the development programs. several very important questions must be addressed by the researchers or the companies:(i)what are the potential industry applications and the market need of that particular activity;(ii)what is the target price/kg of the final bioactive (i)what is the formulation desired and the route of administration (iv)what is the manufacturing process and how sustainable is the supply:(v)how can the product reach the market value chain.The high number of NP hits and leads coming out of the HTS technologies has stressed out the need for a focused strategy on this field.Small and Medium Enterprises (SME's)have a commercialization goal and,therefore,introduce very early on their discovery and development programs the issues indicated earlier.It is crucial for them to have a clearly defined strategy,otherwise the risk of failing and running out of cash fast is high.It is important to be aware that the cost of technology and manufacturing processes,sometimes with poo yields,raises the market cost per kilogram and may render these products economically unviable.This is particularly true in personal care industry where recombinant technologies are not acceptable and the profit margins are too small to introduce very expensive ingredients per pack.Recently,academia has started to be more aware of the "market issues as it became obvious that most of the discoveries on the NP pipeline where barely reaching the market and consumers.This has been partially achieved by serious encouragement of industry-academia partnerships,both at national and transnational levels that went beyond the traditional funding by the industry of small research projects of academia.These alliances benefit both partners that work side-by-side,with a common set of goals and in a win-win collaboration system.Academia gets knowledge.publications and funding and industry gets new NP with higher probabilities of market success. Bearing in mind all the challenges just pointed out,NP developers can thrive to find better models of development to surpass or minimize their impact. 4.Marketed Marine Natural Products.Examples of Success Stories The Marine Board of the European Science Foundation has published a position paper in which it provides a roadmap for European research in Marine Biotechnology and sets out an ambitious scienc and policy agenda for the next decade [66].Development of novel drugs,treatments and health and personal care products,is one of the five research areas prioritized in this document that can greatly contribute to key societal challenges An overview of marine drugs and cosmeceuticals that successfully reached the market is the focus of next section.Hopefully,the analysis of the issues related with their development will allow a deeper understanding of the key factors behind their success 4.1.Pharmaceutical Applications As pointed earlier,natural product screening remains one of the most useful avenues for bioactive discovery.In the past decades,studies on MNP have been focused mainly on macroorganisms,i.e., sponges,corals and other marine invertebrates,although significant developments have been made in
Mar. Drugs 2014, 12 1074 3.3. Market Challenges Finally the commercial and market issues are very relevant and most of the times disregarded in the natural product development programs. Since the very early stages of the development programs, several very important questions must be addressed by the researchers or the companies: (i) what are the potential industry applications and the market need of that particular activity; (ii) what is the target price/kg of the final bioactive; (iii) what is the formulation desired and the route of administration; (iv) what is the manufacturing process and how sustainable is the supply; (v) how can the product reach the market value chain. The high number of NP hits and leads coming out of the HTS technologies has stressed out the need for a focused strategy on this field. Small and Medium Enterprises (SME‘s) have a commercialization goal and, therefore, introduce very early on their discovery and development programs the issues indicated earlier. It is crucial for them to have a clearly defined strategy, otherwise the risk of failing and running out of cash fast is high. It is important to be aware that the cost of technology and manufacturing processes, sometimes with poor yields, raises the market cost per kilogram and may render these products economically unviable. This is particularly true in personal care industry where recombinant technologies are not acceptable and the profit margins are too small to introduce very expensive ingredients per pack. Recently, academia has started to be more aware of the ―market issues‖ as it became obvious that most of the discoveries on the NP pipeline where barely reaching the market and consumers. This has been partially achieved by serious encouragement of industry-academia partnerships, both at national and transnational levels that went beyond the traditional funding by the industry of small research projects of academia. These alliances benefit both partners that work side-by-side, with a common set of goals and in a win-win collaboration system. Academia gets knowledge, publications and funding and industry gets new NP with higher probabilities of market success. Bearing in mind all the challenges just pointed out, NP developers can thrive to find better models of development to surpass or minimize their impact. 4. Marketed Marine Natural Products. Examples of Success Stories The Marine Board of the European Science Foundation has published a position paper in which it provides a roadmap for European research in Marine Biotechnology and sets out an ambitious science and policy agenda for the next decade [66]. Development of novel drugs, treatments and health and personal care products, is one of the five research areas prioritized in this document that can greatly contribute to key societal challenges. An overview of marine drugs and cosmeceuticals that successfully reached the market is the focus of next section. Hopefully, the analysis of the issues related with their development will allow a deeper understanding of the key factors behind their success. 4.1. Pharmaceutical Applications As pointed earlier, natural product screening remains one of the most useful avenues for bioactive discovery. In the past decades, studies on MNP have been focused mainly on macroorganisms, i.e., sponges, corals and other marine invertebrates, although significant developments have been made in
Mar.Drugs 2014,12 1075 the microorganisms area.However,despite the large number of NCEs isolated from marine organisms many of them with pronounced biological activity,the great majority does not surpass the pharmaceutical pre-clinical trials and only a very few have been marketed as pharmaceutical products. Besides the usual drawbacks in any drug discovery process,the industrial development of many promising MNP was hampered by additional difficulties such as sustainable source and issues related to structural complexity and scale up.Nevertheless,the global marine pharmaceutical pipeline remains very active and includes,at the moment,eight Food and Drug Admnistration(FDA)or European Medicines Agency (EMEA)approved drugs and several compounds in different phases of the clinical pipeline [67].From the eight compounds currently on the market (Figure 1),only three (Prialt while the rest of them suffered lead optimization,in different steps of their development.Overall,from lead discovery to the entry in the market it took 20 to 30 years.Ensuring natural product supply on an industrial scale.optimization of formulation and ADMET properties were the main blockades faced by pharmaceutical companies.Optimization of NP by structural modifications,synthetic supply of unmodified natural molecule or immunoconjugation of NP was the strategy behind these successful stories.The history of the development of the market drugs will be discussed in this subsection with a focus on the approaches tackled by the pharmaceutical companies that succeeded in marketing their products Figure 1.Chemical structures of marine drugs on the market divided by therapeutic area. Cance N-C ypertriglyceridemi
Mar. Drugs 2014, 12 1075 the microorganisms area. However, despite the large number of NCEs isolated from marine organisms, many of them with pronounced biological activity, the great majority does not surpass the pharmaceutical pre-clinical trials and only a very few have been marketed as pharmaceutical products. Besides the usual drawbacks in any drug discovery process, the industrial development of many promising MNP was hampered by additional difficulties such as sustainable source and issues related to structural complexity and scale up. Nevertheless, the global marine pharmaceutical pipeline remains very active and includes, at the moment, eight Food and Drug Admnistration (FDA) or European Medicines Agency (EMEA) approved drugs and several compounds in different phases of the clinical pipeline [67]. From the eight compounds currently on the market (Figure 1), only three (Prialt® , Yondelis® and Carragelose® ), became drugs without any modification of the original natural molecule, while the rest of them suffered lead optimization, in different steps of their development. Overall, from lead discovery to the entry in the market it took 20 to 30 years. Ensuring natural product supply on an industrial scale, optimization of formulation and ADMET properties were the main blockades faced by pharmaceutical companies. Optimization of NP by structural modifications, synthetic supply of unmodified natural molecule or immunoconjugation of NP was the strategy behind these successful stories. The history of the development of the market drugs will be discussed in this subsection with a focus on the approaches tackled by the pharmaceutical companies that succeeded in marketing their products. Figure 1. Chemical structures of marine drugs on the market divided by therapeutic area