**Meet the editor**

Dr. Chris Rundfeldt looks back on 22 years of experience in drug development, with more than 13 years in pharmaceutical industry. He gained hands on experience in different fields of pharmacology including target validation, drug development, toxicology, and early clinical development. As co-founder and vice president pharmacology, he actively participated in the manage-

ment buyout of Elbion AG, a biopharmaceutical company dedicated to the development of CNS active drugs and immune modulators. He was responsible for translation of pharmacological results and safety data into clinical study programs. In 1996 he obtained the German Board certification for Veterinary Pharmacology and Toxicology. In 2000, he was granted the venia legendi (Assistant Professor) for Veterinary Pharmacology and Toxicology at the Free University of Berlin. Since 2007, he has been working as independent drug development consultant and partner at DrugConsult.Net, a German development expert partnership.

Contents

**Preface IX** 

**Part 1 Novel Approaches to Cancer Treatment 1** 

Chapter 1 **Discovery and Optimization of Inhibitors of DNA** 

Jakyung Yoo and José L. Medina-Franco

Chapter 2 **Development of Novel Secondary Hormonal** 

Rahul Aggarwal and Charles J. Ryan

Karolina Gluza and Paweł Kafarski

Vanina A. Medina, Diego J. Martinel Lamas, Pablo G. Brenzoni, Noelia Massari, Eliana Carabajal

**Therapeutic Agents for Cancer Therapy:** 

Ethirajulu Kantharaj and Ramesh Jayaraman

Chapter 4 **Histamine Receptors as Potential** 

and Elena S. Rivera

**Part 2 Anti-Infectives 121** 

Chapter 6 **Antimicrobial Peptides:** 

Chapter 5 **Histone Deacetylase Inhibitors as** 

Chapter 7 **microRNAs as Therapeutic Targets** 

Elizabeth Hong-Geller and Nan Li

**Methyltransferase as Novel Drugs for Cancer Therapy 3** 

**Therapies for Castrate-Resistant Prostate Cancer 23** 

**Therapeutic Targets for Cancer Drug Development 75** 

**Drug Metabolism and Pharmacokinetic Properties 101** 

**New Frontiers in the Therapy of Infections 123**  Mario Zucca, Sara Scutera and Dianella Savoia

**to Combat Diverse Human Diseases 163** 

Chapter 3 **Inhibitors of Proteinases as Potential Anti-Cancer Agents 39** 

## Contents

## **Preface** XIII


#### **Part 2 Anti-Infectives 121**


X Contents


Contents VII

Chapter 17 **The Gut Microbiota as Target for** 

Joan Vermeiren, Sam Possemiers,

Luiz H. Rosa, Mariana L.A. Vieira,

Carlos L. Zani and Carlos A. Rosa

**for Pharmaceutical Purposes 487** María Estrella Legaz, Roberto de Armas

Degenhard Marx and Matthias Birkhoff

Chapter 21 **Microneedle-Assisted Transdermal Delivery of** 

Stan L. Banks, Audra L. Stinchcomb

**Incentivizing Drug Development 545**

Chapter 23 **Drug Experimentation in Healthy Volunteers 561** Giovanni Gori, Giuseppe Pasqualetti, Catia Castiglioni, Corrado Blandizzi

Chapter 19 **Bioproduction of Depsidones** 

and Carlos Vicente

Chapter 20 **Multi-Dose Container for Nasal and**

and Kalpana S. Paudel

Kristina M. Lybecker

and Mario Del Tacca

Chapter 24 **Changes in Research and Development of** 

Maurizio Scarpa and Antje Neubert

Chapter 22 **Innovative Proposals for**

**Part 4 Drug Development Strategies 543**

**Innovative Drug Development: Perspectives**

Betania B. Cota, Susana Johann,Tânia M.A. Alves,

**Ophthalmic Drugs: A Preservative Free Future? 509**

**Opioid Antagonists for the Treatment of Alcoholism 525** 

**Medicinal Products since the Paediatric Regulation 585**

Adriana Ceci, Mariana Catapano, Cristina Manfredi, Ian Wong, Mine Orlu-Gul, Annarita Meneguz, Paola Baiardi, Oscar Della Pasqua, Achille Iolascon,

Massimo Marzorati and Tom Van de Wiele

Chapter 18 **Endophytic Fungi of Tropical Forests: A Promising Source of Bioactive Prototype Molecules for the Treatment of Neglected Diseases 469**

**and a Case Study of Inflammatory Bowel Diseases 437** 

Rosa, Ana Claudia Fernandes Amaral and Giseli Capaci Rodrigues


VI Contents

Chapter 8 **Potentiation of Available Antibiotics**

Chapter 9 **Antitubercular Drugs Development: Recent Advances in Selected** 

and Liem Nguyen

**by Targeting Resistance – An Emerging Trend in Tuberculosis Drug Development 183**

Virgilio Bocanegra-García, Abraham García,

Chapter 10 **Insight into the Key Structural Features of Potent**

Auradee Punkvang, Pharit Kamsri,

**Part 3 Novel Targets and Technologies** 

Chapter 11 **RNA Interference-Based Therapeutics:**

**Therapeutic Targets and Rational Drug Design 207** 

Jose Prisco Palma-Nicolás, Isidro Palos and Gildardo Rivera

Supa Hannongbua, Peter Wolschann and Pornpan Pungpo

**Enoyl Acyl Carrier Protein Reductase Inhibitors Based on Computer Aided Molecular Design 243**

Kodchakon Kun-asa,Patchreenart Saparpakorn,

**Leading to Improved Treatment Options 263**

Tamara Martinez, Natalia Wright, Covadonga Paneda,

**Harnessing the Powers of Nature 265**

Ana I. Jimenez and Marta Lopez-Fraga

Chapter 12 **P2X Receptors as New Therapeutic Targets 313** Liang Xin, Xiao Yanjuan and Li Zhiyuan

Chapter 13 **Pregnane X Receptor in Drug Development 337**

Chapter 14 **Crosstalk Between the Immune and Central Nervous** 

Rui Ting Liu, Jin Tian Tang, Li Bo Zou,

Chapter 16 **Novel Therapeutic Strategies for Chagas` Disease 399**

Jie Ying Fu and Qiu Jun Lu

**Systems with Special Reference to Drug Development 365**

Takekazu Kubo, Shigeru Tokita and Toshihide Yamashita

**Mouse Model and the Underlying Mechanisms 381**

Alane Beatriz Vermelho, Carlos Alberto Manssour Fraga,

Samir Aquino Carvalho, Edson Ferreira da Silva, Solange Lisboa de Castro, Igor de Almeida Rodrigues, Maria do Socorro dos Santos Rosa, Ana Claudia Fernandes Amaral and Giseli Capaci Rodrigues

Chapter 15 **Liquiritigenin Attenuates Alzheimer's-Like Neuropathology in an Amyloid Protein Precursor Transgenic**

Su Sien Ong, Yue-Ming Wang, Sergio C. Chai and Taosheng Chen

Kerstin A. Wolff, Marissa Sherman

	- **Part 4 Drug Development Strategies 543**

Preface

The term "drug development" depicts the process leading from a selected chemical structure as drug development candidate to the application for marketing authorization. During the development process three different aspects need to be elaborated: the chemical and pharmaceutical quality, the safety and toxicity profile, and the efficacy in patients. The majority of work conducted during the formal development process aims at generating the data required to submit a marketing application dossier, which will be reviewed by local authorities around the world for approval. The most important authorities are the Food and Drug Administration (FDA) in the US, the European Medicines Agency (EMA) and the Ministry of Health, Labor and Welfare (MHLW) in

Data generated during a drug development process should be suitable to be included into a dossier for marketing application in each of these countries and also in other regions. This, however, has not always been possible. In the 1980s, what is today the European Union began harmonizing regulatory requirements. In 1989, Europe, Japan, and the United States began creating plans for harmonization; and only in April 1990 a structure was established which aimed at generating standards which are acceptable in all respective regions. This institution was called "International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use" (ICH). It is composed from the three regulatory agencies representing US, EU and Japan, but it also included participants from the pharmaceutical industry of these regions. The purpose of ICH is to reduce or obviate the need to duplicate the testing carried out during the research and development of new medicines by recommending ways to achieve greater harmonization in the interpretation and

application of technical guidelines and requirements for product registration.

Since its establishment, the ICH has generated several guidelines and standards strictly regulating the requirements for successful drug development. Respective guidelines are often very detailed and describe the required data set and often even the way how such data are to be interpreted. At the same time, the ICH aims at being up to data to represent the best standard of current research. This requires constant update of guidelines and in part generation of novel regulations. Numerous guidelines have been generated and revised as needed in all three sections of drug development, i.e. the pharmaceutical section describing quality aspects of the drug substance and the

Japan. These agencies represent the major markets for pharmaceuticals.

## Preface

The term "drug development" depicts the process leading from a selected chemical structure as drug development candidate to the application for marketing authorization. During the development process three different aspects need to be elaborated: the chemical and pharmaceutical quality, the safety and toxicity profile, and the efficacy in patients. The majority of work conducted during the formal development process aims at generating the data required to submit a marketing application dossier, which will be reviewed by local authorities around the world for approval. The most important authorities are the Food and Drug Administration (FDA) in the US, the European Medicines Agency (EMA) and the Ministry of Health, Labor and Welfare (MHLW) in Japan. These agencies represent the major markets for pharmaceuticals.

Data generated during a drug development process should be suitable to be included into a dossier for marketing application in each of these countries and also in other regions. This, however, has not always been possible. In the 1980s, what is today the European Union began harmonizing regulatory requirements. In 1989, Europe, Japan, and the United States began creating plans for harmonization; and only in April 1990 a structure was established which aimed at generating standards which are acceptable in all respective regions. This institution was called "International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use" (ICH). It is composed from the three regulatory agencies representing US, EU and Japan, but it also included participants from the pharmaceutical industry of these regions. The purpose of ICH is to reduce or obviate the need to duplicate the testing carried out during the research and development of new medicines by recommending ways to achieve greater harmonization in the interpretation and application of technical guidelines and requirements for product registration.

Since its establishment, the ICH has generated several guidelines and standards strictly regulating the requirements for successful drug development. Respective guidelines are often very detailed and describe the required data set and often even the way how such data are to be interpreted. At the same time, the ICH aims at being up to data to represent the best standard of current research. This requires constant update of guidelines and in part generation of novel regulations. Numerous guidelines have been generated and revised as needed in all three sections of drug development, i.e. the pharmaceutical section describing quality aspects of the drug substance and the

#### XIV Preface

drug product (guidelines Q1-Q11), safety aspects (guidelines S1-S9) and efficacy aspects (E1-E16). Multidisciplinary guidelines are M1-M8. All guidelines are accessible online.

Preface XI

al. in this book, established antibiotics may be useful for the treatment of tuberculosis, if the mechanisms of resistance are attacked by well selected combination treatment. A different method to counterbalance a limited revenue potential is to reduce the development risks. Adequate studies showing that a given compound has a high chance to be active in a patient population, has a pharmacokinetic property which is in line with a once or twice daily treatment regime, and has a lower than average

In this book, this early drug development stage is described giving interesting

Despite extensive research conducted in the past, the fight against cancer is an ongoing battle with significant, but still only small advances in chemotherapy. In five different chapters, five different novel potential targets for cancer treatment are presented.

An enzyme critically involved in modulation of intracellular signaling by methylation of DNA is presented as potential target, directly affecting cell growth and

Several cancer cell types utilize sex hormones as growth stimulus and reducing this stimulation retards or blocks the growth of prostate and breast cancer. But these cells often escape the initial pharmacological intervention. Rahul Aggarwal and Charles J.

A different strategy is described by Karolina Gluza and Paweł Kafarski. A solid cancer is increasing its malignancy if it is capable to grow invasive. To penetrate cell barriers, the intercellular matrix needs to be dissolved requiring proteinases which are released by invasive cancer cells. The inhibition of these enzymes can reduce invasiveness. An

Vanina A. Medina et al. describe findings linking the histamine receptor to cancer

Histone deacetylase (HDAC) inhibitors are an emerging class of therapeutic agents that induce tumor cell cytostasis, differentiation, and apoptosis in various hematologic and solid malignancies. But currently available chemical scaffolds did not reach the stage of formal drug development. Ethirajulu Kantharaj and Ramesh Jayaraman describe the pharmacokinetics and metabolic properties to show which scaffold could

While antibacterial treatments did revolutionize the medical treatment of bacterial infections in the early years of rational drug development with the development of the sulfonamides in the years between 1910 and 1940, followed by penicillin in 1942, we

potential for toxicity, can attract decision makers to invest in the project.

examples in a number of disease areas.

differentiation (Jakyung Yoo and José L. Medina-Franco).

be best suited for further structure optimization.

2nd section: Anti-infectives

Ryan describe novel strategies to overcome the hormone resistance.

irreversible (mechanism based) inhibition is considered to be most effective.

treatment, which seems to be quite unexpected, but the data are intriguing.

1st section: Cancer treatment

The backbone of drug development is described in the guideline ICH M3 where preclinical safety studies are described which are needed at the different stages of clinical development. The guideline M4 describes the required format of a dossier for marketing application, the so called technical document where all data generated during a development process need to be compiled and evaluated by experts.

As can be seen from the description above, the formal drug development process is a highly regulated procedure and this strict regulation is required to ensure safety of all medicinal products. From a scientific point of view, the most interesting step within the drug development process is the selection of the right development candidate. The available book focusses on this bridging step, where basic research, chemical optimization, and scientific genius cumulate in the selection of a single molecule or at most 2-3 different molecules to be put through the formal process of drug development. This early drug development stage is most critical for the later success. At this stage, future efficacy in patients is predicted by well selected disease models and early risk mitigation procedures are required to reduce the development failure rate. At this stage creativity is not limited by regulatory agencies and the target audience for each data set generated is the management of a company or a group of investors, which need to be convinced that the respective molecule is worth investing several hundred million dollar, since this amount of money is often needed to conduct all the studies and generate all the data required to submit a full marketing authorization dossier. Indeed, drug development is very expensive.

A given development candidate will most likely only enter the development pipeline of a pharmaceutical company, if it can be shown that the development risks are below average and that the revenues which can be generated from future marketing of the drug are capable of paying back the investment. The requirement that a drug candidate must ultimately generate income makes a development difficult for diseases which affect only few people or for diseases which affect mainly poor people which cannot afford expensive medicines. However, if the costs of a specific development project can be reduced compared to the standard, the cost-revenue balance can be accomplished even if the expected sales are not sufficient for a standard development program.

Regulatory agencies in the major markets have already introduced measures to encourage drug development for rare diseases. Companies developing drugs for such rare diseases can get market exclusivity for a defined period, the clinical development program to show efficacy may be reduced and development support is also offered. But no such tools are currently available to encourage development for diseases which mainly affect poor people such as the so called neglected diseases or tuberculosis. Measures to reduce the costs to enable drug development for these diseases are for example to re-use available medicinal products. Indeed, as laid out by Dr. Nguyen et al. in this book, established antibiotics may be useful for the treatment of tuberculosis, if the mechanisms of resistance are attacked by well selected combination treatment. A different method to counterbalance a limited revenue potential is to reduce the development risks. Adequate studies showing that a given compound has a high chance to be active in a patient population, has a pharmacokinetic property which is in line with a once or twice daily treatment regime, and has a lower than average potential for toxicity, can attract decision makers to invest in the project.

In this book, this early drug development stage is described giving interesting examples in a number of disease areas.

#### 1st section: Cancer treatment

X Preface

online.

drug product (guidelines Q1-Q11), safety aspects (guidelines S1-S9) and efficacy aspects (E1-E16). Multidisciplinary guidelines are M1-M8. All guidelines are accessible

The backbone of drug development is described in the guideline ICH M3 where preclinical safety studies are described which are needed at the different stages of clinical development. The guideline M4 describes the required format of a dossier for marketing application, the so called technical document where all data generated

As can be seen from the description above, the formal drug development process is a highly regulated procedure and this strict regulation is required to ensure safety of all medicinal products. From a scientific point of view, the most interesting step within the drug development process is the selection of the right development candidate. The available book focusses on this bridging step, where basic research, chemical optimization, and scientific genius cumulate in the selection of a single molecule or at most 2-3 different molecules to be put through the formal process of drug development. This early drug development stage is most critical for the later success. At this stage, future efficacy in patients is predicted by well selected disease models and early risk mitigation procedures are required to reduce the development failure rate. At this stage creativity is not limited by regulatory agencies and the target audience for each data set generated is the management of a company or a group of investors, which need to be convinced that the respective molecule is worth investing several hundred million dollar, since this amount of money is often needed to conduct all the studies and generate all the data required to submit a full marketing

during a development process need to be compiled and evaluated by experts.

authorization dossier. Indeed, drug development is very expensive.

the expected sales are not sufficient for a standard development program.

A given development candidate will most likely only enter the development pipeline of a pharmaceutical company, if it can be shown that the development risks are below average and that the revenues which can be generated from future marketing of the drug are capable of paying back the investment. The requirement that a drug candidate must ultimately generate income makes a development difficult for diseases which affect only few people or for diseases which affect mainly poor people which cannot afford expensive medicines. However, if the costs of a specific development project can be reduced compared to the standard, the cost-revenue balance can be accomplished even if

Regulatory agencies in the major markets have already introduced measures to encourage drug development for rare diseases. Companies developing drugs for such rare diseases can get market exclusivity for a defined period, the clinical development program to show efficacy may be reduced and development support is also offered. But no such tools are currently available to encourage development for diseases which mainly affect poor people such as the so called neglected diseases or tuberculosis. Measures to reduce the costs to enable drug development for these diseases are for example to re-use available medicinal products. Indeed, as laid out by Dr. Nguyen et

Despite extensive research conducted in the past, the fight against cancer is an ongoing battle with significant, but still only small advances in chemotherapy. In five different chapters, five different novel potential targets for cancer treatment are presented.

An enzyme critically involved in modulation of intracellular signaling by methylation of DNA is presented as potential target, directly affecting cell growth and differentiation (Jakyung Yoo and José L. Medina-Franco).

Several cancer cell types utilize sex hormones as growth stimulus and reducing this stimulation retards or blocks the growth of prostate and breast cancer. But these cells often escape the initial pharmacological intervention. Rahul Aggarwal and Charles J. Ryan describe novel strategies to overcome the hormone resistance.

A different strategy is described by Karolina Gluza and Paweł Kafarski. A solid cancer is increasing its malignancy if it is capable to grow invasive. To penetrate cell barriers, the intercellular matrix needs to be dissolved requiring proteinases which are released by invasive cancer cells. The inhibition of these enzymes can reduce invasiveness. An irreversible (mechanism based) inhibition is considered to be most effective.

Vanina A. Medina et al. describe findings linking the histamine receptor to cancer treatment, which seems to be quite unexpected, but the data are intriguing.

Histone deacetylase (HDAC) inhibitors are an emerging class of therapeutic agents that induce tumor cell cytostasis, differentiation, and apoptosis in various hematologic and solid malignancies. But currently available chemical scaffolds did not reach the stage of formal drug development. Ethirajulu Kantharaj and Ramesh Jayaraman describe the pharmacokinetics and metabolic properties to show which scaffold could be best suited for further structure optimization.

#### 2nd section: Anti-infectives

While antibacterial treatments did revolutionize the medical treatment of bacterial infections in the early years of rational drug development with the development of the sulfonamides in the years between 1910 and 1940, followed by penicillin in 1942, we

#### XVI Preface

are now focusing the problem, that many bacteria are escaping the currently available antibiotics and becoming resistant, even to multiple antibiotics. To combat such multiresistant bacteria, novel strategies are required.

Preface XIII

Liquiritigenin, which is having estrogen-like function, is shown to have potent its

The evaluation of the activity of natural products is also the basis of the next chapter. Chagas disease is a tropical disease which has not attracted active drug development in the recent years. Alane Beatriz Vermelho et al. compare the activity of currently available medicines with the effects of novel lead structures, in part derived from

The interaction of pharmacological agents with a biotope which is often not considered to be of importance, the gut microbiota, is discussed by Joan Vermeiren et al. The composition of the gut bacteria community can have influence on stability, pharmacokinetics, and metabolism of xenobiotics. A better knowledge of this possible interaction can improve drug development. This is explored using inflammatory

The following two chapters explore novel sources for pharmacologically active compounds. While Luiz H. Rosa et al. focuss on endophytic fungi of tropical forests as a unique source for new chemical entities with potential for the treatment of diseases such as leishmaniasis, María Estrella Legaz et al. describe the utilization of the enzymatic properties of lichen to produce a compound class called depsidones. Preclinical data indicated that such compounds may have antiviral, antibacterial and

A different field of drug development is touched by the next two chapters, the pharmaceutical development of adequate dosage forms. Intranasal and transdermal drug administration is used to bypass the gastrointestinal tract and the metabolic capability of the liver. Successful application of these dosing routes requires that the administration results in adequate drug levels at the target organ without risk for the patient. A potential risk for intranasal application is bacterial contamination and hence infection from the nasal applicator. While preservatives can reduce the risk of bacterial growth in the container, such agents can induce irritation on the nasal mucosa and should be avoided. Degenhard Marx and Matthias Birkhoff describe novel technologies which can avoid the use of preservatives in multidose intranasal containers. Transdermal application is often limited by the skin representing a diffusion barrier. A technology to reduce the barrier function by using microneedles

prior to application of the transdermal patch is described by Stan L. Banks et al.

The final book section focusses on issues related to drug development in general. Drug development is very expensive and only if the potential revenues which can be generated by a drug candidate can payback the required investment, a development project can be started. Rare diseases or diseases predominantly affecting poor people are often not sufficiently covered by novel drug developments. Kristina M. Lybecker

4th section: Drug development strategies

activity in a mouse model of Alzheimer's disease.

natural products.

other effects.

bowel disease as case study.

Mario Zucca et al. describe novel antibacterial peptides which could help overcome the growing resistance. But peptides are difficult to develop since they are sensitive to metabolic degradation and may also have problems to penetrate tissues. These aspects are discussed.

Elizabeth Hong-Geller and Nan Li describe microRNA based treatment strategies for infective diseases, utilizing current knowledge of microRNA as cellular signaling tool.

Treatment of tuberculosis is the topic of the next 3 chapters. Mycobacterium tuberculosis is a bacterium which is difficult to treat. Due to its extremely dense cell membrane consisting of multiple layers, and it's very slow life cycle, a treatment requires dosing for many months, which is not only a compliance problem, but can be a commercial problem for the affected person, which often is found among the poor people. Multi drug resistant forms are spreading, requiring the combination of two or even three different drugs. To improve treatment without having to identify novel antibacterial drugs, Kerstin A. Wolff et al. evaluate currently available antibiotics for the treatment of tuberculosis by addressing strategies to combat resistance of mycobacteria. Virgilio Bocanegra-García et al. review potential targets of mycobacteria and evaluate the current development pipeline, and Auradee Punkvang et al. give insight in the technology of chemical structure optimization based on computer aided molecular design, focused on an emerging target of mycobacteria, the enzyme enoyl acyl carrier protein reductase.

3rd section: Novel targets and technologies leading to improved treatment options

Novel technologies may be useful for diverse diseases. RNA interference is such a novel technology, however several hurdles have to be overcome before successful treatments can emerge, including stability of RNA molecules and targeting of the right cells. Tamara Martinez et al. have compiled and excellent overview of this technology.

If the physiology of a novel receptor or a receptor sub-family is explored, the utility of such a receptor as target for different diseases can be deducted. Examples are presented by Liang Xin et al., reviewing the P2X receptor family, and by Sue Sien Ong et al., reviewing the pregnane X receptor.

The elucidation of physiology of specific functions is the basis of the contribution from Takekazu Kubo et al. They describe the interplay between the central nervous system and the immune system, leading to a novel target idea for the treatment of neuroinflammatory diseases such as multiple sclerosis or traumatic brain injury.

A different strategy for drug development was selected by Rui Ting Liu et al., focusing on a natural product extracted from traditional herbal medicine. The flavonoide Liquiritigenin, which is having estrogen-like function, is shown to have potent its activity in a mouse model of Alzheimer's disease.

XII Preface

are discussed.

acyl carrier protein reductase.

et al., reviewing the pregnane X receptor.

are now focusing the problem, that many bacteria are escaping the currently available antibiotics and becoming resistant, even to multiple antibiotics. To combat such multi-

Mario Zucca et al. describe novel antibacterial peptides which could help overcome the growing resistance. But peptides are difficult to develop since they are sensitive to metabolic degradation and may also have problems to penetrate tissues. These aspects

Elizabeth Hong-Geller and Nan Li describe microRNA based treatment strategies for infective diseases, utilizing current knowledge of microRNA as cellular signaling tool.

Treatment of tuberculosis is the topic of the next 3 chapters. Mycobacterium tuberculosis is a bacterium which is difficult to treat. Due to its extremely dense cell membrane consisting of multiple layers, and it's very slow life cycle, a treatment requires dosing for many months, which is not only a compliance problem, but can be a commercial problem for the affected person, which often is found among the poor people. Multi drug resistant forms are spreading, requiring the combination of two or even three different drugs. To improve treatment without having to identify novel antibacterial drugs, Kerstin A. Wolff et al. evaluate currently available antibiotics for the treatment of tuberculosis by addressing strategies to combat resistance of mycobacteria. Virgilio Bocanegra-García et al. review potential targets of mycobacteria and evaluate the current development pipeline, and Auradee Punkvang et al. give insight in the technology of chemical structure optimization based on computer aided molecular design, focused on an emerging target of mycobacteria, the enzyme enoyl

3rd section: Novel targets and technologies leading to improved treatment options

Novel technologies may be useful for diverse diseases. RNA interference is such a novel technology, however several hurdles have to be overcome before successful treatments can emerge, including stability of RNA molecules and targeting of the right cells. Tamara Martinez et al. have compiled and excellent overview of this technology.

If the physiology of a novel receptor or a receptor sub-family is explored, the utility of such a receptor as target for different diseases can be deducted. Examples are presented by Liang Xin et al., reviewing the P2X receptor family, and by Sue Sien Ong

The elucidation of physiology of specific functions is the basis of the contribution from Takekazu Kubo et al. They describe the interplay between the central nervous system and the immune system, leading to a novel target idea for the treatment of

A different strategy for drug development was selected by Rui Ting Liu et al., focusing on a natural product extracted from traditional herbal medicine. The flavonoide

neuroinflammatory diseases such as multiple sclerosis or traumatic brain injury.

resistant bacteria, novel strategies are required.

The evaluation of the activity of natural products is also the basis of the next chapter. Chagas disease is a tropical disease which has not attracted active drug development in the recent years. Alane Beatriz Vermelho et al. compare the activity of currently available medicines with the effects of novel lead structures, in part derived from natural products.

The interaction of pharmacological agents with a biotope which is often not considered to be of importance, the gut microbiota, is discussed by Joan Vermeiren et al. The composition of the gut bacteria community can have influence on stability, pharmacokinetics, and metabolism of xenobiotics. A better knowledge of this possible interaction can improve drug development. This is explored using inflammatory bowel disease as case study.

The following two chapters explore novel sources for pharmacologically active compounds. While Luiz H. Rosa et al. focuss on endophytic fungi of tropical forests as a unique source for new chemical entities with potential for the treatment of diseases such as leishmaniasis, María Estrella Legaz et al. describe the utilization of the enzymatic properties of lichen to produce a compound class called depsidones. Preclinical data indicated that such compounds may have antiviral, antibacterial and other effects.

A different field of drug development is touched by the next two chapters, the pharmaceutical development of adequate dosage forms. Intranasal and transdermal drug administration is used to bypass the gastrointestinal tract and the metabolic capability of the liver. Successful application of these dosing routes requires that the administration results in adequate drug levels at the target organ without risk for the patient. A potential risk for intranasal application is bacterial contamination and hence infection from the nasal applicator. While preservatives can reduce the risk of bacterial growth in the container, such agents can induce irritation on the nasal mucosa and should be avoided. Degenhard Marx and Matthias Birkhoff describe novel technologies which can avoid the use of preservatives in multidose intranasal containers. Transdermal application is often limited by the skin representing a diffusion barrier. A technology to reduce the barrier function by using microneedles prior to application of the transdermal patch is described by Stan L. Banks et al.

#### 4th section: Drug development strategies

The final book section focusses on issues related to drug development in general. Drug development is very expensive and only if the potential revenues which can be generated by a drug candidate can payback the required investment, a development project can be started. Rare diseases or diseases predominantly affecting poor people are often not sufficiently covered by novel drug developments. Kristina M. Lybecker XVIII Preface

describes different incentivation models developed to improve the access of poor people to modern drugs, with special focus on patent rights.

The first step in clinical drug development is the conduct of studies in healthy volunteers. Such clinical studies aim at exploring the safety profile and the pharmacokinetics of a new drug candidate. However no hints on efficacy can be obtained in these studies. Giovanni Gori et al. describe modern tools to expand the options of phase I studies in healthy volunteers. Using biomarkers, modern imaging technology, and specific challenge protocols, hints for efficacy can be obtained and the safety evaluation can be improved.

The final chapter of this section focuses on drug development for children. In former times, drugs were developed in adults and the use of pharmaceutical agents in children was based in most cases on empiric information obtained from the use in children. Regulatory agencies have realized that this procedure can be very dangerous since the juvenile organism differs considerably from the adult organism. In 2007 the pediatric regulations were introduced in the EU requiring now stringent criteria on quality, safety, and efficacy of medicinal products to be used in the pediatric population. Adriana Ceci et al. evaluate how the drug development environment has changed after the introduction of these regulations.

#### Conclusion

This book represents a case study based overview on many different aspects of drug development, ranging from target identification and characterization to chemical optimization for efficacy and safety, as well as bioproduction of natural products utilizing for example lichen. In the last section special aspects of the formal drug development process are discussed. Since drug development is a highly complex multidisciplinary process, case studies are an excellent tool to obtain insight in this field. While each chapter gives specific insight and may be read as independent source of information, the whole book represents a unique collection of different facets giving insight in the complexity of drug development.

#### **Chris Rundfeldt, Ph.D., DVM**

Expert for Drug Development and Translational Medicine Germany
