To Market, To Market — 2007

Natural Products as Sources of New Drugs over the Nearly Four Decades from 01/1981 to 09/2019

This review is an updated and expanded version of the five prior reviews that were published in this journal in 1997, 2003, 2007, 2012, and 2016. For all approved therapeutic agents, the time frame has been extended to cover the almost 39 years from the first of January 1981 to the 30th of September 2019 for all diseases worldwide and from ∼1946 (earliest so far identified) to the 30th of September 2019 for all approved antitumor drugs worldwide. As in earlier reviews, only the first approval of any drug is counted, irrespective of how many "biosimilars" or added approvals were subsequently identified. As in the 2012 and 2016 reviews, we have continued to utilize our secondary subdivision of a "natural product mimic", or "NM", to join the original primary divisions, and the designation "natural product botanical", or "NB", to cover those botanical "defined mixtures" now recognized as drug entities by the FDA (and similar organizations). From the data presented in this review, the utilization of natural products and/or synthetic variations using their novel structures, in order to discover and develop the final drug entity, is still alive and well. For example, in the area of cancer, over the time frame from 1946 to 1980, of the 75 small molecules, 40, or 53.3%, are N or ND. In the 1981 to date time frame the equivalent figures for the N* compounds of the 185 small molecules are 62, or 33.5%, though to these can be added the 58 S* and S*/NMs, bringing the figure to 64.9%. In other areas, the influence of natural product structures is quite marked with, as expected from prior information, the anti-infective area being dependent on natural products and their structures, though as can be seen in the review there are still disease areas (shown in Table 2) for which there are no drugs derived from natural products. Although combinatorial chemistry techniques have succeeded as methods of optimizing structures and have been used very successfully in the optimization of many recently approved agents, we are still able to identify only two de novo combinatorial compounds (one of which is a little speculative) approved as drugs in this 39-year time frame, though there is also one drug that was developed using the "fragment-binding methodology" and approved in 2012. We have also added a discussion of candidate drug entities currently in clinical trials as "warheads" and some very interesting preliminary reports on sources of novel antibiotics from Nature due to the absolute requirement for new agents to combat plasmid-borne resistance genes now in the general populace. We continue to draw the attention of readers to the recognition that a significant number of natural product drugs/leads are actually produced by microbes and/or microbial interactions with the "host from whence it was isolated"; thus we consider that this area of natural product research should be expanded significantly.

Convergent Formal Synthesis of Ecteinascidin 743

A concise formal synthesis of ecteinascidin 743 is described. Key features involve the coupling of the multisubstituted tetrahydroisoquinoline and phenylalaninol moieties via a regio- and stereoselective Pictet-Spengler cyclization as well as the subsequent chemoselective MOM protection of the phenol group, which opens a rapid access to the desirable pentacycle. The synthesis successfully delivered the advanced intermediate with the characteristic macrolactone from sesamol in 23 steps.

Martinez E, Lindbæk M, Outterson K, Røttingen JA, Laxminarayan R. Introduction and geographic availability of new antibiotics approved between 1999 and 2014

BACKGROUND

Despite the urgent need for new, effective antibiotics, few antibiotics of value have entered the market during the past decades. Therefore, incentives have been developed to stimulate antibiotic R&D. For these incentives to be effective, geographic availability for recently approved antibiotics needs to be better understood. In this study, we analyze geographic availability and market introduction of antibiotics approved between 1999 and 2014.

MATERIAL AND METHOD

We identified antibiotics, considered new chemical entities (NCEs) for systemic use approved globally between 1999 and 2014, from national medicine agencies' lists of approved drugs, and data from the WHO Collaborating Center for Drug Statistics. Geographic availability was mapped using sales data from IQVIA, and analyzed with regards to class, indication, safety, and origin.

RESULTS

Of the 25 identified NCEs, only 12 had registered sales in more than 10 countries. NCEs with the widest geographic availability had registered sales in more than 70 countries within a ten-year timeframe and 30 countries within a three-year timeframe, spreading across five different geographic regions and three country income classes. Half (52%) of the NCEs had an indication for infections caused by antibiotic- resistant bacteria, little diversity was seen regarding target pathogen and indication. Antibiotics originated from and/or marketed by companies from the US or Europe had greater geographic availability compared to Japanese antibiotics, which seldom reached outside of Asia. For 20 NCEs developers chose to fully or partially sublicense marketing rights to a number of companies of different sizes.

CONCLUSION

Our findings show great variation in geographic availability of antibiotics, indicating that availability in multiple regions and country income classes is possible, but rarely seen within a few years of market authorization. Sublicensing agreements between multiple companies was common practice. Moreover, differences were seen between countries regarding benefit/risk evaluations and company behavior. These findings could be a potential source of uncertainties, and create barriers to assure that working antibiotics are developed and made available according to public health needs.

Analysis of new drugs registered in Brazil in view of the Unified Health System and the disease burden

The most important aspect of a new drug in terms of public health is its therapeutic value and benefit it provides for the patient and for the society. The aim of this study was to analyze new drugs registered in Brazil between 2003 and 2013 with respect to Pharmaceutical Assistance programs within the Brazilian health system and to the disease burden in the country. In our retrospective cohort study, new drugs registered in Brazil were identified through document analysis of databases and publicly available documents from National Health Surveillance Agency. The data on disease burden in Brazil was obtained from the Global Burden of Disease Study 2012, published by the World Health Organization. The level of therapeutic innovation was determined using the Motola algorithm. Although a total of 159 new medicines were used in the cohort, only 28 (17.6%) were classified as important therapeutic innovations. There is a disproportionate relationship between the percentage of new drugs and the burden of disease, with an under-representation of drugs for infectious respiratory diseases, heart disease, and digestive diseases. Incentive strategies for research and development of medicines should be prioritized to reduce the disparity regarding the burden of disease and to help develop innovative medicines necessary to improve health throughout the country.

Postmarketing Safety Events Relating to New Drugs Approved in Brazil Between 2003 and 2013: A Retrospective Cohort Study

This study investigated postmarketing safety events (PMSEs) for new drugs approved in Brazil and evaluated whether a range of drug characteristics influenced the time between approval and the first PMSE. This retrospective study included new drugs registered between 2003 and 2013 by the National Health Surveillance Agency (ANVISA), which is responsible for medicines approval in Brazil. PMSEs were defined as any drug safety alert or drug withdrawal from the market. The existence of risk evaluation and mitigation strategies (REMS) by the US Food and Drug Administration (FDA) and Brazil were recorded. A Kaplan-Meier survival curve of the period between the date of ANVISA registration and the PMSE was calculated. We found a statistically significant difference between the time to PMSE for drugs with an FDA REMS compared with those without a REMS, with a log rank value (Mantel Cox) of 0.002. There was no association between the time to PMSE and the other drug characteristics investigated. This study demonstrated that the frequency of PMSEs for new drugs approved by ANVISA was statistically associated with the existence of an FDA REMS. The time between approval and first PMSE was shorter for drugs with an FDA REMS, and this finding may contribute to improved awareness of the risk/benefit balance required to ensure continued safe and effective use of new drugs.

Natural Products as Sources of New Drugs from 1981 to 2014

This contribution is a completely updated and expanded version of the four prior analogous reviews that were published in this journal in 1997, 2003, 2007, and 2012. In the case of all approved therapeutic agents, the time frame has been extended to cover the 34 years from January 1, 1981, to December 31, 2014, for all diseases worldwide, and from 1950 (earliest so far identified) to December 2014 for all approved antitumor drugs worldwide. As mentioned in the 2012 review, we have continued to utilize our secondary subdivision of a "natural product mimic", or "NM", to join the original primary divisions and the designation "natural product botanical", or "NB", to cover those botanical "defined mixtures" now recognized as drug entities by the U.S. FDA (and similar organizations). From the data presented in this review, the utilization of natural products and/or their novel structures, in order to discover and develop the final drug entity, is still alive and well. For example, in the area of cancer, over the time frame from around the 1940s to the end of 2014, of the 175 small molecules approved, 131, or 75%, are other than "S" (synthetic), with 85, or 49%, actually being either natural products or directly derived therefrom. In other areas, the influence of natural product structures is quite marked, with, as expected from prior information, the anti-infective area being dependent on natural products and their structures. We wish to draw the attention of readers to the rapidly evolving recognition that a significant number of natural product drugs/leads are actually produced by microbes and/or microbial interactions with the "host from whence it was isolated", and therefore it is considered that this area of natural product research should be expanded significantly.

Analogue-based drug discovery: Contributions to medicinal chemistry principles and drug design strategies. Microtubule stabilizers as a case in point (Special Topic Article)

The benefits of utilizing marketed drugs as starting points to discover new therapeutic agents have been well documented within the IUPAC series of books that bear the title Analogue-based Drug Discovery (ABDD). Not as clearly demonstrated, however, is that ABDD also contributes to the elaboration of new basic principles and alternative drug design strategies that are useful to the field of medicinal chemistry in general. After reviewing the ABDD programs that have evolved around the area of microtubule-stabilizing chemo-therapeutic agents, the present article delineates the associated research activities that additionally contributed to general strategies that can be useful for prodrug design, identifying pharmacophores, circumventing multidrug resistance (MDR), and achieving targeted drug distribution.

Natural products as sources of new drugs over the 30 years from 1981 to 2010

This review is an updated and expanded version of the three prior reviews that were published in this journal in 1997, 2003, and 2007. In the case of all approved therapeutic agents, the time frame has been extended to cover the 30 years from January 1, 1981, to December 31, 2010, for all diseases worldwide, and from 1950 (earliest so far identified) to December 2010 for all approved antitumor drugs worldwide. We have continued to utilize our secondary subdivision of a "natural product mimic" or "NM" to join the original primary divisions and have added a new designation, "natural product botanical" or "NB", to cover those botanical "defined mixtures" that have now been recognized as drug entities by the FDA and similar organizations. From the data presented, the utility of natural products as sources of novel structures, but not necessarily the final drug entity, is still alive and well. Thus, in the area of cancer, over the time frame from around the 1940s to date, of the 175 small molecules, 131, or 74.8%, are other than "S" (synthetic), with 85, or 48.6%, actually being either natural products or directly derived therefrom. In other areas, the influence of natural product structures is quite marked, with, as expected from prior information, the anti-infective area being dependent on natural products and their structures. Although combinatorial chemistry techniques have succeeded as methods of optimizing structures and have been used very successfully in the optimization of many recently approved agents, we are able to identify only one de novo combinatorial compound approved as a drug in this 30-year time frame. We wish to draw the attention of readers to the rapidly evolving recognition that a significant number of natural product drugs/leads are actually produced by microbes and/or microbial interactions with the "host from whence it was isolated", and therefore we consider that this area of natural product research should be expanded significantly.

Identification of a novel protein synthesis inhibitor active against gram-positive bacteria

In an effort to identify novel antibacterial chemotypes, we performed a whole-cell screen for inhibitors of Staphylococcus aureus growth and pursued those compounds with previously uncharacterized antibacterial activity. This process resulted in the identification of a benzothiazolium salt, ABTZ-1, that displayed potent antibacterial activity against Gram-positive pathogens. Several clinically desirable qualities were demonstrated for ABTZ-1 including potent activity against multidrug-resistant clinical isolates of methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE), retention of this activity in human serum, and low hemolytic activity. The antibacterial activity of ABTZ-1 was attributed to its inhibition of bacterial translation, as this compound prevented the incorporation of [³⁵S]methionine into S. aureus proteins, and ABTZ-1-resistant strains were cross-resistant to known inhibitors of bacterial translation. ABTZ-1 represents a promising new class of antibacterial agents.

Prodrugs: Some thoughts and current issues

The prodrug approach to resolving formulation, delivery, and toxicity limitations on problematic drugs has had its proponents and detractors. Over the last 10 years or so, about 20% of all new small molecule NCEs have been prodrugs-a number that will surprise some. As chemists begin to explore new chemical spaces, larger and more complex molecules present greater drug delivery challenges. Prodrugs provide a means of solving these challenges, but also have their limitations. Prodrugs are becoming an integral part of the drug discovery paradigm in some large pharma companies, and a number of small biotech companies have been built around the design and application of prodrugs to improve drug candidates. Some issues facing the area of prodrug research and the commercialization of prodrugs are discussed.