Drug Development
Introduction
Drug development is a continuous process of studying a disease, hypothesizing and developing treatments, and evaluating those treatments. For treatments deemed to be successful, further studies are needed for continuous evaluation of safety and efficacy in the population.
Development of treatment starts from the clinical observation of a disease from its origin, progression, clinical manifestations, laboratory findings, and clinical outcome. Based on the understanding of the disease, researchers might propose preventive strategies or potential treatments to increase the quality of life of human populations. Experiments may be done through in vitro studies of the chemical and biochemical properties of drugs and in vivo studies of the effects of treatment on living organisms. Ultimately, the goals of these approaches are to determine the absorption, distribution, metabolism, excretion, and toxicity of drugs, physiologic effects of treatment, and drug interactions with other treatments among others.
Before the treatment is tested in human volunteers, adequate preclinical studies should be performed to ensure its safety. Once safety is established, additional trials will be conducted to measure efficacy and effectiveness. Applicable certifications in Good Laboratory Practice (GLP), Good Clinical Practice (GCP), and Good Manufacturing Process (GMP) are required by the Food and Drug Administration (FDA) prior to conducting these studies.
Pharmalytics Corporation and its Role in Drug Discovery and Development
Pharmalytics Corporation has partnered with several governmental and non-governmental institutions in developing drugs from local natural resources. Drug discovery and development, especially those coming from natural resources, was identified as one of the priority areas under the National Unified Health Research Agenda (NUHRA).
As part of the Tuklas Lunas Program of the Department of Science and Technology – Philippine Council for Health Research and Development Council (DOST-PCHRD), Pharmalytics Corporation is one of the implementing partners in the development of a comprehensive manual for the discovery and development of new drugs. Procedures for drug discovery and development detailed in this article are mostly derived from the Tuklas Lunas Protocols for Drug Discovery and Development.
Utility model publications for three herbal plants for Anti-inflammatory (Aegiceras corniculatum, Ipomoea batatas, and Ficus fiskei Elmer) were filed in partnership with Ateneo De Manila University, University of the Philippines, and Herbanext Laboratories. Drug development of herbal drugs were some of the notable research and development activities of Pharmalytics Corporation such as preclinical of anti-inflammatory, anti-diabetic, and anti-cancer herbal drugs and clinical phases of herbal drugs against Dengue and COVID-19.
Drug Discovery and Development
The first step in developing and testing a new drug is preclinical research. Drug discovery can occur through multiple pathways but once chemical entities have been identified, they undergo a rigorous process of testing. Tests are conducted to chemically profile plant samples to validate their identities and determine their physicochemical properties, determine safety and toxicity using animal studies, and provide insight into the development of the final dosage form of the compound. Most often, many candidate chemical entities are produced because not all entities move through the entire process of pharmacopeial testing, bioactivity, and safety and toxicity assessment due to failure in one or more testing stages.
Preformulation Studies
Preformulation studies are groups of testing procedures that aim to assess the test sample’s physicochemical characteristics, powder attributes, stability under different processing and storage conditions, and compatibility with different excipients to be used for formulation studies.
Pharmacopeial testing includes organoleptic and macroscopic description, ash content, extractable matter, moisture content, heavy metals (i.e lead, cadmium, mercury, and arsenic), volatile oils, pesticide residue, microbial limits, aflatoxin limits, soil analysis, foreign matter examination and identification tests.
In organoleptic and macroscopic description, documentation of plant illustration, morphology, color, odor, and taste are observed and compared with a reference material. Surface characteristics, texture, and fracture characteristics are observed with the aid of a magnifying glass.
Calculation of total ash content is specified. Ashes are inorganic residues after ignition or complete oxidation. Determination of ash content is part of nutritional evaluation.
Moisture content determination is a quality control test since it affects the chemical and physical properties of the final product.
Presence of heavy metals such as lead, cadmium, mercury, and arsenic are determined not only as part of quality control but also to quantify levels of metals as these may cause toxicity. Acceptable limits in specifications are set for metals.
Volatile oils can also be referred to as essential oils as they are biologically active substances present in plant materials. Hydrodistillation is used in establishing the identity, purity, and quality of the compounds in plant samples.
Due to agricultural practices, pesticides may accumulate and limits for residues are established in pesticide residue analysis where a representative amount of samples are used.
Microbial contamination is a hazard in pharmaceutical products. Tests for microbial limits include aerobic bacteria, yeasts and molds, Escherichia coli, salmonellae, staphylococcus, and other enterobacteria.
Aflatoxins are metabolites produced by fungal action produced during the process of food production to processing. Toxicity due to this metabolite may result in nausea, vomiting, abdominal pain, convulsions, and other signs of acute liver injury.
Identification is conducted to determine active constituents present in the plants. Chemical profiling is conducted through multi-solvent thin-layer chromatography (TLC), which is a standard method in herbal pharmacopeias.
Bioactivity Assays
Primary assays identify candidates with better efficacy and safety profiles as well as high-value candidates with multiple mechanisms of action through testing compounds for activity against a biological target or pathway. Orthogonal assays, meanwhile, are performed after the primary assay to identify false positives among compounds active against the target. Secondary assays may also be performed, although optional, to confirm the activity of compounds in the primary and orthogonal assay. Unsuccessful outcomes in bioassays are also common and may be due to the degradation of compounds during the purification process, the concentrations of bioactive compounds may be too low to be isolated, and the bioactivity may only be due to synergistic effects with other compounds.
Safety Tests and Animal Toxicity Tests
Safety tests consist of tests for mutagenicity, genotoxicity, hepatotoxicity, nephrotoxicity, and cardiotoxicity among others. High failure rates in drug development can be attributable to these factors.
Mutagenicity test or Ames assay is a procedure for detection of substances inducing mutation in the DNA. The test utilizes bacterial strains that are unable to synthesize a specific amino acid. Meanwhile, mammalian erythrocyte micronucleus test is an in vivo test for genotoxicity which is essential to be determined since the formation of micronucleus can harm the DNA which can cause chromosomal aberrations, genomic instability, or eventually lead to cancer.
Cell-based toxicity tests are conducted in vitro to determine occurrences of cell death in the liver, kidney, and heart muscles. Additional toxicity marker analyses are conducted to determine drug-induced toxicity. Hepatotoxicity and nephrotoxicity are serious adverse events of drugs and tests done during the drug discovery and development can help screen these characteristics to maximize therapeutic benefits and minimize adverse effects.
Acute, subchronic, and chronic toxicity studies are conducted, when applicable, in vivo in experimental animals without the disease of interest. These studies provide information on the estimated range of dosage for compound distribution, organ-specific toxicity, and metabolism. Serious adverse effects identified in these studies prevent the development of the drug to the next stage. The conduct of these studies should have prior approval from the Institutional Animal Care and Use Committee (IACUC).
Acute oral toxicity study estimates the median lethal dose (LD50) and can give a picture of the toxidrome of the test substance. The median lethal dose is the dose of a test substance, when given all at once, which causes death for 50% of the animals in a dose group. The test substance is administered at once at different dose levels with an observation period of 14 days. Animal toxicity testing is required to determine the potential toxicity of a substance prior to testing in humans.
Subchronic toxicity test is a repeat-dose toxicity study generally conducted for 90 days that uses rats as test animals. The results of this study can help predict appropriate doses of the test substance for future chronic toxicity studies.
Chronic toxicity test is a long-term repeat-dose toxicity study that is conducted after the information has been obtained from the subchronic toxicity test. A test substance is administered in graduated doses to several groups of animals on a daily basis. The test will provide information on the toxic effects of the substance and will indicate the target organs as well as the possibility of accumulation after repeated exposure to the test compound. Results can establish safety criteria for human exposure.
If the animal studies demonstrate favorable results, a clinical trial on human participants shall gain authorization from the Food and Drug Administration (FDA) for conduct in the Philippines through the process of approval as stated in DOH AO 2020-0010 entitled, Regulations on the Conduct of Clinical Trials for Investigational Products.
Formulation Studies
Formulation studies cover those for solid dosage forms (tablets and capsules), liquid dosage forms (suspensions and syrups), and semi-solid dosage forms (ointments and creams) from plant materials. A formulation contains the active ingredient (API) and the other inactive ingredients. Each inactive ingredient in the formulation is used to serve specific purposes to ensure product performance and conformance.
Pharmaceutical data for drug products should contain details on the drug substance, manufacturing process, authenticity and quality of raw materials, pharmacopeial testing, quality control procedures, and stability of the finished product. Stability data should demonstrate that the drug is stable at the proposed storage conditions and shelf life. The drug product is tested under different conditions of temperature, light, humidity, and pH.
Clinical Studies
For clinical trial application, the sponsor shall file the Investigational New Drug Application (IND) to the FDA together with data on preclinical and toxicity studies, drug manufacturing information, clinical research protocol for studies to be conducted, and information about the study investigator and drug developer. Complete requirements can be found in DOH AO 2020-0010.
Clinical trials help researchers discover new treatments for diseases and develop new ways to prevent and detect those diseases. They are conducted on human participants to determine the safety and efficacy of treatment. For a drug to be approved by the FDA for marketing approval, the drug should undergo small-scale phase 1 trials to large-scale phase 3 trials.
Clinical testing is time-consuming and resource-intensive. There is room for error in the drug testing process because animal-based tests do not accurately predict the outcomes of human-based tests. Novel drugs can fail in human clinical trials because animal studies were not predictive of the drugs’ effects in humans.
References:
Abaya, L.M., Aliño, P.M., Almeria, A.D., Concepcion, G.P., Davis, K.S., Escueta-De Cadiz, A., Hipol, R.M., Manzano, G.G., Nicolas, M.G., Punzalan, C.V., Salvador-Reyes L.A., Santiago, V.S., Tolentino-Reyes, M.V., and Villaseñor, I.M. (2019). Tuklas lunas® protocols for drug discovery and development manual 1: Collection and extraction of biosources and purification of bioactives. Philippine Council for Health Research and Development.
Algodon S.M., Amor E.C., Cortez A.T., Garcia R.L., Salvador-Reyes, L.A., Tun J., and Concepcion G.P. (2019). Tuklas lunas® protocols for drug discovery and development manual 2A: Safety tests. Philippine Council for Health Research and Development.
Allanigue E.J., Amor E.C., Arguilla E., Bataclan C.C., Fabian M.C.P., Fernandez P.L., Garcia R.L., Hernandez C.C., Manongdo M.A., Martija A.A., Naing M.D., Ong T.T., Opog A.C., Perez Y.P., Tutor J., Yerro J. Z., Salvador-Reyes L.A., Tun J. and Concepcion G.P. (2019). Tuklas lunas® protocols for drug discovery and development manual 2B: Primary bioactivity assays. Philippine Council for Health Research and Development.
Amor E.C., Balotro, B.S., Cortez, A.T., Cruz, P.S., Dayrit, F.M., Lagurin, L.G., Magsalin, J.J., Quibin, R.A., and Sayson, C.D. (2019). Tuklas lunas® protocols for drug discovery and development manual 3: Chemical standardization, preformulation, and formulation. Philippine Council for Health Research and Development.
Bataclan C.C., Garcia R.L., Manongdo M.A., Martija A.A., Ong T., Yu R.T., Salvador-Reyes L.A., Tun J. and Concepcion G.P. (2019). Tuklas lunas® protocols for drug discovery and development manual 2C: Orthogonal and secondary bioactivity assays. Philippine Council for Health Research and Development.
Deore, A. B., Dhumane, J. R., Wagh, R., & Sonawane, R. (2019). The stages of drug discovery and development process. Asian Journal of Pharmaceutical Research and Development, 7(6), 62-67.
Dhakal, A., & Sbar, E. (2021). Aflatoxin toxicity. In StatPearls [Internet]. StatPearls Publishing.
Gooneratne, N. (2019). Overview of drug development. Academic Entrepreneurship for Medical and Health Scientists, 1(3), 16.
Mohs, R. C., & Greig, N. H. (2017). Drug discovery and development: Role of basic biological research. Alzheimer’s & Dementia: Translational Research & Clinical Interventions, 3(4), 651-657.
National Research Council (US) Panel on Handling Missing Data. (2010). Clinical Trials: Overview and Terminology. National Academies Press (US). https://www.ncbi.nlm.nih.gov/books/NBK209903/
Nothias, L. F., Nothias-Esposito, M., Da Silva, R., Wang, M., Protsyuk, I., Zhang, Z., … & Dorrestein, P. C. (2018). Bioactivity-based molecular networking for the discovery of drug leads in natural product bioassay-guided fractionation. Journal of natural products, 81(4), 758-767.
Thorne, N., Auld, D. S., & Inglese, J. (2010). Apparent activity in high-throughput screening: origins of compound-dependent assay interference. Current opinion in chemical biology, 14(3), 315–324. https://doi.org/10.1016/j.cbpa.2010.03.020