The Drug Development Process
Biopharmaceutical Manufacturing
The Drug Development Process
1. Overview of Drug Development Topics
Drug discovery
Genomic/Proteomics
Pharmacogenetics
Product characterisation
Patenting
Delivery of Biopharmaceuticals
Preclinical studies
Clinical trials
Role and remit of regulatory authorities
2. Initial Product Characterisation
Physiochemical Properties: Extensive characterization of new drugs is required prior to clinical trials.
Biopharmaceutical Composition: The majority are proteins, with exceptions including 3rd generation vaccines and nucleic acid therapeutics.
Purification Process: Characterization involves a purified biomolecule typically requiring three or more high-resolution purification chromatography steps.
3. Purification Protocol
The purification protocol is crucial, as it serves as the foundation for pilot scale and process scale purification systems.
Following purification, the biopharmaceutical undergoes various tests to fully characterize the biomolecule.
Results from these tests inform routine quality control (QC) identity tests conducted during commercial manufacturing.
A summary of identity tests will be presented later in the module.
4. Structural Analysis of Therapeutic Proteins
Primary Structure: Determine amino acid composition, N & C terminal analysis, peptide mapping, and full sequencing. Identify disulfide bonds.
Amino Acid Composition: The sequence of amino acids in the protein.
N & C Terminal Analysis: Analysis of the ends of the amino acid chain.
Peptide Mapping and Sequencing: Techniques to identify the order of amino acids.
Disulfide Bonds: Determine the presence and location of these bonds stabilizing the protein structure.
Secondary Structure: Analysis of major secondary structural elements, like alpha helices and beta-pleated sheets.
Tertiary/Quaternary Structure:
Determine the biologically active format (monomers, dimers, etc.).
Analyze the complete 3D structure of the protein.
Post-Translational Modifications (PTMs): Identify carbohydrate side chains and assess oligosaccharide structures, alongside modifications such as carboxylation, hydroxylation, and amidation.
5. Stability Studies of Proteins
Additional to structural characterization, stability studies assess proteins under various conditions, including:
Temperature
pH
Oxygen exposure
Light exposure
Water presence
Contact with potential excipients
Stability information is critical for final product formulation and estimating shelf life.
6. Patenting in Drug Development
Process of Patenting: After discovery and initial characterization, a patent is pursued for potential pharmaceuticals. Information must detail physiochemical characteristics, synthesis methods, and biological effects.
Patenting typically occurs post preclinical and phase I clinical trials focused on safety.
Successful patenting does not grant the right to sell; safety and efficacy must be established in phases II and III, requiring regulatory authority approval.
7. Understanding Patents
Definition of a Patent: A government-granted monopoly allowing the inventor to exploit an invention for a fixed period, typically 20 years. The inventor must also provide a detailed description to facilitate others' future use post-monopoly.
Encouragement of Innovation: Patents encourage research and development. They can be sold or licensed during the fixed period.
8. Patentability Criteria
No global patent office exists, leading to varying practices worldwide.
Global harmonization of patent law is increasing, driven by trade agreements. Key criteria for patentability include:
Novelty: The invention must be unique.
Non-obviousness: The invention must not be just a logical extension of known methods.
Sufficiency of Disclosure: Inventions must be disclosed in sufficient detail for replication.
Utility: Must have real-world applications and serve its intended purpose, though not necessarily better than existing inventions.
9. Patentability of Natural Products
Many natural products (e.g., specific antibiotics, proteins) can be patented. However, mere discovery of a natural substance may not meet patenting criteria until it is enriched, purified, or modified.
A natural product is patentable if the 'hand of man' has influenced its development (e.g., purified Vitamin B12 is patentable).
10. Complexities in Modern Patenting
Advances in technology have made patenting complex. Examples include:
Harvard University's patent on a transgenic mouse prone to cancer.
Patents on human genes related to important biopharmaceuticals such as EPO.
The patenting of genetic material and transgenic organisms invokes ethical and public debate, beyond technical and legal arguments.
11. The European Union Directive
The 1998 European Patent Directive states that any naturally-occurred material can be patentable if isolated/purified and/or produced by technical means (e.g., recombinant DNA).
To be patentable, substances must meet general patentability principles: novelty, non-obviousness, sufficiency of disclosure, and utility.
12. Restrictions on Gene Patenting
The utility requirement restricts patenting of genes with unknown functions.
Inventions exploiting certain areas (e.g., human body, cloning, genetic modification inducing suffering without medical benefit) cannot be patented.
13. Delivery of Biopharmaceuticals
Significant considerations during biopharmaceutical development center on the administration route. Most biopharmaceuticals are administered parenterally (subcutaneous, intramuscular, intravenous).
While parenteral administration is often acceptable for infrequent doses, more convenient non-parenteral routes are preferable for frequent administration (e.g., insulin), enhancing patient compliance.
14. Alternative Delivery Routes
Potential alternative routes include:
Oral
Nasal
Transmucosal
Transdermal
Pulmonary
Obstacles to Administration:
Large molecular weights.
Susceptibility to enzyme and acid inactivation.
Potential aggregation of biopharmaceuticals.
15. Challenges in Oral Delivery Systems
Oral drug delivery is preferred for its convenience but poses challenges:
Inactivation by Stomach Acids: Most biopharmaceuticals are acid-labile and inactive at low pH.
Digestive Protease Inactivation: Proteins can be deactivated by enzymes like trypsin, pepsin, and chymotrypsin.
Absorption Difficulties: High hydrophilicity and large size impede absorption across mucosal membranes.
First Pass Metabolism: Drugs absorbed orally undergo first pass metabolism in the liver, significantly reducing concentration in circulation.
Bioavailability: Typically below 1% for oral delivery.
16. Strategies to Improve Bioavailability
Various approaches to enhance drug delivery and protect against adverse factors include:
Encapsulation: Using enteric coatings that resist low pH.
Microcapsules and Microspheres: Employing various polymers to protect drug candidates.
Liposomes and Nanoparticles: Utilizing nanotechnology to enhance delivery.
17. Delivery Systems and Bioavailability
Enteric-Coated Drugs: Focus on maintaining integrity in acidic stomach conditions while dissolving in alkaline conditions of the small intestine.
18. Mucoadhesive Delivery Systems
Utilizing encapsulated biopharmaceuticals interacting with the gastrointestinal (GI) mucosal lining, improving retention at absorption sites.
19. Various Nanoparticle Technologies
Different types of nanoparticles being explored include:
Polymer nanoparticles
Liposomes
Dendrimers
Solid lipid nanoparticles
Cyclodextrin
Gold nanoparticles
Magnetic nanoparticles
Mesoporous silica nanoparticles
Micelles for colorectal cancer treatment
20. Pulmonary Delivery Systems
This approach is promising compared to parenteral routes. Example: Exubera (2006) was an inhalable insulin approved product.
Macromolecular absorption can occur rapidly, allowing large biological molecules up to 500kDa to enter the bloodstream quickly (bioavailability approaching 50%), but it was withdrawn from phase III clinical trials).
Factors contributing to efficient pulmonary absorption:
Large surface area of the lungs.
Low surface fluid volume.
Thin diffusional layer.
Slow cell surface clearance.
Presence of proteolytic inhibitors.
21. Advantages and Disadvantages of Pulmonary Delivery
Advantages:
Bypass first-pass metabolism in the liver.
Availability of Metered Dose Inhalers (MDIs) and Dry Powder Inhalers (DPIs) for dosing accuracy.
Disadvantages:
Potential complications associated with this method of delivery.
22. Nasal, Transmucosal, and Transdermal Delivery Systems
Nasal Delivery Route:
Attractiveness stems from ease of access and high blood supply in nasal cavities, offering large absorption surface area and bypassing first-pass metabolism.
Disadvantages:
Drug clearance occurs due to mucous ciliary action.
Presence of proteases degrading larger molecules.
Low uptake for peptides and polypeptides, and difficulty for molecules over 10 kDa crossing endothelial barriers; long-term use can damage endothelial cells.
23. Immune Response Model with LAIV
Model shows immune reactions post intranasal LAIV immunization:
Intranasal immunization introduces viral antigen.
Antigen transported to tonsils/adenoids by dendritic cells.
T/B cell activation and proliferation occurs, aided by CD4+ T-cells.
Activated cells migrate to the infection site and enter circulation.
Plasma cells secrete antibodies into blood and mucosal surfaces.
24. Research Directions in Mucosal Delivery
Exploring mucosal delivery avenues for peptides/proteins via:
Buccal
Vaginal
Rectal routes.
Typically low bioavailability; modest increases noted with permeation enhancers, although rapid clearance is common.
Exploring transdermal delivery systems, possibly involving methods like helium jet or low-voltage application to enhance protein passage across the skin.