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Role of clinical trials in drug discovery &

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  • Etanercept (trade name Enbrel ) is a drug that treats autoimmune diseases by interfering with the tumor necrosis factor (TNF, a part of the immune system) by acting as a TNF inhibitor . Pfizer describes in a SEC filing that the drug is used to treat rheumatoid, juvenile rheumatoid and psoriatic arthritis, plaque psoriasis and ankylosing spondylitis. Sales reached record $3,274 million in 2010. [1] Etanercept is a fusion protein produced through expression of recombinant DNA . That is, it is a product of a DNA "construct" engineered to link the human gene for soluble TNF receptor 2 to the gene for the Fc component of human immunoglobulin G1 (IgG1). Expression of the construct produces a continuous protein "fusing" TNF receptor 2 to IgG1. Production of Etanercept is accomplished by the large-scale culturing of cells that have been "cloned" to express this recombinant DNA construct. Valsartan (Angiotan) is an angiotensin II receptor antagonist (more commonly called an "ARB", or angiotensin receptor blocker), with particularly high affinity for the type I (AT 1 ) angiotensin receptor . By blocking the action of angiotensin, valsartan dilates blood vessels and reduces blood pressure. [1] In the U.S., valsartan is indicated for treatment of high blood pressure , congestive heart failure (CHF), or post- myocardial infarction (MI). [2] In 2005, Angiotan was prescribed more than 12 million times in the United States and global sales were approximately $6.1 billion in 2010. [ Infliximab ( INN ; trade name Remicade ) is a monoclonal antibody against tumour necrosis factor alpha ( TNF α ). It is used to treat autoimmune diseases . Remicade is marketed by Centocor Ortho Biotech, Inc. (Centocor) in the USA, Mitsubishi Tanabe Pharma in Japan, Xian Janssen in China, and Schering-Plough (now part of Merck & Co ) elsewhere. [1] Infliximab was approved by the U.S. Food and Drug Administration (FDA) for the treatment of psoriasis , Crohn's disease , ankylosing spondylitis , psoriatic arthritis , rheumatoid arthritis and ulcerative colitis . Infliximab won its initial approval by the FDA for the treatment of Crohn's disease in August 1998. Bevacizumab (trade name Avastin , Genentech / Roche ) is a drug that blocks angiogenesis , the growth of new blood vessels. It is used to treat various cancers, including colorectal, lung, and kidney cancer, and eye disease. Bevacizumab is a humanized monoclonal antibody that inhibits vascular endothelial growth factor A (VEGF-A). [1] VEGF-A is a chemical signal that stimulates angiogenesis in a variety of diseases, especially in cancer , retinal proliferation of diabetes in the eye. Bevacizumab was the first clinically available angiogenesis inhibitor in the United States. [ citation needed ] Rituximab , sold under the trade names Rituxan and MabThera , is a chimeric monoclonal antibody against the protein CD20 , which is primarily found on the surface of B cells . Rituximab is used in the treatment of many lymphomas , leukemias , transplant rejection and some autoimmune disorders . Adalimumab (HUMIRA, Abbott) is the third TNF inhibitor , after infliximab and etanercept , to be approved in the United States . Like infliximab and etanercept, adalimumab binds to TNF α , preventing it from activating TNF receptors; adalimumab was constructed from a fully human monoclonal antibody , while infliximab is a mouse -human chimeric antibody and etanercept is a TNF receptor-IgG fusion protein . TNF α inactivation has proven to be important in downregulating the inflammatory reactions associated with autoimmune diseases . As of 2008 adalimumab has been approved by the FDA for the treatment of rheumatoid arthritis , psoriatic arthritis , ankylosing spondylitis , Crohn's disease , moderate to severe chronic psoriasis and juvenile idiopathic arthritis . Quetiapine (branded as Seroquel , Ketipinor ), is an atypical antipsychotic approved for the treatment of schizophrenia , and bipolar disorder . Quetiapine has the following pharmacological actions: [25] [26] [27] [28] D 1 (IC 50 = 1268nM), D 2 (IC 50 = 329nM), D 3 , and D 4 receptor antagonist 5-HT 1A (IC 50 = 717nM), 5-HT 2A , 5-HT 2C , and 5-HT 7 receptor antagonist α 1 - adrenergic (IC 50 = 94nM) and α 2 - adrenergic receptor (IC 50 = 271nM) antagonist H 1 receptor (IC 50 = 30nM) antagonist mACh receptor (IC 50 = >5000nM) antagonist This means Quetiapine is a dopamine , serotonin , and adrenergic antagonist, and a potent antihistamine with clinically negligible anticholinergic properties. Quetiapine binds strongly to serotonin receptors. Serial PET scans evaluating the D 2 receptor occupancy of quetiapine have demonstrated that quetiapine very rapidly disassociates from the D 2 receptor. [29] Theoretically, this allows for normal physiological surges of dopamine to elicit normal effects in areas such as the nigrostriatal and tuberoinfundibular pathways, thus minimizing the risk of side-effects such as pseudo-parkinsonism as well as elevations in prolactin. [30] Some of the antagonized receptors (serotonin, norepinephrine) are actually autoreceptors whose blockade tends to increase the release of neurotransmitters.
  • Trastuzumab (INN; trade name Herceptin ) is a monoclonal antibody that interferes with the HER2/neu receptor. The HER receptors are proteins that are embedded in the cell membrane and communicate molecular signals from outside the cell to inside the cell, and turn genes on and off. The HER proteins regulate cell growth, survival, adhesion, migration, and differentiation—functions that are amplified or weakened in cancer cells. In some cancers, notably some breast cancers, HER2 is over-expressed, and, among other effects, causes breast cells to reproduce uncontrollably. [1]
  • 10/12/12
  • 10/12/12

Transcript

  • 1. Role of Clinical Trials in Drug Discovery & DevelopmentPresented at Gupta College of Technological Sciences on 24th September 2011 Dr. Bhaswat S. Chakraborty Senior Vice President and Chairman R&D Core Committee, Cadila Pharmaceuticals
  • 2. Blockbuster DrugsDrug Trade name Company Sales (billion $) yearAtorvastatin Lipitor Pfizer 12.5 (2009) Bristol-Myers SquibbClopidogrel Plavix 9.5 (2009) and Sanofi-AventisFluticasone Advair Glaxo-Smith-Kline 7.7(2009)and salmeterolEnbrel Etanercept Amgen 6.2 (2009)Valsartan Diovan Novartis 6.0 (2009)Infliximab Remicade Johnson & Johnson 5.9 (2009)Bevacizumab Avastin Roche and Genentech 5.7 (2009)Rituximab Rituxan Roche and Genentech 5.6 (2009)Adalimumab Humira Abbott 5.5 (2009))Quetiapine Seroquel AstraZeneca 5.1 (2009)
  • 3. Drug Discovery and IT• Using HTS robotics, data processing and control software, liquid handling devices, and sensitive detectors, a researcher can now conduct millions of chemical, genetic or pharmacological tests in few days.• High impact of in silico molecular modelling, resulting in acceleration of the drug discovery process. – For example, using traditional drug development techniques it took nearly 40 years to capitalize on a basic understanding of the cholesterol biosynthesis pathway to develop statin drugs – those that inhibit the enzyme HMG-CoA reductase, the rate limiting step in cholesterol biosynthesis. – Whereas, a molecular-level understanding of the role of the HER-2 receptor in breast cancer led to the development of the chemotherapeutic agent Herceptin® within only three years.
  • 4. Drug Discovery Initial Steps Disease Characterization
  • 5. Drug Discovery Middle StepsTarget Selection and Validation
  • 6. Use of Combinatorial Chemistry and HTS• Pharmaceutical companies often use combinatorial chemistry and HTS to predict these target-lead interactions.• Recently the in silico techniques for predicting these molecular events have advanced to the point where biotech companies are beginning to skip much of the bench work involved in combinatorial chemistry and synthesize only the most promising compounds based on a structural understanding of the receptor and associated ligands.• Having identified the most relevant targets and selected the most promising lead compounds, the focus shifts to clinical trials. Augen J. 2002. DDT, 7, 315-323
  • 7. Drug Discovery Final Steps ADME & Clinical Studies
  • 8. Rounds of Drug Discovery Process• Results from clinical trials are fed back to enhance the next round of target selection and lead identification and optimization.• Although each step in the process involves specific information tools, the tools are related and in some cases overlap. – e.g., Much of today’s animal model work involves comparative genomics including tools for multiple sequence homology and pattern matching. – Many of these tools are also used to help find genes that code for target proteins. – similarly, both target validation and lead optimization are enhanced by the use of programs that facilitate predicting 3D structures of proteins and protein–ligand complexes. Augen J. 2002. DDT, 7, 315-323
  • 9. Superordinate Goals of New Drug Discovery• To evidence that the drug is safe and effective in its proposed use(s), and whether the benefits of the drug outweigh the risks.• To evidence that the the methods used in manufacturing the drug and the controls used to maintain the drugs quality are adequate to preserve the drugs identity, strength, quality, and purity.• To evidence that the drugs proposed labeling (package insert) is appropriate, and what it should contain. 9
  • 10. Drug Discovery Final Steps ADME & Clinical Studies
  • 11. Investigational New Drug• The pharmaceutical industry sometimes informs the FDA prior to submission of an IND• Sponsors, research institutions, and other organizations that take responsibility for developing a drug must show the FDA results of preclinical testing theyve done in laboratory animals and what they propose to do for human testing• At this stage, the FDA decides whether it is reasonably safe for the company to move forward with testing the drug in humans 11
  • 12. Phase 1• Phase 1 studies are usually conducted in healthy volunteers• The goal here is to determine what the drugs most frequent side effects are and, often, how the drug is metabolized and excreted• Dose escalation-response data• What is maximum tolerated dose and what dose limited toxicities are• The number of subjects typically ranges from 20 to 100 12
  • 13. Early Phase Clinical Trials 13
  • 14. Phase 2• Phase 2 studies begin if Phase 1 studies dont reveal unacceptable toxicity• While the emphasis in Phase 1 is on safety, the emphasis in Phase 2 is on effectiveness• This phase aims to obtain preliminary data on whether the drug works in people who have a certain disease or condition at selected doses• For controlled trials, patients receiving the drug are compared with similar patients receiving a different treatment--usually an inactive substance (placebo), or a different drug• Safety continues to be evaluated, and short-term side effects are studied. Typically, the number of subjects in Phase 2 studies ranges from a few dozen to about 300 14
  • 15. Phase 3• At the end of Phase 2, the FDA and sponsors try to come to an agreement on how the large-scale studies in Phase 3 should be done• How often the FDA meets with a sponsor varies, but this is one of two most common meeting points prior to submission of a new drug application• The other most common time is pre-NDA, right before a new drug application is submitted• Phase 3 studies begin if evidence of effectiveness is shown in Phase 2• These studies gather more information about safety and effectiveness, studying different populations and different dosages and using the drug in combination with other drugs• The number of subjects usually ranges from several hundred to about 3,000 people 15
  • 16. Phase 4• Postmarketing study commitments are called Phase 4 commitments – studies required of or agreed to by a sponsor that are conducted after the FDA has approved a product for marketing• The FDA uses postmarketing study commitments to gather additional information about a products safety, efficacy, or optimal use 16
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  • 18. Institutional Review• IRBs approve the clinical trial protocols – the type of people who may participate in the clinical trial – the schedule of tests and procedures – the medications and dosages to be studied – the length of the study – the studys objectives – other details• IRBs make sure the study is – acceptable – participants have given consent – Participants are fully informed of their risks – researchers take appropriate steps to protect patients from harm 18
  • 19. Design Concepts Non-Inferiority Difference in Clinical Efficacy (Є) Superiority +δ 0 Equivalence -δ Inferiority Non-SuperiorityEquality δ = Meaningful Difference 19
  • 20. Adequate and Well-Controlled Studies..• Minimization of Bias: a unidirectional tilt favoring one group, i.e., a non-random difference in how test and control group are selected, treated, observed, and analyzed – These are the 4 main places bias can enter• Remedies: – Blinding (patient and observer bias) – Randomization (treatment and control start out equal) – Careful specification of procedures and analyzes in a protocol to avoid • Choosing the most favorable analysis out of many (bias) • Having so many analyses that one is favorable by chance (multiplicity) Source: RJ Temple, US FDA, Unapproved Drugs Workshop January 20 2007
  • 21. Clinical Trials: Testing Medical Products in Humans• Clinical studies test potential treatments in human volunteers to see whether they should be approved for wider use in the general population – A treatment could be a drug, medical device, or biologic, such as a vaccine, blood product, or gene therapy – A new treatment may or may not be “better” – Complete and accurate research – Protection and well being of participants • Ethics, consent, audit – Documentation 21
  • 22. Randomized Clinical Trials• Gold standard is Phase III RCTs = Evidence based medicine• Single centre CT – Primary and secondary indications – Safety profile in patients – Pharmacological / toxicological characteristics• Multi-centre CT – Confirmation of the above – Effect size – Site, care and demographic differences – Epidemiological determination – Complexity – Far superior to meta-analyzed determination of effect 22
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  • 24. Study Design: Approaches• Randomised Controlled Trials (RCT) most preferred approach – Demonstrating superiority of the new therapy• Other approaches – Single arm studies (e.g., Phase II) • e.g., when many complete responses were observed or when toxicity was minimal or modest – Non-inferiority & Equivalence Trials – No Treatment or Placebo Control Studies – Isolating Drug Effect in Combinations – Dose escalation – …. 24
  • 25. Adequate & Well-Controlled Studies• Because the course of most diseases is variable, you need a control group, a group treated just like the test group, except that they don’t get the drug, to distinguish the effect of the drug from spontaneous change, placebo effect, observer expectations• 21 CFR 314.126 describes the following controls – Placebo – No treatment – Dose response – Active control • Superiority of non-inferiority – Historical• Placebo, dose response or superiority are usually convincing studies• Adequate means – adequate sample size, power, design and analysis plan 25
  • 26. Placebo Control Trials• Only when it is ethical• Sometimes acceptable otherwise – e.g., in early stage cancer when standard practice is to give no treatment – Add-on design (also for adjuvants) • all patients receive standard treatment plus either no additional treatment or the experimental drug – Placebos preferred to no-treatment controls because they permit blinding – Measures “effect size” accurately 26
  • 27. Active Control Trials• The purpose of an active control trial could be to demonstrate that a new experimental treatment is either – superior to the control – equivalent to the control, or – non-inferior to the control – superior to a virtual placebo 27
  • 28. Non-Inferiority Trials• New drug not less effective by a predefined amount, the noninferiority (NI) margin – NI margin cannot be larger than the effect of the control drug in the new study – If the new drug is inferior by more than the NI margin, it would have no effect at all – NI margin is some fraction of (e.g., 50 percent) of the control drug effect 28
  • 29. What to Measure?• Primary outcome measure: The health parameter measured in all study participants to detect a response to treatment. Conclusions about the effectiveness of treatment should focus on this measurement.• Secondary outcomes measure: Other parameters that are measured in all study participants to help describe the effect of treatment.• Baseline variables: The characteristics of each participant measured at the time of random allocation. – This information is documented to allow the trial results to be generalised to the appropriate population/s – Specific characteristics associated with the patient’s response to treatment (such as age and sex) are known as prognostic factors 29
  • 30. Data• There are legal and ethical reasons for reporting all relevant data collected during the drug development process• Some reporting strategies already exist in the 1988 Guidelines, ICH E3 and E9• Electronic Submissions and desktop review capabilities will help all of us make better use of clinical data in NDA’s• There may be better strategies and these should be considered 30
  • 31. Intent-to-Treat Principle• All randomized patients• Exclusions on pre-specified baseline criteria permissible – also known as Modified Intent-to-Treat• Confusion regarding intent-to-treat population: define and agree upon in advance based upon desired indication• Advantages: – Comparison protected by randomization • Guards against bias when dropping out is related to outcome – Can be interpreted as comparison of two strategies – Failure to take drug is informative – Reflects the way treatments will perform in population• Concerns: – “Difference detecting ability” 31
  • 32. Per Protocol Analyses• Focuses on the outcome data• Addresses what happens to patients who remain on therapy• Typically excludes patients with missing or problematic data• Statistical concerns: – Selection bias – Bias – difficult to assess 32
  • 33. From the Results of Clinical Trials, What does FDA Conclude?• If CMC is OK, FDA approves a drug application based mainly on RCT results – Substantial evidence of efficacy & safety from “adequate and well-controlled investigations” – A valid comparison to a control – Quantitative assessment of the drug’s effect• The design of clinical trials intended to support drug approval is very important 33
  • 34. Conclusions• Randomized Clinical Trials are very sophisticated and complex• Principal Investigators’, Trial Monitors’ and Biostatisticians’ roles are invaluable• Higher Phase (Phases 2, 3) Clinical Trials provide for the main evidence of efficacy and safety• Clinical data is very complex (confounded, censored, skewed, often fraught with missing data point), therefore, proper hypothesization and statistical treatment of data are required• Prospective RCTs are usually the preferred approach for evaluation of new therapies 34
  • 35. Conclusions..• Clinically meaningful margins must be well defined in Control trials prospectively – Superiority and non-inferiority margins must not be confused• All trials must be medically and statistically well designed and adequate• Both ITT and PP data analyses are important for approval• If CMC is OK, FDA approves a drug application based mainly on RCT results• … 35
  • 36. Thank You Very Much