16 Safety Testing New Medicines Flashcards
ICH approved non-clinical
safety testing
• ICH: International conference on harmonization (US, EU, Japan)
• Toxicokinetics
– PK studies associated with toxicology studies
• Doses
– Single dose - “acute toxicity”
– Repeat dose (between 2 weeks and 6-9 months) –“chronic toxicity”
– NOEL & NOAEL (No Observed Effect Level; No Observed Adverse Effect Level)
• Studies to assess:
– Safety Pharmacology
– Reproductive toxicology
– Genotoxicity (Mutagenicity)
– Carcinogenicity
– Local tolerance (for route of administration)
– Any special considerations relating to the drug
Toxicokinetics
The study of how a chemical or toxin gets into the body and what the body does to the chemical
By obtaining toxicokinetic data we can:
- Understand relationship between dose and systemic exposure
- Understand relevance to human exposure at high dose
- Relate observed toxicity to exposure (including tissue distribution)
- Show the toxicity measured in animals is a reasonable model of what might happen in clinical trials
- Level of exposure relevant
- Metabolites relevant
- Pharmacology of toxicology
Single-dose toxicity studies
- Two mammalian species (often rodent)
- Two routes of administration
- Route to be used in man
- Route giving F=1 (eg i.v.)
- Measure exposure
- Range of drug doses to observe Therapeutic exposure & NOEL → NOAEL →LD (Lethal Dose)
- Observe for ≥14 days for evidence of toxicity (eg body weight, behaviour)
- Autopsy: organs with macroscopic abnormality undergo histopathological examination
Repeat-dose toxicity studies
• Rodent (mouse, rat) and non-rodent (dog, monkey)
• Exposure (dose/PK, duration, route) to reflect expected clinical use
– 28 day (Normally non-regulatory – justifies investment in longer studies)
– 6-12 months carried out to GLP (For very short clinical trials may be shorter)
• Toxicokinetics
• Monitor
– Weight, behaviour, hematology, urine analysis, food consumption, cardiovascular (rate, bp, ECG)
– Organ weights, gross pathology, histology
• Mutagenicity
• Indication of reproductive toxicology (fertility, pre & post
natal development)
• Indication of carcinogenicity
Repeat-dose drug distribution
studies
• Single-dose drug distribution studies performed routinely as part of toxicokinetics package
• Repeated dose distribution studies performed when
– Plasma levels higher after repeated dose than single dose
– Slow elimination from tissues seen in single dose studies
– Unexpected histopathological (tissues become diseased) effect observed compared to results from single dose distribution study
GLP
Good Laboratory Practice
• 1970s - FDA investigation identified poor laboratory practice in US toxicology labs
-Examples of some of these poor
lab practices found were
1. Equipment not been calibrated to standard form , therefore giving wrong measurements.
2. Incorrect/inaccurate accounts of the actual lab study
3. Inadequate test systems
-Industrial Bio Test – excluded mice suffering severe adverse events from safety-testing studies for cosmetics
Safety Pharmacology
• Investigation of undesirable pharmaco-dynamic effects (eg receptor antagonism)
– Test: drug and major metabolite
• In particular look for effects on – cardiovascular system,
– respiration,
– CNS.
• Supplementary tests
– Renal/urinary system; autonomic nervous system; GI function
• Also any effects anticipated from:
– Target class; Drug class; Target physiological function
• Use: animals, organs, tissue, cells in vitro, cell fragments, enzyme assay, receptor binding assays
– Relatively few models have regulatory recognition
– Used by Pharma companies for internal decision-making
– Some may be incorporated into make-test drug discovery cycle
Reproductive toxicity
• To asses:
– Fertility (♀ & ♂),Embryonic, fetal and post-natal development
• Species
– Same as for other toxicity studies (often rat)
– Teratogenicity – include second non rodent species (often rabbit)
• Study for full life cycle:
– Pre-mating→Conception→implantation →embryo →fetus →birth →weaning →sexual maturity
• Phase 1&2 trials can be carried out without Reprotox studies
– Only in Men & Women Not of Childbearing Potential
Preclinical tests for Genotoxicity
In vitro • Ames bacterial reverse mutation • Mammalian cells – Metaphase chromosome aberration – Micronucleus – Mouse Lymphoma TK assay
In vivo
• Can be part of repeated dose study
• Chromosome aberration assay or micronucleus assay
What ames test
The Ames test is a widely employed method that uses bacteria to test whether a given chemical can cause mutations in the DNA of the test organism.
Ames test for mutation
- Salmonella strain requires Histidine for growth on agar due to DNA mutation
- Test for reversal of mutation – point mutation and frameshift
- Optional: Liver homogenate to generate & test drug metabolites – biotransformation
Tests for chromosomal aberration & aneuploidy
Cells treated with drug (in vitro or in vivo) –>
Giemsa Stain
-Metaphase chromosome aberration assay • Light microscopy • Metaphase cells • Count chromosomes • Morphological assessment
-Micronucleus Assay
•Light microscopy •Chromosome fragment not incorporated into daughter cell’s nucleus
-Mouse Lymphoma TK assay
•If drug induces mutation in Thymidine kinase gene– cells survive
•Detects broad spectrum of DNA alterations – anything that interferes with function of TK
•Point mutations, frameshifts, translocations, deletions, aneuploidy
Define aneuploidy
presence of an abnormal number of chromosomes in a cell
Carcinogenicity
• Most human carcinogens are also carcinogens in animals
• Study design:
– 2 year or animal lifetime study
– Drug dose MTD & 0.5 x MTD (maximum tolerated dose) – Rat or mouse
– Monitor appearance of tumours
• Only performed if
– Drug will be used continually > 6 months (eg anti depresants) – OR if there is cause for concern
• Compound class/SAR
• Evidence of carcinogenicity from repeat dose study • Slow elimination
• Genotoxic – presumed to be carcinogenic
• Sometimes delayed until/after MAA for serious disease and not required if life expectancy short – i.e may not be done before First in Human (FIH) trial!
Clinical Trials
Phase 1
Safety Tolerance –identify ADR Define MTD, DLT Pharmacokinetics Exposure, metabolism Pharmacodynamics Study type Single & Repeat dose Dose escalation Drug interactions
Clinical Trials
Phase 2
Safety - prolonged dosing
Efficacy
Exploratory use
Identify dose(s) for phase 3 Explore PD, efficacy endpoints
Clinical Trials
Phase 3
Efficacy (can be comparative)
Safety
Clinical Trials
Phase 4
Less common ADR
Refine dose, risk/benefit
FIH: First-in-human Studies
• Can only be carried out after IND (Investigational new drug) application granted by appropriate regulatory authorities
• FIH: First part of phase 1
• Assess risk based on preclinical data
– Mode of action of drug
– (Other) physiological functions of the drug target
– Preclinical pharmacology suggests potential benefit
– Preclinical safety studies: Single & repeat dose, safety pharmacology core battery, in vitro genotoxicity
• Quality
– Manufactured to Good Manufacturing Practice (GMP) standards and any/all impurities deemed safe
• First dose
– Scale dose to man based on (usually*) mg/m2 or mg/kg
– NOAEL x safety factor
– MABEL x safety factor
• Mitigate risk
– Healthy volunteers
– clinical facility with trained staff who understand the IND; access to emergency care
– plan to respond to expected ADR
– delayed sequential administration to subjects with observation
– stopping rules
– careful dose escalation
– Review data and adjust before moving to next cohort
Phase 1 trial design
• Single Ascending Dose – Small cohort (3-6) healthy volunteers – Initial dose well below MABEL – Check PK & Safety – Repeat with higher doses until • Target Exposure (based on predicted efficacy) achieved or • ADR’s prevent further increases • Multiple Ascending Doses – As above but with 7-14 days repeated dosing
ADR during clinical trials
• In general (for drugs intended for long term treatment):
– > 300-600 patients treated for 6 months
– Some treated for 12 months (in case of delayed onset)
• Case report form
– A document that records all information required by the trial protocol on each trial subject that is to be reported to the trial sponsor
– Adverse events are recorded
– Allows adverse events to be analysed at end of trial different arms of the study
• Common ADR, serious ADR
• # patients, drug dose
• Any laboratory tests
• Compare different arms of study (eg treated v placebo)
• Unexpected ADR
– “Investigator’s Brochure” alerts physicians to likely adverse events (summarizes preclinical toxicology)
– Serious (life threatening) ADR - “expedited reporting” within 7days (or phone, FAX!)
– Non life threatening ,15 days
What went wrong with TGN1412?
Toxicology studies were flawed
•Safety assessed in monkeys & rodents but potency not compared in human and monkey cells
•“No observable effect level” was not identified
•Standard tests may not have been appropriate for a immuno- modulatory drug
•Some indications of adverse events were overlooked
Timing of administration
•drug given over 3-6 minutes yet given over 1 hour in animal safety studies
•Insufficient time between each trial subject
Delay in administration of steroids to suppress cytokine release
•Even though identified as potential therapy in case of adverse reaction
Clinical Trial provides evidence of..
efficacy and safety (quality needed too)
Some ADR may not be..
be identified in clinical trials. Hence need for monitoring of marketed drugs
The Aim Of GLP Certification
Ensure the application of rigorous processes for
• Test systems
• Archiving of records and materials.
• Apparatus, material and reagent facilities.
• Quality assurance programs.
• Performance of the study.
• Reporting of study results.
• Standard operating procedures (SOP)
• Personnel and test facility organization
Standard Operating Procedures
SOP
• Written procedures for a laboratories program.
– Define how to carry out protocol-specified activities.
– Chronological listing of action steps.
– Ensure that procedure is carried out identically regardless of
operative
• Should include all of the following:
– Routine inspection, cleaning, maintenance, testing and
calibration.
– Actions to be taken in response to equipment failure.
– Analytical methods
– Definition of raw data
– Record-keeping and data-handling processes
• Both Facilities and Personnel must be
certified for GLP studies
ICH principles of Good Clinical
Practise for clinical trials
- Declaration of Helsinki – ethics of research on humans
- Assess Risk v benefit of trial
- Protect safety & rights of trial subjects
- Sufficient data to justify the trial
- Scientifically sound & specific protocol
- IRB (Institutional review board) & IEC (Independent ethical committee) approval
- Medical care –qualified physician
- Appropriately qualified personnel
- Informed consent
- Appropriate data handling
- Confidentiality of trial subjects
- GMP
- Quality
