Progeria and Clinical trials (Dr. Smallwood)

NO PHARAMCOKINETICS

What is Progeria

Progeria, also known as Hutchinson-Gilford Progeria Syndrome, is a rare genetic disorder characterized by accelerated aging in children, resulting in symptoms such as growth failure, hair loss, and cardiovascular problems.

What type of inheritance is progeria

• The mutation is autosomal dominant

• Progeria patients have one normal allele (one normal copy of the LMNA gene) and one mutant allele

• One copy of the mutant allele is enough to cause progeria

What differentiates classical progeria from progeria

• Classical Progeria is caused by a mutation of the LMNA gene

• Mutated LMNA gene - Abnormal lamin A protein (progerin) - Progeria

• LMNA gene should just produce Lamin A protein
  

What gene is affected in progeria

The LMNA gene is affected in progeria, which encodes the protein lamin A.

Mutations in this gene lead to the production of an abnormal version of the protein, resulting in accelerated aging symptoms.

What changes happen to the progeria nuclei compared to normal

• Filament protein

• Forms basketwork structure called the nuclear lamina

• Located just inside the inner nuclear membrane

• Provides structure and shape to the nucleus

• In progeria lamin A protein (progerin) is damaged, does not form the correct basketwork structure and gives progeria nuclei an abnormal shape

What are the normal Lamin A interactions

• Lamin A interacts with many other proteins and chromatin

• Essential for normal gene transcription

• However: these interactions can go wrong in progeria

What are some phenotypes realted to progeria

• Heart disease

• Low weight

• Short stature

• Low body fat

• Aged skin

• Osteoporosis

• Osteolysis

• Joint stiffness

• Hair loss

Where does the muations for Lamin A on LMNA gene happen

Classical progeria mutation is located in exon 11 in the LMNA gene

• LMNA gene mutation: c.1824C>T

• Lamin A protein mutation: p.G608G (GGC>GGT), mostly just written G608G

What does alternative splicing mean in progeria

Which exons are involved in alternative splicing in progerin

How many amino acids are deleted

50 missing amino acids
(50 amino acid internal deletion

What events occur in post-translational processing

• Common method of targeting proteins to membranes is to add a lipid group
  

• Farnesyl group is one type of lipid (there are many)

What is the sequence of normal events for prelamin A to mature lamina A

1. Prelamin A C-terminus ends in 4
   amino acids (CSIM)

2. Enzyme farnesyltransferase adds a
   farnesyl (lipid) group to amino acid C

3. Next there are 2 cleavage steps by
   enzyme ZMPSTE24

4. Cleavage 1 removes the 3 C-
   terminal amino acids SIM

5. Cleavage 2 removes a further C-
   terminal 15 amino acids including the farnesyl group

6. Processed protein is mature lamin A

What is the sequence of abnormal events for prelamin A to mature lamin A

1. Preprogerin C-terminus ends in 4 amino acids (CSIM)

2. Enzyme farnesyltransferase adds a farnesyl (lipid) group to amino acid C

3. Next there is 1 cleavage step by enzyme ZMPSTE24

   • Cleavage 1 removes the 3 C-terminal amino acids SIM

   • Cleavage 2 cannot happen because 2nd ZMPSTE24 binding site is absent due to 50 amino acid internal deletion

4. The farnesyl group remains attached

5. Processed protein is progerin (LAD50) / Preprogerin (614 amino acids)

What is lonafarnib drug

An inhibitor of farnesyltransferase used in clinical trials to treat progeria, aiming to prevent the farnesylation of prelamin A.

What are clinical trials

Research studies that evaluate the safety and effectiveness of new treatments or drugs in humans before they receive regulatory approval.

What are randomised controlled trials (RCTs)

A type of clinical trial that randomly assigns participants into experimental or control groups to compare outcomes and assess the efficacy of treatment.

What is the purpose of randomized controlled trials (RCTs)

The purpose of randomized controlled trials (RCTs) is to determine the effectiveness of a treatment by eliminating biases, ensuring random assignment to groups, and comparing outcomes between the experimental and control groups.

What is the Health research authority (HRA)

An organization that oversees ethical standards and regulations for research involving human participants in the UK, ensuring proper conduct and protection of rights.

 What is the Research ethics committee

• Participant information sheets provide clear information on involvement/risk/withdrawal and complaints

• Informed consent occurs

• Participants understand how their data and samples will be used, stored and shared

• Ethical approval and regulation – informed
  consent of participants
  

What is the phase I trial

• First trial in humans

• Small number of healthy volunteers

• Is the drug toxic?

• What dose is safe?

• Are there side effects and are they acceptable?

• Small numbers of patients

• Minimum therapeutic dose (lowest effective dose)

What are side effects and why are they there

• Side effects are unintended consequences of a drug treatment, resulting from the drug's interaction with biological processes.

• They may arise due to the mechanism of action, dosage, or individual patient factors.

What is the phase II trials

Several hundred patients
• Does the drug work?
• What dose is effective?

What is the phase III trials

Large numbers of patients (usually thousands)

• How well does the new drug work?

• Often (not always) RCTs:

• new drug versus standard treatment

• new drug versus placebo

What makes RCT gold standard

• Controlled

• Participants allocated into control or treatment groups using randomisation methods

• Employ methods of bias reduction

• Large numbers increase data quality

What is bias and its impact in clinical trials

Bias is prejudice for or against something

• Bias makes clinical trial findings less valid:

  • Systematic error in trial design or conduct

  • Skews/deviates results from the truth

  • Can lead to under or over estimation of the effect of a treatment

What are the 4 types of bias

• Allocation Bias

• Performance Bias

• Assessment Bias

• Attrition Bias

Explain what is allocation bias

• Bias in the way trial participants are allocated into groups

• Trial staff are unlikely to be biased deliberately, bias can be unconscious

• Believing a new treatment is better so unconsciously placing sicker patients in the treatment group

• Knowing a drug has side effects so unconsciously avoiding putting sicker patients in the treatment group

How can we mitigate allocation bias

• Simple randomisation

  • Assign participants randomly to control or treatment group

  • Reduces bias

  • 50:50 chance of being in treatment or control group

    Problems:

  • Smaller trials could end up with unequal numbers

  • Participant characteristics could influence results

• Block randomisation

  • Method of allocating patients into treatment or control groups (usually by computer)

  • Prevents trial staff accidentally predicting the patient trial group by sequence

• Covariates (participant characteristics not linked to response to the trial drug)
  – Age
  – Gender
  – Race
  

• Confounding factors (participant characteristics likely to influence response to the trial drug)
  – Disease severity
  – Co-morbidities
  – Other specific drug treatments
  

What is performance bias

Participant response to treatment (performance) can be affected by:

• Knowing their trial group

• Trial groups receiving different care plans

• Trial groups responding to expectations of trial staff

How do we minimise performance bias

Blinding - hiding the treatment group

• Single blind - hiding group from participants

• Double blind - hiding group from participants and trial staff

• Treating all groups the same

• Same care

• Injections/tablets/tests appear identical for drug and placebo

What is assessment bias

Assessment of participant response to treatment can be affected by:

• Trial staff or doctor assessment of participants is influenced by knowing the treatment group

• Samples from different groups are assessed differently

How to Minimise:

• Blinding

• Standardise assessment methods and equipment

• Use calibrated equipment
  

 What is attrition bias

• Participants drop out of a study

• Can make group numbers unequal

• Can reduce trial impact due to low participant number

What are ways to minimise attrition bias

• Participation incentives

• Good communication

• Good trial management and organisation

What are phase IV trials

• Drug has been approved and is for sale

• Are there long term side effects?

• Is the drug effective long term?

• New drug

What other bias are there in clinical trials

Selection bias, performance bias, detection bias, reporting bias.