PSC2002/L09 Cystic Fibrosis III

Question 1

Which drug exists for F508del/F508del + F508del/other?

Answer 1

2 correctors (Teza + Elexacaftor)
+ potentiator (Ivacaftor)

Question 2

What drugs exist for G542D + 9 gating + 23 RF mutations?

Answer 2

Potentiator (Ivacaftor)

Question 3

What drugs exist for other mutations?

Answer 3

No drug
General hypothesis: these patients may benefit from genetic therapies and/or regulation of non-CFTR channels

Question 4

Define genetic therapy.

Answer 4

Therapeutic approaches that: deliver copies of the healthy gene using gene addition
Fix chromosomal DNA using genome editing (e.g., CRISPR/Cas9-based approaches such as prime and base editing

Question 5

Describe viral vector gene therapy in cystic fibrosis. (4)

Answer 5

Humoral immunity (healthy CFTR gene) within viral vector delivered
Endocytosis into endosome
Delivered into nucleus and transcription/translation
CTFR & cytotoxic T cells produced for viral proteins

Question 6

Describe liposome vector gene therapy in cystic fibrosis. (5)

Answer 6

CFTR cDNA mixed with cationic liposome
Inserted into lysosome
Lipid accumulation
Gene transcribed and translated
CFTR expressed in membrane

Question 7

Describe the CF Trust UK and Gene Therapy Consortium (GTC) Trial.

Answer 7

July 2015 phase 2b clinical trial using nebulised liposome vector + CFTR cDNA
Showed 3% improvement of ppFEV(1.0)
First proof of concept trial and largest gene therapy trial for CF to date

Question 8

How can gene transfer agents (GTA) improve efficacy of gene therapy? (3)

Answer 8

Lentivirus, AAV - long term, stable correction from a single dose because gene is integrated into DNA
Modify virus to make them less immunogenic
Use other non-viral approaches e.g., nanoparticles

Question 9

Give 2 problems with using gene transfer agents (GTAs) for improving efficacy of gene therapy.

Answer 9

Need to target right cells in lungs - best would be basal (stem) cells
Mucus important barrier to gene therapy still
Potential for disruption of other genes

Question 10

Give 2 other genetic and cell-based approaches to CF gene therapy.

Answer 10

Nucleic acids
Cell therapy

Question 11

Describe nucleic acids as an approach to treat CF. (3)

Answer 11

DNA addition and gene editing
tRNA/mRNA
Antisense oligonucleotides
Combined with a delivery vehicle
Direct in vivo delivery

Question 12

Describe cell therapy to treat CF. (3)

Answer 12

Generation of induced pluripotent stem cells
Correct CFTR mutation to wildtype condition
Differentiate cells to basal airway stem cells

Question 13

Describe mRNA-mediated therapy. (3)

Answer 13

Clinical trial of MRT5005 by Translate Bio to introduce normal CFTR mRNA into lung cells (mutation-independent)
March 2021 - interim report showed no improvement in ppFEV(1.0)
Other companies for positive preclinical results and phase II trials in 2024

Question 14

Which kind of mutations is antisense oligonucleotide (ASO)-mediated therapy useful for?

Answer 14

Class I mutations (nonsense, splicing and frameshift)

Question 15

How does alternate channel therapy work? (2)

Answer 15

Using alternative chloride channels (ACCs) present in CF cells to bypass defective CFTR and restore Cl-/Hco3- and fluid transport
Use inhibitors of ENaC to help reduce salt and fluid absorption

Question 16

Which companies are developing drugs to target ACCs and ENaC?

Answer 16

Enterprise therapeutics

Question 17

What is the main target of alternative chloride channels?

Answer 17

TMEM16A

Question 18

How do alternative chloride channels work? (3)

Answer 18

Activation of TMEM16A increases Cl- & fluid secretion in CF airway cells by physiological agonists such as ATP and UTP
ATP/UTP released from epithelial cells into ASL during normal breathing cycles
Bind to purinergic receptors to increase cytosolic Ca2+ activating TMEM16A
Effect of UTP on fluid secretion was relatively short-lived

Question 19

What is required of an alternative chloride channel to be effective?

Answer 19

Direct activation of channel without involving Ca2+ (channel opener) OR
Potentiates channel activity to boost fluid secretion above normal and by-pass defective CFTR

Question 20

How can ENaC activity be decreased?

Answer 20

Use amiloride-like drugs
Target ENaC regulation

Question 21

How can SPLUNC1 be used to decrease ENaC activity?

Answer 21

Acid-resistant version of SLUNC1 (SPX-101) passed phase I trials in 2017
Did not meet end-targets for phase II trial (on ppFEV1.0)

Question 22

Give 2 other approaches to CF treatment.

Answer 22

Synthetic anion channels & transporters (anionophores)
Target SLC26A exchangers that modulate pH
Target H+ ATPase in airway cells that acidifies AS