Antivirals

Question 1

Aciclovir is an analogue of which DNA base pair?

Answer 1

Guanine

Question 2

Is aciclovir active on administration?

Answer 2

No. Needs to be phosphorylated by viral thymadine kinase

Question 3

MOA of aciclovir?

Answer 3

Inhibits DNA synthesis by terminating the chain and inhibiting DNA polymerase

Question 4

Most common mechanism for resistance against aciclovir?

Answer 4

Virus becomes deficient in TK and uses the host’s TK for replication

Question 5

AZT full name?

Answer 5

Azidothymidine

Question 6

What does NRTI and NNRTI stand for?

Answer 6

(Non-)nucleoside reverse transcriptase inhibitor

Question 7

Which base pair is AZT an analogue of?

Answer 7

Thymidine

Question 8

MOA of AZT?

Answer 8

Inhibits the viral reverse transcriptase enzyme

Question 9

Role of the viral reverse transcriptase enzyme?

Answer 9

Converts the viral RNA into DNA, which then gets incorporated into the host cell’s genome

Question 10

How does azidothymidine get activated?

Answer 10

The host’s thymadine kinase phosphorylates it. (Different to aciclovir which uses the viral TK)

Question 11

Name an NNRTI

Answer 11

Nevirapine

Question 12

Is nevirapine a prodrug?

Answer 12

No

Question 13

MOA of saquinavir?

Answer 13

HIV protease inhibitor - blocks the enzyme that hydrolyses hiv proteins into smaller parts to allow for assembly

Question 14

Which drug develops resistance rapidly, so it commonly combined with AZT?

Answer 14

Saquinavir

Question 15

Explain HAART

Answer 15

Highly active antiretroviral therapy. Multi-drug approach to treat HIV - limits resistance and reduces doses required

Question 16

Compare oseltamivir and zamamivir

Answer 16

Both are neuraminidase inhibitors. Oseltamivir is oral, whereas zamamivir is inhaled

Question 17

Explain how neuraminidase inhibitors work

Answer 17

They prevent the cleavage of the bond between HA and sialic acid. This means the virion is stuck to the outside of the infected cell, which allows it to be targeted by the immune system

Question 18

MOA of amantidine?

Answer 18

Blocks the M2 channel, preventing the endocytosed vehicle from becoming acidic, which prevents the uncoating of the virus

Question 19

Discuss amantidine resistance

Answer 19

Pretty much all influenza strains are now resistant to amantidine. A single amino acid change in the M2 ion channel is all it takes to modify it and prevent amantidine from binding

Question 20

MOA of chloroquine and mefloquine?

Answer 20

They are anti malarials. They inhibit the haem polymerase enzyme which prevents the parasite’s from detoxifying free haem, killing the parasite

Question 21

Role of haem polymerase?

Answer 21

Polymerases the free haem proteins into haemozoin crystals

Question 22

Compare the MOAs of the combination product atovaquone and proguanil

Answer 22

Ato - inhibits the production of ATP in the parasite by interrupting the mitochondrial transport chain
Pro - inhibits the parasite’s DHFR enzyme