Lecture 2: Discovery of novel anti-infectives

Question 1

History of antivirals
→ first antiviral, which one ?
→ now, for which virus ?
→ 3 groups
→ examples for the group

Answer 1

→ first 1963 Idoxuridine against HBV

→ now 90 approved, HIV, HCV, HSV, Influenza

→ Retro-, DNA- and RNA-Virus

Retro: HIV
DNA-Virus: HBV, HPV, HSV, VZV, HCMV
RNA-Virus: HCV, RSV, Influenza

Question 2

General development of antiviral drug

Answer 2

Target identification
→ Lead identification
→ Lead omptimized
→ Preclinical testing
→ Efficacy, safety, toxicity, pharmacology
→ Clinical trials 1-2
→ Clinical trial phase 3

Question 3

Why so few antiviral drugs ?

Answer 3

→ difficult to study → BSL-4 labs
→ viral functions linked to host cell functions
→ pathogenesis complicated
→ few good animal models
→ novel threats constantly emerging (zoonotic, global warming, vector migration

Question 4

What is the goal of antivirals ?
→ 2 mechanism resulting in disease
→ antiviral considerations for both mechanism
→ example

Answer 4

1.Damage caused by Virus
→ cytopathic effects, inhibition of host protein and RNA synthesis, Syncytium formation by enveloped viruses, virus induced apoptosis, programmed cell death
→ blocking virus replication in early stage to stop pathogenesis
→ example HSV

2. Damage caused by immune system
   → inflammation via CD4+, CD8+, antibody dependent cell. cytotoxicity and enhancement
   → blocking virus replication insufficient
   → example Hepatitis B, SARS-CoV2 antivirals that block IL-1 receptors

Question 5

Which step in viral cycle can be blocked ?
→ different virus genomes and example
→ different drug mode of actions

Answer 5

Genomes
→ ssDNA → Parvo
→ dsDNA → Herpes
→ dsDNA (RT) → Hepadna
→ +RNA (RT) → Retro
→ + RNA → Corona
→ dsRNA → Birna
→ - RNA → Borna

Drug mode of action
→ Immunomodulation
→ Binding inhibitors, Fusion inhibitors
→ Virus uncoating inhibitors
→ Integrase inhibitor, (N)NRTIs
→ Protease inhibitors
→ Assembly inhibitors
→ Release inhibitors

Question 6

Which antivirals groups stop DNA RNA synthesis and replication ?
→ examples, mode of action, drug example

→ example viruses

Answer 6

→ interfere with RNA/DNA synthesis terminating growth of the nascent chain upon incorporation

examples are ATP-like mostly
→ 5-sub. 2´deoxyuridine analogues
. → Idoxuridine, Brivudine, Trifluridine
→ nucleoside analogues
. → Telbivuine, Entecavir, Vidarabine, FV100
→ Pyrophosphate analogues
. → Foscarnet
→ acyclic guanosin analogues
→ acyclic nucleoside phosphonate analogues

→ HSV, HCMV

Question 7

Which antivirals stop RT or Integrase ?
→ examples, drug example

Answer 7

Nucleoside RT inhibitors (NRTIs)
→ Zidovudine for HIV

nonnucleoside RT inhibitors (NNRTIs)
→ Nevirapine for HIV

Integrase inhibitors
→ Dolutegravir

Question 8

Protease inhibitors
→ example of virus proteases, one example of drug
→ mode of action for examples

Answer 8

→ example: HIV, HCV, Coronavirus main, Cellular

HCV:
→ small genome → polyproteins that are cleaved in course of viral replication → temporal regulation

Coronavirus:
→ relicase polyprotein PP1ab
→ Paxlovid for inhibition

Cellular proteases
→ might be required for trimming of viral glycoproteins → example TMPRSS2 to prime spike proteases of SARS-CoV-2

Question 9

Enty inhibitors
→ 3 classes

Answer 9

→ heterogenous

classes
→ Co receptor blocker
→ fusion inhibitors
→ nonoclonal antibodies → Trogarzo, Synagis

Question 10

Monotherapy vs combination therapy ?

Answer 10

combination therapy is required
→ mutation + selective pressure would cause resistance virus

Question 11

Protein vs nucleic acid
→ mechanism

Answer 11

Nucleic acid
suppresion of expression of essential viral gene
→ short interfering RNAs
→ antisense oligonucleotides
→ CRISPR-Cas9
→ deoxyribozymes
→ ribozymes

Protein
→ inhibtion of viral enzymes, protein-protein interactions

Question 12

Enzyme inhibition vs PPI inhibition
→ example
→ +/-

Answer 12

Enzyme
→ Sofosbuvir: HCV polymerase
→ 20k-30k proteins
→ more conserved
→ taregting active site easier

Protein
→ Palivizumab: RSV enty
→ 650k PPI
→ less conserved
→ immune system can be used

Question 13

Pharmacokinetics

Answer 13

→ ADME (adsorption, distribution, Metabolism, excretion
→ Bioavailability
→ mode of transmission
→ aerosols (Influenza)
→ surfaces (Noro)
→ parenteral (HIV)
→ sexual (HPV)
→ vertical (fetus)
→ tissue tropism

Question 14

Viral target vs host target

Ideal target for antiviral traget

Answer 14

Viral target like Fusion inhibitors might be resistent

Host target like chemokine antagonists might cause side effects

→ not resemble any celular protein and cannot escape the drug action by escape mutations

Question 15

Frequently used screening methods

Answer 15

High throughput screening (cell based assays, biochemical)
→ blind screening of large 100k-1M compund libraries

Fragment based screening (X-Ray, NMR, …)
→ blind screening of fragment 1k libraries, fragment 200-300 Da, low affinity, lead compunds have to be bigger, so merge fragments

In silico methods (Mol. docking)
→ 750M compounds
→ database → docking → scoring → selection and in vitro assays

Rational drug design
→ prior knowledge

Biologicals
→