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GS-441524 vs. Remdesivir for Covid-19
1. Remdesivir:
An underwhelming Covid-19 drug with
room for improvement
Victoria Yan
Graduate Research Assistant
Muller Lab
May 15, 2020
Notes/Disclosures: No affiliations with Gilead Sciences, Inc. Inventor on a prophetic invention disclosure describing novel remdesivir
derivatives (not discussed in this presentation). Inventor on a provisional patent disclosing novel phosphonate pro-drug inhibitors of
Enolase. Any discussions on possible therapeutic interventions in this presentation should not be taken as professional medical advice.
2. Covid-19 has had an unprecedented, profound global impact
May 15, 2020
3. Covid-19 has had an unprecedented, profound global impact
Graph continues halfway
into the article
6. Covid-19 has spurred a global scientific effort to identify
effective therapies
Examples of repurposed
inhibitors under clinical
investigation
Interferon-β
NCT04385095
Chloroquine
NCT04328493
NH
N
N
Cl
Hydroxychloroquine
NCT04351620
N
OH
HN
NCl
Favipiravir
NCT04358549
N
N
O
NH2
OH
F
Lopinavir
NCT04307693
N
H
N
H
N
NH
O
O
O
HO
O
Ritonavir
NCT04307693
N
H
H
N
O
HO
NH
O
O
N
O
S
N
N
S
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
NCT04280705
O
O
OHHO
HO
HO
Ascorbic acid
NCT04323514
Azithromycin
NCT04329832
O
O
O
O
OH
O
O
O
OH
N
OH
N
OH
OH
Ciclesonide
NCT04381364
O
O
HO
O
O
H
H
H
H
O
O
O
O
O
O
O
HN
O
Colchicine
NCT04360980
N
N
O
S
O
O
N
HN N
N
O
Sildenafil
NCT04304313
Darunavir
NCT04252274
O
HN
O
O
O
N
S
HO
O
O
H2N
H
H
H
O
O
H
N NH2
NH
O
O
N
O Camostat
NCT04321096
7. Covid-19 has spurred a global scientific effort to identify
effective therapies
Examples of repurposed
inhibitors under clinical
investigation
Interferon-β
NCT04385095
Chloroquine
NCT04328493
Hydroxychloroquine
NCT04351620
Favipiravir
NCT04358549
Lopinavir
NCT04307693
Ritonavir
NCT04307693
Remdesivir
NCT04280705
Ascorbic acid
NCT04323514
Azithromycin
NCT04329832
Ciclesonide
NCT04381364
Colchicine
NCT04360980
Sildenafil
NCT04304313
Darunavir
NCT04252274
Camostat
NCT04321096
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
8. May 1, 2020: FDA issues emergency use authorization of
remdesivir to treat Covid-19
May 7, 2020: Japan approves remdesivir (Veklury®) to treat Covid-19
9. “It [Remdesivir] was expected to have
a whopping effect…it clearly does
not have that.”
–Dr. Eric Topol, director & founder of the Scripps
Research Translational Institute
April 29, 2020
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
(NCT04280705)
(NCT04257656)
10. How can two similar studies
come to such different
conclusions?
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
April 29, 2020
(NCT04280705)
(NCT04257656)
11. 1. What is remdesivir and why it is not designed to
target the lungs
2. How does remdesivir work
(Also: why I am qualified to talk about this!)
3. Why did remdesivir underperform?
4. Immediate solutions
12. 1. What is remdesivir and why it is not designed to
target the lungs
2. How does remdesivir work
(Also: why I am qualified to talk about this!)
3. Why did remdesivir underperform?
4. Immediate solutions
13. What is remdesivir?
A nucleotide monophosphate analogue
Remdesivir
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
NN
N
N
NH2
O
OHHO
O
P
OHO
O
Adenosine monophosphate
(AMP)
14. What is remdesivir?
A nucleotide monophosphate analogue
Remdesivir
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
NN
N
N
NH2
O
OHHO
O
P
OHO
O
Adenosine monophosphate
(AMP)
Nitrogenous
base
Nitrogenous
base
15. What is remdesivir?
A nucleotide monophosphate analogue
NN
N
N
NH2
O
OHHO
O
P
OHO
O
Adenosine monophosphate
(AMP)
Ribose
sugar
Ribose
sugar
Remdesivir
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
16. What is remdesivir?
A nucleotide monophosphate analogue
NN
N
N
NH2
O
OHHO
O
P
OHO
O
Adenosine monophosphate
(AMP)
Phosphate
Protected
phosphate
Remdesivir
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
17. What is remdesivir?
A nucleotide monophosphate analogue
Remdesivir
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
NN
N
N
NH2
O
OHHO
O
P
OHO
O
Adenosine monophosphate
(AMP)
McGuigan (ProTide) pro-drug
Purpose: increase cell permeability
22. N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
What is remdesivir?
A nucleotide monophosphate analogue
McGuigan (ProTide) pro-drug
Purposes: increase cell permeability
Can also enhance organ specificity by
capitalizing on the expression of tissue-specific
bioactivating enzymes
23. McGuigan pro-drugs are preferentially activated by enzymes in the liver
What enzymes are supposed to hydrolyze the McGuigan pro-drug?
*Intramolecular cyclization and displacement of the
phenoxy group, then hydrolytic re-opening of the ring
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
McGuigan (ProTide) pro-drug
1. CES1/CTSA
then
“hydrolysis”*
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
2. HINT1
N
N
N
NH2
O
CN
OHHO
OP
HO
O
O
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524
triphosphate
Inhibits viral
RNA synthesis
Ideally, this would all happen inside the (lung) cell.
24. McGuigan pro-drugs are preferentially activated by enzymes in the liver
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
CTSA/CES1
HINT1 (or 2, 3)
Adapted from the Human Protein Atlas
25. McGuigan pro-drugs are preferentially activated by enzymes in the liver
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
CTSA/CES1
HINT1 (or 2, 3)
Adapted from the Human Protein Atlas
26. Remdesivir is not easy to synthesize!
Remdesivir
7 steps!
Seigel et al. J. Med. Chem. (2017)
29. List of problems with remdesivir
1. Pro-drugs not designed to target the lungs.
2. Hard to synthesize and mass produce N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
30. 1. What is remdesivir and why it is not designed to
target the lungs
2. How does remdesivir work
(Also: why I am qualified to talk about this!)
3. Why did remdesivir underperform?
4. Immediate solutions
31. How is remdesivir supposed to work?
(+Why Victoria is qualified to talk about this)
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
My projectRemdesivir
POMHEX
Intracellular
32. How is remdesivir supposed to work?
(+Why Victoria is qualified to talk about this)
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
My projectRemdesivir
POMHEX
Intracellular
POMHEX
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
33. How is remdesivir supposed to work?
(+Why Victoria is qualified to talk about this)
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
My projectRemdesivir
POMHEX
Intracellular
POMHEX
CES
HemiPOMHEX
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O CES1/
CTSA
HINT1
N
N
N
NH2
O
CN
OHHO
OP
HO
O
O
34. How is remdesivir supposed to work?
(+Why Victoria is qualified to talk about this)
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
My projectRemdesivir
POMHEX
Intracellular
POMHEX
CES
HEX
(active
Enolase inhibitor)
HemiPOMHEX
PDE
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O CES1/
CTSA
HINT1
N
N
N
NH2
O
CN
OHHO
OP
HO
O
O
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
35. How does remdesivir actually work in vivo?
(+Why Victoria is qualified to talk about this)
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
My projectRemdesivir
POMHEX
Intracellular
POMHEX
CES
HEX
(active
Enolase inhibitor)
HemiPOMHEX
PDE
CES1/
CTSA
HINT1
Kinases
GS-441524 triphosphate
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
39. My projectRemdesivir
POMHEX
Intracellular
HemiPOMHEX
Esterase
Poorly cell permeable
due to exposed
negative charge
Remdesivir
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Esterase
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate (TP)
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Phosphatase
Nucleoside
transporter
Ala metabolite
Or passive
diffusion
How does remdesivir actually work in vivo?
(+Why Victoria is qualified to talk about this)
40. Remdesivir
1. How do we know that
premature pro-drug hydrolysis
actually happens?
2. Why does this matter if GS-
441524 (Nuc) can still get into
the cell?
Remdesivir
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Esterase
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate (TP)
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Phosphatase
Nucleoside
transporter
Ala metabolite
Or passive
diffusion
How does remdesivir actually work in vivo?
(+Why Victoria is qualified to talk about this)
41. 1. How do we know that premature pro-drug hydrolysis actually
happens?
Remdesivir (GS-5734) Figure 2a in Warren et al. Nature (2016)
Or passive
diffusion
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Esterase
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate (TP)
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Phosphatase
Nucleoside
transporter
Ala metabolite
Remdesivir
Ala metabolite
GS-441524 (Nuc)
[NTP] in PBMCs10 mg/kg IV in a
primate model of
EBOV
Concentrations
in blood plasma
Note: Remdesivir = GS-5734
“Upon intravenous administration of a 10 mg kg−1 dose
in rhesus monkeys, GS-5734 exhibited a short plasma
half-life (t1/2 = 0.39 h) with fast systemic elimination
followed by the sequential appearance of transient
systemic levels of the key intracellular intermediate
alanine metabolite and more persistent levels of Nuc
(Fig. 2a).”
42. 1. How do we know that premature pro-drug hydrolysis actually
happens?
Remdesivir (GS-5734) Figure 4a in Sheahan et al. Sci. Transl. Med. (2017)
Or passive
diffusion
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Esterase
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate (TP)
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Phosphatase
Nucleoside
transporter
Ala metabolite
Remdesivir
Ala metabolite
GS-441524 (Nuc)
50 mg/kg SC in a
Ces1c-/- mouse model
of SARS-CoV
“Plasma concentrations of prodrug diminished rapidly,
accompanied by transient exposure to the alanine
metabolite (Ala-Met) and more persistent exposure to the
nucleoside analog (Fig. 4A).”
43. 1. How do we know that premature pro-drug hydrolysis actually
happens?
Remdesivir (GS-5734) Summary of Supplementary Figure S1 in
Williamson et al. bioRxiv (2020)
Or passive
diffusion
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Esterase
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate (TP)
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Phosphatase
Nucleoside
transporter
Ala metabolite
Metabolite
Approx. serum
concentration (nM)
Remdesivir 0.4
Intermediate
(GS-704277)
35
Nucleoside
(GS-441524)
375
7 days post infection, treated every 24 h
~1,000-
fold
higher
10 mg/kg IV in a
primate model of
SARS-CoV-2
“Serum levels of the prodrug and
the downstream metabolites
were consistent with previously
published plasma levels of these
compounds in healthy rhesus
macaques, which showed a
short systemic half-life for GS-
5734 (0.39 hrs) resulting in
transient conversion to the
intermediate GS-704277 and
persistence of the downstream
GS-441524 product at higher
plasma levels17. ”
44. 2. Why does this matter if GS-441524 (Nuc) can still get into the cell?
Remdesivir (GS-5734)
Or passive
diffusion
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Esterase
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate (TP)
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Phosphatase
Nucleoside
transporter
Ala metabolite
45. 2. Why does this matter if GS-441524 (Nuc) can still get into the cell?
Remdesivir (GS-5734)
Or passive
diffusion
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Esterase
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate (TP)
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Phosphatase
Nucleoside
transporter
Ala metabolite
Initial phosphorylation of
GS-441524 (Nuc) is slow
46. Initial phosphorylation of GS-441524 is rate-limiting
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
ADK*
slow#
#Murakami et al. Antimicrob. Agents Chemother. (2006)
*Nayar et al. JCI (2017)
N
N
N
NH2
O
CN
OHHO
OP
O
O
OP
OO
O
O
P
HO
O
GS-441524 TPGS-441524
monophosphate
N
N
N
NH2
O
CN
OHHO
OP
HO
O
O
Kinases
47. Initial phosphorylation of GS-441524 is rate-limiting
Remdesivir was designed to bypass the first phosphorylation
step by pre-installing the phosphate
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
ADK*
slow#
#Murakami et al. Antimicrob. Agents Chemother. (2006)
*Nayar et al. JCI (2017)
N
N
N
NH2
O
CN
OHHO
OP
O
O
OP
OO
O
O
P
HO
O
GS-441524 TP
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
GS-441524
monophosphate
N
N
N
NH2
O
CN
OHHO
OP
HO
O
O
Kinases
1. CES1/CTSA
2. HINT1
Remdesivir
48. Initial phosphorylation of GS-441524 is rate-limiting
Remdesivir was designed to bypass the first phosphorylation
step by pre-installing the phosphate
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
ADK
slow
N
N
N
NH2
O
CN
OHHO
OP
O
O
OP
OO
O
O
P
HO
O
GS-441524 TP
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
GS-441524
monophosphate
N
N
N
NH2
O
CN
OHHO
OP
HO
O
O
Kinases
1. CES1/CTSA
2. HINT1
Remdesivir
Virus Cells Remdesivir GS-441524
SARS-CoV* HAE 0.069 ± 0.036 0.18 ± 0.14
MERS-CoV* HAE 0.074 ± 0.023 0.86 ± 0.78
β-2a-CoV*
(MHV)
DBT 0.03 1.1
EBOV# HMVEC 0.053 0.78
RSV# HEp-2 0.015 0.53
HCV 1b# Huh-7 0.057 4.1
EC50 comparison for various viruses
*Agostini et al. mBio (2018)
#Seigel et al. J. Med. Chem. (2017)
49. 2. Why does this matter if GS-441524 (Nuc) can still get into the cell?
Remdesivir (GS-5734)
Or passive
diffusion
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Esterase
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
Kinases
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524 triphosphate (TP)
(active agent)
Incorporated
into viral RNA,
delayed chain
termination
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Phosphatase
Nucleoside
transporter
Ala metabolite
Preemptive pro-drug hydrolysis
means that the drug cannot
bypass the rate-limiting
phosphorylation step
50. List of problems with remdesivir
1. Pro-drugs not designed to target the lungs.
2. Hard to synthesize and mass produce N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
51. List of problems with remdesivir
1. Pro-drugs not designed to target the lungs.
2. Hard to synthesize and mass produce
3. Short pro-drug half-life and gets
dephosphorylated in plasma
4. Preemptively releases GS-441524, so cannot
bypass rate-limiting phosphorylation step
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
52. 1. What is remdesivir and why it is not designed to
target the lungs
2. How does remdesivir work
(Also: why I am qualified to talk about this!)
3. Why did remdesivir underperform?
4. Immediate solutions
53. de Wit et al. PNAS (2020)
But first: what was expected of remdesivir?
5 mg/kg IV in a
primate model of
MERS-CoV
Vehicle CT
Therapeutic
Prophylactic
(24h before infection)
Figure 2b
54. But first: what was expected of remdesivir?
de Wit et al. PNAS (2020)
Vehicle CT
Therapeutic
Prophylactic
(24h before infection)
Figure 2c
To detect pulmonary infiltrates
5 mg/kg IV in a
primate model of
MERS-CoV
55. But first: what was expected of remdesivir?
de Wit et al. PNAS (2020)
Figure 3b
In lung lobes from all 18 assessed primates
5 mg/kg IV in a
primate model of
MERS-CoV
Vehicle CT
Therapeutic
Prophylactic
(24h before infection)
56. But first: what was expected of remdesivir?
Sheahan et al. Sci. Transl. Med. (2017)
Remdesivir 50 mg/kg Remdesivir 25 mg/kgVehicle CT
Figure 5d. Photomicrographs
of lung sections stained with
SARS-CoV antigen (brown)
and nuclei (blue)
Prophylactic 50 or 25
mg/kg SC in a Ces1c-/-
mouse model of
SARS-CoV
57. But first: what was expected of remdesivir?
10 mg/kg loading,
then 5 mg/kg IV in a
primate model of
SARS-CoV-2
Williamson et al. bioRxiv (2020)
Figure 1c. Ventro-dorsal radiographs taken on 7 dpi.
Red circles = areas of pulmonary inflammation
58. But first: what was expected of remdesivir?
10 mg/kg loading,
then 5 mg/kg IV in a
primate model of
SARS-CoV-2
Figure 6. Dorsal view of lungs treated with either
remdesivir (a, left) or vehicle (b, right)
“In contrast, all six vehicle controls had visible lesions, resulting in statistically
significantly difference in the area of the lungs affected by lesions.”
59. NCT04257656
Wang et al. Lancet (2020)
What do clinical trial results with remdesivir show?
“The primary
endpoint was time to clinical
improvement up to day 28,
defined as the time (in days)
from randomisation to the
point of a decline of two
levels on a six-point ordinal
scale of clinical status (from
1=discharged to 6=death) or
discharged alive from
hospital, whichever came
first.”
60. NCT04257656
Wang et al. Lancet (2020)
Table 3
What do clinical trial results with remdesivir show?
“The primary endpoint was time to clinical improvement up
to day 28, defined as the time (in days) from randomisation
to the point of a decline of two levels on a six-point ordinal
scale of clinical status (from 1=discharged to 6=death) or
discharged alive from hospital, whichever came first.”
62. NCT04280705
NIH News Release *Note: preliminary data and analysis
What do clinical trial results with remdesivir show?
63. Why were clinical trial results underwhelming?
Figure 3a. Diffuse alveolar damage with
hyaline membranes
Autopsy report from
Wichmann et al. Ann. Intern. Med. (2020)
“The histopathologic changes in most of
our cases with diffuse alveolar damage
as the main finding resemble those
described by Xu and colleagues…”
1. Both the Chinese clinical trial and
NIAID trials were conducted in
patients with severe or advanced
Covid-19.
2. Severe/advanced patients have
high viral loads in the lungs
(especially in type II alveolar cells)
64. Why were clinical trial results underwhelming?
Figure 3a. Diffuse alveolar damage with
hyaline membranes
Autopsy report from
Wichmann et al. Ann. Intern. Med. (2020)
“The histopathologic changes in most of
our cases with diffuse alveolar damage
as the main finding resemble those
described by Xu and colleagues…”
1. Both the Chinese clinical trial and
NIAID trials were conducted in
patients with severe or advanced
Covid-19.
2. Severe/advanced patients have
high viral loads in the lungs
(especially in type II alveolar cells)
3. The strongest antiviral activity in
pre-clinical models was when
remdesivir was given
prophylactically
65. Why were clinical trial results underwhelming?
1. Both the Chinese clinical trial and
NIAID trials were conducted in
patients with severe or advanced
Covid-19.
2. Severe/advanced patients have
high viral loads in the lungs
(especially in type II alveolar cells)
3. The strongest antiviral activity in
pre-clinical models was when
remdesivir was given
prophylactically
4. Decent antiviral effects with
remdesivir in pre-clinical models
occurred when animals were dosed
12-24 hours post infection.
Wang et al. Lancet (2020)
Williamson et al. bioRxiv (2020)
Sheahan et al. Sci. Transl. Med. (2020)
Pre-clinical:
start treating
between 12-24 h
Clinical: start treating after 12 days max; median = 10 days
66. Early intervention (and prophylaxis) is more beneficial
NCT04257656
Wang et al. Lancet (2020)
67. List of problems with remdesivir
1. Pro-drugs not designed to target the lungs.
2. Hard to synthesize and mass produce
3. Short pro-drug half-life and gets
dephosphorylated in plasma
4. Preemptively releases GS-441524, so cannot
bypass rate-limiting phosphorylation step
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
68. List of problems with remdesivir
1. Pro-drugs not designed to target the lungs.
2. Hard to synthesize and mass produce
3. Short pro-drug half-life and gets
dephosphorylated in plasma
4. Preemptively releases GS-441524, so cannot
bypass rate-limiting phosphorylation step
5. Underwhelming clinical trial results likely due
to late-stage intervention
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
70. 1. What is remdesivir and why it is not designed to
target the lungs
2. How does remdesivir work
(Also: why I am qualified to talk about this!)
3. Why did remdesivir underperform?
4. Immediate solutions
71. List of problems with remdesivir
1. Pro-drugs not designed to target the lungs.
2. Hard to synthesize and mass produce
3. Short pro-drug half-life and gets
dephosphorylated in plasma
4. Preemptively releases GS-441524, so cannot
bypass rate-limiting phosphorylation step
5. Underwhelming clinical trial results likely due
to late-stage intervention
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
72. List of problems with remdesivir
1. Pro-drugs not designed to target the lungs.
2. Hard to synthesize and mass produce
3. Short pro-drug half-life and gets
dephosphorylated in plasma
4. Preemptively releases GS-441524, so
cannot bypass rate-limiting
phosphorylation step
5. Underwhelming clinical trial results likely due
to late-stage intervention
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
73. List of problems with remdesivir
1. Pro-drugs not designed to target the lungs.
2. Hard to synthesize and mass produce
3. Short pro-drug half-life and gets
dephosphorylated in plasma
4. Preemptively releases GS-441524, so
cannot bypass rate-limiting
phosphorylation step
5. Underwhelming clinical trial results likely due
to late-stage intervention
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Remdesivir
GS-441524 should be investigated as an anti-
Covid-19 therapeutic and prophylactic
74. GS-441524 should be investigated as an anti-Covid-19
therapeutic and prophylactic
It is the predominant species that reaches the lungs
N
N
N
NH2
O
CN
OHHO
OP
OO
O
O
P
O
O
HO
P
O
O
GS-441524
triphosphate (TP)
(active agent)
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
O
O
Ala metabolite
(GS-704277)
SARS-CoV-2 primate model
Williamson et al. bioRxiv 2020
Serum transformation
75. GS-441524 should be investigated as an anti-Covid-19
therapeutic and prophylactic
GS-441524
3 steps!
Remdesivir
7 steps!
Seigel et al. J. Med. Chem. (2017)
Easier to synthesize
76. GS-441524 should be investigated as an anti-Covid-19
therapeutic and prophylactic
Initial phosphorylation may not be as slow as we think
N
N
N
NH2
O
CN
OHHO
HO
GS-441524 (Nuc)
ADK
slow
N
N
N
NH2
O
CN
OHHO
OP
O
O
OP
OO
O
O
P
HO
O
GS-441524 TPGS-441524
monophosphate
N
N
N
NH2
O
CN
OHHO
OP
HO
O
O
Kinases
(Remdesivir)
(Remdesivir)
Note huge standard deviations
Agostini et al. mBio (2018)
Figure 2a
HAE: primary human airway epithelial cells
77. GS-441524 should be investigated as an anti-Covid-19
therapeutic and prophylactic
GS-441524 has demonstrated antiviral activity against feline
coronavirus
N
N
N
NH2
O
CN
OHHO
HO
Molecular Weight: 291.27
Log P: -3.67
tPSA: 147.69
GS-441524
Feline infectious peritonitis = caused by feline coronavirus
96% cure rate
78. GS-441524 should be investigated as an anti-Covid-19
therapeutic and prophylactic
GS-441524 is more hydrophilic and has a low molecular weight,
making it easier to aerosolize for inhalable prophylaxis
N
N
N
NH2
O
CN
OHHO
OP
O
HN
O
Molecular Weight: 602.58
Log P: 1.29
tPSA: 201.32
O
O
Remdesivir
N
N
N
NH2
O
CN
OHHO
HO
Molecular Weight: 291.27
Log P: -3.67
tPSA: 147.69
GS-441524
Patton et al. Proc. Amer. Thor. Soc. (2004)
79. Advantages of GS-441524
1. It is already the main species that reaches the
lungs when remdesivir is administered.
N
N
N
NH2
O
CN
OHHO
HO
Molecular Weight: 291.27
Log P: -3.67
tPSA: 147.69
GS-441524
80. Advantages of GS-441524
1. It is already the main species that reaches the
lungs when remdesivir is administered.
2. Much easier to synthesize. Makes large-scale
production easier.
N
N
N
NH2
O
CN
OHHO
HO
Molecular Weight: 291.27
Log P: -3.67
tPSA: 147.69
GS-441524
81. Advantages of GS-441524
1. It is already the main species that reaches the
lungs when remdesivir is administered.
2. Much easier to synthesize. Makes large-scale
production easier.
3. Demonstrated efficacy in cat coronavirus and
inadvertent antiviral activity in primate models of
coronavirus (MERS-CoV, SARS-CoV-2).
N
N
N
NH2
O
CN
OHHO
HO
Molecular Weight: 291.27
Log P: -3.67
tPSA: 147.69
GS-441524
82. Advantages of GS-441524
1. It is already the main species that reaches the
lungs when remdesivir is administered.
2. Much easier to synthesize. Makes large-scale
production easier.
3. Demonstrated efficacy in cat coronavirus and
inadvertent antiviral activity in primate models of
coronavirus (MERS-CoV, SARS-CoV-2).
4. Low molecular weight, hydrophilic drug that can
be aerosolized for inhalable prophylaxis.
N
N
N
NH2
O
CN
OHHO
HO
Molecular Weight: 291.27
Log P: -3.67
tPSA: 147.69
GS-441524
83. Acknowledgements
Muller Lab
Florian Muller, Ph.D.
Cong-Dat Pham, Ph.D.
Kristine Yang, B.S.
Sunada Khadkha, B.S.
Yasaman Barekatain, M.S.
Jeff Ackroyd, B.S.
Kenisha Arthur, B.S.
Dimitra Georgiou, Ph.D.
Peter Cserjesi, Ph.D.
Morgan Knight, Ph.D. (BCM)
David Corry, M.D. (BCM)
Niels Pedersen, DVM, Ph.D. (UC Davis)
Richard Mackman, Ph.D. (Gilead)
Emmie deWit, Ph.D. (NIH)
Pat Skerett (STAT)
Additional questions:
victoriacyanide@gmail.com
@victoriacyanide
#GS441524
Editor's Notes
There was a clear increase in respiration rates in the vehicle-treated animals (Fig. 2B), while respiration rates in prophylactically treated animals remained normal throughout the study. Although respiration rate was increased in therapeutically treated animals at 1 dpi, respiration was statistically significantly lower than in vehicle-treated controls at 3 and 6 dpi (Fig. 2B).
On examination days, radiographs were collected from all animals and analyzed for the presence of infiltrates; from 3 dpi onward, lung infiltrates became visible on X-ray (SI Appendix, Fig. S1). At 6 dpi, there was statistically significantly less infiltration in the lungs of animals treated both prophylactically and therapeutically with remdesivir as compared to vehicle-treated control animals (Fig. 2C).
Radiographic pulmonary infiltrates are one of the hallmarks of COVID-19 in humans. Radiographs taken on 0, 1, 3, 5, and 7 dpi showed significantly less lung lobe involvement and less severe of pulmonary infiltration in animals treated with remdesivir as compared to those receiving vehicle (Fig. 1B and C).
In contrast, all six vehicle controls had visible lesions, resulting in statistically significantly difference in the area of the lungs affected by lesions (Fig. 5A, B and Fig. 6A, B)
