Thread by @__ice9

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 In early hospitalized cases.

By definition, endosomal entry inhibitors only protect against free virions, entering by endocytosis.

The mechanism is not relevant to cell-cell fusion, or to TMPRSS2-mediated fusion with a free virion at the cell membrane itself.

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer noticed reply on possible effects from variation in receptor expression on the rate of syncytial cell-cell fusion, in spite of structural support from the infected cell's cytoskeleton, and thought this thread might interest you.

https://twitter.com/macroliter/status/1277513200318189569?s=19

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer Also see this paper on entry routes:

ncbi.nlm.nih.gov/pmc/articles/P…

This is a good overview of comparative CoV entry for SARS-CoV, MERS-CoV, and SARS-CoV-2.

This section discusses what I mentioned about fusion at the cell membrane directly if TMPRSS2 is available.

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer Given TMPRSS2 is indeed available in type II pneumocytes, it appears likely that endocytosis may not even be necessary in order for free virions to infect them.

They could just fuse immediately at the cell surface.

ncbi.nlm.nih.gov/pmc/articles/P…

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer Conversely, ordinary Vero cells do not express TMPRSS2, meaning results from them are presumably of less relevance to the pulmonary epithelial phase of the infection.

researchgate.net/figure/Effect-…

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer Thread discussing another paper comparing in vitro results for various antivirals across multiple different cell lines, finding considerable variation in EC50:

https://twitter.com/__ice9/status/1274273484168970240?s=19

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer HCQ also seems to work in vitro in other cell lines derived from kidney, liver, cervical, etc. tissue.

However: there is no test of HCQ for SARS-CoV-2 specifically on pulmonary derived cell lines in this collection--

https://twitter.com/__ice9/status/1272643526392758273?s=19

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer I just accidentally deleted the Calu cells post. This is disappointing, as I am not aware of any means of reverting that to repair that thread.

Anyway here is the paper again:
biorxiv.org/content/10.110…

Hydroxychloroquine does not work on Calu cells.

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer Hydroxychloroquine alone may protect some organs from entry by SARS-CoV-2, particularly the kidneys.

However, a TMPRSS2 inhibitor like bromhexine, ambroxol, or nafamostat must also be used for the lungs.

biorxiv.org/content/10.110…

biomedgrid.com/pdf/AJBSR.MS.I…

ncbi.nlm.nih.gov/pmc/articles/P…

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer @richardursomd @JamesTodaroMD

Entry-mechanism-based argument for adding a TMPRSS2 inhibitor (bromhexine, ambroxol, nafamostat, likely not camostat due to awful bioavailability) to endosomal entry inhibitors (HCQ, mefloquine, niclosamide, nitazoxanide, amodiaquine, etc.).

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer @richardursomd @JamesTodaroMD Adding further paper that just came out.

https://twitter.com/NG20194/status/1286649808652922880?s=20

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer @richardursomd @JamesTodaroMD >in the absence of TMPRSS2, SARS-CoV-2 utilizes cathepsin L much less efficiently in comparison to SARS-CoV-1

>may be explained by the relative instability of the wild-type SARS-CoV-2 S-protein

This is why TMPRSS2 inhibitors are still decent alone-- endosomal route is slow.

@monarchdiaries @halvorz @lewistlc @pathdoc3 @88549439 @csentropy @AndyBiotech @julienpotet @Crashcart @gstanchev @Hongma123 @YinPD @assur153 @macroliter @VirusWhisperer @richardursomd @JamesTodaroMD Note only a subset of the ACE2+ cells in airways express TMPRSS2, which may perhaps explain why HCQ monotherapy seems to help to some degree if started very early.

nature.com/articles/s4159…

Use of interferon, as in the Chinese studies, would also likely slow this 'shortcut' path.