Replies to post #361583 on Innovation Pharmaceuticals Inc (IPIX)

[MaskedCat]

So why Brilacidin vs Remdesivir should be well understood after these wonderful post.

[loanranger]

"Fortunately Brilacidin is not limited by these factors."

Earlier you said:
"In addition Remdesivir's hepatotoxicity limits higher dosing."

That 7 syllable monster is 3 more than I can handle but we don't know the dosing in the Brilacidin trial. It must have SOME limitation based on either that or some other 7 syllable constraint, no?
We know more about R dosing than we do about B dosing regardless of its vaunted safety, don't we? Didn't dosing become an issue in the B-ABSSSI trial?
This doesn't obviate whatever those issues were, does it?
"It does not have to be converted to an active form so with infusion it kills the virus at first in the serum."

[olden_grumpini]

I appreciate your post and have appreciated many of your posts in the past. Full disclosure, I don’t often read the articles in your links.

I’m certain you’ve read the viruses paper and have looked at Figures 5B and 5C on page 9. I assume you read those figures the same way I did: Remdesivir, when tested alone, reduced viral titer by 99% and brilacidin, when tested alone, reduced viral titer by 90% at the highest concentrations tested. Remdesivir and brilacidin, when tested in combination, reduced viral titer by >99% at the highest concentrations tested.

You point out that the in vitro promise shown by remdesivir didn’t translate to the clinical setting and you presented numerous reasons why brilacidin should do better.

I’m curious to get your opinion on the importance of preincubating the virus with brilacidin during the in vitro testing. Here’s some of my thinking on it and what impact it might have on the potential for brilacidin in the clinical trial.

In section 3.3, where brilacidin is tested in Calu-3 cells, they first test brilacidin without preincubation. These are the result:
10µM = 39% reduction
20µM = 61% reduction

They then did the following:

However, when the experiment was modified to include a brilacidin-treated inoculum—with preincubation of the virus with brilacidin for 1 h prior to infection, and with infection carried out in the presence of the compound—the extent of inhibition dramatically increased, resulting in 95% and 97% reduction of infectious viral titer at the 10 and 20 µM concentration of the compound, respectively (Figure 3B).

Preincubation makes a big difference. The 10µM concentration went from 39% to 95% -- an improvement of 243%.

The virus was preincubated with brilacidin for calculating the SI. The paper makes a point of telling their audience:

Quantification of the inhibitory response—when the virus was directly preincubated with brilacidin prior to infection; cells were treated prior to infection; brilacidin was present during infection; and infected cells were maintained in the presence of brilacidin postinfection . . . .

If we were to recalculate the SI without preincubation we would get a much lower number. And the CC50 of 241µM is totally off the charts for what could happen in the real world. I know that's not taken into account when a SI is calculated, but it is important when thinking about how in vitro results translate to the real world. For example, the ABSSSI P2 trial used a maximum single dose that was 1/24th the in vitro CC50.

It should also be noted that the virus was preincubated with brilacidin when it was compared to remdesivir. That comparison would have been much less favorable without preincubation.

The clinical trial . . .
The old saying, “First, do no harm”. I think it’s logical that the dosing for the trial would be less than what was used in the 3-day dosing regimen for the ABSSSI P2 trial (0.6 mg/kg, 0.3 mg/kg, 0.3 mg/kg). That 3-day dosing regimen had TRAEs of 92%, and hypertension of 26%. The fact that the dosing was extended from 3 to 5 days reinforces my opinion that the dosing is lower.

I tried to come up with a dose that would be well tolerated and then extrapolated a viral reduction based upon the in vitro results from the testing of the Calu-3 cells at 10µM and 20µM that had no preincubation. I kept in mind that the in vitro testing exposed the virus to brilacidin at a steady concentration for >24 hours whereas brilacidin’s half life is <24 hours. I came up with a prediction that a dose that was safe enough to allow dosing to be extended from 3 to 5 days will reduce the virus by a small amount, perhaps single digits over a 24-hour period. The virus replicates every 9 hours.

I recognize that brilacidin has other attibutes that were not taken into account in the in vitro testing. I also recognize that I could have my math wrong, I might not have a sufficient understanding of in vitro viral testing, or perhaps I misread the paper. But as of right now I have serious doubts as to the success of the clinical trial.

You can do your own math using the figures here:
The preprint (not the peer review) included pharmacokinetics from the Phase 2b ABSSSI trial which showed a median Cmax in plasma was 7.67µM brilacidin (free-base) from a single IV dose of 0.6 mg/kg.
The Calu-3 cells testing before preincubation is below along with the conversion to a mg/kg dose:
10µM = 39% reduction (0.782 mg/kg)
20µM = 61% reduction (1.565 mg/kg)
The maximum single dose given in the ABSSSI P2 trial was 0.8 mg/kg.