@InBeforeTheCure,
I actually never have asked you about this matter. You are one of the most knowledgeable guys if not the most on this forum so your opinion is welcome.
Tofacitinib IC50 of 1nM towards JAK3 (less selective against JAK1 and JAK2)
Finasteride IC50 of 4.2nM towards 5ar2. (remember that finasteride fully saturates 5ar2 at 1mg orally).
Take that as a rough model.
You obviously understand that since both topical formulations and oral formulations work for AA it must mean that the drugs exert their biological activity sufficiently towards JAK3 somewhere at or around the hair follicle (tofactinib is most selective for JAK3).
This makes per definition the notion of A.M Christiano flat out wrong in this article, since topical formulations are on the market already that do penetrate the skin. In fact there is a pharmacy that has released one that works on people with AA. Not only that Brett King has even made a topical formulation that works.
But let's get on the oral side because that's where I'm at. Remember to keep the pharmacology and pharmacokinetics in mind of Tofacitinib and that it has been tested across of hundreds if not thousands people of Androgenetic Alopecia orally over a long period of time. The dosage that already shows to be effective is twice a day dosage of 5 mg a day for AA. But it has been trialed in people across long periods of time at even higher dosages.
Now this means similarly that the drug exerts it's biological activity and saturates one of the JAK enzymes in close proximity of the bulb when taken orally. If it didn't after all it wouldn't work for AA. But it's most selective for JAK3.
Now the only legit comment I have heard out of the camp of Aclaris is the following from the CEO that isn't flat out laughable;
“We are going to develop a topical JAK inhibitor we know that a systemic JAK inhibitor doesn’t work in this indication. And there is actually a pretty good reason for that. You can’t achieve the right concentration… When you think about the drug going through the superficial dermal plexus, it can’t migrate up to the hair follicle bulge. So in AA it works because it works at the hair follicle bulb which is deeper down and more accessible through systemic circulation. Drugs don’t normally migrate up, so you have through the opposite way and go topically through the hair follicle, and we have actually shown this through pre-clinical models. ”
This is actually the same point I made before the CEO said this which is funny, but I said that it is highly damn unlikely that the drug doesn't exert it's biological activity sufficiently at the bulge but only does on the bulb when taken orally. Why? Well observations support this again since oral JAK inhibitors work for many other ailments like psoriasis, vitiligo, keratosis etc. These ailments for instance vitiligo and psoriasis take place in the epidermis, which as you know is actually the outermost layer of the skin and pretty much non-vascularized. So these observations support that these drugs exert their biological activity in the whole skin, including the outermost layers. Not only at the height of the bulb.
Now ok these are observations which are pretty important. They make his reasoning already very weak. But what really checkmates Aclaris is that even a study has shown that tofacitinib rapidly exerts it's biological activity in the epidermis after a single (!!!!) dosage (not even repeated dosing...)
The study confirms the observations with data and came out recently from a phase 2 trial
http://www.sciencedirect.com/science/article/pii/S0091674916001263
The picture says all, tofacitinib has a rapid effect on keratinocytes;
The picture speaks for itself top right corner keratinocytes which are located in the epidermis. The epidermis is highly non-vascularized as you know.
"The epidermis has no blood supply and is nourished almost exclusively by diffused oxygen from the surrounding air.[6] It is 95% keratinocytes"
Rapid inhibition of JAK/STAT signalling even towards JAK1 where tofactinib has less potency too lol....
So not only observations but data from a clinical trial totally contradicts the statement of the CEO of Aclaris.
Now do you agree with me that this is quite a hopeless endeavor?
The worst thing about this is the whole context. A.M Christiano literally looks at a mice model and draws a (weird) conclusion while totally neglecting observations and data in actual HUMANS.
Besides after all the mice that got the drug orally grew hair anyway, it just wasn't as quick and robust. But they did grew hair. A more logical conclusion for instance would be that a topical distributes itself quicker to the target location than when taken systemically.
Anyway can you understand why I find this the worst endeavor in many years for hair loss? In fact I find it beyond hopeless. I have never seen such a bad display of science throughout the years.