Category Archives: Selective JAK3 Inhibitor


I have covered janus kinase inhibitors (JAK) in numerous posts on this blog in the past and you can do a search via the categories menu to learn more. They were by far the biggest news story in the hair loss world in 2014 due to several groundbreaking studies (with spectacular before and after photos of humans instead of mice) that showed that using oral JAK inhibitors ruxolitinib or tocafitinib cured alopecia areata (AA) and psoriasis and vitiligo in many patients. However, less than 5 percent of hair loss sufferers have alopecia areata (an autoimmune disease), with the vast majority having androgenetic alopecia (AGA) instead.

At the time, the famous hair loss researcher Dr. Angela Christiano maintained that JAK inhibitors could also work on AGA. This statement was later expanded and it was postulated that only “selective topical covalently bound JAK 3 inhibitors” could work, while oral ones would probably not work. Moreover, of the at the time two main FDA approved JAK inhibitors: 1) ruxolitinib only inhibits JAK 1 and JAK 2; and 2) while tofacitinib inhibits both JAK 1 and JAK 3, I am guessing that its impact on JAK 3 is not very significant or especially “selective” (please correct me if wrong) because…

Aclaris Therapeutics to Test Decernotinib on AGA Patients?

Today morning, I got a press release e-mail from Aclaris (which is the company that holds all the patents for JAK inhibitors and hair loss disorders) linking to an article titled “Aclaris Therapeutics Announces Notice of Allowance for Two U.S. Patent Applications Covering Baricitnib and Decernotinib, Respectively, for Hair Loss Disorders“. Several readers also posted other links about this news or e-mailed me, and of course some mentioned “nasa_rs”, a former NASA employee who comments on this blog all the time. If I had to summarize, most of “nasa_rs”‘ comments are in the form of “JAK inhibitors will cure hair loss or its all over” but once in a while he also posts something extremely unique and useful.

The most interesting part of Aclaris’ press release is that they finally named the selective JAK 3 inhibitor that they will probably use to test on AGA patients when they start clinical trials. This particular JAK inhibitor is called decernotinib (VX-509), and it is a highly selective JAK 3 inhibitor (also see Mr. Neal Walker’s comments in this recent post). In Aclaris’ latest press release, the below pasted sentence is the key one (with the “respectively” implying AA–>baricitinib and AGA–>decenotinib relationships):

The claims of these newly allowed patent applications cover methods of inducing hair growth and treating various hair loss disorders, including alopecia areata and androgenetic alopecia, by administering baricitinib or decernotinib, respectively.

Interestingly, decernotinib has no separate wikipedia entry at present (unlike most of the other other “-tinibs” out there). Even more surprising, the wikipedia entry on JAK inhibitors lists all the FDA approved JAK inhibitors that we have discussed as well as numerous others currently in clinical trials (see under the compounds section in there) except for decernotinib.