Tofacitinib has a "box warning"
and is dose limited to 5mg bid, which is why Pfizer set out to find another safer drug for Alopecia Areata. The drug that they settled on is PF-06651600. Head to head comparison's of their new drug to CTP-543, have already been dissected many times over, since they both completed phase 2 clinical trials.
It's good to see Ruxolitinib's safety profile in the study posted, which gives me more confidence that CTP-543 12mg bid, may be well-tolerated also. CTP-543 could be comparable to Ruxolitinib to around 14.4mg, as it was shown to have approximately 20% increase in phase 1 clinical trials.