Jasper Therapeutics has reported complete responses in 10 of the 12 chronic hives patients who received the high dose of its c-Kit antibody. But, with some patients relapsing within weeks, the biotech has begun trialing a higher dose in pursuit of deeper, more durable responses.
The phase 1b/2a trial enrolled 15 people with chronic inducible urticaria, an inflammatory skin condition, to receive a single dose of briquilimab. Three people received 40 mg of the anti-c-Kit antibody, a dose that Jasper execs have called subtherapeutic. The other 12 patients were on a 120-mg dose. After six weeks, one patient on 40 mg and 10 participants who received 120 mg had a complete response.
Jasper saw fast, steep reductions in serum tryptase, a mast cell biomarker. However, tryptase levels were only stable for around four weeks. After that, levels of the biomarker began to rise and patients started to relapse. The number of complete responders fell from 10 to six by Week 12.
The pattern of fast response and similarly speedy relapse is in line with data on rival drugs. Celldex saw (PDF) a similar cadence in a study of its c-Kit antibody barzolvolimab. Acelyrin is also developing a c-Kit drug candidate.
Celldex reported greater durability as it moved to a higher dose. Jasper is now set to find out whether it can squeeze a longer response out of briquilimab by dialing up the dose, in its case to 180 mg. The biotech is enrolling 12 patients to receive the higher dose. Edwin Tucker, M.D., chief medical officer at Jasper, discussed the implications of studying the 180-mg dose on a conference call about the study results.
“It possibly means that the depth of our responses could be deeper and the durability could be longer. But ... the 120 [mg data] in itself is very encouraging from a drug perspective and also a dosing frequency perspective,” Tucker said. “We anticipate that both this data here and the additional data will provide us a lot of insight in deciding what those doses and frequencies will be in our registration programs.”
William Blair analysts said the data “shows clear activity for briquilimab, with a rapid onset of action across both response rate and serum tryptase reductions” but called out the speed at which the effects waned. Based on the Celldex trial, the analysts believe the 180 mg dose will trigger more durable responses.
Jasper is aiming to present full data from the trial in the first half of next year.