Sienna slumps as acne asset flunks phase 3 trials

Sienna Biopharmaceuticals’ acne candidate SNA-001 has comprehensively failed two phase 3 trials. The addition of the silver particle treatment to laser light therapy failed to improve outcomes against three key endpoints, leaving the future of Sienna’s most advanced candidate in doubt.

Westlake Village, California-based Sienna designed SNA-001 to absorb light and convert the energy to heat, thereby injuring adjacent tissues. In the case of acne, Sienna hoped to use the mechanism to damage the sebaceous glands that underpin the dermatological condition. A small feasibility trial left scope to doubt if the idea worked in practice, but Sienna pushed SNA-001 into two pivotal studies.

The pivotal trials have magnified the doubts. SNA-001 was no better than a placebo at reducing inflammatory lesion counts when heated by an 810 nm or 1064 nm laser. That resulted in both trials missing their primary endpoints.

Sienna had no more joy on the secondary endpoints. Neither trial reported a statistically significant decline in absolute inflammatory lesions or Investigator Global Assessment 1-grade responder rate, resulting in misses against two key secondary endpoints. The adverse event data were the only slight positive.

That hope, however, gives Sienna a modicum of encouragement as it heads toward data from three pivotal trials of SNA-001 as a treatment for light-pigmented hair. Sienna also has a readout from a third acne trial coming up in the fourth quarter, but hopes for the candidate in either indication are now low. 

If SNA-001 flames out, the Sienna management team, some of whom were last seen leading Kythera to a takeover by Allergan, will fall back on the other assets in the company’s pipeline. 

"Sienna was founded on a strategy of developing a diversified multi-asset pipeline by a highly experienced team," said Frederick Beddingfield, M.D., Ph.D. "We have several additional clinical studies from two separate technology platforms across a number of therapeutic indications and development stages reading out over the next three quarters, and remain highly focused on delivering innovative therapies that matter for patients."

Data from the ongoing trials of SNA-001 are due in the fourth quarter of 2018 and first quarter of 2019. Sienna expects to post clinical data on its single and dual kinase inhibitors, SNA-120 and SNA-125, over the same period.

Shares in Sienna fell by more than 20% in premarket trading. 

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