A potential first-in-class or best-in-class treatment for immunological skin diseases

Orismilast is a high-potency PDE4 inhibitor targeting the PDE4 subtypes linked to inflammation. It operates early in the inflammation cascade, inducing a broad range of anti-inflammatory effects across multiple cytokines involved in many dermatological and immunological diseases.

Orismilast has been selected as lead molecule based on its attractive therapeutic window (i.e., the combination of improved efficacy and tolerability) and because of its potential to inhibit many inflammatory pathways involved in immunologic diseases due to the broad range of anti-inflammatory effects.

Over the course of Phase 1 and Phase 2 trials, orismilast has been demonstrated to be safe in both oral and topical dosage forms and the PDE4 mode-of-action has been verified as an effective, well-tolerated approach to treatment of patients across multiple diseases, with no need for monitoring.

UNION is developing orismilast as an oral formulation for the treatment of AD, psoriasis and HS. 


+ 0 M

13,4M suffers from Psoriasis in the US, EU5 and Japan

PDE4 inhibitor

Dermatology market and include
topical roflumilast cream

PDE4 Market and include
topical roflumilast cream


= 0 M

People in the US suffer from Psoriasis

TNF-Q + 11-17

Plaque psoriasis and atopic

Acim quam ratem eos dis ma

Checkpoint-for Psoriasis

= 0 M

People in EU5 suffer from Psoriasis


Exerting anti-inflammatory effect
reducing psoriasis scale formation

PDE4 Market and include
topical roflumilast cream

Orismilast development programs

The current development status of oral orismilast is the following:

  • Psoriasis: Phase 2b topline results reported on 9 January 2023 supporting the target product profile of orismilast and confirming the well-established favorable safety profile of PDE4 inhibition. In November 2020, the US Food and Drug Administration (FDA) approved UNION’s Investigational New Drug Program (IND) for advancing oral orismilast into a Phase 2b trial in patients with moderate to severe psoriasis. ClinicalTrials.gov Identifier: NCT05190419
  • AD: The FDA has granted Fast Track designation to oral orismilast for the treatment of moderate to severe AD, and UNION initiated a Phase 2b dose finding study in July 2022. The ClinicalTrials.gov Identifier is NCT05469464
  • HS: The FDA has granted Fast Track designation to oral orismilast for the treatment of moderate to severe HS. In the Fall of 2021, OSIRIS, an investigator sponsored Phase 2a, open label, proof-of-concept study in patients with mild to severe hidradenitis suppurativa (HS) was initiated with support from UNION. ClinicalTrials.gov Identifier: NCT04982432 

UNION has also tested orismilast as a topical formulation in a Phase 2a study. In the Phase 2a proof-of-concept study in AD topical orismilast demonstrated statistically significant efficacy compared to placebo with no stinging, burning or pain at the application site.  

Preclinical and Phase 2a data on orismilast

Professor of Dermatology Jonathan Silverberg presented new data on orismilast at the 31st EADV Congress, 7-10 September 2022.