Hellerup, Denmark, June 21, 2023 – UNION therapeutics A/S (UNION), a privately-held, clinical stage, pharmaceutical development company focused on immunology and infectious disease, today announces positive topline results from the OSIRIS investigator-initiated proof-of-concept study with oral orismilast in adult patients with HS. HS is a painful, scarring, inflammatory skin disease with few or limited treatment options.

The study demonstrated clinically relevant improvements in HS for patients who completed the planned 16 weeks of treatment with oral orismilast. Importantly, the improvements included reduction of pain (Global Pain Assessment) and improvement in patient-reported quality of life (DLQI). Most responders had moderate or severe HS at baseline, including several prior failures to biologics treatment.

The conclusion on the doses explored is consistent with the findings from the subsequent IASOS Phase 2b dose-finding study in psoriasis recently reported. The target product profile of oral orismilast was confirmed including the well-established favorable safety profile of PDE4 inhibition.

The results will be presented by the sponsoring investigator at an upcoming scientific conference, and UNION expects to further progress the development of oral orismilast in HS.

Professor Gregor B. Jemec, PhD, MD, Founding Chairman of the Department of Dermatology, Zealand University Hospital Roskilde, Denmark and sponsoring investigator of the study said:

“Hidradenitis suppurativa is an inflammatory systemic skin disease where a strong unmet need remains for safe and effective oral treatments. Patients suffer from pain discharge and scarring of intimate skin areas. The positive topline data from the OSIRIS study are very encouraging.”


Kim Kjøller, Chief Executive Officer of UNION therapeutics said:

“We are delighted to see positive topline results from the OSIRIS study. The results are very encouraging, including not least seeing patients in this difficult to treat patient population achieving HiSCR90 and HiSCR100 response. Equally important, patients experienced significant reduction in pain, which is a great burden for patients with HS, and most responders had moderate or severe HS at baseline, including several prior failures to biologics treatment. The study supports the target product profile of orismilast as a high-potency PDE4 inhibitor consistent with the recent IASOS Phase 2b study in psoriasis. We are looking forward to advancing orismilast in HS and will engage with the regulatory authorities around the best path to approval.”

About the OSIRIS Phase 2 study

OSIRIS is an open-label, single-center, prospective, single arm, investigator-initiated proof-of-concept study investigating the efficacy, safety, and tolerability of oral orismilast taken twice daily for up to 16 weeks in adult patients with mild, moderate, and severe HS.


About HS and treatment of HS

HS is a chronic, inflammatory skin disease which results in painful inflammation of the hair follicles, most notably in the armpit and genital regions. The clinical hallmarks of the disease include very painful inflammatory nodules, boils or abscesses that typically open and release odorous inflammatory fluids. HS patients suffer primarily from pain and significant discomfort resulting from the constant formation of pus, often requiring the use of bandages and diapers, resulting in social isolation. Patients are often stigmatized by these symptoms. HS severely and adversely affects patients' quality of life and is associated with an increased overall mortality rate due to cardiovascular disease and suicides.1)

Currently, only one drug (a biologic) is approved for treatment of moderate to severe HS in the US. For mild HS there are no treatments approved. The general standard of care for HS patients, although off-label, includes topical, oral or intravenous antibiotic treatment which often provides only temporary symptomatic relief. Antibiotics do not target the underlying inflammation and they are associated with resistance development.2)


About orismilast

Orismilast is a high-potency, next-generation 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.3)

UNION is developing orismilast as an efficacious but safe oral treatment across immunology, initially targeting best-in-class or first-in-class positions in atopic dermatitis, hidradenitis suppurativa and psoriasis.

The FDA has cleared UNION’s Investigational New Drug (IND) application for oral orismilast and granted Fast Track designation for oral orismilast for the treatment of moderate to severe AD as well as for the treatment of moderate to severe HS. In 2021, UNION entered a strategic partnership with Innovent Biologics for the development of orismilast in Mainland China, Hong Kong, Macau, and Taiwan.


1)      Ballard et al., Hidradenitis Suppurativa, StatPearls 2022: https://www.ncbi.nlm.nih.gov/books/NBK534867/ and

Thorlacius et al., Increased Suicide Risk in Patients with Hidradenitis Suppurativa, The Journal of Investigatory Dermatology, 2018: https://pubmed.ncbi.nlm.nih.gov/28942360/

2)      Saunte et al., Hidradenitis Suppurativa: Advances in Diagnosis and Treatment, JAMA, 2017: https://pubmed.ncbi.nlm.nih.gov/29183082/

3)      Silverberg J.I. et al., Pharmacology of orismilast, a potent and selective PDE4 inhibitor, JEADV 2022: https://onlinelibrary.wiley.com/doi/10.1111/jdv.18818  &

Warren R.B. et al., Efficacy and safety in moderate-severe psoriasis and development of modified release tablets, JEADV 2022: https://onlinelibrary.wiley.com/doi/10.1111/jdv.18812



Morten Boesen, Chief Financial Officer, UNION therapeutics A/S

+45 2381 5487

[email protected]


Sarah Toft-Jørgensen, Director of Communications and IR, UNION therapeutics A/S

+45 5385 3044

[email protected]


About UNION therapeutics

UNION therapeutics is a privately held, mid- to late-stage, pharmaceutical development company advancing novel treatment options within immunology and infectious diseases, two large and fast-growing therapeutic areas. UNION is headquartered in Hellerup, Denmark, and led by an international team combining biotech entrepreneurs and seasoned pharma executives, with a track record of developing and launching more than fifteen marketed drugs. Read more at http://www.uniontherapeutics.com