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Press Release

Principia Biopharma Presents Late-Breaking Interim Phase 2 Data of PRN1008 in Pemphigus at European Academy of Dermatology and Venereology Meeting

Principia Biopharma Inc.
Posted on: 18 Sep 17

Principia Biopharma, a private, clinical-stage biopharmaceutical company, today announced a late-breaking oral presentation of interim data from a Phase 2 trial of PRN1008, a reversible covalent Bruton’s Tyrosine Kinase (BTK) inhibitor, in patients with pemphigus, a severe autoimmune skin disease. The data were presented at the 26th European Academy of Dermatology and Venereology (EADV) Congress in Geneva, Switzerland on September 16, 2017 (abstract #4351).

In an intent-to-treat analysis of this open-label study, 42 percent of the first 12 patients met the primary endpoint of control of disease activity (CDA) within four weeks, on a background of no or low dose corticosteroids (CS). In eight patients that completed 12 weeks of treatment, 75 percent had achieved CDA, and 50 percent had achieved a complete response. Pemphigus disease activity index (PDAI) scores fell substantially over the first few weeks in the majority of patients consistent with the early anti-inflammatory effect of the drug. The average daily dose of prednisolone at study start was 14 mg and further reduced during treatment. No clinically significant safety signals have been observed.

“PRN1008 as an oral, B-cell targeted therapy has the potential to be an alternative to moderate and high dose corticosteroids. Patients with pemphigus have very few treatment options available, and in general take corticosteroids for months or years, incurring the related side effects,” said Dedee Murrell, MA, BMBCh, MD, FAAD, FACD, FRCP, UNSW Medical School, Department of Dermatology, Sydney, Australia. “A new treatment modality that can eliminate or significantly reduce the side effects of corticosteroids is needed for this disease.”

About the Believe-PV study of pemphigus

Believe-PV is an on-going, open-label Phase 2 trial evaluating the safety and efficacy of PRN1008 in naïve or relapsing patients with mild to moderate pemphigus vulgaris (PV). Entry criteria include prior biopsy confirming PV, PDAI score of 8 to 45 points, and entry doses of prednisolone ≤ 0.5 mg/kg. Based on these entry criteria, some patients classified as PV but with an autoantibody profile diagnostic of pemphigus foliaceus (PF) may be included. Patients are treated for 12 weeks with PRN1008 and followed up for an additional 12 weeks to assess the durability of responses.

About PRN1008

PRN1008 is an oral, reversible covalent BTK (Bruton’s Tyrosine Kinase – a component of B-cell signaling and inflammatory pathways in most white blood cell types other than T-cells and plasma cells) inhibitor. This investigational, small molecule therapy acts by blocking BTK. It was designed using Principia’s proprietary Tailored Covalency™ technology to optimize its safety and efficacy profile, resulting in a prolonged and reversible action at the target site while being rapidly eliminated from the body. This approach limits systemic exposure of PRN1008 and enables rapid clinical reversibility. PRN1008 has been granted orphan drug designation by the FDA for the treatment of pemphigus vulgaris.

About pemphigus

Pemphigus is a group of rare, orphan, potentially life-threatening, autoimmune skin disorders, affecting approximately 40,000 patients in the U.S. and more than 200,000 worldwide that causes blistering of the skin and ulcers in the mouth and genitals. Pemphigus foliaceus (PF) affects the skin only while pemphigus vulgaris (PV) affects both skin and mucosal tissue. Men and women are equally affected and the disease is typically seen in middle-aged or older individuals. PV and PF are known to be caused by autoantibodies which break the bond between the skin cells and cause inflammation. Pemphigus is traditionally treated with high doses of corticosteroids, often combined with a steroid-sparing immunosuppressant drug.

About BTK inhibition in autoimmune disease

Bruton’s Tyrosine Kinase (BTK) is a protein important to the proper function of the immune system. BTK is a key part of the signaling pathway downstream of the B-cell and FcƔ receptors on most types of white blood cells except T-cells and plasma cells. Inhibition of BTK results in the down-regulation of various cellular activities that are activated in autoimmune and inflammatory diseases.

About Principia Biopharma

Principia Biopharma Inc., a private, clinical-stage biopharmaceutical company, has created a revolutionary new way to design and develop oral small molecule therapies that are more potent, selective, durable and safer than currently available drugs. The Company has utilized its proprietary Tailored Covalency™ technology to develop a portfolio of drug candidates that exhibit antibody-like specificity to benefit patients with autoimmune and inflammatory diseases and cancer. PRN1008, a reversible covalent BTK inhibitor, is currently being evaluated in a Phase 2 clinical trial in patients with pemphigus, an orphan autoimmune disease. PRN1371, a covalent FGFR1-4 inhibitor, is currently being evaluated in a Phase 1 clinical trial in cancer patients with various solid tumors. PRN2246, a low dose covalent BTK inhibitor which crosses the blood brain barrier, has successfully completed IND-enabling studies. For more information, please visit the Company's website at

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Last updated on: 18/09/2017

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