A Study of PRN1008 in Adult Patients With Pemphigus Vulgaris

Open-label cohort study in adult patients with newly diagnosed or relapsing pemphigus vulgaris, with intra-patient dose-adjustment based on clinical response and BTK occupancy, and with conventional immunosuppressive "rescue treatment", if indicated. The duration of therapy in Part A will be 12 weeks, followed by 12 weeks of follow up. The extension phase, Part B includes 24 weeks of therapy, followed by 4 weeks of follow-up.

Primary Objectives:

To evaluate the safety of PRN1008 in patients with pemphigus vulgaris (PV)

To evaluate the clinical activity of PRN1008 in patients with PV, per criteria in the European Academy of Dermatology and Venereology (EADV) 2014 Pemphigus S2 Guideline (Hertl et al. 2015)

Secondary Objectives

To evaluate the pharmacokinetics (PK) and the pharmacodynamics (PD) of multiple doses of PRN1008 in patients with PV

To evaluate the relationship of PK and PD to each other and to efficacy and safety in this patient population

Eligibility Criteria:
Inclusion Criteria:

* Male or female patients, aged 18 to 80 years old, with biopsy-proven, mild-moderate PV (PDAI 8 to 45) in Part A and mild to severe PV in Part B (PDAI 8 to 60) that are either:

  * newly diagnosed patients (i.e. naïve to an effective induction treatment regimen) for whom an initial period of PRN1008 monotherapy is judged clinically acceptable, or
  * relapsing patients, for whom an initial period of PRN1008 monotherapy, or combination therapy with any of low dose corticosteroid, ie.0.5 mg/kg of prednis(ol)one per day

Exclusion Criteria:

* Pregnant or lactating women
* A history of malignancy of any type, other than surgically excised non-melanoma skin cancers or in situ cervical cancer within 5 years before the day of dosing
* Use of immunologic response modifiers with the following periods prior to Day 1: 1 week: cyclophosphamide; 4 weeks: intravenous immunoglobulin, Kinaret (anakinra) and Enbrel (etanercept); 12 weeks: Remicade (infliximab), Humira (adalimumab), Simponi (golimumab), Orencia (abatacept), Actemra (tocilizumab), Cimzia (certolizumab), Cosentyx (secukinumab), plasmapheresis; 6 months: Rituxan/MabThera (rituximab), ofatumumab, any other anti-CD20 antibody, other long acting biologics
* More than 0.5 mg/kg of prednis(ol)one per day ("low dose corticosteroids") within the two weeks prior to Day 1
* Use of proton pump inhibitor drugs such as omeprazole and esomeprazole
* Has received any investigational drug (or is currently using an investigational device) within the 30 days before receiving the first dose of study medication, or at least 5 times the respective elimination half-life time (whichever is longer)
* History of drug abuse within the precious 12 months
* Alcoholism or excessive alcohol use, defined as regular consumption of more than approximately 3 standard drinks per day
* Refractory nausea and vomiting, malabsorption, external biliary shunt, significant bowel resection that would preclude adequate study drug absorption
* History of anorexia nervosa or periods of three months or more of low body weight in the past 5 years
* Donation of a unit or more of blood or blood products within 4 weeks prior to Day 1
* History of solid organ transplant
* History of epilepsy or other forms of seizures in the last 5 years
* Positive for screening for human immunodeficiency virus, hepatitis B (surface and core antibodies unrelated to vaccination), or hepatitis C (anti-HCV antibody confirmed with Hep C RNA)
* History of active or latent tuberculosis (TB) infection (must test negative using the QuantiFERON test to be eligible)
* History of serious infections requiring intravenous (by catheter that delivers antibiotics into your blood) treatment
* Live vaccine within 28 days prior to baseline or plan to receive one during the study