Positive Results from Phase 2 Trial Could Lead to Lower Doses of Corticosteroids for Pemphigus Patients


Pemphigus is a rare autoimmune condition which causes the skin to blister. There are two main forms of the disease called pemphigus foliaceus (PF) and pemphigus vulgaris (PV). Pemphigus is generally treated with corticosteroids which help to heal the skin. However, prolonged use of these steroids can produce severe adverse events for patients. This, along with the fact that the disease itself can be debilitating, indicate a high unmet need for this patient population.

A Phase 2 trial conducted by Principia Biopharma and led by Dr. Dedee Murrell of Australia has recently examined a new potential treatment for this condition. It’s called PRN1008 and researchers believe that when administered with low doses of corticosteroids, it could prove efficacious for pemphigus patients.

The results from this trial, called Believe-PV, have just been announced at the American Academy of Dermatology’s annual meeting held in Washington D.C.


This Phase 2 trial included 24 patients who were diagnosed with mild to severe pemphigus. Some of these patients had PV and some had PF. The aim was to evaluate the efficacy of PRN1008 as a treatment for this condition. PRN1008 has already received Orphan Drug Designation for PV by the FDA and Orphan Drug Designation for pemphigus by the European Commission.

The primary endpoint of this trial was control of disease activity (CDA) with PRN1008 while only taking low doses of corticosteroids. CDA is measured by the healing of skin lesions and the lack of formation of new lesions. Secondary endpoints were reduced levels of the anti-desmoglein antibody and complete remission rates.

Believe-PV lasted 24 weeks, with a 12 week treatment period, and a 12 week follow-up. At four weeks, CDA was measured. 54% of participants achieved CDA by week 4. Across the subgroups of the disease, this outcome was generally consistent. By week 12, the end of the treatment regime, 73% of participants had achieved CDA. 17% of all participants achieved complete response by the end of the treatment period and 25% achieved complete response by week 24.

Thankfully, PRN1008 was also generally well-tolerated. Only one serious adverse event was reported. This patient had a patch of cellulitis on their leg. This individual stopped treatment with PRN1008 for three days and then resumed with no further events. Other, more common, but less serious events included headache, abdominal pain, and nausea.

Ongoing Phase 3 Trial

To continue the investigation of PRN1008, Principia has initiated a global Phase 3 trial. It is called the PEGASUS study. They plan to enroll 120 patients. Its aim is to examine the effect of PRN1008 vs placebo when used with tapering doses of corticosteroids.

This trial is actively enrolling.

In addition to this Phase 3 trial, Principia has started a Phase 2 extension study. In this follow-up to Believe-PV, Principia is investigating the effect of PRN1008 when the treatment is administered for 24 weeks as opposed to just 12. The results from this extension study should be announced in the fourth quarter of this year.

You can read more about PRN1008 and its potential to reduce corticosteroid use in pemphigus here.

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