Bill Sheridan
Analyst · JPMorgan. Your line is now open
Thanks, Jon. Our remarks today relates to the variation in phenotype in patients with hereditary angioedema and how this variation might impact studies of prophylactic treatments in this disease. The frequency of angioedema attacks in HAE is well known to cover a very broad spectrum. Some patients had very infrequent attacks, some had moderately frequent attacks, some had extremely frequent attacks. Dr. Bruce Zuraw noted in his review in the New England Journal of Medicine in 2008, untreated patients have attacks every 7 to 14 days on average with the frequency ranging from virtually never to every three days. A lot of work by many investigators has been directed at understanding the biological basis underlying this natural variation in frequency of attacks or more broadly severity of illness and recently, studies by leading groups have provided important insights into this question. One case study from [indiscernible] and published by Susanna Cunningham and colleagues in Clinical Immunology in 2010 looked into the levels of the primary natural kallikrein inhibitor, C-1 inhibitor at diagnosis of 115 patients. At this center, each patient’s plasma sample was assayed with a level of functional C1-inhibitor. In each case, the clinical severity of the illness was also graded according to a scale published by Dr. Agostoni [ph] and colleagues in the Journal of Allergy and Clinical Immunology in 2004 as part of the report from a collaborative workshop in hereditary angioedema. This categorizes the illness from asymptomatic, which is chosen as five to progressively more severe illness accounted as minimal, four, mild, three, moderate, two and severe accounted as one. The parameters evaluated included the impact on daily activities, need for emergency treatment and need for long-term prophylaxis in the disease and the scores are summed over the course of one year. In essence, the resulting category for an individual patient is a product of the average attack score times the attack frequency plus component for medical intervention. And this quarter is heavily influenced by attack frequency as we've confirmed in discussion with the investigators. The laboratory evaluation clearly showed that patients with more severe categories of illness had low levels of functional C1 inhibitor, findings that was highly statistically significant with an overall p-value of 0.0003. Second key study came from [indiscernible] and colleagues in Clinical & Experimental Allergy in 2014. This study evaluated [indiscernible] activity of contact activation pathway including the levels of the large and longstanding fragments of high molecular weight kininogen for HK that are produced to kallikrein digest kininogen and releases bradykinin. This measurement is turned to cleaved HK and is reported as percent of the total HK content. Investigators studied plasma samples from a 162 patients during the routine clinic visit and 81 healthy controls and reported the value of HAE patients categorized by frequency of attacks at angioedema. Patients with more frequent attacks were found to have higher levels of cleaved HK indicating a greater degree of activation at the contact pathway in patients with more frequent attacks. We’ve informed tonight that within each category of HAE patients, whether one uses an overall disease severity score or simply counter attack frequency, there is substantial variation in each of the measures we've discussed today, functional C1 inhibitor and cleaved HK. That’s common for biological assays and to see the reported relationships between assay results and disease activity; you should expect that a large dynamic range of the disease score or attack frequency would be less there in the analysis. We put these two studies together, a reasonable assessment is the variation in phenotypic expression in patients with HAE is significantly driven by underlying biological differences in the amount of natural inhibitor of plasma kallikrein and this shows up also in a degree of activation of the contact pathway. I think biology also suggests that pharmacologic plasma kallikrein inhibitor therapy is likely to be more successful in categories of patients with less frequency attacks or less disease score. It is therefore important to consider the main frequency of angioedema attacks in the population of the study in designing and interpreting studies of investigational prophylactic drugs in this indication. In OPuS-1, we studied patients who had narrow reach of about five adjudicated attacks in four weeks during the placebo period on study in light of 1.27 attacks per week and it showed that BCX4161 reduced the attack rates over four weeks by an average of about 1.8 attacks. In OPuS-2 study, which has a duration of 12 weeks, we don't yet know what the final attack rate would turn out to be in placebo group but we have liberalized the inclusion criteria in OPuS-2 compared to OPuS-2, so we expect it will be lower than in OPuS-1. The OPuS-2 study will help to expand our understanding of the potential of BCX4161 as a prophylactic treatment for HAE patients. We very much look forward to finishing this study and reporting the results. Tom will now review the financial results.