Mixed Actimmune Data
Mixed Actimmune Data
January 09, 2003
InterMune’s (NASDAQ: ITMN) Actimmune (interferon g-1b) continues to generate mixed data from its randomized, double-blind, placebo-controlled, phase III clinical trial program in the management of patients with idiopathic pulmonary fibrosis (IPF). In spite of the mixed data, Actimmune has a better than average probability of expanding its use to include IPF.
330 patients were randomized into a phase III clinical trial assessing Actimmune’s clinical utility for the treatment of IPF. Study subjects received either placebo or Actimmune 200 micrograms subcutaneously three times per week. The post-treatment phase data were appraised August 29, 2002; three to five additional months of patient follow-up generated the current data.
In a conservative analysis, Actimmune provided a 25% relative mortality reduction (16% vs. 21.4%). Subgroup analysis indicated that a 49% relative mortality reduction (10.3% vs. 20.3%) was observed for mild to moderately affected participants. The difference in outcomes was statistically significant for only the mild to moderately affected subgroup. More refined subgroup analyses suggested analogous trends.
These data highlight the fact that statistical and clinical significance can be uncoupled. The fewer incident, prevalent, or studied cases there are, the more likely are statistically insignificant trends to be clinically significant. Conversely, the greater numbers of incident, prevalent, or studied cases there are, the less likely statistical significance conveys clinical significance.
Magnitudes of treatment effects often drive use decisions more so than statistical significance. Relative mortality reduction is an appropriate measure of therapeutic effect magnitude. The 25% reduction of the risk of death, though down from 41% at earlier analysis, remains a clinically significant effect even in the absence of achieving conventionally accepted cutoffs for statistical significance. For real-world medical practice decision-making, clinicians are more likely to look at the magnitudes of treatment effect of the drug, especially when it is already marketed and slated to be offered to a limited population such as IPF.
InterMune has transitioned approximately 80% of subjects in both experimental and control groups into open-label extensions designed to track longer- term outcomes for a minimum of one year. Overall, the probability for limited use expansion followed by eventual label expansion into IPF remains slightly above average.
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