Alnylam Pharmaceuticals (ALNY -2.9%) is down, albeit on light volume, on the heels of its announcement of new data from its open-label extension studies of RNAi therapeutic givosiran in patients with acute hepatic porphyrias (AHPs). The results were presented at the International LIver Congress in Paris.
Treatment with givosiran lowered aminolevulinic acid (ALA), the primary toxin in AFPs, and a compound called porphobilinogen (PBG) which led to an 83% decrease in annualized attack rate (AAR) compared to placebo. The average reduction in AAR was 93% in patients treated in the Phase 1 study who continued treatment in the extension portion (n=11/12).
Investors appear disappointed that the higher monthly dose of givosran (5.0 mg/kg) did not lower ALA and PBG levels further compared to the lower dose (2.5 mg/kg). Also, the monthly regimen was more effective than the quarterly regimen dashing hopes for less-frequent administration.
The other bit of bad news was one case of a serious allergic reaction to givosiran after the third dose. The situation was resolved but the patient withdrew from the study.
Enrollment in the Phase 3 ENVISION trial is proceeding with interim data expected mid-year. If positive, the company intends to file a U.S. marketing application.
Previously: Alnylam launches late-stage study assessing givosiran in AHPs (Nov. 7, 2017)
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