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Stock Analyst Update

Safety Concerns Ding Ionis

The string of severe adverse events with Ionis' inotersen program puts competitor Alnylam in a more favorable position.


Safety concerns from  Ionis(IONS) pivotal NEURO-TTR study evaluating inotersen (formerly IONIS-TTRRx) in familial amyloid polyneuropathy--a rare, hereditary disease that causes toxic buildup in the nervous system--sent Alnylam’s and Ionis’ stocks ricocheting in opposite directions. While Alnylam’s amyloidosis drug patisiran, which is also in pivotal testing and is expected to release top-line results this September, has its own side effect issues, we believe the string of severe adverse events with Ionis’s inotersen program puts Alnylam in a more favorable position. Probability-weighted inotersen sales have limited impact to our $43 per share fair value estimate for Ionis; however, we expect to raise our $56 per share fair value estimate for Alnylam to reflect our expectations for greater patisiran market share, should the drug successfully reach the market. Despite our valuation adjustments, we anticipate both stocks to fall within 3-star territory and recommend investors wait for a higher margin of safety before investing.

While Ionis’s pivotal NEURO-TTR study met both of its primary endpoints, several incidences of severe thrombocytopenia (platelet lowering) and renal complications dampened the otherwise encouraging top-line efficacy data. Three patients showed severe thrombocytopenia, one of whom died from brain hemorrhage, and four patients had renal complications with one of the four progressing to renal failure. Last year, a trial evaluating the same molecule in a slightly different patient population with familial amyloid cardiomyopathy was discontinued due to concerns of increased thrombocytopenia in the NEURO-TTR study.

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Kelsey Tsai does not own (actual or beneficial) shares in any of the securities mentioned above. Find out about Morningstar’s editorial policies.