Alnylam back on track with fitusiran as FDA lifts clinical hold

illustration of red blood cells in blood vessel
With the clinical hold lifted, Alnylam expects to pick its hemophilia trials back up by the end of the year.

Alnylam, which put its hemophilia program on hold in September, has gotten the all-clear from the FDA to resume trials of its RNAi drug fitusiran.

The RNAi specialist suspended dosing in trials investigating the drug in hemophilia A or B after a patient died from a thrombotic event in a phase 2 study.

Hoping to get the studies up and running by the end of the year, Alnylam worked on a strategy to improve safety monitoring and mitigate the risk of fatal blood clots striking more patients.


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Its risk mitigation plan includes educating investigators and patients on treating breakthrough bleeds in the studies, the company said in a statement. The FDA has approved Alnylam’s changes to the clinical protocol, lifting the clinical hold on the program.

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Alnylam will continue the phase 2, open-label study, as well as its phase 3 Atlas program, which was put on hold before dosing could begin.

“We are pleased with the FDA’s decision to lift the clinical hold, as fitusiran holds the potential to help improve the lives of people living with hemophilia,” said Akin Akinc, vice president and general manager, fitusiran at Alnylam, in the statement. “With the additional risk mitigation measures in place, we look forward to the continued late-stage development of fitusiran and expect to resume dosing around year-end.”

Although the patient death could have had wide-reaching implications for Alnylam’s other drugs, the blood clot behind the death could be linked to the knocking down of antithrombin, not gene-silencing in general. And the event seems not to have touched the company’s other programs—a couple of weeks later, its patisiran met all of its endpoints in a late-stage study in hereditary ATTR amyloidosis.

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