Alnylam Pharmaceuticals, Inc., recently reported positive interim results from a part of its ongoing international Phase 1 study with fitusiran, the company’s investigational RNAi therapy, in patients with hemophilia A and B with inhibitors. These results were presented in a poster at the 58th Annual Meeting of the American Society of Hematology (ASH), held December 3-6, 2016, in San Diego, CA.
Fitusiran is a subcutaneous therapy (administered under the skin) that employs small interfering RNA (siRNA) technology to target antithrombin (AT), a liver-generated clotting protein that plays a key role in the regulation of blood clots. siRNA molecules are segments of RNA (ribonucleic acid) that block or “silence” the activity of certain genes through RNA interference, a natural biological process common in plants and mammals. Fitusiran works by silencing the gene responsible for AT, which inhibits the protein’s anticoagulant function. This then compensates for the imbalance caused by deficiencies in other clotting proteins, such as factor VIII (hemophilia A) or factor IX (hemophilia B).
The report showed that monthly subcutaneous administration of fitusiran achieved lowering of AT and increases in thrombin generation, resulting in a median estimated annualized bleeding rate (ABR) of zero in patients with hemophilia A or B with inhibitors. These results encompass an October 6, 2016, “data cut-off date” presented from Part D of the ongoing study, which included two separate dosing groups. The first group included a monthly administration of 50 milligrams (mg) and the second, a larger monthly administration of 80mg.
In the 80mg group, 70% (7 out of 10) of patients were bleed-free and 90% (9 out of 10) of patients experienced 0 spontaneous bleeds. The company also reported that as of the October 6th cut-off, the therapy was generally well tolerated with no thromboembolic events, including in circumstances when bypassing agents were administered to treat breakthrough bleeding events.
“As many as one-third of severe hemophilia A patients will develop inhibitors, one of the most serious treatment-related complications of hemophilia. We believe that achievement of a median ABR of zero in this study population is very encouraging, as the prophylactic treatment options for patients with inhibitors are limited and may be suboptimal for many patients,” said Akin Akinc, PhD, Vice President and General Manager at Fitusiran. “We look forward to continuing to study fitusiran in hemophilia patients with and without inhibitors, and plan to initiate our Phase 3 program in early 2017.”
Source: Alnylam press release dated December 3, 2016
