Fitusiran is an antithrombin-directed double-stranded small interfering RNA (siRNA) designed to reduce antithrombin production by targeting SERPINC1 mRNA. Fitusiran is covalently linked to a triantennary N-acetylgalactosamine (GalNAc) ligand to facilitate delivery to hepatocytes.
Fitusiran is supplied as a drug substance in sodium form and is described as a white to pale yellow powder. It is freely soluble in water and phosphate-buffered saline. A 1% aqueous solution in 50 mM KCl has a reported pH of 5.4, with a range of 4.4–7.3.
Fitusiran sodium has a reported molecular formula of C520H636F21N175Na43O309P43S6 and a molecular weight of approximately 17,193 Da.
Fitusiran is used as a prophylactic therapy to prevent or reduce bleeding episodes in patients with hemophilia A or hemophilia B.
Fitusiran drug substance is characterized using analytical techniques appropriate for oligonucleotide/siRNA products, including chromatographic and identity methods. Publicly available development data report duplex purity of NLT 90.0 area% by non-denaturing IP-RP-HPLC for the drug product.
| Parameter | Specification |
|---|---|
| Appearance | White to off-white crystalline powder |
| Identification | Conforms by IP-RP-HPLC / appropriate siRNA identity testing |
| Assay (HPLC) | NLT 90.0 area% |
| pH (1% Solution) | 5.4 (range 4.4–7.3) |
| Individual Impurity | NMT 0.20 area% |
| Total Impurities | NMT 10.0 area% |