BACKGROUND Experimental data indicate that reducing factor XI levels attenuates thrombosis without causing bleeding, but the role of factor XI in the prevention of postoperative venous thrombosis in humans is unknown. FXI-ASO (ISIS 416858) is a second-generation antisense oligonucleotide that specifically reduces factor XI levels. We compared the efficacy and safety of FXI-ASO with those of enoxaparin in patients undergoing total knee arthroplasty. METHODS In this open-label, parallel-group study, we randomly assigned 300 patients who were undergoing elective primary unilateral total knee arthroplasty to receive one of two doses of FXI-ASO (200 mg or 300 mg) or 40 mg of enoxaparin once daily. The primary efficacy outcome was the incidence of venous thromboembolism (assessed by mandatory bilateral venography or report of symptomatic events). The principal safety outcome was major or clinically relevant nonmajor bleeding. RESULTS Around the time of surgery, the mean (±SE) factor XI levels were 0.38±0.01 units per milliliter in the 200-mg FXI-ASO group, 0.20±0.01 units per milliliter in the 300-mg FXI-ASO group, and 0.93±0.02 units per milliliter in the enoxaparin group. The primary efficacy outcome occurred in 36 of 134 patients (27%) who received the 200-mg dose of FXI-ASO and in 3 of 71 patients (4%) who received the 300-mg dose of FXI-ASO, as compared with 21 of 69 patients (30%) who received enoxaparin. The 200-mg regimen was noninferior, and the 300-mg regimen was superior, to enoxaparin (P<0.001). Bleeding occurred in 3%, 3%, and 8% of the patients in the three study groups, respectively. CONCLUSIONS This study showed that factor XI contributes to postoperative venous thromboembolism; reducing factor XI levels in patients undergoing elective primary unilateral total knee arthroplasty was an effective method for its prevention and appeared to be safe with respect to the risk of bleeding. (Funded by Isis Pharmaceuticals; FXI-ASO TKA ClinicalTrials.gov number, NCT01713361.)

BACKGROUND: Patients undergoing total knee arthroplasty are at risk for postoperative venous thromboembolism (VTE). The pathogenesis of postoperative VTE is incompletely understood, but tissue factor exposed at the surgical site is thought to be the major driver through the extrinsic pathway of coagulation. Experimental data indicate that reducing factor XI (FXI), a key component of the intrinsic pathway, attenuates thrombosis without causing bleeding, but the role of FXI in postoperative VTE in humans is unknown. There is evidence that patients with congenital FXI deficiency are at a reduced risk of VTE. FXI levels can be lowered with ISIS 416858 (FXI-ASO), an antisense oligonucleotide that specifically reduces human FXI mRNA expression in the liver. To determine whether lowering FXI levels prevents VTE without increasing the risk of bleeding, we compared several doses of FXI-ASO with enoxaparin on the rates of postoperative VTE and bleeding in patients undergoing total knee arthroplasty. METHODS: We randomized 300 patients to one of two FXI-ASO regimens (200 or 300 mg) or to 40 mg enoxaparin once daily in an open-label, parallel group study. FXI-ASO was administered as 9 subcutaneous injections starting 36 days before surgery with the last dose given 3 days postoperatively. Enoxaparin was to be continued for at least 8 days postoperatively. The primary efficacy outcome was the incidence of VTE detected by mandatory bilateral venography (performed on days 8 to 12 postoperatively) or symptomatic events. The principal safety outcome was major and clinically relevant nonmajor bleeding. All outcomes were adjudicated by a committee blinded to treatment allocation. RESULTS: FXI-ASO prolonged the activated partial thromboplastin time in a dose-dependent manner, but had no effect on the prothrombin time. Around the time of surgery, mean FXI activities were 0.38 ± 0.01, 0.20 ± 0.01 and 0.93 ± 0.02 units/ml in patients given the 200 and 300 mg FXI-ASO regimens and enoxaparin, respectively. In contrast, levels of FXII, FIX and FVIII, other components of the intrinsic pathway, were unaffected by FXI-ASO. The primary efficacy outcome occurred in 36 of 134 (26.9%) and 3 of 71 (4.2%) patients given the 200 and 300 mg FXI-ASO regimens, respectively, compared with 21 of 69 (30.4%) patients in the enoxaparin group. The 200 mg regimen was non-inferior, while the 300 mg regimen was superior to enoxaparin (P<0.001). Bleeding occurred in 2.8%, 2.6% and 8.3% of patients in the 200 mg, 300 mg, and enoxaparin groups, respectively. Preoperative and postoperative hemoglobin values and transfusion requirements were similar in the three treatment groups. CONCLUSIONS: This study is the first to show that FXI contributes to postoperative VTE and that lowering FXI levels is very effective for its prevention and appears to be safe. Additional studies are needed to confirm the safety of FXI-ASO, although the fact that patients receiving this therapy safely underwent major orthopedic surgery is reassuring. Our findings support the concept that thrombosis and hemostasis can be dissociated with strategies that target FXI. The profile of FXI-ASO renders it an appealing option for treatment of patients with a wide range of chronic thrombotic conditions. Disclosures Buller: Isis Pharmaceuticals Daiichi-Sankyo Bayer Health-Care Pfizer Bristol-Myers-Squibb: Consultancy, Honoraria. Bethune:Isis Pharmaceuticals: Employment. Bhanot:Isis Pharmaceuticals: Employment. Gailani:Aronora: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Dyax: Consultancy, Research Funding; Instrument Laboratory: Consultancy, Research Funding; Isis: Consultancy; Merck: Consultancy; Novartis: Consultancy. Monia:Isis Pharmaceuticals, Inc.: Employment. Raskob:Bayer Healthcare: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Janssen Pharmaceuticals: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; ISIS Pharmaceuticals: Consultancy, Honoraria. Segers:Isis Pharmaceuticals Daiichi-Sankyo Bayer Health-Care Pfizer Bristol-Myers-Squibb: Medical Director ofAcademic Research Organization which received services fees for the scientific coordination of clinical studies Other. Weitz:Pfizer, Inc.: Consultancy, Honoraria.

No abstract

IONIS-FXI RX (BAY2306001) is an antisense oligonucleotide that inhibits the synthesis of coagulation factor XI and has been investigated in healthy volunteers and end-stage renal disease (ESRD) patients. FXI-LICA (BAY2976217) shares the same RNA sequence as IONIS-FXI RX but contains a GalNAc-conjugation that facilitates asialoglycoprotein receptor (ASGPR)-mediated uptake into hepatocytes. FXI-LICA has been studied in healthy volunteers and is currently investigated in ESRD patients on hemodialysis.We present a model-informed bridging approach that facilitates the extrapolation of the dose-exposure-FXI relationship from IONIS-FXI RX to FXI-LICA in ESRD patients and, thus, supports the selection of FX-LICA doses being investigated in ESRD patients. A two-compartment PK model, with mixed first-and zero-order subcutaneous absorption and first-order elimination, was combined with an indirect response model for the inhibitory effect on the FXI synthesis rate via an effect compartment. This PK/PD model adequately described the median trends, as well as the inter-individual variabilities for plasma drug concentration and FXI activity in healthy volunteers of IONIS-FXI RX and FXI-LICA, and in ESRD patients of IONIS-FXI RX . The Accepted ArticleThis article is protected by copyright. All rights reserved model was then used to predict dose dependent steady-state FXI activity following repeat once-monthly doses of FXI-LICA in a virtual ESRD patient population.Under the assumption of similar ASGPR expression in ESRD patients and healthy volunteers, doses of 40mg, 80mg, and 120mg FXI-LICA are expected to cover the target range of clinical interest for steadystate FXI activity in the Phase 2b study of FXI-LICA in ESRD patients undergoing hemodialysis.

Observational studies of patients with established rheumatoid arthritis (RA) document a positive correlation between C-reactive protein (CRP) blood concentration and worsening of RA symptoms, but whether this association is causal or not is not known. Using CRP transgenic mice (CRPTg) with collagen-induced arthritis (CIA; a rodent model of RA), we explored causality by testing if CRP lowering via treatment with antisense oligonucleotides (ASOs) targeting human CRP mRNA was efficacious and of clinical benefit. We found that in CRPtg with established CIA, ASO-mediated lowering of blood human CRP levels improved the clinical signs of arthritis. In addition, in healthy human volunteers the ASO was well tolerated and efficacious i.e., treatment achieved significant CRP lowering. ASOs targeting CRP should provide a specific and effective way to lower human CRP levels, which might be an effective therapy in patients with established RA.