Safety Of Emicizumab Research Articles

Reduced doses of emicizumab achieve good efficacy: Results from a national-wide multicentre real-world study in China.

Reduced doses of emicizumab improve the affordability among patients in developing countries. However, the relationship between variant dose selection and efficacy in the real world of China is still unclear. This study aimed to investigate the efficacy and safety of emicizumab especially in those on reduced dose regimens in a real-world setting. We carried out a multicentre study from 28 hospitals between June 2019 and June 2023 in China and retrospectively analysed the characteristics including demographics, diagnosis, treatment, bleeding episodes, and surgical procedures. In total, 127 patients with haemophilia A, including 42 with inhibitors, were followed for a median duration of 16.0 (IQR: 9.0-30.0) months. Median age at emicizumab initiation was 2.0 (IQR: 1.0-4.0) years. Median (IQR) consumption for loading and maintenance was 12.0 (8.0-12.0) and 4.2 (3.0-6.0) mg/kg/4weeks, respectively. While on emicizumab, 67 (52.8%) patients had no bleeds, whereas 60 (47.2%) patients had any bleeds, including 26 with treated bleeds. Compared to previous treatments, patients on emicizumab had significantly decreased annualized bleeding rate, annualized joint bleeding rate, target joints and intracerebral haemorrhage. Different dosages had similar efficacy except the proportion of patients with treated spontaneous bleeds and target joints. Adverse events were reported in 12 (9.4%) patients. Postoperative excessive bleeding occurred following two of nine procedures. This is the largest study describing patients with HA receiving emicizumab prophylaxis on variant dose regimens in China. We confirmed that nonstandard dose is efficacious and can be considered where full-dose emicizumab is ill affordable.

Statistically significant improvement in hemophilia A control: a retrospective analysis of the effectiveness and safety of emicizumab in children with severe and inhibitor forms of hemophilia A

Statistically significant improvement in hemophilia A control: a retrospective analysis of the effectiveness and safety of emicizumab in children with severe and inhibitor forms of hemophilia A

Emicizumab is efficacious in people with hemophilia A with comorbidities aged ≥50 years: analysis of 4 phase III trials

BackgroundThe treatment of older people with hemophilia A (HA) can be complicated by comorbidities. ObjectivesThis post hoc analysis evaluates the efficacy and safety of emicizumab in people with HA aged ≥50 years with cardiovascular (CV) risk factors or HIV and/or hepatitis C virus (HCV) infection. MethodsThe HAVEN 1 (NCT02622321), HAVEN 3 (NCT02847637), HAVEN 4 (NCT03020160), and STASEY (NCT03191799) studies enrolled adults/adolescents with severe HA. Participants were categorized as having a comorbidity if they had any CV risk factors (including history of CV disease, hypertension, diabetes, hyperlipidemia, prior stroke, or obesity), HIV, and/or HCV infection. Efficacy and safety outcomes were compared by age (<50 vs ≥50 years). ResultsOf 504 participants at data cutoff, 408 were aged <50 years and 96 were aged ≥50 years. In people with HA aged <50 years, 26.7% had ≥1 CV risk factor and 29.4% had HIV and/or HCV infection. In people with HA aged ≥50 years, 72.9% had ≥1 CV risk factor and 74.0% had HIV and/or HCV infection. The mean (95% CI) annualized bleed rate for treated bleeds was 1.29 (0.07-6.06) for people with HA aged <50 years and 1.82 (0.19-6.93) for people with HA aged ≥50 years. No significant differences in annualized bleed rates were observed for those with comorbidities compared with those without. Safety outcomes were similar regardless of age. ConclusionThis pooled analysis suggests that emicizumab efficacy and safety in people with HA aged ≥50 years with CV and HIV/HCV comorbidities were consistent with those in people with HA aged <50 years enrolled in the HAVEN 1, 3, and 4 and STASEY studies.

Pharmacokinetics and coagulation biomarkers in children and adults with hemophilia A receiving emicizumab prophylaxis every 1, 2, or 4 weeks

BackgroundEmicizumab is a bispecific antibody that bridges activated factor (F)IX and FX, mimicking the function of missing activated FVIII and thus improving hemostasis in people with hemophilia A. The efficacy and safety of emicizumab were demonstrated in 4 phase III clinical trials (HAVEN 1-4). ObjectivesHere, we describe pharmacokinetics (PKs), pharmacodynamics (PDs), and exploratory safety biomarkers in HAVEN 1 to 4. MethodsParticipants received emicizumab at a loading dose of 3 mg/kg weekly for 4 weeks, followed by maintenance doses of 1.5 mg/kg weekly, 3 mg/kg every 2 weeks, or 6 mg/kg every 4 weeks. PKs, PDs, and safety biomarkers were assessed in samples collected at regular intervals during the trials. ResultsEmicizumab plasma trough concentrations increased during the loading dose period, reaching a mean of 52.9 μg/mL (SD, 13.6 μg/mL) at week 5, and were sustained at 42.1 to 52.3 μg/mL thereafter with maintenance dosing. Activated partial thromboplastin time shortened following the first emicizumab dose. Mean FVIII-like activity and thrombin generation peak height increased to 25.2 IU/dL (SD, 6.9 IU/dL) and 115.2 nM (SD, 42.5 nM) at week 5, with levels sustained at 17 to 23 IU/dL and >116 nM thereafter, respectively. Emicizumab did not notably affect FIX or FX plasma antigen levels, prothrombin time, or concentrations of exploratory safety markers of coagulation activation (D-dimer, prothrombin fragment 1 + 2, and fibrinogen). ConclusionIn HAVEN 1 to 4, emicizumab demonstrated sustained PKs and PDs and improved coagulation parameters without affecting safety biomarkers.

The role of emicizumab in acquired hemophilia A.

Acquired hemophilia is a rare bleeding disorder that predominantly affects older people with potential underlying comorbidities, including cardiovascular and thrombotic risk factors. The current standard therapies with hemostatic agents for acute bleeding and immunosuppression often require inpatient management, are not approved for routine bleeding prophylaxis, and contribute to the high mortality in this population. Emicizumab is a factor VIII (FVIII) mimetic approved for bleeding prophylaxis in congenital hemophilia A with and without FVIII inhibitors. Given subcutaneously, it may allow easier outpatient bleeding prophylaxis and reduce intensity of immunosuppression. This article summarizes the currently available data on the efficacy and safety of emicizumab in acquired hemophilia A.

Emicizumab Prophylaxis for the Treatment of Chinese Hemophilia A Patients in the Real World: A Multi-Center Retrospective Analysis

Background The real-world experiences of Hemophilia A (HA) patients receiving emicizumab prophylaxis in China are insufficient due to the high cost and later approval of emicizumab. In this study, we retrospectively analyzed Chinese HA patients with or without factor VIII (FVIII) inhibitors receiving emicizumab prophylaxis with the aim to investigate the efficacy and safety of emicizumab as well as the current status and effect of different doses of emicizumab in a real-world setting. Methods HA patients with or without FVIII inhibitors receiving emicizumab prophylaxis between June 2019 and June 2023 in China were included in the study. Data of HA patients including children and adults were retrospectively gathered from 27 hospitals all over the country. For each patient, the anonymized data were collected and telephone follow-ups were conducted to make sure the intact information collected as much as possible. Low dose and higher dose of emicizumab were defined as monthly dose &amp;lt;3 mg/kg and monthly dose ≥3 mg/kg, respectively. All analyses were performed using SPSS software version 25.0 (IBM Corporation, Armonk, New York, USA). Intraindividual comparisons were performed by nonparametric paired tests. Results A total of 127 male patients (10.2% [n=13] ≥18 years old; 89.8% [n=114] &amp;lt;18 years old) were enrolled in our study (severe: moderate = 103:24). Of these, 42 (33.1%) had FVIII inhibitors at initiating emicizumab. The median (interquartile range [IQR]) duration of emicizumab treatment was 16.0 (9.0-30.0) months. The median (IQR) annualized bleeding rate (ABR) and annualized joint bleeding rate (AJBR) after emicizumab were 0.5 (0-1.5) and 0 (0-0), respectively (calculated in patients treated with emicizumab &amp;gt;6 months). Among the 127 patients, 67 (52.8%) patients had no bleeds at all. No intracranial hemorrhage occurred after emicizumab. Adverse events were reported in 12 (9.4%) patients and 10 (83.3%) were injection-site reactions. There were no deaths, thromboembolic events, or thrombotic microangiopathies in our study. Two (8.0%) patients had treated epistaxis after emicizumab with low dose compared with 0 (0.0%) with higher dose ( P =0.037). Four (16.0%) patients had target joints after emicizumab with low dose compared with 1 (1.0%) with higher dose ( P =0.005) (Table 1). There were no significant differences between low dose and higher dose of emicizumab prophylaxis in ABR, AJBR, the proportion of zero bleeds, the proportion of adverse events, and so on. The median (IQR) ABR was 5.0 (2.0-14.0) with prior treatment compared with 0.5 (0-1.5) with emicizumab, an 90% reduction in ABR with P value &amp;lt;0.001 (Table 2).Also, the use of emicizumab was also associated with significant reduction in AJBR ( P &amp;lt;0.001), number of target joints ( P &amp;lt;0.001), number of intracerebral hemorrhages ( P &amp;lt;0.001), inhibitor titer ( P =0.016), and days away from school/work ( P &amp;lt;0.001). Conclusion In this multi-center study, we indicated the efficacy and safety of emicizumab and that low dose and higher dose of emicizumab had similar efficacy in Chinese HA patients without increasing adverse events.

Post-Immune Tolerance Induction Prophylactic FVIII Infusions May Not be Necessary for Tolerized Hemophilia a Patients on Emicizumab

Background: Hemophilia A is a hereditary bleeding disorder characterized by low factor VIII (FVIII) activity. Patients with severe bleeding phenotypes are at risk for significant bleeding-related morbidity and mortality including the development of hemophilic arthropathy. In recent years, prophylaxis with emicizumab, a bispecific monoclonal antibody, has supplanted prophylactic FVIII infusions due to its ease of self-administration, long half-life, and low annual bleeding rate (ABR), independent of tolerization status to alloantibodies against FVIII (inhibitors). However, it is unclear if emicizumab FVIII-mimic activity is sufficient to achieve hemostasis in moderate-severe bleeds, and therefore, FVIII replacement may still be necessary. Despite its well-established benefits, the use of emicizumab in previously untreated patients (PUPs), and patients with under 20 exposures to FVIII is still not well understood due to a lack of long-term experience and understanding of its impact on the pathophysiology of FVIII inhibitors. Further investigation is also needed regarding the risk of inhibitor recurrence in patients with previous inhibitors and the concomitant use of emicizumab. At our institution, patients on emicizumab with a history of inhibitors do not continue post-immune tolerance induction prophylactic FVIII infusions. We also initiate emicizumab before 20 exposures to FVIII, and sometimes before immune tolerance induction (ITI). We explored our patient population to understand inhibitor incidence and recurrence amidst emicizumab prophylaxis. Methods: We performed a single center retrospective analysis of patients served by the Hemophilia Center of Western Pennsylvania. We identified patients with Hemophilia A on emicizumab prophylaxis. Relevant data was collected including demographics, inhibitor status at time of transition to emicizumab and in the available follow-up period, bleeding events after transition, and number of FVIII exposures before and after transition. Inhibitor recurrence was defined as laboratory evidence of inhibitor using chromogenic Bethesda assay and/or unexplained breakthrough bleeding events despite on-demand FVIII infusions. Results: Data was reviewed for 36 patients on emicizumab prophylaxis. Three patients were lost to follow-up. Median age was 15.3 years (range 1.2 - 82). Median follow-up time on emicizumab was 3.5 years (range 0.5 - 5). Two patients had &amp;lt; 20 FVIII exposures prior to emicizumab, and one of those had an inhibitor before emicizumab. In total, 15 patients (45%) were diagnosed with an inhibitor prior to emicizumab. Of these, 8 patients (53%) were tolerized prior to emicizumab, and 7 patients (47%) were not tolerized prior to emicizumab. Median peak inhibitor titer was 4.2 Bethesda units (range 0.7 - 281 Bethesda units). After transition to emicizumab, no tolerized patients for which inhibitor status was tested during the follow-up period had inhibitor recurrence, and 1 non-tolerized patient's inhibitor became undetectable after 4 years of emicizumab therapy (the same patient who had developed an inhibitor with &amp;lt; 20 FVIII exposures prior to emicizumab). Mean ABR was 0.33 events/year for tolerized patients (median 0, range 0 - 3); 0.17 events/year for non-tolerized patients (median 0, range 0 - 1); and 0.60 events/year for patients with no history of inhibitor (median 0, range 0 - 4). Mean number of FVIII exposures per year was 0.09 for tolerized patients (median 0, range 0 - 1); 0.07 for non-tolerized patients (median 0, range 0 - 1); and 1.2 for patients with no history of inhibitor (median 0, range 0 - 20). Conclusion: In our small cohort, no patient who was tolerized prior to emicizumab had recurrence of clinical or laboratory evidence of inhibitor while on emicizumab therapy, despite infrequent exposure to FVIII infusion. We did not have enough power to determine whether patients with &amp;lt; 20 FVIII exposures before emicizumab developed inhibitors, though one such patient had inhibitor resolution on emicizumab without ITI. Consistent with other works, overall ABRs in all patients on emicizumab therapy were low. These findings add to other studies on the safety of emicizumab and its impact on the natural history of FVIII inhibitors. Our study also suggests that continuing post-ITI prophylactic FVIII infusions in tolerized patients on emicizumab may not be necessary. Larger-scale studies are required to substantiate our findings.

Untreated bleeds: Unveiling the subtleties and challenges of bleeding event counts and patient experience in clinical trials for bleeding disorders

Emicizumab, the bispecific human antibody that mimics factor VIII by bringing together activated factor IX and factor X, has significantly improved care for persons with hemophilia A (HA), by providing a subcutaneous means of prophylaxis that is given less frequently than intravenous factor infusions. The HAVEN studies,1–4 which have demonstrated the efficacy and safety of emicizumab, differed from most previous hemophilia studies not only in prophylaxis mechanism; they presented bleeding event data for both treated and untreated bleeds.

Real-World Experience with Emicizumab Prophylaxis in the Milan Cohort: A Single-Center Experience

▪ INTRODUCTIONEmicizumab is a humanised bispecific monoclonal antibody, which replaces the function of factor VIII (FVIII) by bridging activated factor IX and factor X. Emicizumab is approved for prophylaxis of patients with Hemophilia A (HA), both with and without inhibitors. Real-world data on the efficacy and safety of emicizumab were recently reported from a few hemophilia treatment centers, but more data are needed to assess the efficacy and safety of emicizumab in comparison to standard prophylactic treatment. OBJECTIVETo evaluate the safety and efficacy of emicizumab prophylaxis in a single cohort of patients with HA, with and without inhibitors. METHODSWe performed an observational prospective study including patients affected with HA, with and without inhibitors, switched to emicizumab prophylaxis in the post-marketing era. Data regarding inhibitor status, Annualized Bleeding Rate (ABR), cause of bleeding, type and location of bleeds, Emicizumab Plasmatic Concentration [Emi] and activated partial thromboplastin time (aPTT) were collected for each patient. Hemophilia Joint Health Scores (HJHS) and General Health Visual Analogue Scale (GH-VAS) were collected by trained physiotherapists before switching to emicizumab and 12 months after treatment start. RESULTSA total of 22 patients, 21 with severe and 1 with moderate HA, were enrolled. Twenty patients were without inhibitor against FVIII and 2 adults with inhibitor were previously treated with bypassing agents. All patients started emicizumab prophylaxis with a loading dose of 3 mg/kg once weekly for 4 weeks, followed by a maintenance dosage of 1.5 mg/kg weekly. Within the children cohort, 3 were Previously Untreated Patients (PUPs) and 2 were previously treated with FVIII without developing inhibitor. The ABR showed a reduction of 74% in the entire cohort, as reported in Table 1. When stratifying for age groups, the ABR reduction was 70% for adults and 100% for children. Within the adults, the zero-bleeding patients increased from 2 to 11 patients (from 12 to 64%, respectively). In the adult cohort, 6 patients experienced 11 bleeding events over a mean follow-up of 300 days. Five out of 11 events were experienced in 6 months by a single patient who developed anti-drug antibodies (ADA) against emicizumab around the 5 th week ([Emi] 31.7 ug/ml). The prophylaxis with emicizumab was interrupted due to the treatment failure, which occurred despite spontaneous ADA clearance. Another patient developed ADA around the 9 th week ([Emi] 28.3 ug/ml), but without associated bleedings in up to 14 weeks of follow-up (minimum [Emi] 17 ug/ml). Of the remaining 5 adults who experienced bleedings during emicizumab prophylaxis, one patient developed spontaneous soft tissue bleeding, another one developed a spontaneous hemarthrosis in his target joint and the remaining 3 patients experienced post-traumatic joint bleedings, 2 out of 3 bleedings were in target joints. The analysis of the number of total joint bleedings before and after switching stratified for spontaneous and post-traumatic, revealed a reduction in target joint bleedings of 73% and a reduction of spontaneous and post-traumatic bleeding of 80% and 43%, respectively. All events were managed in outpatient clinic and required only a single infusion of FVIII concentrate. The plasmatic concentrations of emicizumab at steady state were within previous reported normal range for all patients, with exception of the two patients who developed ADA. Interestingly, steady state concentration was higher in children than in adults (median [Emi] 64.9 ug/ml and 49.85, respectively). The HJHS and GH-VAS scores at baseline and after 12 months of emicizumab prophylaxis available in 6 adults showed improvement in joint health and self-perceived global health, as shown in Figures 2 and 3. No thrombotic events were reported in the entire cohort. DISCUSSIONWe report our Milan single center experience on the use of emicizumab prophylaxis in children and adults with HA, with and without inhibitors. Our experience shows a good efficacy of emicizumab both in children and adults, with few post-traumatic bleedings occurring mainly in target joints of adult patients. In addition, physician's and self-assessed scores revealed an improvement of patient's joint health after 12 months of emicizumab prophylaxis. [Display omitted] DisclosuresPeyvandi: Roche: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Sobi: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria.

Emicizumab Prophylaxis in Persons with Hemophilia A, Aged ≥50 Years, with Comorbidities - Pooled Data from Four Phase III Studies (HAVEN 1, 3, and 4, and STASEY)

Emicizumab Prophylaxis in Persons with Hemophilia A, Aged ≥50 Years, with Comorbidities - Pooled Data from Four Phase III Studies (HAVEN 1, 3, and 4, and STASEY)

CHOLECYSTECTOMY IN A MAN WITH HEMOPHILIA A AND INHIBITOR ON EMICIZUMAB PROPHYLAXIS: A CASE REPORT

There are few reports about the hemostatic effectiveness and safety of emicizumab on major surgeries, especially non-orthopedic ones. We described a man with severe hemophilia A and high-responding inhibitor under emicizumab prophylaxis who was submitted to an open cholecystectomy due to acute-on-chronic calculous cholecystitis. A 32-year-old man first visited the Emergency Department complaining severe diffuse abdominal colic unresponsive to oral analgesics, in the last 7h. He denied fever, nausea, or diarrhea. He had severe hemophilia A with high-response inhibitor, receiving prophylaxis with emicizumab (1.5 mg/kg weekly). He also had been submitted to several abdominal surgeries (appendicectomy, midgut volvulus, and abdominal trauma). Physical examination was unremarkable. Aspartate and alanine aminotransferases were mildly elevated (56 and 83 U/L, respectively). He was discharged home after ameliorating with dipyrone, tramadol, and bromopride. He came back 4 days later, with the same complaints. He had a positive Murphy's sign and a negative Blumberg's sign. Blood tests were unremarkable. The gallbladder had a normal wall thickness (0.6 cm) with several mobile calculi (from 0.9 to 1.8 cm) by abdominal ultrasound, without dilation of the biliary tract, alteration of the pancreas/pancreatic duct, or lymphadenomegaly. He declined hospitalization and returned 5 days later, after having discussed with his Hematologist about the surgical procedure. Emicizumab was maintained throughout the described period. Before the procedure, he received intravenous rFVIIa 93 μg/kg and tranexamic acid (TxA) 1 g. rFVIIa was maintained each 2h, during the first 24h. The procedure was performed under general anesthesia. Videolaparoscopic cholecystectomy was withheld, due to adhesions precluding peritoneal inflation. Upon a right subcostal incision, a hydropic gallbladder was removed (anatomopathological analysis confirmed acute-on-chronic calculous cholecystitis). A purified pigskin sterile absorbable gelatin sponge was placed on his hepatic bed, before closing the surgical wound. The surgeon reported an above-the-usual bleeding during the procedure (estimated blood loss of 500 mL against usually minimal blood loss). Ceftriaxone and metronidazole were prescribed throughout the hospitalization. rFVIIa 77 μg/kg was scattered on a daily base: every 2h until every 12h along 1 week (total 2,400 μg/kg). TxA 1 g every 8h was prescribed during the same period. He had mild hematic drainage (less than 30 mL on the post-operatory day and decreasing in the following days). This was judged as good hemostasis by the surgeon. The drain was removed in the 4 th post-operative day. Hemoglobin decreased from 13.7 g/dL at the day of the procedure until 9.4 g/dL the day before discharge (lowest 8.9 g/dL). No blood transfusion was required throughout the hospitalization. He was discharged home 1 week after surgery. No bleeding event was reported during the outpatient follow-up within 3 weeks. No symptoms nor signs of thrombosis were reported. In conclusion, we would like to reinforce the importance for the surgeons (a) to know that people with hemophilia A, with or without inhibitors, are susceptible to the same risks of developing gastrointestinal diseases as individuals without hemophilia; (b) in such cases, an interdisciplinary approach is always the best option; and (c) there is a biopharmaceutical which may effective and safely reduce the bleeding risk in the periprocedural period.

Safety evaluation of emicizumab prophylaxis in individuals with haemophilia A

ABSTRACT Introduction Emicizumab is a bispecific-humanized monoclonal antibody that improves hemostasis by bridging activated factor IX and factor X to substitute for the function of missing activated FVIII. It is an alternative to prophylaxis with factor VIII replacement and is associated with improved outcomes in individuals with hemophilia A with and without inhibitors. Areas covered Emicizumab is efficacious in reducing bleeding events when compared to on-demand treatment and factor-based prophylaxis. Except for the few thrombotic microangiopathy and thrombotic event cases mainly seen in the HAVEN 1 trial, emicizumab has an overall excellent safety profile with minimal side effects. Expert opinion Knowledge gaps include the efficacy and safety of emicizumab in younger age groups and those with mild or moderate hemophilia A. Future directions for research include exploring the risk of inhibitor recurrence in patients with a history of high titer inhibitor who have been successfully tolerized, who switch from factor prophylaxis to emicizumab, as well as conducting ‘real world studies’ to evaluate the patient’s perception of emicizumab in regard to ease and tolerability in order to optimize individualized treatment plans.

Safety and Efficacy of Emicizumab in Persons with Hemophilia a with or without FVIII Inhibitors: Pooled Data from Four Phase III Studies (HAVEN 1-4)

Safety and Efficacy of Emicizumab in Persons with Hemophilia a with or without FVIII Inhibitors: Pooled Data from Four Phase III Studies (HAVEN 1-4)

Evaluating the safety of emicizumab in patients with hemophilia A

ABSTRACTIntroduction: Patients affected by hemophilia A often require frequent prophylactic and therapeutic self-infusion. For those who develop inhibitors, treatment options are limited and mortality is increased. Emicizumab, a bispecific antibody to Factors IXa and X that carries out the function of Factor VIII (FVIII), represents a novel therapeutic approach.Areas covered: We review the clinical trials and key laboratory assay research for emicizumab. Emicizumab reduced the annualized bleeding rate by 87% compared to placebo in patients with inhibitors. For patients without inhibitors, emicizumab reduced the annualized bleeding rate 96–97% compared to no prophylaxis and 68% compared to prior FVIII prophylaxis. Three patients developed a thrombotic microangiopathy (TMA) and two patients had thrombotic events while on emicizumab in combination with activated prothrombin complex concentration (aPCC) alone or concurrent with activated recombinant factor FVII (rFVIIa).Expert opinion: Emicizumab represents a much-needed alternative approach to managing Factor VIII deficiency, especially for those with inhibitors or limited ability to self-infuse. For patients with inhibitors, thrombotic complications including TMA, not seen with other bypassing agents, raises concern about the use of emicizumab in combination with aPCC and how patients who have breakthrough bleeding can be safely managed.

A bispecific antibody mimicking factor VIII in hemophilia A therapy.

Serious issues in current hemostatic treatment of hemophilia A are the requirement for frequent intravenous administrations of factor (F) VIII, FVIII inhibitor development, and hemostatic treatment for patients with this inhibitor. For the purpose of overcoming these challenges, the FVIIIa-substituting bispecific antibody against FIXa/FX (ACE910, INN emicizumab) was produced. Emicizumab demonstrated marked hemostatic effects on both ongoing and spontaneous joint bleeding in the acquired hemophilia A primate model. The clinical phase 1 study designed to assess the pharmacokinetics, pharmacodynamics and safety of emicizumab has been initiated. Severe emicizumab-related adverse events were minimal. The t1/2 was approximately 30 days, and bleeding events were significantly decreased by weekly subcutaneous administration in severe hemophilia A patients, independently of the presence of the inhibitor. Currently, the phase 1/2 extension study is ongoing. We anticipate that emicizumab will show the benefits of prophylactic efficacy with subcutaneous administration at a much lower frequency.