Population Pharmacokinetic Analysis and Exploratory Exposure-Bleeding Rate Relationship of Emicizumab in Adult and Pediatric Persons with Hemophilia A

Transitioning from emicizumab prophylaxis to valoctocogene roxaparvovec gene therapy: A simulation study for individuals with severe haemophilia A

INTRODUCTION

Valoctocogene roxaparvovec, a gene therapy evaluated in the phase 3 GENEr8-1 trial, supports endogenous factor VIII (FVIII) production to prevent bleeding in people with severe haemophilia A. Individuals receiving emicizumab, an antibody mimicking the function of activated FVIII, were excluded from GENEr8-1 enrolment since emicizumab was an investigational therapy at the time of trial initiation.

AIM

Utilize pharmacokinetic simulations to provide guidance on best practices for maintaining haemostatic control while transitioning from emicizumab prophylaxis to valoctocogene roxaparvovec.

METHODS

To estimate bleeding risk at weekly intervals following valoctocogene roxaparvovec infusion, a published emicizumab pharmacokinetic model was used to simulate emicizumab concentrations and merged with FVIII activity time-course data for participants in GENEr8-1. The analysis investigated three approved emicizumab dosing regimens for two transition scenarios that varied whether the last dose of emicizumab was administered on the same day or 4 weeks after valoctocogene roxaparvovec infusion.

RESULTS

Simulations demonstrated administering the last emicizumab dose the day of valoctocogene roxaparvovec infusion and 4 weeks after offered similar levels of haemostatic control, and bleeding risk was similar for all emicizumab dosing regimens. An algorithm was developed to provide guidance for discontinuation of emicizumab. Theoretical cases based on GENEr8-1 participants are presented to illustrate how decisions may vary among individuals.

CONCLUSION

Pharmacokinetic simulations demonstrated no clinically meaningful difference in bleeding risk caused by decaying emicizumab levels and rising gene therapy-derived endogenous FVIII for all examined emicizumab doses and dosing regimens. Therefore, multiple approaches can safely transition individuals from emicizumab prophylaxis to valoctocogene roxaparvovec.

Impact of covariate model building methods on their clinical relevance evaluation in population pharmacokinetic analyses: comparison of the full model, stepwise covariate model (SCM) and SCM+ approaches

Covariate analysis in population pharmacokinetics is key for adjusting doses for patients. The main objective of this work was to compare the adequacy of various modeling approaches on covariate clinical relevance decision-making. The full model, stepwise covariate model (SCM) and SCM+ PsN algorithms were compared in a clinical trial simulation of a 383-patient population pharmacokinetic study mixing rich and sparse designs. A one-compartment model with first-order absorption was used. A base model including a body weight effect on CL/F and V/F and a covariate model including 4 additional covariates-parameters relationships were simulated. As for forest plots, ratios between covariates at a specific value and that of a typical individual were calculated with their 90% confidence interval (CI90) using standard errors. Covariates on CL, V and KA were considered relevant if their CI90 fell completely outside the reference area [0.8-1.2]. All approaches provided unbiased covariate ratio estimates. For covariates with a simulated effect, the 3 approaches correctly identify their clinical relevance. However, significant covariates were missed in up to 15% of cases with SCM/SCM+. For covariate with no simulated effects, the full model mainly identified them as non-relevant or with insufficient information while SCM/SCM+ mainly did not select them. SCM/SCM+ assume that non-selected covariates are non-relevant when it could be due to insufficient information, whereas the full model does not make this assumption and is faster. This study must be extended to other methods and completed by a more complex high-dimensional simulation framework.

Emicizumab prophylaxis in infants with hemophilia A (HAVEN 7): primary analysis of a phase 3b open-label trial

ABSTRACT

Subcutaneous emicizumab enables prophylaxis for people with hemophilia A (HA) from birth, potentially reducing risk of bleeding and intracranial hemorrhage (ICH). HAVEN 7 (NCT04431726) is the first clinical trial of emicizumab dedicated to infants, designed to investigate the efficacy, safety, pharmacokinetics, and pharmacodynamics of emicizumab in those aged ≤12 months with severe HA without factor VIII (FVIII) inhibitors. Participants in this phase 3b trial received emicizumab 3 mg/kg maintenance dose every 2 weeks for 52 weeks and are continuing emicizumab during the 7-year long-term follow-up. Efficacy end points included annualized bleed rate (ABR): treated, all, treated spontaneous, and treated joint bleeds. Safety end points included adverse events (AEs), thromboembolic events (TEs), thrombotic microangiopathies (TMAs), and immunogenicity (anti-emicizumab antibodies [ADAs] and FVIII inhibitors). At primary analysis, 55 male participants had received emicizumab (median treatment duration: 100.3; range, 52-118 weeks). Median age at informed consent was 4.0 months (range, 9 days to 11 months 30 days). Model-based ABR for treated bleeds was 0.4 (95% confidence interval, 0.30-0.63), with 54.5% of participants (n = 30) having zero treated bleeds. No ICH occurred. All 42 treated bleeds in 25 participants (45.5%) were traumatic. Nine participants (16.4%) had ≥1 emicizumab-related AE (all grade 1 injection-site reactions). No AE led to treatment changes. No deaths, TEs, or TMAs occurred. No participant tested positive for ADAs. Two participants were confirmed positive for FVIII inhibitors. This primary analysis of HAVEN 7 indicates that emicizumab is efficacious and well tolerated in infants with severe HA without FVIII inhibitors.

Nothing short of a revolution: Novel extended half-life factor VIII replacement products and non-replacement agents reshape the treatment landscape in hemophilia A

Hemophilia A, an X-linked genetic disorder, is characterized by a deficiency or dysfunction of clotting Factor VIII. The treatment landscape has substantially changed by introducing novel extended half-life factor VIII (EHL-FVIII) replacement therapies such as efanesoctocog Alfa and non-factor replacement therapy such as emicizumab. These agents signal a shift from treatments requiring multiple weekly infusions to advanced therapies with long half-lives, offering superior protection against bleeding and improving patient adherence and quality of life. While EHL-FVIII treatment might lead to inhibitor development in some patients, non-factor replacement therapy carries thrombotic risks. Therefore, ongoing research and the generation of robust clinical evidence remain vital to guide the selection of optimal and cost-effective first-line therapies for hemophilia A patients.

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

Background

Emicizumab 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).

Objectives

Here, we describe pharmacokinetics (PKs), pharmacodynamics (PDs), and exploratory safety biomarkers in HAVEN 1 to 4.

Methods

Participants 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.

Results

Emicizumab 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).

Conclusion

In HAVEN 1 to 4, emicizumab demonstrated sustained PKs and PDs and improved coagulation parameters without affecting safety biomarkers.

Emicizumab prophylaxis in patients with acquired haemophilia A (GTH-AHA-EMI): an open-label, single-arm, multicentre, phase 2 study

BACKGROUND

Acquired haemophilia A is caused by neutralising autoantibodies against coagulation factor VIII, leading to severe bleeding. Standard treatment involves immunosuppressive therapy, which is associated with adverse events and mortality in the frail population of patients with acquired haemophilia A. This study investigated whether emicizumab, a factor VIIIa mimetic antibody, protects patients with acquired haemophilia A from bleeding and allows deferral of immunosuppression during the first 12 weeks after diagnosis.

METHODS

We report final results of an open-label, single-arm, phase 2 clinical trial. Adult patients with acquired haemophilia A from 16 haemophilia treatment centres in Germany and Austria were eligible if they had not previously received immunosuppression. Patients received emicizumab subcutaneously (6 and 3 mg/kg on days 1 and 2, 1·5 mg/kg weekly until week 12), but no immunosuppression. Follow-up was until week 24. The primary endpoint was the number of clinically relevant bleeds per patient-week until week 12. Emicizumab was considered effective if the mean bleeding rate was significantly below 0·15 bleeds per patient-week, the rate observed in a previous study of patients with acquired haemophilia A treated with bypassing agents and immunosuppression but no emicizumab. The study is registered with clinicaltrials.gov, NCT04188639 and is complete.

FINDINGS

Of 49 patients screened from March 25, 2021, to June 10, 2022, 47 were enrolled (23 women, 24 men). Median age was 76 years (IQR 66-80), 46 (98%) of 47 patients were White, median factor VIII activity was 1·4 IU/dL (0·3-5·6), and median inhibitor concentration was 11·4 Bethesda units per mL (3·9-42·7). Mean breakthrough bleeding rate was 0·04 bleeds per patient-week (upper 97·5% CI 0·06). 33 (70%) of 47 patients had no bleeding events, seven patients (15%) had one bleed, six patients (13%) had two bleeds, and one patient (2%) had three bleeds. Adverse events of grade 3 or worse included COVID-19 (n=2), acute kidney injury (n=2), and stroke (n=1). Four of 47 patients died, including two deaths related to bleeding, one from COVID-19, and one from cardiac arrest (none were judged as related to emicizumab).

INTERPRETATION

This study suggests that emicizumab prophylaxis prevents bleeding in patients with acquired haemophilia A and that immunosuppressive therapy can be deferred while patients are receiving this treatment. The low number of thromboembolic events, severe infections, and fatalities observed in this study are promising.

FUNDING

This study was supported by funding from Hoffman-La Roche.

The road to implementation of pharmacokinetic-guided dosing of factor replacement therapy in hemophilia and allied bleeding disorders. Identifying knowledge gaps by mapping barriers and facilitators

Clinical guidelines and expert groups recommend the use of pharmacokinetic (PK)-guided dosing of factor replacement therapy for the treatment of bleeding disorders, especially for patients with hemophilia. Although PK-guided dosing is increasingly applied, it is generally not considered standard clinical practice. The aim of this scoping review is to map barriers and facilitators for the implementation of PK-guided dosing in clinical practice and to identify knowledge gaps. A literature search was performed and 110 articles were included that describe PK-guided dosing in patients with bleeding disorders, mostly hemophilia A. We defined two overarching themes, efficacy and feasibility, and discuss five topics within each theme. For each topic, barriers, facilitators and knowledge gaps were described. Although consensus was found with regard to some topics, contradicting reports were found for others, especially with respect to the efficacy of PK-guided dosing. These contradictions highlight the need for future research to elucidate current ambiguities.

Mechanism-based pharmacokinetic and pharmacodynamic modeling for bispecific antibodies: challenges and opportunities

INTRODUCTION

Unlike conventional antibodies, bispecific antibodies (bsAbs) are engineered antibody- or antibody fragment-based molecules that can simultaneously recognize two different epitopes or antigens. Over the past decade, there has been an explosion of bsAbs being developed across therapeutic areas. Development of bsAbs presents unique challenges and mechanism-based pharmacokinetic/pharmacodynamic (PK/PD) modeling has served as a powerful tool to optimize their development and realize their clinical utility.

AREAS COVERED

In this review, the guiding principles and case examples of how fit-for-purpose, mechanism-based PK/PD models have been applied to answer questions commonly encountered in bsAb development are presented. Such models characterize the key pharmacological elements of bsAbs, and they can be utilized for model-informed drug development. We also include the discussion of challenges, knowledge gaps and future direction for such models.

EXPERT OPINION

Mechanistic PK/PD modeling is a powerful tool to support the development of bsAbs. These models can be extrapolated to predict treatment outcomes based on mechanisms of action (MoA) and clinical observations to form positive learn-and-confirm cycles during drug development, due to their abilities to differentiate system- and drug-specific parameters. Meanwhile, the models should keep being adapted according to novel drug design and MoA, providing continuous opportunities for model-informed drug development.

Clinical pharmacology of emicizumab for the treatment of hemophilia A

INTRODUCTION

Emicizumab is a humanized bispecific antibody approved for the routine prophylaxis of bleeding episodes in patients with hemophilia A (PwHA) regardless of the presence of factor VIII (FVIII) inhibitors. It mimics the cofactor function of missing activated FVIII by bridging activated factor IX and factor X, thereby restoring hemostasis.

AREAS COVERED

This review covers the clinical pharmacology of emicizumab and the translation of its pharmacokinetics (PK) and pharmacodynamics (PD) to clinical efficacy and safety. The PK of emicizumab is linear, with an approximately 1-month half-life. Once-weekly to every-4-week subcutaneous (SC) administrations maintain effective trough concentrations throughout the dosing intervals, associated with a coagulation potential analogous to that in patients with mild hemophilia A. In combination with activated prothrombin complex concentrate, and to a lesser extent with recombinant activated factor VII, emicizumab exerts a synergistic effect, whereas combination with FVIII may result in a non-additive coagulation potential at normal FVIII activity.

EXPERT OPINION

The translation of emicizumab PK/PD into clinical effects was demonstrated in several phase III studies, which showed remarkable bleed control and a favorable safety profile in PwHA. These emicizumab attributes, together with the convenience of use (infrequent SC injections), offer a novel paradigm for the management of PwHA.

DosEmi study protocol: a phase IV, multicentre, open-label, crossover study to evaluate non-inferiority of pharmacokinetic-guided reduced dosing compared with conventional dosing of emicizumab in people with haemophilia A

INTRODUCTION

Emicizumab effectively prevents bleeding in people with haemophilia A (PwHA), but is a burden for national healthcare budgets and consequently may limit access. According to the drug label, dosing of emicizumab is based on body weight with fixed intervals of 7, 14 or 28 days, which leads to mean plasma concentrations of 55 µg/mL (SD 15 µg/mL). However, a moderate variability of concentrations and a minimal effective concentration of 30 µg/mL have been suggested in studies. Therefore, a dose of emicizumab that targets a trough concentration of 30 µg/mL is hypothesised to be equally effective as conventional dosing in the prevention of bleeding.

METHODS AND ANALYSIS

We designed a phase IV, multicentre, open-label, crossover study to evaluate non-inferiority of bleed control of ≥6 months on conventional dosing in comparison to ≥6 months on dose intervention. This dose intervention consists of reducing the dose of emicizumab to target a trough concentrations of 30 µg/mL using individual pharmacokinetic (PK) parameters. Ninety-five PwHA aged >1 years who received conventional dosing of emicizumab for ≥12 months with good bleeding control during the last 6 months will be recruited from all Dutch haemophilia treatment centres. The study is powered to detect a clinically relevant decrease (risk difference) of 15% in the proportion of patients without treated bleeds during follow-up. Secondary endpoints are spontaneous joint or muscle bleeds, and annualised treated bleeding rates (using negative binomial regression). Cost-effectivity between conventional dosing and individualised PK-guided dosing of emicizumab will be compared.

ETHICS AND DISSEMINATION

The DosEmi study was approved by the Medical Ethics Review Committee NedMec of the University Medical Center of Utrecht, The Netherlands. Study results will be communicated through publications in international scientific journals and presentations at (inter)national conferences.

TRIAL REGISTRATION NUMBER

EUCTR2021-004039-10-NL at https://trialsearch.who.int.

PROTOCOL VERSION

V.4.1 on 28 October 2022 (DosEmi protocol_V4.1; NL81112.041.22).

Hemophilia A: Emicizumab monitoring and impact on coagulation testing

Hemophilia A is an X-linked recessive bleeding disorder characterized by absent or ineffective coagulation factor VIII, a condition that could result in a severe and potentially life-threatening bleed. Although the current standard of care involves prophylactic replacement therapy of factor VIII, the development of neutralizing anti-factor VIII alloantibody inhibitors often complicates such therapeutic treatment. Emicizumab (Hemlibra®), a novel recombinant therapeutic agent for patients with hemophilia A, is a humanized asymmetric bispecific IgG4 monoclonal antibody designed to mimic activated factor VIII by bridging factor IXa and factor X thus effecting hemostasis. Importantly, this drug eliminates the need for factor VIII and complications associated with inhibitor generation. Emicizumab has been approved for use in several countries including the United States and Japan for prophylaxis of bleeding episodes in hemophilia A with and without FVIII inhibitors. Therapy is also approved in the European Union for routine prophylaxis of bleeds in hemophilia A with inhibitors or severe hemophilia A without inhibitors. Unfortunately, emicizumab therapy presents unique challenges for routine and specialty coagulation tests currently used to monitor hemophilia A. In this review, hemophilia A is presented, the biochemistry of factor VIII is discussed, and the impact of the therapeutic agent emicizumab is highlighted.

Emicizumab in people with moderate or mild haemophilia A (HAVEN 6): a multicentre, open-label, single-arm, phase 3 study

BACKGROUND

Clinical trial data are scarce for the use of prophylaxis in people with non-severe haemophilia A. The HAVEN 6 study aims to assess safety and efficacy of emicizumab prophylaxis in people with non-severe haemophilia A without factor VIII (FVIII) inhibitors.

METHODS

HAVEN 6 is a multicentre, open-label, single-arm, phase 3 study taking place in 22 specialty clinics and hospitals in Europe, North America, and South Africa. Eligible participants were people of all ages weighing at least 3 kg with a diagnosis of moderate (FVIII activity ≥1%-≤5%) or mild (FVIII >5%-<40%) haemophilia A without FVIII inhibitors requiring prophylaxis as assessed by the treating physician. Participants received subcutaneous emicizumab 3 mg/kg of bodyweight once weekly for 4 weeks, followed by the participant's choice of maintenance dose: 1·5 mg/kg once weekly, 3 mg/kg every 2 weeks, or 6 mg/kg every 4 weeks. Safety was the primary objective of the study. Safety endpoints included adverse events, serious adverse events, and adverse events of special interest including thromboembolic events and thrombotic microangiopathies. The primary efficacy endpoint was the annualised bleed rate for treated bleeds. Analyses were done for participants who received at least one dose of emicizumab. This study is registered with ClinicalTrials.gov, number NCT04158648, and is active but not recruiting.

FINDINGS

Between Feb 10, 2020, and Aug 31, 2021, we assigned 73 people to treatment. 72 participants received at least one dose of emicizumab (51 moderate [71%]; 21 mild [29%]; 69 male [96%]; three female [4%]; and 61 White [85%]). Median age was 23·5 years (IQR 12·0-36·0); median follow-up was 55·6 weeks (IQR 52·3-61·6) weeks. At baseline, 24 participants (33%) had target joints and 37 (51%) were receiving FVIII prophylaxis. 60 participants (83%) had at least one adverse event; the most common adverse events were headache (in 12 participants [17%]), injection-site reaction (12 [17%]), and arthralgia (11 [15%]). 15 (21%) had at least one emicizumab-related adverse event; no adverse events led to treatment withdrawal, modification, or interruption. Eight participants (11%) reported ten serious adverse events in total, none emicizumab-related. There were no deaths or thrombotic microangiopathies. One participant had grade 1 thrombosed haemorrhoids (classified as a thromboembolic event), unrelated to emicizumab. The annualised bleed rate was 0·9 (95% CI 0·55-1·52) for treated bleeds. 48 participants (67%) had no treated bleeds. All-bleed annualised bleed rates were 10·1 (95% CI 6·93-14·76) from 24 weeks pre-study and 2·3 (1·67-3·12) on-study after a median follow-up of 55·6 weeks.

INTERPRETATION

These data show efficacy and a favourable safety profile of emicizumab in people with non-severe haemophilia A without FVIII inhibitors who warrant prophylaxis, confirming emicizumab as a valuable treatment option in this population.

FUNDING

F Hoffmann-La Roche.

Decrease in in vivo coagulant potential of emicizumab in a patient with hemophilia A and inhibitor complicated with infectious mononucleosis

Emicizumab prophylaxis significantly reduces bleeding episodes in patients with hemophilia A (PwHA). There is little information on coagulant potentials in emicizumab-treated PwHA with infection, however. We encountered an emicizumab-treated PwHA with inhibitor, complicated with Epstein-Barr virus-associated infectious mononucleosis (IM) in phase 1/2 study (ACE001JP/ACE002JP). Although it was a typical clinical course of IM, activated partial thromboplastin time was mildly prolonged but rotational thromboelastometry revealed severely impaired coagulant potential. The blood concentration of emicizumab decreased moderately in the low concentration range, resulting in an increased risk of bleeding and possibly leading to severe ileocecal bleeds requiring coil embolization. The blood concentrations of factors IX/X little decreased and antiemicizumab antibodies did not develop, however. After the influence by IM resolved, his coagulant potentials gradually recovered with the recovery of emicizumab concentration, and parameters by global coagulation assays improved. An IM case for emicizumab-treated PwHA may need to monitor using global coagulation assays.

A prospective, multicenter, open-label phase III study of emicizumab prophylaxis in patients with acquired hemophilia A

BACKGROUND

Emicizumab is a bispecific antibody that mimics the cofactor function of activated factor (F) VIII. It prevents bleeds in patients with congenital hemophilia A regardless of the inhibitor status; however, no prospective clinical studies have been conducted for emicizumab in patients with acquired hemophilia A (PwAHA).

OBJECTIVES

To describe the primary analysis results from a prospective, multicenter, open-label phase III study evaluating the efficacy, safety, and pharmacokinetics of emicizumab in PwAHA (AGEHA; JapicCTI-205151).

METHODS

Emicizumab was administered subcutaneously at 6 mg/kg on day 1 and 3 mg/kg on day 2, followed by 1.5 mg/kg once weekly from day 8 onward. Predefined criteria for the completion of dosing included FVIII activity of >50 IU/dL.

RESULTS

By the cutoff date (April 23, 2021), 12 patients on immunosuppressive therapy were enrolled, and 11 of them (91.7%) completed emicizumab treatment. The mean trough plasma emicizumab concentration rapidly reached a steady state (1 week), achieving the efficacious level that was established in patients with congenital hemophilia A (>30 μg/mL). Before first emicizumab administration, 7 patients (58.3%) experienced 77 major bleeds. During emicizumab treatment, no major bleeds occurred in any patient. Neither death due to bleeding or infection nor any study treatment-related serious adverse event was reported. One asymptomatic, nonserious deep vein thrombosis was discovered with no laboratory findings indicating any trend toward hypercoagulation.

CONCLUSION

These results suggest that emicizumab prophylaxis with the tested dosing regimen and completion criteria may have a favorable benefit-risk profile in PwAHA.

The efficacy of the entire-vial dosing of emicizumab: Real-world evidence on plasma concentrations, bleeds, and drug waste

Background

Prophylaxis with emicizumab provides effective bleeding protection in persons with hemophilia A (PwHA) but pressures healthcare budgets. The body weight-adjusted dosing at 7-, 14-, or 28-day intervals, according to the label, often mismatches the vial content. Entire-vial dosing resulted in therapeutic concentrations according to pharmacokinetic simulations and was introduced to avoid waste.

Objectives

The objective of this study was to evaluate the efficacy of entire-vial dosing of emicizumab by investigating real-world evidence of plasma concentrations, bleeds, and drug waste.

Methods

This is a single-center, observational study with PwHA receiving emicizumab in mg/kg doses according to label but dosing interval extrapolated to the nearest vial size. Patient characteristics and bleeds were compared 1 year before starting emicizumab and during emicizumab until January 2022. Concentrations were assessed at weeks 4, 12, and annually. The mean (95% CI) annualized bleed rates were compared by using negative binomial regression. Drug waste between label-based dosing and entire-vial dosing was compared.

Results

A total of 112 individuals (94% severe phenotype and 9% positive FVIII inhibitors) were followed for a median of 56 weeks (interquartile range [IQR] 52-68) before and 51 weeks (IQR 29-75) after starting emicizumab. The median emicizumab dose was 5.9 (IQR 5.5-6.2) mg/kg/4 wk with median concentrations of 63 (IQR 51-80) μg/mL. The annualized bleed rate of treated bleeds before emicizumab was 3.6 (95% CI 2.9-4.4) and was 0.8 (95% CI 0.6-1.1) during emicizumab (P < .001). Drug waste was reduced by 9%.

Conclusion

The entire-vial dosing of emicizumab is an attractive treatment option for PwHA leading to therapeutic plasma concentrations, good bleeding control, and drug waste avoidance.

Efficacy of emicizumab is maintained throughout dosing intervals for bleed prophylaxis

Background

Across the HAVEN clinical trial program, the efficacy of emicizumab has been demonstrated in children, adolescents, and adults with hemophilia A, with or without factor VIII inhibitors. After the 4-week loading dose period, emicizumab concentrations are expected to remain at levels that provide bleed protection throughout the entire dosing interval, regardless of the chosen maintenance dosing regimen, ie, weekly, every 2 weeks, or every 4 weeks.

Objectives

The objective of this study was to examine the timing of treated bleeds within the dosing intervals for emicizumab administered during the HAVEN 1 to 4 studies.

Methods

In this post hoc analysis, we pooled data from all the participants of the HAVEN 1 to 4 studies and analyzed the timing of treated bleeds in relation to the emicizumab dose.

Results

A total of 392 participants were included in this analysis, with a median (range) age of 28.0 years (1.1-77.0 years). Target joints were identified in 237 of 392 (60.5%) participants before the study entry. Overall, 211 of 392 (53.8%) participants experienced 907 treated bleeding events. The total mean (SD) annualized bleeding rate across the 4 studies was 1.6 (5.9). There was no evidence that bleeding events clustered on any 1 particular day in any dosing schedule from HAVEN 1 to 4 (P > .05 for all 3 treatment regimens).

Conclusion

Data from the HAVEN 1 to 4 trials show consistent bleed prevention within the dosing interval, regardless of the dosing regimen chosen. These findings provide further evidence of the sustained efficacy of emicizumab across all approved dosing regimens to reduce bleeding in people with hemophilia A.

Emicizumab dose up-titration in case of suboptimal bleeding control in people with haemophilia A

INTRODUCTION

Emicizumab promotes effective haemostasis in people with haemophilia A (PwHA). It is indicated for routine prophylaxis of bleeding episodes in PwHA with or without factor (F)VIII inhibitors.

AIM

To investigate the effect of emicizumab dose up-titration in PwHA with suboptimal bleeding control.

METHODS

Data from seven completed or ongoing phase III studies were pooled. Pharmacokinetics, pharmacodynamics and bleeding events were evaluated before and after dose up-titration. Adverse events (AEs) were compared between PwHA with and without dose up-titration.

RESULTS

Of 675 PwHA evaluable for the analysis, 24 (3.6%) had their maintenance dose up-titrated to 3 mg/kg once weekly (QW). Two participants had neutralising antibodies (nAbs) associated with decreased emicizumab exposure, and dose increase did not compensate for the effect of nAbs. In the other 22 participants, mean emicizumab steady-state trough concentrations increased from 44.0 to 86.2 μg/mL after up-titration. The median (interquartile range [IQR]) efficacy period prior to up-titration was 24.6 (24.0-32.0) weeks. The model-based annualised bleed rate for 'treated bleeds' and 'all bleeds' decreased by 70.2% and 72.9%, respectively, after a median (IQR) follow-up of 97.1 (48.4-123.3) weeks in the up-titration period. Incidences of injection-site reactions and serious AEs were higher in PwHA with up-titration; however, this was already observed in these participants before the dose up-titration. Overall, the safety profile appeared similar between PwHA with and without up-titration.

CONCLUSION

The dose up-titration to 3 mg/kg QW was well tolerated. Bleed control improved in most participants whose bleeding tendency was inadequately controlled during clinical trials.

Surgical outcomes in people with hemophilia A taking emicizumab prophylaxis: experience from the HAVEN 1-4 studies

Many people with hemophilia A (PwHA) undergo surgery in their lifetime, often because of complications of their disease. Emicizumab is the first bispecific monoclonal antibody prophylactic therapy for PwHA, and its efficacy and safety have been previously demonstrated; however, there is a need to build an evidence base on the management of PwHA on emicizumab undergoing surgery. Data from the HAVEN 1-4 phase 3 clinical trials were pooled to provide a summary of all minor and major surgeries in PwHA with or without factor VIII (FVIII) inhibitors who were receiving emicizumab prophylaxis. Overall, 233 surgeries were carried out during the HAVEN 1-4 trials: 215 minor surgeries (including minor dental and joint procedures, central venous access device placement or removal, and endoscopies) in 115 PwHA (64 with FVIII inhibitors) and 18 major surgeries (including arthroplasty and synovectomy) in 18 PwHA (10 with FVIII inhibitors). Perioperative hemostatic support was at the discretion of the treating physician. Overall, the median (interquartile range [IQR]) age was 33.5 (13.0-49.0) years and the median (IQR) emicizumab exposure time before surgery was 278.0 (177.0-431.0) days. Among the 215 minor surgeries, 141 (65.6%) were managed without additional prophylactic factor concentrate, and of those, 121 (85.8%) were not associated with a postoperative bleed. The majority (15 of 18 [83.3%]) of major surgeries were managed with additional prophylactic factor concentrate. Twelve (80.0%) of these 15 surgeries were associated with no intraoperative or postoperative bleeds. The data demonstrate that minor and major surgeries can be performed safely in PwHA receiving emicizumab prophylaxis. These trials are registered at www.clinicaltrials.gov as #NCT02622321, #NCT02795767, #NCT02847637, and #NCT03020160.

Emicizumab state-of-the-art update

Introduction

Emicizumab is a bispecific monoclonal antibody developed to address the unmet needs of clotting factor replacement therapy and has become the benchmark for optimal prophylaxis in managing patients with haemophilia A with inhibitors. We describe the emicizumab rollout and pharmacokinetic strategies and their use in paediatric patients.

Methods

The evolving real‐world experience in using emicizumab has confirmed its safety, efficacy and pharmacokinetic profile in paediatric, adolescent and adult patients receiving emicizumab at various prophylactic dosing regimens. The emicizumab current global rollout includes over 100 countries with 29 low to middle‐income countries accessing emicizumab through the World Federation of Haemophilia (WFH) Humanitarian Aid Program. The diversity of emicizumab dosing and pharmacokinetic tools such as the Calibra® and the WAPPS‐Hemo platforms make it possible to achieve prophylaxis goals in line with the WFH Haemophilia treatment guidelines recommendations, with minimal drug wastage. The emerging experience from long term clinical trials and long‐term real‐world follow‐up confirm the safety, efficacy, and pharmacokinetic profile of emicizumab in paediatric haemophilia A patients. A few questions, including inhibitor recurrence, concurrent use of emicizumab with various replacement therapies and inhibitor eradication, are being addressed through multiple ongoing clinical studies.

Conclusion

The current global rollout of emicizumab is remarkable, and versatile dosing regimens and evolving pharmacokinetic tools such as the Calibra® and WAPPS‐Hemo platforms make it a treatment choice available also for pharmacokinetic guided personalised treatment. Data from paediatric studies are consistent with those seen in adolescent and adult Haemophilia A.

Prophylactic emicizumab for hemophilia A in the Asia‐Pacific region: A randomized study (HAVEN 5)

Background

Methods

Results

Conclusion

Pharmacokinetics and Associated Efficacy of Emicizumab in Humans: A Systematic Review

INTRODUCTION

Emicizumab is an effective new treatment option for people with hemophilia A (PwHA). The approved dosing regimens are based on body weight, without the necessity for laboratory monitoring. This assumes a clear dose-concentration-response relationship, with acceptable variability due to factors other than body weight. To investigate this assumption, a systematic review on the pharmacokinetics (PK) and associated efficacy of emicizumab in humans was conducted.

METHODS

The EMBASE, Pubmed and CENTRAL databases were systematically searched to November 2020 to identify studies on the PK data of emicizumab in humans. Data on the study, population, PK and efficacy (annualized bleeding rate of treated [joint] bleeds) were extracted and synthesized, and exposure effects modeling was performed using non-linear least squares regression in a maximum effect (Emax) model.

RESULTS

The 15 included studies reported on data for 140 volunteers and 467 PwHA, including children (0 to <12 years) and adolescents and adults (≥12 years), both with and without factor VIII (FVIII) inhibitors. Emicizumab demonstrated dose-linear PK. The interindividual variability of trough concentrations was moderate (32%) and was similar across various subgroups, such as FVIII inhibitor status, age group and dosing interval. The control of bleeds did not further improve above emicizumab concentrations of 30 µg/mL, potentially enabling lower dosing in a substantial proportion of PwHA.

CONCLUSION

This review supports body weight-based dosing, although individualized monitoring of emicizumab concentrations may allow for more cost-effective dosing.

A Model-Based Framework to Inform the Dose Selection and Study Design of Emicizumab for Pediatric Patients With Hemophilia A

Emicizumab is a bispecific antibody mimicking the cofactor function of activated coagulation factor VIII to prevent bleeds in patients with hemophilia A. The dose selection for the first-in-child phase III study of emicizumab was addressed by pediatric pharmacokinetic prediction using an adult/adolescent population pharmacokinetic model developed in phase I-I/II studies. The model was modified to incorporate functions describing the age-dependent increase in body weight (BW) with or without clearance maturation to account for the differences in emicizumab pharmacokinetics between adults/adolescents and children. A minimal dose anticipated to achieve in children the same target efficacious exposure as for adults/adolescents was identified when considering BW and clearance maturation. It was the same BW-based dose as for adults/adolescents and was selected for the starting dose for the pediatric study. Whether considering clearance maturation or not in addition to BW led to uncertainty in the pediatric pharmacokinetic prediction and dose selection, which informed implementation of a dose-adapting scheme in the study design. Exposure matching to adults/adolescents was ultimately achieved in children with the starting dose, indicating that consideration of clearance maturation in addition to BW provided adequate pediatric pharmacokinetic predictions for emicizumab. This pharmacokinetic finding in conjunction with exposure-response information served as a basis for the efficacy demonstrated in children, avoiding a time-consuming process for exploring an optimal pediatric dose of emicizumab. This experience indicates that a model-based framework helped optimize the pediatric dose selection and study design, thereby streamlining the development process with extrapolation, of emicizumab for children.

Low immunogenicity of emicizumab in persons with haemophilia A

INTRODUCTION

Emicizumab is a humanised, bispecific monoclonal antibody mimicking the cofactor function of activated factor (F)VIII. It is indicated for routine prophylaxis of bleeding episodes in persons with haemophilia A (PwHA) with/without FVIII inhibitors.

AIM

To evaluate the development of anti-emicizumab antibodies and their impact on pharmacokinetics (PK), pharmacodynamics (PD), efficacy and safety in PwHA.

METHODS

Data from seven completed or ongoing phase 3 studies were pooled. The assessment of the immunogenicity profile of emicizumab included anti-drug antibody (ADA) measurement and the association of ADAs with PK, PD, bleeding events, and adverse events.

RESULTS

Of 668 PwHA evaluable for immunogenicity analysis, 34 (5.1%) developed ADAs after exposure to emicizumab. ADAs were transient in 14/34 PwHA (41.2%). ADAs were neutralising in vitro in 18/34 PwHA (52.9%) and associated with decreased emicizumab concentration in 4/668 evaluable PwHA (.6%); of those, one (.1%) discontinued emicizumab due to loss of efficacy. ADAs without decreased exposure did not impact emicizumab efficacy. The proportion of PwHA who had injection-site reactions (ISRs) was higher in ADA-positive PwHA (29.4% vs. 20.8%); however, the safety profile was similar between ADA-positive and ADA-negative PwHA, overall. No cases of anaphylaxis or hypersensitivity were reported in ADA-positive participants.

CONCLUSION

The immunogenicity risk of emicizumab in phase 3 studies was low. ADAs, including in vitro neutralising ADAs, were not associated with a change in safety profile. Routine surveillance is, therefore, not warranted; however, in cases where a loss and/or waning of efficacy are observed, prompt evaluation by a healthcare provider should be sought.

Determining the approximate factor VIII level of patients with severe haemophilia A on emicizumab using in vivo global haemostasis assays

INTRODUCTION

Emicizumab is a recombinant, humanized bispecific monoclonal antibody that mimics the function of factor VIII (FVIII) which results in a significant reduction in the annualized bleeding rate in patients with haemophilia A (HA), however, the degree with which emicizumab corrects the coagulation defect remains unclear. The objective of this study was to predict the approximate FVIII level in severe haemophilia A patients with inhibitors on emicizumab using global haemostasis assays.

MATERIALS AND METHODS

Patients with moderate and mild HA in the non-bleeding state and healthy controls had FVIII levels and thrombin generation assessed. Linear regression was utilized to model the FVIII levels as a function of the thrombin generation assay parameters and to make a calibration curve of FVIII levels versus peak thrombin and endogenous thrombin potential. Patients with severe haemophilia A with inhibitors on emicizumab had thrombin generation performed in the same manner and their peak thrombin and endogenous thrombin potential results were placed on the calibration curve to calculate their FVIII Equivalency of Emicizumab by Thrombin Generation (F8EmT).

RESULTS

All patients with severe HA with inhibitors on emicizumab had F8EmT >10%, suggesting they had been converted to a mild haemophilia phenotype. The patient's weight was inversely correlated to their F8EmT.

CONCLUSION

The results from this study suggest that the F8EmT in patients with severe HA on emicizumab falls within the range of mild haemophilia which is consistent with the data noted in the emicizumab clinical trials and in vivo studies in animals.

Emicizumab Dosing in Children and Adults with Hemophilia A: Simulating a User-Friendly and Cost-Efficient Regimen

BACKGROUND

 When emicizumab is dosed according to label, clinicians are obligated to discard or overdose medication due to discrepancies between calculated dose and vial content. The aim of this study was to compose a cost-efficient emicizumab maintenance dosing regimen using Monte Carlo simulation based on vial size, patient-friendly intervals, and patient characteristics, while striving for similar plasma concentrations as observed in clinical trials.

METHODS

 Monte Carlo simulations were used to investigate alternative dosing regimens in patients weighing 3 to 150 kg. Simulated regimens were targeted to achieve median emicizumab plasma concentrations at a steady state (C _av,ss) of 40 to 60 (90% range: 25-95) µg/mL. The cost-efficiency of the alternative dosing regimen was calculated in mg and costs saved per patient per year.

RESULTS

 The developed alternative dosing regimen achieved similar emicizumab C _av,ss levels compared with the registered dosing regimen with a median deviation of less than 2 µg/mL in 78% of the body-weight categories. A dose of 60 mg every 3 weeks was advised for children weighing 12 to 16 kg, while adults weighing 76 to 85 kg can receive 120 mg emicizumab every week. Compared with the registered weekly dosing of 1.5 mg/kg, alternative dosing saved €35,434 per year in children weighing between 12 and 16 kg. For patients weighing 76 to 85 kg, the median saving was €29,529 (range: €0-€59,057).

CONCLUSION

 This alternative maintenance dosing scheme-applicable in patients with hemophilia A receiving emicizumab prophylaxis-reduces financial costs, avoids medication spillage, and is patient-friendly without loss of efficacy.

Exposure-Bleeding Count Modeling of Emicizumab for the Prophylaxis of Bleeding in Persons with Hemophilia A with/Without Inhibitors Against Factor VIII

Background and Objective

Emicizumab is a monoclonal antibody that bridges activated coagulation factor IX and factor X to restore effective hemostasis in persons with hemophilia A. It is indicated for routine prophylaxis of bleeding episodes in persons with hemophilia A. The aim of the present study is to describe the exposure–response relationship between emicizumab concentrations and bleeding frequency, and to confirm adequate bleeding control of the investigated dosing regimens 1.5 mg/kg once weekly, 3 mg/kg every 2 weeks, and 6 mg/kg every 4 weeks.

Methods

Treated bleeding events were pooled from 445 persons with hemophilia A with and without inhibitors against factor VIII, participating in six clinical studies. Emicizumab concentrations were predicted using a previously developed population pharmacokinetic model. A count model was used to quantify the exposure–response relationship. These models were used to illustrate the relationship between emicizumab concentrations and cumulative count of bleeding over 1 year (annualized bleeding rate).

Results

The final exposure–response model, based on a generalized Poisson distribution and an inhibitory E_max relationship, adequately describes the relationship between daily emicizumab concentrations and daily bleed frequency. A significant effect of factor VIII prophylaxis among persons with hemophilia A without inhibitors was found. Annualized bleeding rate simulations show that the three emicizumab dosing regimens maintain the concentrations close to the plateau of the effect. At the average steady-state concentration across all regimens (53.5 µg/mL), the predicted mean annualized bleeding rate is 1.28, corresponding to a 94.0% reduction from baseline.

Conclusions

These results confirm that average emicizumab concentrations achieved with all three emicizumab dosing regimens provide adequate bleeding control.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01006-0.

Pharmacokinetics and Pharmacodynamics of Emicizumab in Persons with Hemophilia A with Factor VIII Inhibitors: HAVEN 1 Study

Emicizumab, a bispecific monoclonal antibody, bridges activated factor IX (FIXa) and FX, replacing the function of missing FVIIIa to restore effective hemostasis in persons with hemophilia A (PwHA). Here we assess pharmacokinetic (PK) and pharmacodynamic (PD) biomarkers in PwHA with FVIII inhibitors in the Phase III HAVEN 1 study (NCT02622321). Blood samples from 112 PwHA receiving 1.5 mg/kg once-weekly subcutaneous emicizumab were analyzed at central laboratories. Emicizumab concentrations for PK analysis were measured via validated immunoassay. PD effects were assessed using FVIII chromogenic activity assay containing human factors (Hyphen Biophen FVIII:C), and by FXIa-triggered thrombin generation (TG). Activated partial thromboplastin time (aPTT), prothrombin time (PT), antigen levels of FIX and FX, fibrinogen, D-dimer, and prothrombin fragment 1.2 (PF1.2) levels were determined. Emicizumab trough concentrations ≥ 50 µg/mL were maintained throughout the study. FVIII-like activity and TG (peak height) correlated with emicizumab concentrations and remained above 20 U/dL and 100 nM, respectively, with a weekly maintenance dose, theoretically converting persons with severe hemophilia A to a mild disease phenotype. aPTT was normalized at subtherapeutic concentrations of emicizumab. Plasma concentrations of target antigens FIX and FX were not significantly affected by emicizumab treatment; nor were fibrinogen, PT (international normalized ratio), D-dimer, or PF1.2. The PK profile of once-weekly emicizumab in HAVEN 1 provides sustained therapeutic plasma levels, consistent with population PK models. Both the PK profile and the PD and safety biomarkers are consistent with the established efficacy of emicizumab prophylaxis in PwHA with FVIII inhibitors.