Post-authorization pharmacovigilance for hemophilia in Europe and the USA: Independence and transparency are keys

Outcome measures in hemophilia: current and future perspectives

INTRODUCTION

Hemophilia can detrimentally affect patients' quality of life and likelihood of survival. In the evolving landscape of therapies, the therapeutic gain of each treatment must be understood to accurately position it in the therapeutic armamentarium. Accordingly, appropriate outcomes must be measured with appropriate tools.

AREAS COVERED

Our narrative review (PubMed search for 'hemophilia AND outcome' until June 2023), provides a compendium of outcome measures used in hemophilia clinical research. To define each outcome measure's relative value and applicability, several characteristics are critically discussed.

EXPERT OPINION

Bleeding assessment, first annual/annualized bleeding rate, remains central in evaluating the efficacy and safety of hemophilia treatments. As modern therapies improve clinical outcomes toward zero bleeding events, this endpoint may become less sensitive to detect differences between therapeutic approaches. Technological advancements necessitate the adaptation of outcome measures to address infrequent bleeding events, age-related comorbidities, and laboratory parameters with limited comparability after different treatments. Considerable effort has been dedicated to the development of tools that comprehensively assess coagulation, such as thrombin generation assays. Patient-reported outcome measures are gaining importance although limited by their subjectivity. A definitive set of research outcome measures remains elusive. Outcomes may need to be tailored to different therapeutic interventions.

Safety and efficacy of damoctocog alfa pegol prophylaxis in patients with severe haemophilia A: Results of an interventional, post-marketing study

INTRODUCTION

Damoctocog alfa pegol (BAY 94-9027, Jivi® ) is an approved extended half-life factor VIII (FVIII) for treatment of previously treated patients with haemophilia A aged ≥12 years. We report the final results of an interventional, post-marketing study of damoctocog alfa pegol prophylaxis in patients with severe haemophilia A.

METHODS

In this open-label, interventional, post-marketing, phase 4 trial (NCT04085458), previously FVIII-treated patients with severe haemophilia A aged ≥18 years received damoctocog alfa pegol for ≥100 exposure days (EDs). Patients initially received 45 IU/kg every 5 days (recommended) or 40 IU/kg twice-weekly. At Visit 3, patients' doses could be increased, or treatment frequency adapted. The primary endpoint was FVIII inhibitor development (titre ≥.6 Bethesda units). Secondary endpoints included anti-polyethylene glycol (PEG) antibody development, treatment-emergent adverse events (AEs) and annualized bleeding rate (ABR).

RESULTS

Overall, 36 patients were enrolled; 32 patients received treatment, of whom, 27 completed the study. No patients developed FVIII inhibitors; three tested transiently positive for low-titre anti-PEG antibodies without clinical relevance. Three patients reported study-drug-related AEs of mild or moderate intensity. Two patients discontinued the study due to AEs. No deaths occurred. Most patients (70%) were treated with E5D/E7D regimens. The median (Q1;Q3) total ABR (N = 30) was 3.0 (.0;9.0) pre-study and 1.8 (.7;5.9) during the study.

CONCLUSION

Damoctocog alfa pegol individualized prophylaxis regimens were well-tolerated with no immunogenicity concerns. ABRs improved following the switch from pre-study prophylaxis to damoctocog alfa pegol prophylaxis. These results support the favourable safety and efficacy profile of damoctocog alfa pegol prophylaxis.

Hemophilia treatment innovation: 50 years of progress and more to come

With the goal of emphasizing the striking advances that materialized in hemophilia care particularly in the last 10 years, the progress of knowledge that started from the 1970s will first be sketched as background. Subsequently, the unmet needs pertaining to therapeutic adherence and thus to prophylaxis effectiveness led to the availability of factor VIII and IX products with an extended plasma half-life as well as to emicizumab, the first nonfactor medicine for subcutaneous administration in patients with hemophilia A with or without inhibitor. The issue of a still lacking cure for the disease is approached by means of gene therapy, the first products of which were approved in 2022 for adults with both hemophilia types. Finally, views will be offered on further progress that is expected in the next few years and how patients and their care providers may make personalized choices among the wide array of therapeutic options.

From a bispecific monoclonal antibody to gene therapy: A new era in the treatment of hemophilia A

The treatment of hemophilia A has progressed amazingly in recent years. Emicizumab, a bispecific-humanized monoclonal antibody, is able to improve coagulation by bridging activated factor IX and factor X. Emicizumab is administered subcutaneously and much less often compared to factor VIII products. It has low immunogenicity, does not require dose adjustment, and can be administered regardless of the presence of factor VIII inhibitors. Thrombin generation assays but not factor VIII activity are indicated to guide and monitor the treatment. Emicizumab has enabled the conversion of patients with severe forms into patients with milder forms of hemophilia A. It has reduced the number of bleeding episodes compared to both on-demand and prophylactic substitution therapy and has an excellent safety profile. Gene therapy can elevate factor VIII plasma levels for many years after a single treatment course, could offer long-term protection from bleeding episodes, and minimize or eliminate the need for substitutive treatment with factor VIII concentrates. Gene therapy can provoke an immune response, manifested by an increase in common liver enzymes, that require immunotherapy. Long term monitoring is necessary to identify possible adverse effects. Future objectives are: the development of an ideal viral vector, the possibility of its re-administration, the use of gene therapy in hemophiliac children, and determining whether it can be successfully used to induce immune tolerance to factor VIII ceteri paribus. The future will determine the place of each type of treatment and group of patients for which it is indicated.

Progress, and prospects in the therapeutic armamentarium of persons with congenital hemophilia. Defining the place for liver-directed gene therapy

In persons with congenital severe hemophilia A (HA) living in high-income countries, twice weekly intravenous infusions of extended half-life (EHL) factor VIII (FVIII) products, or weekly/biweekly/monthly subcutaneous injections of emicizumab are the gold standard home treatments to grant days without hurdles and limitations. Once weekly/twice monthly infusions of EHL Factor IX (FIX) products achieve the same target in severe hemophilia B (HB). Gene therapy, which is likely to be licensed for clinical use within 1-2 years, embodies a shift beyond these standards. At an individual patient level, a single functional gene transfer leads to a > 10-yr almost full correction of the hemostatic defect in HB and to a sustained (3-6-yrs) expression of FVIII sufficient to discontinue exogenous clotting factor administrations. At the doses employed, the limited liver toxicity of systemically infused recombinant adeno-associated virus (rAAV) vectors is documented by long-term (12-15 yrs) follow-ups, and pre-existing high-titer neutralizing antibodies to the AAV5 vector are no longer an exclusion criterion for effective transgene expression with this vector. A safe durable treatment that converts a challenging illness to a phenotypically curable disease, allows persons to feel virtually free from the fears and the obligations of hemophilia for years/decades. Along with patient organizations and health care professionals, communicating to government authorities and reimbursement agencies the liberating potential of this substantial innovation, and disseminating across the Centers updated information on benefits and risks of this strategy, will align expectations of different stakeholders and establish the notion of a potentially lifelong cure of hemophilia.

Patient-centered pharmacovigilance: priority actions from the inherited bleeding disorders community

Pharmacovigilance, the science and practice of monitoring the effects of medicinals and their safety, is the responsibility of all stakeholders involved in the development, manufacture, regulation, distribution, prescription, and use of drugs and devices. The patient is the stakeholder most impacted by and the greatest source of information on safety issues. It is rare, however, for the patient to take a central role and exert leadership in the design and execution of pharmacovigilance. Patient organizations in the inherited bleeding disorders community are among the most established and empowered, particularly in the rare disorders. In this review, two of the largest bleeding disorders patient organizations, Hemophilia Federation of America (HFA) and National Hemophilia Foundation (NHF), offer insights into the priority actions required of all stakeholders to improve pharmacovigilance. The recent and ongoing increase in incidents raising safety concerns and a therapeutic landscape on the cusp of unprecedented expansion heighten the urgency of a recommitment to the primacy of patient safety and well-being in drug development and distribution.

Plain Language Summary

Patients at the center of product safety Every medical device and therapeutic product has potential benefits and harms. The pharmaceutical and biomedical companies that develop them must demonstrate that they are effective, and the safety risks are limited or manageable, for regulators to approve them for use and sale. After the product has been approved and people are using it in their daily lives, it is important to continue to collect information about any negative side effects or adverse events; this is called pharmacovigilance. Regulators, like the United States (US) Food and Drug Administration, the companies that sell and distribute the products, and healthcare professionals who prescribe them are all required to participate in collecting, reporting, analyzing, and communicating this information. The people with the most firsthand knowledge of the benefits and harms of the drug or device are the patients who use them. They have an important responsibility to learn how to recognize adverse events, how to report them, and to stay informed of any news about the product from the other partners in the pharmacovigilance network. Those partners have a crucial responsibility to provide clear, easy-to-understand information to patients about any new safety concerns that come to light. The community of people with inherited bleeding disorders has recently encountered problems with poor communication of product safety issues, prompting two large US patient organizations, National Hemophilia Foundation and Hemophilia Federation of America, to hold a Safety Summit with all the pharmacovigilance network partners. Together they developed recommendations to improve the collection and communication of information about product safety so that patients can make well-informed, timely decisions about their use of drugs and devices. This article presents these recommendations in the context of how pharmacovigilance is supposed to work and some of the challenges encountered by the community.

Updates on Novel Non-Replacement Drugs for Hemophilia

Over the last decade, the world of hemophilia has experienced an unprecedented therapeutic advance, thanks to the progress in bioengineering technologies, leading to the introduction of drugs with novel mechanisms of action based on restoring thrombin generation or coagulation factor VIII mimicking. Apart from the bispecific monoclonal antibody emicizumab, already approved for patients with severe hemophilia A with and without inhibitors, novel non-replacement drugs designed to reduce the treatment burden of patients with hemophilia A or B with or without inhibitors are undergoing evaluation in clinical trials. Thanks to their innovative mechanism of action and subcutaneous administration, these drugs promise to provide effective bleeding protection together with improved adherence and improve health-related quality of life for patients with hemophilia. On the other hand, rare thromboembolic events have been reported with some of these drugs and warrant continuous post-marketing surveillance and investigation of predisposing factors, although the overall safety profile of most of these drugs is good. Finally, new challenges need to be faced in the clinical and laboratory monitoring of the hemostatic status in patients treated with these innovative therapies. In this review, we provide an update on the available data on novel non-replacement drugs currently undergoing evaluation in clinical trials for patients with hemophilia.