Daratumumab in rituximab-refractory autoimmune haemolytic anaemia

2025 update on clinical trials in immune thrombocytopenia

Although the development and regulatory approval of the thrombopoietin receptor agonists revolutionized aspects of the immune thrombocytopenia (ITP) treatment landscape over the past two decades, there remain many areas of high unmet need. Therefore, a number of investigational and repurposed agents are currently undergoing clinical development in ITP. In a departure from historical trials, which largely focused on the indefinite treatment of persistent or chronic ITP, ongoing trials run the gamut of disease phases, and include novel agents being evaluated in early phases of the disease to attempt to modify the disease course. Many agents in development target disease pathophysiologic mechanisms not previously targeted by agents in current use, including platelet autoantibody recycling, B-cell maturation and differentiation, long-lived plasma cells, and the complement system, among others. These agents represent promising treatment options for patients with otherwise refractory disease or who are intolerant of currently available therapies. Additionally, with our increasing understanding of the diverse immune mechanisms at play in ITP, the expansion of the therapeutic armamentarium to include agents targeting diverse pathophysiologic mechanisms may allow a more personalized therapeutic selection in the future. This manuscript provides an up-to-date, in-depth overview of recently completed and ongoing clinical trials in ITP.

Therapeutic Approach to Autoimmune Neurologic Disorders

OBJECTIVE

Autoimmune neurologic disorders encompass a broad category of diseases characterized by immune system attack of the central, peripheral, or autonomic nervous systems. This article provides information on both acute and maintenance immunotherapy used to treat autoimmune neurologic disorders as well as a review of symptomatic management and special considerations when caring for patients with these diseases.

LATEST DEVELOPMENTS

Over the past 20 years, more than 50 antibodies have been identified and associated with autoimmune neurologic disorders. Although advances in diagnostic testing have allowed for more rapid diagnosis, the therapeutic approach to these disorders has largely continued to rely on expert opinion, case series, and case reports. With US Food and Drug Administration (FDA) approval of biologic agents to treat neuromyelitis optica spectrum disorder (NMOSD) and myasthenia gravis as well as ongoing clinical trials for the treatment of autoimmune encephalitis, the landscape of immunotherapy options continues to expand. Consideration of the unique pathogenesis of individual autoimmune neurologic disorders as well as the mechanism of action of the diverse range of treatment options can help guide treatment decisions today while evidence from clinical trials informs new therapeutics in the future.

ESSENTIAL POINTS

Recognizing patients who have a clinical history and examination findings concerning for autoimmune neurologic disorders and conducting a thorough and directed imaging and laboratory evaluation aimed at ruling out mimics, identifying specific autoimmune syndromes, and screening for factors that may have an impact on immunotherapy choices early in the clinical course are essential to providing optimal care for these patients. Providers must consider immunotherapy, symptomatic treatment, and a multidisciplinary approach that addresses each patient's unique needs when treating patients with autoimmune neurologic disorders.

Efficacy of thrombopoietin receptor agonists versus rituximab in non-responsive immune thrombocytopenia-A single centre retrospective analysis

Management of immune thrombocytopenia (ITP) beyond initial glucocorticoid therapy is challenging. In this retrospective single-centre cohort study, we compared all ITP patients relapsed or non-responsive to glucocorticoid therapy treated with either continuous TPO-RAs (n = 35) or rituximab induction (n = 20) between 2015 and 2022. While both groups showed high initial complete response rates (CR, 68.6 vs. 80.0%, ns), the overall rate of progression to the next therapy was higher after time-limited rituximab (75.0 vs. 42.9%), resulting in a lower relapse-free survival (median 16.6 vs. 25.8 months, log-rank; p < 0.05). We conclude that both treatments show similar initial efficacy and their ideal duration of therapy warrants further investigation.

Daratumumab monotherapy in refractory warm autoimmune hemolytic anemia and cold agglutinin disease

ABSTRACT

Autoimmune hemolytic anemia (AIHA) is a rare autoantibody-mediated disease. For steroid and/or rituximab-refractory AIHA, there is no consensus on optimal treatment. Daratumumab, a monoclonal antibody targeting CD38, could be beneficial by suppression of CD38+ plasma cells and thus autoantibody secretion. In addition, because CD38 is also expressed by activated T cells, daratumumab may also act via immunomodulatory effects. We evaluated the efficacy and safety of daratumumab monotherapy in an international retrospective study including 19 adult patients with heavily pretreated refractory AIHA. In warm AIHA (wAIHA, n = 12), overall response was 50% with a median response duration of 5.5 months (range, 2-12), including ongoing response in 2 patients after 6 and 12 months. Of 6 nonresponders, 4 had Evans syndrome. In cold AIHA (cAIHA, n = 7) overall hemoglobin (Hb) response was 57%, with ongoing response in 3 of 7 patients. One additional patient with nonanemic cAIHA was treated for severe acrocyanosis and reached a clinical acrocyanosis response as well as a Hb increase. Of 6 patients with cAIHA with acrocyanosis, 4 had improved symptoms after daratumumab treatment. In 2 patients with wAIHA treated with daratumumab, in whom we prospectively collected blood samples, we found complete CD38+ T-cell depletion after daratumumab, as well as altered T-cell subset differentiation and a severely diminished capacity for cell activation and proliferation. Reappearance of CD38+ T cells coincided with disease relapse in 1 patient. In conclusion, our data show that daratumumab therapy may be a treatment option for refractory AIHA. The observed immunomodulatory effects that may contribute to the clinical response deserve further exploration.

Emerging approaches to induce immune tolerance to therapeutic proteins

Immunogenicity affects the safety and efficacy of therapeutic proteins. This review is focused on approaches for inducing immunological tolerance to circumvent the immunogenicity of therapeutic proteins in the clinic. The few immune tolerance strategies that are used in the clinic tend to be inefficient and expensive and typically involve global immunosuppression, putting patients at risk of infections. The hallmark of a desirable immune tolerance regimen is the specific alleviation of immune responses to the therapeutic protein. In the past decade, proof-of-principle studies have demonstrated that emerging technologies, including nanoparticle-based delivery of immunomodulators, cellular targeting and depletion, cellular engineering, gene therapy, and gene editing, can be leveraged to promote tolerance to therapeutic proteins. We discuss the potential of these novel approaches and the barriers that need to be overcome for translation into the clinic.

Novel therapeutics and future directions for refractory immune thrombocytopenia

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder affecting approximately 1 in 20 000 people. While most patients with ITP are successfully managed with the current set of standard and approved therapeutics, patients who cannot be adequately managed with these therapies, considered to have refractory ITP, are not uncommon. Therefore, there remains an ongoing need for novel therapeutics and drug development in ITP. Several agents exploiting novel targets and mechanisms in ITP are presently under clinical development, with trials primarily recruiting heavily pretreated patients and those with otherwise refractory disease. Such agents include the neonatal Fc receptor antagonist efgartigimod, the Bruton tyrosine kinase inhibitor rilzabrutinib, the complement inhibitors sutimlimab and iptacopan and anti-CD38 monoclonal antibodies such as daratumumab and mezagitamab, among others. Each of these agents exploits therapeutic targets or other aspects of ITP pathophysiology currently not targeted by the existing approved agents (thrombopoietin receptor agonists and fostamatinib). This manuscript offers an in-depth review of the current available data for novel therapeutics in ITP presently undergoing phase 2 or 3 studies in patients with heavily pretreated or refractory ITP. It additionally highlights the future directions for drug development in refractory ITP, including discussion of innovative clinical trial designs, health-related quality of life as an indispensable clinical trial end-point and balancing potential toxicities of drugs with their potential benefits in a bleeding disorder in which few patients suffer life-threatening bleeding.

The Role of the Spleen and the Place of Splenectomy in Autoimmune Hemolytic Anemia-A Review of Current Knowledge

Autoimmune hemolytic anemia (AIHA) is a rare, very heterogeneous, and sometimes life-threatening acquired hematologic disease characterized by increased red blood cell (RBC) destruction by autoantibodies (autoAbs), either with or without complement involvement. Recent studies have shown that the involvement of T- and B-cell dysregulation and an imbalance of T-helper 2 (Th2) and Th17 phenotypes play major roles in the pathogenesis of AIHA. AIHA can be primary (idiopathic) but is more often secondary, triggered by infections or drug use or as a part of other diseases. As the location of origin of autoAbs and the location of autoAb-mediated RBC clearance, as well as the location of extramedullary hematopoiesis, the spleen is crucially involved in all the steps of AIHA pathobiology. Splenectomy, which was the established second-line therapeutic option in corticosteroid-resistant AIHA patients for decades, has become less common due to increasing knowledge of immunopathogenesis and the introduction of targeted therapy. This article provides a comprehensive overview of current knowledge regarding the place of the spleen in the immunological background of AIHA and the rapidly growing spectrum of novel therapeutic approaches. Furthermore, this review emphasizes the still-existing expediency of laparoscopic splenectomy with appropriate perioperative thromboprophylaxis and the prevention of infection as a safe and reliable therapeutic option in the context of the limited availability of rituximab and other novel therapies.

Antibody based therapeutics for autoimmune hemolytic anemia

INTRODUCTION

Autoimmune hemolytic anemia (AIHA) treatment has been revolutionized by the introduction of target therapies, mainly monoclonal antibodies (MoAbs).

AREAS COVERED

The anti-CD20 rituximab, which targets Ab production by B-cells, induces 80% of response in warm-type AIHA (wAIHA) and 50-60% in cold agglutinin disease (CAD). Other B-cell targeting MoAbs including ianalumab, povetacicept, and obexelimab are under active study. The anti-CD38 MoAb daratumumab has been used in several reports to target long-lived plasma-cells responsible for AIHA relapse, being effective even in multi-refractory cases. Anti-complement MoAbs will soon change the treatment paradigm in CAD; the anti-C1s sutimlimab rapidly increased Hb in more than 80% of the cases. Finally, MoAbs inhibiting the neonatal Fc receptor (FcRn), such as nipocalimab, can reduce the half-life of the pathogenic autoAbs, representing a promising treatment for wAIHA.

EXPERT OPINION

MoAbs offer the potential to improve efficacy by reducing toxicity. However, there is a huge need for clinical trials exploring response duration rather than short-term efficacy. Complement inhibitors and anti-FcRns do not abrogate autoAb production and are being developed as long-term therapies. Thus, the combination of B-cell/plasma cell targeting drugs deserves to be explored. On the other hand, their rapid efficacy should be exploited for the acute AIHA phase.

[Autoimmune haemolytic anaemia]

Autoimmune haemolytic anaemias (AIHA) are acquired haematological disorders caused by increased peripheral erythrocyte destruction mediated by autoantibodies against erythrocyte antigens. They classified according to aetiology into primary and secondary, and according to the type of antibody and reaction temperature into AIHA due to warm antibodies (w-AIHA) and AIHA due to cold antibodies (c-AIHA). The mainstay of management in w-AIHA remains glucocorticoid therapy, and the early addition of rituximab has shown good results in recent studies. Primary c-AIHA is mainly treated with rituximab, alone or in combination with chemotherapy. New drugs such as Syk inhibitors, anti-FcRn Ig and complement inhibitors are in advanced development and will expand the therapeutic arsenal, especially in refractory or relapsed cases.

Targeted treatment of autoimmune cytopenias in primary immunodeficiencies

Primary Immunodeficiencies (PID) are a group of rare congenital disorders of the immune system. Autoimmune cytopenia (AIC) represents the most common autoimmune manifestation in PID patients. Treatment of AIC in PID patients can be really challenging, since they are often chronic, relapsing and refractory to first line therapies, thus requiring a broad variety of alternative therapeutic options. Moreover, immunosuppression should be fine balanced considering the increased susceptibility to infections in these patients. Specific therapeutic guidelines for AIC in PID patients are lacking. Treatment choice should be guided by the underlying disease. The study of the pathogenic mechanisms involved in the genesis of AIC in PID and our growing ability to define the molecular underpinnings of immune dysregulation has paved the way for the development of novel targeted treatments. Ideally, targeted therapy is directed against an overexpressed or overactive gene product or substitutes a defective protein, restoring the impaired pathway. Actually, the molecular diagnosis or a specific drug is not always available. However, defining the category of PID or the immunological phenotype can help to choose a semi-targeted therapy directed towards the suspected pathogenic mechanism. In this review we overview all the therapeutic interventions available for AIC in PID patients, according to different immunologic targets. In particular, we focus on T and/or B cells targeting therapies. To support decision making in the future, prospective studies to define treatment response and predicting/stratifying biomarkers for patients with AIC and PID are needed.

Development of New Drugs for Autoimmune Hemolytic Anemia

Autoimmune hemolytic anemia (AIHA) is a rare disorder characterized by the autoantibody-mediated destruction of red blood cells, and treatments for it still remain challenging. Traditional first-line immunosuppressive therapy, which includes corticosteroids and rituximab, is associated with adverse effects as well as treatment failures, and relapses are common. Subsequent lines of therapy are associated with higher rates of toxicity, and some patients remain refractory to currently available treatments. Novel therapies have become promising for this vulnerable population. In this review, we will discuss the mechanism of action, existing data, and ongoing clinical trials of current novel therapies for AIHA, including B-cell-directed therapy, phagocytosis inhibition, plasma cell-directed therapy, and complement inhibition.