Lusutrombopag: A Review in Thrombocytopenia in Patients with Chronic Liver Disease Prior to a Scheduled Procedure

Thrombopoietin, the Primary Regulator of Platelet Production: From Mythos to Logos, a Thirty-Year Journey

Thrombopoietin, the primary regulator of blood platelet production, was postulated to exist in 1958, but was only proven to exist when the cDNA for the hormone was cloned in 1994. Since its initial cloning and characterization, the hormone has revealed many surprises. For example, instead of acting as the postulated differentiation factor for platelet precursors, megakaryocytes, it is the most potent stimulator of megakaryocyte progenitor expansion known. Moreover, it also stimulates the survival, and in combination with stem cell factor leads to the expansion of hematopoietic stem cells. All of these growth-promoting activities have resulted in its clinical use in patients with thrombocytopenia and aplastic anemia, although the clinical development of the native molecule illustrated that "it's not wise to mess with mother nature", as a highly engineered version of the native hormone led to autoantibody formation and severe thrombocytopenia. Finally, another unexpected finding was the role of the thrombopoietin receptor in stem cell biology, including the development of myeloproliferative neoplasms, an important disorder of hematopoietic stem cells. Overall, the past 30 years of clinical and basic research has yielded many important insights, which are reviewed in this paper.

Minimum platelet count threshold before invasive procedures in cirrhosis: Evolution of the guidelines

Cirrhotic patients with severe thrombocytopenia are at increased risk of bleeding during invasive procedures. The need for preprocedural prophylaxis aimed at reducing the risk of bleeding in cirrhotic patients with thrombocytopenia who undergo scheduled procedures is assessed via the platelet count; however, establishing a minimum threshold considered safe is challenging. A platelet count ≥ 50000/μL is a frequent target, but levels vary by provider, procedure, and specific patient. Over the years, this value has changed several times according to the different guidelines proposed in the literature. According to the latest guidelines, many procedures can be performed at any level of platelet count, which should not necessarily be checked before the procedure. In this review, we aim to investigate and describe how the guidelines have evolved in recent years in the evaluation of the minimum platelet count threshold required to perform different invasive procedures, according to their bleeding risk.

A single course of lusutrombopag for multiple invasive procedures in cirrhosis-associated thrombocytopenia: A case series

RATIONALE

Lusutrombopag is a thrombopoietin receptor agonist which reduces the need for platelet transfusions before planned invasive procedures. A post hoc analysis of data from the registration trials observed that lusutrombopag-treated patients who achieved a platelet count > 50 × 109/L (responder patients) did so in a median of 6 days and the effect on platelet count lasted for nearly 3 weeks in total. Since patients with cirrhosis often require repeat invasive procedures, this kind of response-time trend sheds light on the possibility of placing more than one invasive procedure within a single course of lusutrombopag treatment.

PATIENT CONCERNS

Platelet transfusion represents the gold standard in this setting, but is limited by the risk of adverse events and limited availability.

DIAGNOSES

We describe our experience with lusutrombopag in three patients with severe cirrhosis-associated thrombocytopenia who underwent multiple invasive procedures after a single course of treatment.

INTERVENTIONS

The treatment schedule is lusutrombopag orally 3 mg/daily for 7 days and then a time window of 6 days (day 9-14) for the elective invasive procedure.

OUTCOMES

All three patients achieved good response to lusutrombopag treatment and were able to undergone more invasive procedures in the same course of treatment without need of platelet transfusion.

LESSONS

our preliminary experience supports the safety and the effectiveness of lusutrombopag in patients with severe cirrhosis-associated thrombocytopenia who underwent multiple invasive elective procedures after a single course.

An updated evaluation of avatrombopag for the treatment of chronic immune thrombocytopenia

INTRODUCTION

Multiple agents are available for the management of chronic immune thrombocytopenia (ITP), including thrombopoietin-receptor agonists (TPO-RAs), rituximab, and fostamatinib. Although TPO-RAs are often selected as treatments for chronic ITP, when choosing between the TPO-RAs, clinicians must balance safety profile, dosing restrictions, and method of administration incorporating patient preference.

AREAS COVERED

We provide an overview of the thrombopoietin receptor agonists with a particular focus on avatrombopag, the newest agent in this class. In phase II and III clinical trials, avatrombopag was shown to offer durable improvement in platelet counts. We also include recent real-world evidence describing avatrombopag effectiveness in patients with poor response to prior treatments (including other TPO-RAs).

EXPERT OPINION

Compared with other TPO-RAs used to treat ITP, avatrombopag offers practical oral dosing with a single pill strength, does not require long-term dietary restrictions, and has no warning for hepatotoxicity. It is frequently effective after use of other TPO-RAs in ITP. The primary downside with avatrombopag use at present is the lack of longer-term safety data in ITP that presently exists for romiplostim and eltrombopag.

The efficacy and safety of thrombopoietin receptor agonists in patients with chronic liver disease undergoing elective procedures: a systematic review and meta-analysis

Thrombopoietin receptor agonists (TPO-RAs) can mitigate preprocedural thrombocytopenia in patients with chronic liver disease (CLD) however their effects on procedural outcomes is unclear. In this meta-analysis, we aimed to better define the efficacy, thrombotic risk and bleeding mitigation associated with the use of preoperative TPO-RAs in patients with CLD. We performed a systematic review and meta-analysis of randomized placebo-controlled clinical trials to assess the use of preprocedural TPO-RAs in patients with CLD, searching MEDLINE, EMBASE and the Cochrane library database. Six publications comprising eight randomized trials (1229 patients; 717 received TPO-RAs, 512 received placebo) and three unique TPO-RAs were retrieved. The majority of the included procedures were endoscopic. TPO-RAs were significantly more likely to result in a preoperative platelet count greater than 50 x 109/L (72.1% vs 15.6%, RR 4.8, 95% CI 3.6-6.4 p < .00001. NNT 1.8) and reduced the incidence of platelet transfusions (22.5% vs 67.8%, RR 0.33, 95% CI 0.3-0.4 p < .00001. NNT 2.2). Total periprocedural bleeding was decreased in patients who received TPO-RAs (11.6% vs 15.6%, RR 0.64, 95% CI 0.5-0.9 p = .01. NNT 24.7) and there was no increase in the rate of thrombosis (2.2% vs 1.8% RR 1.25, 95% CI 0.6-2.9 p = .60. NNH 211.1). In patients with CLD the use of preprocedural TPO-RAs resulted in significant increased platelet counts, and decreased the incidence of platelet transfusions as compared to placebo. TPO use likewise decreased the incidence of total periprocedural bleeding without increasing the rate of thrombosis.

An evaluation of avatrombopag for the treatment of thrombocytopenia

Introduction: The thrombopoietin receptor agonists (TPO-RAs) are a class of drugs that have been FDA-approved for immune thrombocytopenia (ITP), periprocedural thrombocytopenia in patients with chronic liver disease (CLD), aplastic anemia, and thrombocytopenia associated with antiviral treatment of hepatitis C. Avatrombopag is a TPO-RA that is currently FDA-approved for ITP and periprocedural thrombocytopenia in patients with CLD and is currently undergoing evaluation for chemotherapy-induced thrombocytopenia (CIT) in an international phase III clinical trial. Areas covered: This paper summarizes the chemistry, pharmacodynamics, and pharmacokinetics of avatrombopag. In addition, the authors review the efficacy and safety of avatrombopag, covering clinical trials in patients with ITP and in patients with CLD scheduled to undergo a procedure. Expert opinion: Avatrombopag has demonstrated efficacy in patients with ITP. With its low side-effect burden, absence of hepatotoxicity, ease of use as an oral medication, and lack of food-drug interactions, avatrombopag is a favorable option for ITP, though there is a lack of long-term safety data. In periprocedural thrombocytopenia in patients with CLD, avatrombopag is comparable to lusutrombopag, another TPO-RA. Finally, the results of the study of avatrombopag in CIT are eagerly awaited, as there are no currently approved medications for this indication in the USA.

Treating ITP: What are the options in the era of new guidelines and new drugs?

Primary immune thrombocytopenia (ITP) is an autoimmune disease characterized by isolated thrombocytopenia. Treating ITP may be challenging since different treatment modalities are available. While choosing the suitable option for every patient, a physician should take into account both patient's medical characteristics and wishes. The first line treatment options include: corticosteroids, intravenous immunoglobulins and intravenous anti-D immunoglobulin. Second line treatment options comprise medical (thrombopoietin receptor agonists, rituximab, fostamatinib, azathioprine, cyclophosphamide, cyclosporin A, hydroxychloroquine, mycophenolate mofetil, danazol, dapsone, vinca-alcaloids) and surgical (splenectomy) approach. However, there are some treatment gaps which remain uncovered with existing treatment modalities. Therefore, development of novel therapeutic strategies is required. The aim of this review is to provide an illustrative overview of novel treatments for adult ITP.