Real-life experience of lusutrombopag for cirrhotic patients with low platelet counts being prepared for invasive procedures

The evolving knowledge on primary hemostasis in patients with cirrhosis: A comprehensive review

Patients with cirrhosis develop complex alterations in primary hemostasis that include both hypocoagulable and hypercoagulable features. This includes thrombocytopenia, multiple alterations of platelet function, and increased plasma levels of von Willebrand factor. Contrary to the historical view that platelet dysfunction in cirrhosis might be responsible for an increased bleeding tendency, the current theory posits a rebalanced hemostasis in patients with cirrhosis. Severe thrombocytopenia is not indicative of the bleeding risk in patients undergoing invasive procedures and does not dictate per se the need for pre-procedural prophylaxis. A more comprehensive and individualized risk assessment should combine hemostatic impairment, the severity of decompensation and systemic inflammation, and the presence of additional factors that may impair platelet function, such as acute kidney injury and bacterial infections. Although there are multiple, complex alterations of platelet function in cirrhosis, their net effect is not yet fully understood. More investigations evaluating the association between alterations of platelet function and bleeding/thrombosis may improve risk stratification in patients with decompensated cirrhosis. Besides hemostasis, the assessment of von Willebrand factor Ag and ADP-induced, whole-blood platelet aggregation normalized by platelet count (VITRO score and PLT ratio) are promising biomarkers to predict the risk of hepatic decompensation and survival in both compensated and decompensated patients. Further investigations into the in vivo interplay between platelets, circulating blood elements, and endothelial cells may help advance our understanding of cirrhotic coagulopathy. Here, we review the complex changes in platelets and primary hemostasis in cirrhosis and their potential clinical implications.

A study on prevention of bleeding complications using lusutrombopag for safe RFA in patients with hepatocellular carcinoma with low platelet counts: prospective observational study

BACKGROUND

Platelet (PLT) transfusion was the most practical way to increase patients' PLT counts before invasive hepatic procedures such as radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC). A novel drug that raises the PLT count by acting on the thrombopoietin receptor has recently become available.

METHODS

Lusutrombopag 3 mg was administered daily for 7 days to patients who underwent RFA for liver tumors with low PLT counts (< 50,000 PLT µL^- 1). We collected demographic data concerning the patients' liver function and PLT counts.

RESULTS

Lusutrombopag was administered to 91 patients, with a median age of 71 years (range 51-86). Forty-two patients had hepatitis C, 12 had hepatitis B, 21 had alcoholic liver disease, 11 had nonalcoholic steatohepatitis, and five had other diseases. The median Child-Pugh score was 7 (range 5-11). Thirty-seven patients had stage I tumors, 41 had Stage II, 12 had stage III, and one had stage IV. PLT count was elevated from 4.4 × 10⁴ ± 1.4 × 10⁴ to 8.6 × 10⁴ ± 2.5 × 10⁴ PLT µL^- 1. Lusutrombopag administration prevented PLT transfusions in 84/91 patients (92%). No patient had bleeding complications after RFA. One had portal thrombosis after lusutrombopag administration. Patients who achieved PLT counts of > 50,000 PLT µL^- 1 had higher PLT counts before lusutrombopag administration. The degree of splenomegaly did not affect the rate of PLT count elevation. There was no specific adverse effect by administrating lusutrombopag for patients with PLT counts of around 50,000 µL^- 1 but > 50,000 µL^- 1.

CONCLUSIONS

Lusutrombopag administration before RFA was effective and seemed to be relatively safe for hepatocellular carcinoma patients with low PLT counts.

TRIAL REGISTRATION

This study was approved by Japanese Red Cross Medical Center Institutional Reseach Comittie (#862, 07/03/2016), and was registered in a publically accessible primary register (#UMIN000046629, registered date: 14/01/2022).

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.

Thrombocytopenia in chronic liver disease: Physiopathology and new therapeutic strategies before invasive procedures

Chronic liver disease is characterized by several hematological derangements resulting in a complex and barely rebalanced haemostatic environment. Thrombocytopenia is the most common abnormality observed in these patients and recent advances have led to researchers focus the attention on the multifactorial origin of thrombocytopenia and on the key role of thrombopoietin (TPO) in its physiopathology. Severe thrombocytopenia (platelet count < 50000/μL) complicates the management of patients with chronic liver disease by increasing the potential risk of bleeding for invasive procedures, which may be therefore delayed or canceled even if lifesaving. In the very last years, the development of new drugs which exceed the limits of the current standard of care (platelet transfusions, either immediately before or during the procedure) paves the way to a new scenario in the management of this population of patients. Novel agents, such as the TPO-receptor agonists avatrombopag and lusutrombopag, have been developed in order to increase platelet production as an alternative to platelet transfusions. These agents have demonstrated a good profile in terms of efficacy and safety and will hopefully allow reducing limitations and risks associated with platelet transfusion, without any delay in scheduled interventions. Altogether, it is expected that patients with chronic liver disease will be able to face invasive procedures with one more string in their bow.

Lusutrombopag has slightly stronger effects on patients with mild thrombocytopenia compared with those with severe thrombocytopenia; a multicenter propensity score matching study

BACKGROUND

Lusutrombopag effectively increases platelet count in patients with severe thrombocytopenia. However, no multicenter studies analyzing the effects of Lusutrombopag on patients with mild thrombocytopenia (platelet count > 50,000/µL) have been performed. We here aimed to clarify the efficacy of Lusutrombopag on these patients by unifying background factors by propensity score matching.

METHODS

A total of 139 patients with thrombocytopenia were enrolled, and matched for age, sex, etiology, disease, treatment, liver function, renal function, peripheral blood count, and spleen index. The primary endpoint was to compare the increase in platelet count from baseline between the high-platelet group (> 50,000/µL) and the low-platelet group (< 50,000/µL) after Lusutrombopag treatment, using propensity score matching. The secondary endpoint was to clarify platelet transfusion avoidance rate and adverse events, moreover to identify independent predictors associated with the increase in platelet count.

RESULTS

The mean increase in platelet count was 67,000/μL vs. 48,000/μL in all patients (high- vs. low-platelet group, p = 0.024), and 64,000 /μL vs. 48,000 /μL (p = 0.12) after propensity score matching. The increase in platelet count and the platelet transfusion avoidance rate tended to be higher in the high-platelet group. There was no significant difference about adverse events. Predictors associated with an increase in platelet count were sex, estimated glomerular filtration rate, and spleen index by multivariate analysis.

CONCLUSION

Lusutrombopag has a little stronger effect in patients with mild thrombocytopenia than those with severe thrombocytopenia and showed a more substantial effect in patients with impaired renal function and small spleen.

Treatment algorithm for thrombocytopenia in patients with chronic liver disease undergoing planned invasive procedures

Thrombocytopenia is highly prevalent in patients with chronic liver disease (CLD) and these patients often require invasive procedures that carry a risk of bleeding. To prevent bleeding, guidelines recommend increasing platelet counts in patients with CLD who have thrombocytopenia and are planned to undergo invasive procedures. There are currently two options to increase platelet counts in patients in this setting: platelet transfusion or thrombopoietin receptor agonists (TPORAs). Several treatment algorithms have been developed in the US to help physicians choose the best course of treatment for each patient; however, to date, no such algorithm has been proposed in other countries, where the choice of treatment has been based on each physician's judgment and experience. Here, we discuss the pathogenesis and treatment of thrombocytopenia in patients with CLD, we review and present current evidence of the efficacy of TPORAs for the treatment of thrombocytopenia in patients with CLD, and we present our expert opinion on a Japanese treatment algorithm for thrombocytopenia in patients with CLD who are planned to undergo invasive procedures. This algorithm aims to provide guidance for optimal decision making in the selection of TPORA therapy or platelet transfusion based on the latest evidence and according to actual clinical practice.

Impact of Platelet Count on Perioperative Bleeding in Patients With Cirrhosis Undergoing Surgical Treatments of Liver Cancer

In patients with cirrhosis with severe thrombocytopenia (platelet count [PC] <50 × 10⁹/L) and undergoing invasive procedures, it is common clinical practice to increase the PC with platelet transfusions or thrombopoietin receptor agonists to reduce the risk of major periprocedural bleeding. The aim of our study was to investigate the association between native PC and perioperative bleeding in patients with cirrhosis undergoing surgical procedures for the treatment of hepatocellular carcinoma (HCC). We retrospectively evaluated 996 patients with cirrhosis between 1996 and 2018 who underwent surgical treatments of HCC by liver resection (LR) or radiofrequency ablation (RFA) without prophylactic platelet transfusions. Patients were allocated to the following three groups based on PC: high (>100 × 10⁹/L), intermediate (51‐100 × 10⁹/L), and low (≤50 × 10⁹/L). PC was also analyzed as a continuous covariate on multivariable analysis. The primary endpoint was major perioperative bleeding. The overall event rate of major perioperative bleeding was 8.9% and was not found to differ significantly between the high, intermediate, and low platelet groups (8.1% vs. 10.2% vs. 10.8%, P = 0.48). On multivariable analysis, greater age, aspartate aminotransferase, lower hemoglobin, and treatment with LR (vs. RFA) were found to be significant independent predictors of major perioperative bleeding, with associations with disease etiology and year of surgery also observed. After adjusting for these factors, the association between PC and major perioperative bleeding remained nonsignificant. Conclusion: Major perioperative bleeding was not significantly associated with PC in patients with cirrhosis undergoing surgical treatment of HCC, even when their PC was <50 × 10⁹/L. With the limit of a retrospective analysis, our data do not support the recommendation of increasing PC in patients with severe thrombocytopenia in order to decrease their perioperative bleeding risk.

Quantitative systems pharmacology model of thrombopoiesis and platelet life-cycle, and its application to thrombocytopenia based on chronic liver disease

Platelets are produced by hematopoietic stem cells via megakaryocytes in the bone marrow and play a critical role in hemostasis. The aim of this study was to develop a new platelet model based on the thrombopoiesis and platelet life-cycle by a quantitative systems pharmacology modeling approach, which could describe changes in platelet count profiles in platelet-related diseases and drug intervention. The proposed platelet model consists of 44 components. The model was applied to thrombopoiesis of a thrombopoietin receptor agonist, lusutrombopag. It could well describe the observed platelet count profiles after administration of lusutrombopag for both healthy subjects and patients with chronic liver disease and thrombocytopenia. This model should be useful for understanding the disease progression of platelet-related conditions, such as thrombocytopenia and for predicting platelet count profiles in various disease situations related to platelets and drug administration in drug development.

Assessing the periprocedural magnitude of platelet count change in response to lusutrombopag

BACKGROUND & AIMS

Despite limitations, platelet transfusion has been used to minimise bleeding risk in patients with thrombocytopaenia. Lusutrombopag is an oral, thrombopoietin receptor agonist approved for treatment of thrombocytopaenia associated with chronic liver disease in patients undergoing planned invasive procedures. This post-hoc analysis assessed the magnitude of platelet count change based on the integrated per-protocol population from 2 similar phase III multicentre, randomised, double-blind, placebo-controlled trials.

METHODS

Adults with chronic liver disease-induced thrombocytopaenia and platelet count <50 (× 109/L) received lusutrombopag 3 mg or placebo ≤7 days before invasive procedure scheduled 9-14 days after randomisation. Platelet transfusion was required per protocol if the platelet count remained <50 no more than 2 days before the planned invasive procedure. Post-hoc analysis included: proportion of patients with platelet count ≥50, ≥1.5-fold increase, and a doubling of platelet count; maximum and maximum change in platelet count; and platelet count time course.

RESULTS

Platelet count ≥50, a platelet count increase ≥1.5-fold, and at least a doubling in platelet count were achieved in 88.3%, 86.9%, and 52.6% of patients in the lusutrombopag group (n = 137) vs. 58.6%, 32.3%, and 6.0% of patients in the placebo group (n = 133), respectively. In the lusutrombopag group, median maximum platelet count across baseline platelet counts of <30, ≥30 to <40, and ≥40 was 46, 76, and 87, respectively. Median maximum change in platelet count by baseline platelet count was +24, +42, and +40, respectively. Patients who received lusutrombopag without platelet transfusion achieved a median platelet count ≥50 for 3 weeks.

CONCLUSIONS

Patients treated with lusutrombopag experienced a clinically relevant response in platelet count for a substantial duration of time.

LAY SUMMARY

Patients with low platelet counts caused by chronic liver disease may not receive planned invasive procedures or surgeries because of an increased risk of bleeding. Lusutrombopag has previously demonstrated efficacy in raising platelet counts and is approved to treat chronic liver disease patients with low platelet counts in advance of a planned surgery. Physicians need to understand more clearly what to expect in terms of platelet count change when using lusutrombopag; this integrated analysis provides data to help guide its clinical application.

Efficacy of Lusutrombopag for Thrombocytopenia in Patients with Chronic Liver Disease Scheduled to Undergo Invasive Procedures

Objective Lusutrombopag is a thrombopoietin receptor agonist that improves thrombocytopenia in patients with chronic liver disease scheduled to undergo invasive procedures. However, information on the efficacy of repeated lusutrombopag treatment and factors associated with the treatment is scarce. We analyzed the efficacy of repeated lusutrombopag treatment and the factors associated with a response to lusutrombopag. Methods Thirty-nine patients with chronic liver disease who received lusutrombopag treatment before undergoing invasive procedures were enrolled in this retrospective study. Of the 39 patients, 10 received lusutrombopag treatment multiple times for a total of 53 regimens of lusutrombopag treatment. Changes in platelet counts, the effects of repeated lusutrombopag treatment, and factors associated with response to lusutrombopag were analyzed. Results The median platelet count increased significantly from 4.5×10⁴/μL before lusutrombopag treatment to 7.2×10⁴/μL before the invasive procedure (p<0.01), and patients undergoing 49 of the 53 (92%) treatment regimens succeeded in undergoing invasive procedures without needing platelet transfusions. In patients who received lusutrombopag treatment repeatedly, the median platelet count significantly increased following the second administration of lusutrombopag, and the effects of lusutrombopag were similar between the first and second administration. A multivariate analysis identified the absence of diabetes mellitus (odds ratio, 5.56 for presence; p=0.04) as a significant and independent predictor of a response to lusutrombopag. Conclusion Lusutrombopag treatment significantly increased platelet counts in patients with chronic liver disease, making it possible to receive invasive procedures. The treatment produced identical effects when it was repeated. The efficacy of lusutrombopag might be decreased in patients with diabetes mellitus.

Lusutrombopag is effective and safe in patients with chronic liver disease and severe thrombocytopenia: a multicenter retrospective study

Background

Chronic liver disease (CLD) is often complicated by severe thrombocytopenia (platelet count < 50,000/µL). Platelet transfusion has been a gold standard for increasing the platelet count to prevent hemorrhagic events in such patients. Lusutrombopag, a thrombopoietin receptor agonist, can increase the platelet count in such patients when invasive procedures are scheduled. Former studies on lusutrombopag included patients with a platelet count of > 50,000/µL at baseline: the proportions of patients who did not require platelet transfusion were 84–96%, which might be overestimated.

Methods

The efficacy and safety of lusutrombopag were retrospectively investigated in CLD patients with platelet count of < 50,000/µL, a criterion for platelet transfusion, in real-world settings. We examined the proportion of patients who did not require platelet transfusion in 31 CLD patients, which exceeded a minimum required sample size (21 patients) calculated by 80% power at a significance level of 5%. Lusutrombopag, 3 mg once daily, was administered 8–18 days before scheduled invasive procedures.

Results

Among 31 patients who received lusutrombopag, 23 patients (74.2%) patients showed a platelet count of ≥ 50,000/µL (Group A) and did not require platelet transfusion. The remaining 8 patients (25.8%) did not reached platelet ≥ 50,000/µL (Group B). The means of platelet increase were 38,000/µL and 12,000/µL in groups A and B, respectively. A low platelet count at baseline was a characteristic of patients in group B. Among 13 patients who repeatedly used lusutrombopag, lusutrombopag significantly increased the platelet count as the initial treatment. When all repeated uses of lusutrombopag were counted among these 13 patients, platelet transfusion was not required in 82.1% (23/28) of treatments. Although one patient showed portal thrombosis after lusutrombopag treatment, the thrombosis was disappeared by anticoagulant treatment for 35 days. The degree of platelet increase with lusutrombopag was larger than that in their previous platelet transfusion.

Conclusions

The proportion of patients who did not require platelet transfusion was 74.2%, which is smaller than that in former studies which included CLD patients with a platelet count of > 50,000/µL. However, lusutrombopag is effective and safe for CLD patients with a platelet count of < 50,000/µL.

Thrombopoietin Receptor Agonists in Patients with Chronic Liver Disease

Thrombocytopenia is one of the most common hematologic complications in cirrhosis. Despite limited data linking platelet count and bleeding risk in patients with cirrhosis, the use of platelets transfusions for invasive procedures has been a common practice. Recently, thrombopoietin (TPO) receptor agonists have been approved for use in patients with chronic liver disease (CLD) undergoing invasive procedures. The aim of this study was to review current literature on bleeding risk in patients with cirrhosis and the use of platelet transfusions and TPO receptor agonists in the context of invasive procedures. PubMed search was conducted to find articles relating to cirrhosis, thrombocytopenia, and new novel treatments for this condition. Search terms included CLD, cirrhosis, thrombocytopenia, bleeding, thrombosis, coagulopathy, hemostasis, and TPO receptor agonists. Romiplostim, eltrombopag, avatrombopag, and lusutrombopag are approved TPO receptor agonists, with avatrombopag and lusutrombopag specifically approved for use in patients with CLD undergoing invasive procedures. In patients with platelet counts < 50,000/mm³, avatrombopag and lusutrombopag increased the platelet counts above this threshold in the majority of treated patients and reduced the frequency of platelet transfusions. At the approved doses, incidence of thrombosis was not increased and therapies were well tolerated. Studies were not powered to assess whether risk of bleeding complications was reduced and the fundamental question of whether correction of thrombocytopenia is warranted in patients undergoing invasive procedures remains unanswered. The use of TPO receptor agonists has resulted in less requirement for platelet transfusions. In patients with cirrhosis undergoing invasive procedures for whom platelet transfusion is planned, TPO receptor agonists are an alternative and avoid the risks associated with transfusions. However, there is need for a thoughtful approach to manage bleeding risk in patients with cirrhosis undergoing procedures, with the consideration of a comprehensive hemostatic profile, the severity of portal hypertension, and the complexity of the invasive procedure to guide decisions regarding transfusions or use of TPO receptor agonists.

Thrombopoietin-receptor agonists in perioperative treatment of patients with chronic liver disease

Thrombocytopenia is a multifactorial disorder that is common in patients with chronic liver disease (CLD), leading to challenging perioperative planning. As thrombocytopenia in CLD is associated with thrombopoietin (TPO) deficiency, the use of TPO-receptor agonists (TPO-RAs) to increase platelet counts is a promising approach. This has led to the development of various TPO-RAs, including romiplostim, eltrombopag, avatrombopag, and lusutrombopag. Of these, only avatrombopag and lusutrombopag are approved by the United States Food and Drug Administration for the perioperative treatment of thrombocytopenia in patients with CLD. Platelet transfusion is commonly used for the clinical management of thrombocytopenia in patients with CLD undergoing invasive procedures. However, the limitations and possible risks of transfusion, including short duration of efficacy, development of antiplatelet antibodies, risk of infections and such complications as transfusion-related acute lung injury or circulatory overload, and possibility of refractoriness, limit its use. Moreover, there is no consensus among guidelines as to the platelet count at which transfusions are indicated. Results from studies using TPO-RAs perioperatively in patients with thrombocytopenia and CLD are promising and provide an alternative to platelet transfusions in the pre- and post-operative setting. These TPO-RAs are the subject of this review, with focus on their use in the perioperative setting in patients with thrombocytopenia, associated supporting clinical trials, efficacy and safety data, and their use with respect to platelet transfusions.

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

Lusutrombopag (Mulpleta^®), an orally bioavailable, small molecule thrombopoietin receptor agonist, is approved for the treatment of thrombocytopenia in adult patients with chronic liver disease who are scheduled to undergo a procedure. In placebo-controlled phase 3 clinical trials, lusutrombopag significantly increased the proportion of patients who did not require a platelet transfusion prior to the procedure or rescue therapy for bleeding up to 7 days after the scheduled procedure. Lusutrombopag also significantly increased the proportion of patients who were responders (i.e. had a platelet count ≥ 50 × 10⁹/L and an increase of ≥ 20 × 10⁹/L from baseline) compared with placebo. Lusutrombopag is well tolerated, with headache being the most common adverse reaction in lusutrombopag recipients in clinical trials. Thus, lusutrombopag represents a promising emerging therapeutic option for the treatment of thrombocytopenia in adult patients with chronic liver disease who are scheduled to undergo a procedure.

Safety and effectiveness of lusutrombopag in Japanese chronic liver disease patients with thrombocytopenia undergoing invasive procedures: Interim results of a postmarketing surveillance

AIM

Lusutrombopag is approved for the treatment of thrombocytopenia in chronic liver disease patients undergoing invasive procedures. This real-world surveillance assesses the safety and effectiveness of lusutrombopag in Japan.

METHODS

This ongoing, multicenter, prospective, real-world surveillance is collecting data from case report forms between October 2016 and May 2021. Interim data up to September 2018 were used to evaluate safety (adverse events and adverse drug reactions [ADRs]) and effectiveness (proportion of patients avoiding preoperative platelet transfusion and change in platelet count from baseline).

RESULTS

The safety analysis set included 331 patients. The mean baseline platelet count was 46.2 ± 13.7 × 10⁹ /L. Of 377 invasive procedures, radiofrequency ablation (110 procedures, 29.2%) was the most frequent. The mean time from starting lusutrombopag treatment to invasive procedure was 12.3 days. Incidences of serious adverse events and ADRs were 8.76% and 3.32%, respectively. Six cases (1.81%) of portal vein thrombosis were considered serious adverse events; of these, four cases (1.21%) were classified as serious ADRs. Of 300 patients who underwent an invasive procedure (excluding those with platelet transfusion refractoriness), 282 (94.0%) avoided preoperative platelet transfusion. In patients with platelet measurements before and after lusutrombopag administration who did not undergo platelet transfusion, the mean maximum change in platelet count from baseline was 41.7 ± 31.4 × 10⁹ /L (range, -6 to 276; n = 286). All patients receiving second (n = 20) and third (n = 1) treatments avoided preoperative platelet transfusion without developing any ADRs.

CONCLUSIONS

This real-world surveillance further supports the safety and effectiveness of lusutrombopag in patients with chronic liver disease undergoing invasive procedures.

New Small Molecule Drugs for Thrombocytopenia: Chemical, Pharmacological, and Therapeutic Use Considerations

This review provides details about three small molecules that were recently approved by the FDA for the treatment of thrombocytopenia. The new treatments include lusutrombopag, avatrombopag, and fostamatinib. The first two drugs are orally active thrombopoietin receptor (TPO-R) agonists which are FDA-approved for the treatment of thrombocytopenia in adult patients with chronic liver disease who are scheduled to undergo a procedure. Fostamatinib is orally active prodrug that, after activation, becomes spleen tyrosine kinase (SYK) inhibitor. Fostamatinib is currently used to treat chronic and refractory immune thrombocytopenia in patients who have had insufficient response to previous treatment. Chemical structures, available dosage forms, recommended dosing, pharmacokinetics, results of toxicity studies in animals, most frequent adverse effects, significant outcomes of the corresponding clinical trials, and their use in specific patient populations are thoroughly described. Described also is a comparative summary of the different aspects of five currently available therapies targeting TPO-R or SYK for the treatment of thrombocytopenia.