Efficacy of Romiplostim in the Treatment of Chemotherapy Induced Thrombocytopenia (CIT) in a Patient with Mantle Cell Lymphoma

Chemotherapy-induced thrombocytopenia: literature review

Chemotherapy-induced thrombocytopenia (CIT) is a common condition that frequently results in reduced chemotherapy dosages, postponed treatment, bleeding, and unfavorable oncological outcomes. At present, there is no clear suggestions for preventing or treating CIT. Thrombopoietin (TPO) replacement therapy has been invented and used to treat CIT to promote the production of megakaryocytes and stimulate the formation of platelets. However, this treatment is limited to the risk of immunogenicity and cancer progression. Therefore, an unmet need exists for exploring alternatives to TPO to address the clinical issue of CIT. Application of appropriate therapeutic drugs may be due to understanding the potential mechanisms of CIT. Studies have shown that chemotherapy significantly affects various cells in bone marrow (BM) microenvironment, reduces their ability to support normal hematopoiesis, and may lead to BM damage, including CIT in cancer patients. This review focuses on the epidemiology and treatment of cancer patients with CIT. We also introduce some recent progress to understand the cellular and molecular mechanisms of chemotherapy inhibiting normal hematopoiesis and causing thrombocytopenia.

Efficacy and Immunomodulating Properties of Eltrombopag in Aplastic Anemia following Autologous Stem Cell Transplant: Case Report and Review of the Literature

Thrombopoietin receptor agonists (TPO-RA) are currently indicated for the treatment of chronic immune thrombocytopenia and relapsed refractory aplastic anemia. However, the off-label use of these drugs is more and more frequent, including in the setting of aplasia secondary to chemotherapy and hemopoietic stem cell transplant (SCT). Growing evidence suggests that mechanisms of action of TPO-RA go beyond the TPO-receptor stimulation and point at the immunomodulating properties of these drugs. Here, we present a case of prolonged bone marrow aplasia secondary to autologous SCT treated with eltrombopag. We describe the clinical efficacy and the immunomodulating effect of this drug on inflammatory cytokine profile and bone marrow histology. Furthermore, we provide a review of the most recent literature highlighting the efficacy and safety of TPO-RA after SCT and chemotherapy for hematologic conditions.

A Review of Romiplostim Mechanism of Action and Clinical Applicability

Thrombocytopenia results from a variety of conditions, including radiation, chemotherapy, autoimmune disease, bone marrow disorders, pathologic conditions associated with surgical procedures, hematopoietic stem cell transplant (HSCT), and hematologic disorders associated with severe aplastic anemia. Immune thrombocytopenia (ITP) is caused by immune reactions that accelerate destruction and reduce production of platelets. Thrombopoietin (TPO) is a critical component of platelet production pathways, and TPO receptor agonists (TPO-RAs) are important for the management of ITP by increasing platelet production and reducing the need for other treatments. Romiplostim is a TPO-RA approved for use in patients with ITP in the United States, European Union, Australia, and several countries in Africa and Asia, as well as for use in patients with refractory aplastic anemia in Japan and Korea. Romiplostim binds to and activates the TPO receptor on megakaryocyte precursors, thus promoting cell proliferation and viability, resulting in increased platelet production. Through this mechanism, romiplostim reduces the need for other treatments and decreases bleeding events in patients with thrombocytopenia. In addition to its efficacy in ITP, studies have shown that romiplostim is effective in improving platelet counts in various settings, thereby highlighting the versatility of romiplostim. The efficacy of romiplostim in such disorders is currently under investigation. Here, we review the structure, mechanism, pharmacokinetics, and pharmacodynamics of romiplostim. We also summarize the clinical evidence supporting its use in ITP and other disorders that involve thrombocytopenia, including chemotherapy-induced thrombocytopenia, aplastic anemia, acute radiation syndrome, perisurgical thrombocytopenia, post-HSCT thrombocytopenia, and liver disease.

Clinical challenges and promising therapies for chemotherapy-induced thrombocytopenia

Introduction: Chemotherapy-induced thrombocytop enia (CIT) is a common complication of cancer treatment causing chemotherapy delays, dose reductions, and treatment discontinuation, negatively impacting treatment outcomes and putting patients at risk for bleeding complications. There is no FDA-approved agent available to manage CIT.Areas covered: This article covers the diagnosis, definitions, and clinical challenges of CIT, and then focuses on the therapeutics developed to manage CIT. The first-generation thrombopoietic agents (oprelvekin and recombinant human thrombopoietins) are reviewed for critical background and context, followed by a detailed discussion of the data for the thrombopoietin receptor agonists (TPO-RAs) to manage CIT. Efficacy of TPO-RAs in treatment and prevention of CIT, as well as safety concerns such as the risk of thromboembolic complications, are reviewed in detail. For this review, a PubMed/MEDLINE literature search was undertaken for relevant articles published from 1995-2021.Expert opinion: After over two decades of drug development for CIT, multiple clinical trials and observational studies have found TPO-RAs, in particular romiplostim, to be safe and effective agents to manage patients with CIT, although no agent is yet FDA-approved for this indication. Active management of CIT with TPO-RAs is likely to improve oncologic outcomes, although additional data are needed. Phase 3 trials are ongoing.

A multicenter study of romiplostim for chemotherapy-induced thrombocytopenia in solid tumors and hematologic malignancies

Chemotherapy-induced thrombocytopenia (CIT) frequently complicates cancer treatment causing chemotherapy delays, dose reductions, and discontinuation. There is no FDA-approved agent available to manage CIT. This study retrospectively evaluated patients with CIT treated on institutional romiplostim treatment pathways at 4 U.S. centers. The primary outcome was achievement of a romiplostim response [median on-romiplostim platelet count (Plt) ≥75x109/L and ≥30x109/L above baseline]. Secondary outcomes included time to Plt≥100x109/L and rates of the following: Plt<100x109/L, Plt<75x109/L, Plt<50x109/L, thrombocytosis, chemotherapy dose reduction/treatment delay, platelet transfusion, bleeding, and thromboembolism. Multivariable regression was used to identify predictors of romiplostim non-response and compare weekly dosing with intracycle/intermittent dosing. 173 patients (153 solid tumor, 20 lymphoma or myeloma) were treated, with 170 (98%) receiving a median of 4 (range, 1-36) additional chemotherapy cycles on romiplostim. Romiplostim was effective in solid tumor patients: 71% of patients achieved a romiplostim response, 79% avoided chemotherapy dose reductions/treatment delays and 89% avoided platelet transfusions. Median per-patient Plt on romiplostim was significantly higher than baseline (116x109/L vs. 60x109/L, P<0.001). Bone marrow tumor invasion, prior pelvic irradiation, and prior temozolomide predicted romiplostim non-response. Bleeding rates were lower than historical CIT cohorts and thrombosis rates were not elevated. Weekly dosing was superior to intracycle dosing with higher response rates and less chemotherapy dose reductions/treatment delays (IRR 3.00, 95% CI 1.30-6.91, P=0.010) or bleeding (IRR 4.84, 95% CI 1.18-19.89, P=0.029). Blunted response (10% response rate) was seen in non-myeloid hematologic malignancy patients with bone marrow involvement. In conclusion, romiplostim was safe and effective for CIT in most solid tumor patients.

Repeated successful use of eltrombopag in chronic primary immune thrombocytopenia: description of an intriguing case

Thrombopoietin receptor agonists (TPO‐RAs) are used as effective alternative treatments in ITP patients unresponsive to first‐/second‐line therapies. TPO‐RAs can also be used to normalize platelet count to safely perform invasive procedures and chemotherapy, in case of malignancies. In few responsive patients, TPO‐RAs can be suspended maintaining a sustained response.

2-Arachidonoylglycerol enhances platelet formation from human megakaryoblasts

Platelets modulate vascular system integrity, and their loss is critical in haematological pathologies and after chemotherapy. Therefore, identification of molecules enhancing platelet production would be useful to counteract thrombocytopenia. We have previously shown that 2-arachidonoylglycerol (2-AG) acts as a true agonist of platelets, as well as it commits erythroid precursors toward the megakaryocytic lineage. Against this background, we sought to further interrogate the role of 2-AG in megakaryocyte/platelet physiology by investigating terminal differentiation, and subsequent thrombopoiesis. To this end, we used MEG-01 cells, a human megakaryoblastic cell line able to produce in vitro platelet-like particles. 2-AG increased the number of cells showing ruffled surface and enhanced surface expression of specific megakaryocyte/platelet surface antigens, typical hallmarks of terminal megakaryocytic differentiation and platelet production. Changes in cytoskeleton modeling also occurred in differentiated megakaryocytes and blebbing platelets. 2-AG acted by binding to CB1 and CB2 receptors, because specific antagonists reverted its effect. Platelets were split off from megakaryocytes and were functional: they contained the platelet-specific surface markers CD61 and CD49, whose levels increased following stimulation with a natural agonist like collagen. Given the importance of 2-AG for driving megakaryopoiesis and thrombopoiesis, not surprisingly we found that its hydrolytic enzymes were tightly controlled by classical inducers of megakaryocyte differentiation. In conclusion 2-AG, by triggering megakaryocyte maturation and platelet release, may have clinical efficacy to counteract thrombocytopenia-related diseases.

The biology of thrombopoietin and thrombopoietin receptor agonists

Thrombopoietin (TPO) is the major physiological regulator of platelet production. TPO binds the TPO receptor, activates JAK and STAT pathways, thus stimulating megakaryocyte growth and platelet production. There is no "sensor" of the platelet count; rather TPO is produced in the liver at a constant rate and cleared by TPO receptors on platelets. TPO levels are inversely proportional to the rate of platelet production. Early recombinant TPO molecules were potent stimulators of platelet production and increased platelets in patients with immune thrombocytopenia, chemotherapy-induced thrombocytopenia, myelodysplastic syndromes and platelet apheresis donors. Neutralizing antibodies formed against one recombinant protein and ended their development. A second generation of TPO receptor agonists, romiplostim and eltrombopag, has been developed. Romiplostim is an IgG heavy chain into which four TPO agonist peptides have been inserted. Eltrombopag is an oral small molecule. These activate the TPO receptor by different mechanisms to increase megakaryocyte growth and platelet production. After administration of either to healthy volunteers, there is a delay of 5 days before the platelet count rises and subsequently reaches a peak after 12-14 days. Both have been highly effective in treating ITP and hepatitis C thrombocytopenia. Studies in a wide variety of other thrombocytopenic conditions are underway.

Advances in megakaryocytopoiesis and thrombopoiesis: from bench to bedside

Megakaryocytopoiesis involves the commitment of haematopoietic stem cells, proliferation and terminal differentiation of megakaryocytic progenitors (MK-p) and maturation of megakaryocytes (MKs) to produce functional platelets. This complex process occurs in specialized niches in the bone marrow where MKs align adjacent to vascular endothelial cells, form proplatelet projections and release platelets into the circulation. Thrombopoietin (THPO, TPO) is the primary growth factor for the MK lineage and necessary at all stages of development. THPO is constitutively produced in the liver, and binds to MPL (c-Mpl) receptor on platelets and MKs. This activates a cascade of signalling molecules, which induce transcription factors to drive MK development and thrombopoiesis. Decreased turnover rate and platelet number result in increased levels of free THPO, which induces a concentration-dependent compensatory response of marrow-MKs to enhance platelet production. Newly developed thrombopoietic agents operating via MPL receptor facilitate platelet production in thrombocytopenic states, primarily immune thrombocytopenia. Other drugs are available for attenuating malignant thrombocytosis. Herein, we review the regulation of megakaryocytopoiesis and platelet production in normal and disease states, and the innovative drugs and therapeutic modalities to stimulate or decrease thrombopoiesis.

Simultaneous romiplostin, eltrombopag, and prednisone were successful in severe thrombocytopenia of Evans syndrome refractory to hydrocortisone, splenectomy, intravenous IgG, and rituximab

A 58-year-old woman presented with rheumatoid arthritis-associated Evans syndrome (simultaneous autoimmune hemolytic anemia and autoimmune thrombocytopenic purpura); she was treated unsuccessfully with steroids, romiplostin, rituximab, immunoglobulin G, and splenectomy. The platelet count responded to the combined use of prednisone, eltrombopag, and romiplostin. It may be more reasonable to use combined treatments than sequential monotherapies.

Thrombopoietin-receptor agonists

PURPOSE OF REVIEW

Thrombopoietin-receptor agonists (TPO-RAs) have been approved for use in immune thrombocytopenia (ITP) after showing safety and efficacy. There is increasing interest to expand the role of TPO-RAs, both in ITP as well as in other thrombocytopenic disorders.

RECENT FINDINGS

In ITP, more studies are providing evidence of TPO-RA efficacy and safety, as well as their applicability to various patient groups, including children. Use of TPO-RAs in hepatitis C has shown early success in allowing treatments in patients who would otherwise be excluded due to thrombocytopenia. Use in congenital thrombocytopenias has also shown early success. The use of TPO-RAs in myelodysplastic syndrome (MDS) is questionable after reports of increasing blasts and leukemic transformation, whereas in other chemotherapy-induced thrombocytopenias (C-ITs) reports are few. Bone marrow fibrosis remains an area of active study, although the data to date suggest this is seen in a small minority of patients, and is reversible and of questionable clinical relevance. Thrombotic complications are also an area of concern and need further close follow-up.

SUMMARY

The use of TPO-RAs continues to grow as more evidence of safety and efficacy is found. More studies are needed to determine their utility in other diseases as well as to better characterize adverse events observed to date.

Use of the novel thrombopoietin receptor-agonist romiplostim, in combination with steroids and immunoglobulins for the increase of platelets prior to splenectomy, in refractory immune thrombocytopenia: a case report

This case report describes a patient with relapsed primary immune thrombocytopenic purpura (ITP), in which splenectomy was not possible due to the persistence of a low platelet count despite treatment with corticosteroids, intravenous immunoglobulins (IVIG) and platelet transfusion treatment. As an attempt to increase platelet count prior to performing splenectomy, the thrombopoietin receptor agonist, romiplostim, was administered in combination with steroids and IVIG. A single administration of romiplostim was found to be markedly effective, allowing a rapid and notable platelet increase, required for a well tolerated splenectomy. This case confirms the potent activity of romiplostim in ITP, and indicates that patients with recurrent primary ITP who are unresponsive to conventional immunosuppressive therapy may benefit from the addition of a short course of romiplostim.

A rare hematological adverse event induced by bevacizumab: severe thrombocytopenia

BACKGROUND

Bevacizumab, a monoclonal antibody to vascular endothelial growth factor-A, is approved for the treatment of various malignancies, and its hematological toxicities are considered infrequent.

METHODS

A colorectal cancer patient receiving chemotherapy (5-fluorouracil and oxaliplatin) plus bevacizumab developed acute, severe thrombocytopenia. We postulated that this thrombocytopenia could be directly triggered by bevacizumab.

RESULTS

A man with stage IV colorectal cancer and synchronous liver metastasis had received 10 cycles of FOLFOX plus bevacizumab (5 mg/kg) without significant hematological toxicity. Due to thrombocytopenia, oxaliplatin was withdrawn after cycle 11. On cycle 12, shortly after bevacizumab infusion and before 5-fluorouracil infusion, the patient developed fever, lower limbs purpura, grade 1 proctorrhagia, and epistaxis. Platelets had decreased from 105,000/mm(3) to 3000/mm(3) within 1 hour after bevacizumab infusion. Flow cytometry identified platelet-associated immunoglobulins. Despite 2 apheresis-derived platelet transfusions, oral corticotherapy, and gamma globulin infusions, thrombocytopenia persisted, but was finally successfully treated with a peptibody thrombopoietin mimetic, which was introduced 28 days after the last bevacizumab infusion.

CONCLUSIONS

Clinicians should keep in mind that bevacizumab can induce acute and potentially severe immune-mediated thrombocytopenia.