Thrombopoietin receptor agonist in chemotherapy-induced thrombocytopenia

Thrombopoietin receptor agonist antibody for treating chemotherapy-induced thrombocytopenia

BACKGROUND

Thrombocytopenia is a common complication in cancer patients undergoing chemotherapy. Chemotherapy-induced thrombocytopenia (CIT) leads to dose reduction and treatment delays, lowering chemotherapy efficacy and survival rate. Thus, rapid recovery and continuous maintenance of platelet count during chemotherapy cycles are crucial in patients with CIT. Thrombopoietin (TPO) and its receptor, myeloid proliferative leukemia (MPL) protein, play a major role in platelet production. Although several MPL agonists have been developed to regulate thrombopoiesis, none have been approved for the management of CIT due to concerns regarding efficacy or safety. Therefore, the development of effective MPL agonists for treating CIT needs to be further expanded.

METHODS

Anti-MPL antibodies were selected from the human combinatorial antibody phage libraries using phage display. We identified 2R13 as the most active clone among the binding antibodies via cell proliferation assay using BaF3/MPL cells. The effect of 2R13 on megakaryocyte differentiation was evaluated in peripheral blood CD34⁺ cells by analyzing megakaryocyte-specific differentiation markers (CD41a⁺ and CD42b⁺) and DNA ploidy using flow cytometry. The 2R13-induced platelet production was examined in 8- to 10-week-old wild-type BALB/c female mice and a thrombocytopenia mouse model established by intraperitoneal injection of 5-fluorouracil (150 mg/kg). The platelet counts were monitored twice a week over 14 days post-initiation of treatment with a single injection of 2R13, or recombinant human TPO (rhTPO) for seven consecutive days.

RESULTS

We found that 2R13 specifically interacted with MPL and activated its signaling pathways. 2R13 stimulated megakaryocyte differentiation, evidenced by increasing the proportion of high-ploidy (≥ 8N) megakaryocytes in peripheral blood-CD34⁺ cells. The platelet count was increased by a single injection of 2R13 for up to 14 days. Injection of 5-fluorouracil considerably reduced the platelet count by day 4, which was recovered by 2R13. The platelets produced by 2R13 sustained a higher count than that achieved using seven consecutive injections of rhTPO.

CONCLUSIONS

Our findings suggest that 2R13 is a promising therapeutic agent for CIT treatment.

Feasibility and Toxicity of Interval-Compressed Chemotherapy in Asian Children and Young Adults with Sarcoma

Twelve Asian patients with sarcoma received interval-compressed (ic-) chemotherapy scheduled every 14 days with a regimen of vincristine (2 mg/m²), doxorubicin (75 mg/m²), and cyclophosphamide (1200-2200 mg/m²) (VDC) alternating with a regimen of ifosfamide (9000 mg/m²) and etoposide (500 mg/m²) (IE), with filgrastim (5-10 mcg/kg/day) between cycles. Carboplatin (800 mg/m²) was added for CIC-rearranged sarcoma. The patients were treated with 129 cycles of ic-VDC/IE with a median interval of 19 days (interquartile range [IQR], 15-24 days. Median nadirs (IQR) were neutrophil count, 134 (30-396) × 10⁶/L at day 11 (10-12), recovery by day 15 (14-17) and platelet count, 35 (23-83) × 10⁹/L at day 11 (10-13), recovery by day 17 (14-21). Fever and bacteremia were observed in 36% and 8% of cycles, respectively. The diagnoses were Ewing sarcoma (6), rhabdomyosarcoma (3), myoepithelial carcinoma (1), malignant peripheral nerve sheath tumor (1), and CIC-DUX4 Sarcoma (1). Seven of the nine patients with measurable tumors responded (one CR and six PR). Interval-compressed chemotherapy is feasible in the treatment of Asian children and young adults with sarcomas.

Avatrombopag is effective in patients with chemoradiotherapy-induced aplastic anemia: a single-center, retrospective study

Aplastic anemia (AA) secondary to radiotherapy presents a difficult situation in the treatment of both the malignant tumor and AA itself. We aimed to evaluate the efficacy of avatrombopag (AVA), a thrombopoietin receptor agonist, in patients with AA secondary to chemoradiotherapy. In this retrospective study, patients with malignant tumors who were diagnosed with AA after radiotherapy and chemotherapy and accepted AVA between September 2020 and October 2021 at Peking Union Medical College Hospital were selected. A total of 34 patients were enrolled, including 13 (38.2%) men, with a median age of 60 (20-71) years. At a median of 8 (6-18) months of follow-up, the overall response rates (ORRs) at 1, 3, and 6 months were 32.4%, 55.9%, and 58.8%, respectively, and the complete response rates (CRRs) were 5.9%, 14.7%, and 23.5%, respectively. The median time to respond was 3 (1-6) months. In total, 15.0% of patients relapsed during follow-up, but no clonal evolution was noticed. Mild side effects were observed in 17.6% of patients without drug withdrawal. At the end of follow-up, 17.6% of patients had tumors relapsed. Four patients died, three from tumor relapse and one from cerebral hemorrhage. The ORR and CRR did not correlate with eltrombopag before AVA (p > 0.05) but increased when the total exposure of AVA increased (p = 0.011), and the threshold for AVA response was a cumulative dose > 3,000 mg (p = 0.013). AVA yielded good response and tolerance in patients treated for AA secondary to chemoradiotherapy, and a higher dose may correlate with better response.

Managing Side Effects of Cytotoxic Chemotherapy in Patients With High Grade Gliomas

Cytotoxic chemotherapy has been a mainstay of cancer treatment since the 1940s. In the recent era of emergent targeted therapies and immunotherapies, many cytotoxic chemotherapy agents including temozolomide are still one of main weapons for the treatment of high grade gliomas. However, cytotoxic chemotherapy often causes side effects. Proper management of chemotherapy-induced toxicity can have a significant impact on a patient's quality of life and clinical outcomes. Many supportive care advances have transformed our ability to give full doses of chemotherapy, which is important for achieving their full efficacy. Prevention and treatment strategies have been developed for many chemotherapy-related toxicities. This review focused on managing gastrointestinal toxicity, chemotherapy-induced nausea and vomiting, and hematologic toxicities such as thrombocytopenia during cytotoxic chemotherapy treatment in high-grade brain tumors.