Genetic Landscape and Its Prognostic Impact in Children With Langerhans Cell Histiocytosis.

CONTEXT.­: Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm that predominantly affects young children. OBJECTIVE.­: To investigate genetic alterations and their correlation with clinical characteristics and prognosis in pediatric LCH. DESIGN.­: We performed targeted sequencing to detect mutations in LCH lesions from pediatric patients. RESULTS.­: A total of 30 genomic alterations in 5 genes of the MAPK pathway were identified in 187 of 223 patients (83.9%). BRAF V600E (B-Raf proto-oncogene, serine/threonine kinase) was the most common mutation (51.6%), followed by MAP2K1 (mitogen-activated protein kinase kinase 1) alterations (17.0%) and other BRAF mutations (13.0%). ARAF (A-Raf proto-oncogene, serine/threonine kinase) and KRAS (KRAS proto-oncogene, GTPase) mutations were relatively rare (2.2% and 0.9%, respectively). Additionally, FNBP1 (formin-binding protein 1)::BRAF fusion and MAP3K10 (mitogen-activated protein kinase kinase 10) mutations A17T and R823C were identified in 1 case each, with possible constitutive activation of ERK1/2 phosphorylation. BRAF V600E was more frequent in patients with risk organ involvement, while MAP2K1 mutation was more prevalent in patients with single-system LCH (P = .001). BRAF V600E was associated with craniofacial bone, skin, liver, spleen, and ear involvement (all P < .05). Patients with other BRAF mutations had a higher proportion of spinal column involvement (P = .006). Univariate analysis showed a significant difference in progression-free survival among the 4 molecular subgroups for patients treated with first-line therapy (P = .02). According to multivariate analysis, risk organ involvement was the strongest independent adverse prognostic factor (hazard ratio, 8.854; P < .001); BRAF or MAP2K1 mutation was not an independent prognostic factor. CONCLUSIONS.­: Most pediatric patients with LCH carry somatic mutations involving the MAPK pathway, correlating with clinical characteristics and outcomes for first-line chemotherapy.

The plasma-soluble CSF1R level is a promising prognostic indicator for pediatric Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare hematologic neoplasm characterized by the clonal proliferation of Langerhans-like cells. Colony-stimulating factor 1 receptor (CSF1R) is a membrane-bound receptor that is highly expressed in LCH cells and tumor-associated macrophages. In this study, a soluble form of CSF1R protein (sCSF1R) was identified by plasma proteome profiling, and its role in evaluating LCH prognosis was explored. We prospectively measured plasma sCSF1R levels in 104 LCH patients and 10 healthy children using ELISA. Plasma sCSF1R levels were greater in LCH patients than in healthy controls (p < .001) and significantly differed among the three disease extents, with the highest level in MS RO+ LCH patients (p < .001). Accordingly, immunofluorescence showed the highest level of membrane-bound CSF1R in MS RO+ patients. Furthermore, the plasma sCSF1R concentration at diagnosis could efficiently predict the prognosis of LCH patients treated with standard first-line treatment (AUC = 0.782, p < .001). Notably, dynamic monitoring of sCSF1R levels could predict relapse early in patients receiving BRAF inhibitor treatment. In vitro drug sensitivity data showed that sCSF1R increased resistance to Ara-C in THP-1 cells expressing ectopic BRAF-V600E. Overall, the plasma sCSF1R level at diagnosis and during follow-up is of great clinical importance in pediatric LCH patients.

Relationship between subtype-specific minimal residual disease level and long-term prognosis in children with acute lymphoblastic leukemia.

Minimal residual disease (MRD) based risk stratification criteria for specific genetic subtypes remained unclear in childhood acute lymphoblastic leukemia (ALL). Among 723 children with newly diagnosed ALL treated with the Chinese Children Leukemia Group CCLG-2008 protocol, MRD was assessed at time point 1 (TP1, at the end of induction) and TP2 (before consolidation treatment) and the MRD levels significantly differed in patients with different fusion genes or immunophenotypes (P all < 0.001). Moreover, the prognostic impact of MRD varied by distinct molecular subtypes. We stratified patients in each molecular subtype into two MRD groups based on the results. For patients carrying BCR::ABL1 or KMT2A rearrangements, we classified patients with MRD < 10-2 at both TP1 and TP2 as the low MRD group and the others as the high MRD group. ETV6::RUNX1+ patients with TP1 MRD < 10-3 and TP2 MRD-negative were classified as the low MRD group and the others as the high MRD group. For T-ALL, We defined children with TP1 MRD ≥ 10-3 as the high MRD group and the others as the low MRD group. The 10-year relapse-free survival of low MRD group was significantly better than that of high MRD group. We verified the prognostic impact of the subtype-specific MRD-based stratification in patients treated with the BCH-ALL2003 protocol. In conclusion, the subtype-specific MRD risk stratification may contribute to the precise treatment of childhood ALL.

Delayed-onset adenosine deaminase deficiency with a novel synonymous mutation and a case series from China.

BACKGROUND: Adenosine deaminase (ADA) is a key enzyme in the purine salvage pathway. Genetic defects of the ADA gene can cause a subtype of severe combined immunodeficiency. To date, few Chinese cases have been reported. METHODS: We retrospectively reviewed the medical records of patients diagnosed with ADA deficiency in Beijing Children's Hospital and summarized the previously published ADA deficiency cases from China in the literature. RESULTS: Nine patients were identified with two novel mutations (W272X and Q202 =). Early-onset infection, thymic abnormalities and failure to thrive were the most common manifestations of Chinese ADA-deficient patients. The ADA genotype has a major effect on the clinical phenotype. Notably, a novel synonymous mutation (c.606G>A, p.Q202=) was identified in a delayed-onset patient, which affected pre-mRNA splicing leading to a frameshift and premature truncation of the protein. Furthermore, the patient showed γδT cells expansion with an increased effect or phenotype, which may be associated with the delayed onset of disease. In addition, we reported cerebral aneurysm and intracranial artery stenosis for the first time in ADA deficiency. Five patients died with a median age of four months, while two patients received stem cell transplantation and are alive. CONCLUSIONS: This study described the first case series of Chinese ADA-deficient patients. Early-onset infection, thymic abnormalities and failure to thrive were the most common manifestations in our patients. We identified a synonymous mutation that affected pre-mRNA splicing in the ADA gene, which had never been reported in ADA deficiency. Furthermore, we reported cerebral aneurysm in a delayed-onset patient for the first time. Further study is warranted to investigate the underlying mechanisms.

Efficacy of ruxolitinib for HAVCR2 mutation-associated hemophagocytic lymphohistiocytosis and panniculitis manifestations in children.

Frequent germline mutations of HAVCR2, recently identified in subcutaneous panniculitis-like T-cell lymphoma (SPTCL), are associated with an increased risk of hemophagocytic lymphohistiocytosis (HLH). However, SPTCL-HLH represents a challenge because of the difficulties in treatment with poor survival. Its malignant nature, specifically harbouring HAVCR2 mutations, has also been questioned. To better understand its pathology and treatment, we analysed the clinical data of six patients diagnosed at our centre. The median age at onset was 10.5 years (range, 0.8-12.4). Five patients presented with skin lesions of subcutaneous nodules/plaques and/or ulceration. All patients developed HLH; notably, one infant only had HLH without skin involvement. Histopathologically, only two patients were diagnosed with SPTCL and three were reported as panniculitis with no sufficient evidence of lymphoma. Genetically, germline homozygous mutation of HAVCR2 (p.Y82C) was identified in all patients, with a median diagnosis time of 4.6 months. All patients initially received corticosteroids, immunosuppressants or chemotherapy, achieving unfavourable responses. Strikingly, they responded well to ruxolitinib targeting inflammatory cytokines, allowing rapid disease resolution and/or long-term maintenance of remission. The excellent efficacy of ruxolitinib highlights this disease as an inflammatory condition instead of neoplastic nature and indicates novel agents targeting key inflammatory pathways as an encouraging approach for this disease entity.

Clinical outcomes and prognostic risk factors of Langerhans cell histiocytosis in children: Results from the BCH-LCH 2014 protocol study.

Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm mainly affecting young children. This study aimed to evaluate the outcomes of 449 pediatric patients enrolled in the BCH-LCH 2014 study. 52.6% of patients were classified with single-system (SS) LCH, 28.1% with multisystem (MS) risk organ negative (RO-) LCH, and 19.4% with MS RO+ LCH. Three hundred ninety-six patients (88.2%) were initially treated with first-line therapy based on the vindesine-prednisone combination. One hundred thirty-nine patients who lacked a response to initial treatment were shifted to second-line therapy, 72 to intensive treatment Arm S1 (a combination of cytarabine, cladribine, vindesine, and dexamethasone), and 67 to Arm S2 (without cladribine). The 5-year overall survival (OS), progression-free survival (PFS), and relapse rates were 98.2% (median: 97.6 months), 54.6% (median: 58.3 months), and 29.9%, respectively. MS RO+ patients had the worst prognosis among the three clinical subtypes. For the patients initially treated with first-line therapy, the 5-year OS, PFS, and relapse rates were 99.2%, 54.5%, and 29.3%, respectively. Patients in Arm S1 had a significantly better prognosis than patients in Arm S2 (5-year PFS: 69.2% vs. 46.5%, p = .042; relapse rate: 23.4% vs. 44.2%, p = .031). Multivariate analysis revealed that early treatment response, the involvement of RO, skin, and oral mucosa, as well as laboratory parameters, including CRP and γ-GT, were independent risk factors for the PFS of LCH. Thus, the prognosis of LCH in children has been improved significantly with stratified chemotherapy, and progression and relapse remained the challenges, especially for RO+ patients.

Clinical features and treatment outcomes of pediatric Langerhans cell histiocytosis with macrophage activation syndrome-hemophagocytic lymphohistiocytosis.

BACKGROUND: Langerhans cell histiocytosis (LCH) is a rare myeloid neoplasm. A few LCH patients had Macrophage activation syndrome-hemophagocytic lymphohistiocytosis (MAS-HLH), a life-threatening, hyper-inflammatory syndrome. We retrospectively described the clinical-biological characteristics of a series of 28 pediatric LCH patients with MAS-HLH in a single center. We further analyzed the difference in treatment outcomes between second-line chemotherapy (cytarabine and cladribine) and targeted therapy (dabrafenib) for BRAF-V600E-positive patients. RESULTS: LCH patients with MAS-HLH were aged < 2 years, harbored high frequencies of risk organ, skin, or lymph nodes involvement, and most of them carried BRAF-V600E mutation in lesions (88.0%) or plasma (90.5%). Patients were firstly treated with the initial induction first-line therapy (vindesine-steroid combination), and most of them (26/28) failed to control the active MAS-HLH after one six-week course of induction treatment. Then they were shifted to second-line chemotherapy or targeted therapy dabrafenib. BRAF-V600E-mutant patients treated with dabrafenib had prompt resolution of MAS-HLH signs and symptoms with less toxicity than second-line chemotherapy. Moreover, the progression-free survival (PFS) rate for patients given dabrafenib was much higher than those treated with chemotherapy (4 year-PFS: 75% vs. 14.6%, P = 0.034). CONCLUSIONS: LCH patients with MAS-HLH harbored specific clinical-biology characteristics compared to the multisystem LCH without MAS-HLH. The BRAF inhibitor dabrafenib provides a promising treatment option for LCH with MAS-HLH.

A study of ruxolitinib response-based stratified treatment for pediatric hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a lethal disorder characterized by hyperinflammation. Recently, ruxolitinib (RUX), targeting key cytokines in HLH, has shown promise for HLH treatment. However, there is a lack of robust clinical trials evaluating its efficacy, especially its utility as a frontline therapy. In this study (www.chictr.org.cn, ChiCTR2000031702), we designed ruxolitinib as a first-line agent for pediatric HLH and stratified the treatment based on its early response. Fifty-two newly diagnosed patients were enrolled. The overall response rate (ORR) of ruxolitinib monotherapy (day 28) was 69.2% (36/52), with 42.3% (22/52) achieving sustained complete remission (CR). All responders achieved their first response to ruxolitinib within 3 days. The response to ruxolitinib was significantly associated with the underlying etiology at enrollment (P = .009). Epstein-Barr virus (EBV)-HLH patients were most sensitive to ruxolitinib, with an ORR of 87.5% (58.3% in CR). After ruxolitinib therapy, 57.7% (30/52) of the patients entered intensive therapy with additional chemotherapy. Among them, 53.3% (16/30) patients achieved CR, and 46.7% (14/30) patients dominated by chronic active EBV infection-associated HLH (CAEBV-HLH) developed refractory HLH by week 8. The median interval to additional treatment since the first ruxolitinib administration was 6 days (range, 3-25 days). Altogether, 73.1% (38/52) of the enrolled patients achieved CR after treatment overall. The 12-month overall survival (OS) for all patients was 86.4% (95% confidence interval [CI], 77.1% to 95.7%). Ruxolitinib had low toxicity and was well tolerated compared with intensive chemotherapy. Our study provides clinical evidence for ruxolitinib as a frontline agent for pediatric HLH. The efficacy was particularly exemplified with stratified regimens based on the early differential response to ruxolitinib. This study was registered in the Chinese Clinical Trials Registry Platform (http://www.chictr.org.cn/) as ChiCTR2000031702.

Characteristics and Treatment Outcomes of Pediatric Langerhans Cell Histiocytosis with Thymic Involvement.

OBJECTIVE: To evaluate the characteristics and treatment outcomes of patients with pediatric Langerhans cell histiocytosis (LCH) with thymic involvement. STUDY DESIGN: We retrospectively described the clinical, biological, and imaging characteristics of a series of 19 patients with pediatric LCH with thymic involvement in our center between September 2016 and December 2019. We further analyzed the treatment response and outcomes of patients treated with chemotherapy or targeted therapy. RESULTS: Thymic involvement was found in 4.4% of a 433-consecutive pediatric LCH cohort; all LCH-thymic involvement presented with multisystem disease. Patients with thymic involvement were typically younger, harboring more lung and thyroid involvement and less bone involvement than those without thymic involvement. Most patients with thymic involvement had alteration of immunocompetence with decreased numbers of T-lymphocyte subsets and immunoglobulin G levels. Overall, 47.1% of patients demonstrated a response after 6 weeks of induction therapy, and 92.3% of the patients who did not respond to the first-line treatment had resolution of thymus after the second-line and/or targeted therapy. The progression/relapse rate showed no difference between patients who shifted to second-line therapy and those to dabrafenib (33.3% vs 25%, P = 1.000). The survival for patients with thymic involvement did not differ from those without thymic involvement. More patients treated with second-line chemotherapy had severe adverse events than those given dabrafenib (88.9% vs 0, P < .001). CONCLUSIONS: Thymic involvement was observed rarely in LCH and had specific clinical characteristics. Chemotherapy could resolve most thymic lesions, and BRAF inhibitors might provide a promising treatment option with less toxicity for infants with BRAF-V600E mutation. TRIAL REGISTRATION: http://www.chictr.org.cn, identifier: ChiCTR2000030457 (BCH-LCH 2014 study); ChiCTR2000032844 (dabrafenib study).

Significance of serum Th1/Th2 cytokine levels in underlying disease classification of childhood HLH.

OBJECT: Goal of this research was to investigate values of serum cytokines in childhood HLH with different triggers, with the expectation to find secretion spectrum of 5 main types of underlying diseases. METHOD: 118 newly diagnosed HLH were included, and serum concentrations of 6 cytokines were tested before treatment began. Absolute cytokine levels and ratios between them were then studied in the HLH groups collectively and separately RESULTS: In general, IFN-γ, IL-10 and IL-6 showed differences among 5 HLH groups. Specifically, relative levels of these three cytokines to each other were meaningful in distinguishing 4 types of HLH. Level of IL-6 was higher than those of IFN-γ or IL-10 in HLH driven by Systemic auto-inflammatory disorders (SAIDs) or Langerhans Cell Histiocytosis (LCH), while primary HLH and EBV-HLH shared elevated ratio of IL-10 to IL-6. Although more than one distinctive ratios were found in 3 HLH groups, combination of these parameters didn't offer optimal balance between sensitivity and specificity. CONCLUSION: As a group of easily gained laboratory findings, cytokine levels were reliable in the procedure of roughly classifying HLH cases with the help of patients' clinical phenotype. However, adequate data is still needed to explore the significance of these indicators in identifying one particular underlying disease accurately.

Haploidentical hematopoietic stem cell transplantation for pediatric patients with chronic active Epstein-Barr virus infection: a retrospective analysis of a single center.

BACKGROUND: This study aimed to evaluate the feasibility and clinical effect of haploidentical hematopoietic stem cell transplantation (haplo-HSCT) for the treatment of pediatric patients with chronic active Epstein-Barr virus infection (CAEBV). METHODS: Children with CAEBV who did not have matched donors and underwent haplo-HSCT in Beijing Children's Hospital, Capital Medical University, from October 2016 to June 2020 were analyzed retrospectively. Data relating to the clinical manifestations, engraftment, and prognosis of the children were extracted from medical records. RESULTS: Twenty-five patients, including 16 males and 9 females, with an onset age of 5.0 ± 2.6 years and a transplantation age of 6.9 ± 2.9 years, were enrolled in this study. The mean time from diagnosis to transplantation was 3.8 (2.0-40.2) months. The mean observation time was 19.0 ± 12.0 months. Three patients received the reduced intensity conditioning regimen, and the remaining patients all received the modified myeloablative conditioning regimen. By the end of the follow-up, 23 patients were characterized by disease-free survival (DFS), 22 were characterized by event-free survival (EFS), and two died. One of the patients died of thrombotic microangiopathy (TMA), and another died of graft versus host disease (GVHD); this patient discontinued the treatment for economic reasons. The 3-year overall survival (OS) rate was estimated to be 92.0% ± 5.4%, and the 3-year EFS rate was estimated to be 87.4% ± 6.8%. All active patients survived after HSCT event-free. Acute GVHD degrees 1-3 were observed in ten patients (40.0%), and degree IV was observed in six (24.0%), who were all cured except for one patient. Chronic GVHD was observed in nine (36.0%), and most of these cases were mild. The incidence of TMA and veno-occlusive disease (VOD) was 28.0% and 4.0%. CONCLUSIONS: Haploidentical hematopoietic stem cell transplantation is safe and effective in the treatment of pediatric CAEBV and can be used as an alternative therapy without matched donors or emergency transplantation. Patients with active disease before HSCT also benefited from haplo-HSCT. Haplo-HSCT requires careful monitoring for complications, such as GVHD and TMA. Early detection of TMA and timely treatment can reduce mortality and can improve the survival rate.

BRAF V600E Mutation in Cell-Free DNA, Rather than in Lesion Tissues, at Diagnosis Is An Independent Prognostic Factor in Children with Langerhans Cell Histiocytosis.

The aim of this study was to investigate the prognostic significance of BRAFV600E in cell-free (cf) DNA (cfBRAFV600E) and lesion tissues (ltBRAFV600E) in pediatric Langerhans cell histiocytosis (LCH). This study included a total of 140 patients with successfully detected cfBRAFV600E and ltBRAFV600E at diagnosis. Treatment response at week 6 was correlated with both cfBRAFV600E and ltBRAFV600E Moreover, the patients with positive cfBRAFV600E had a much lower 3-year progression-free survival (PFS) rate and a higher progression/reactivation rate than those with negative cfBRAFV600E (47.1% ± 7.6% vs. 78.4% ± 5.1%, P < 0.0001; 44.6% vs. 19.0%, P = 0.001, respectively). However, no significant difference was found in the 3-year PFS rate or progression/reactivation rate between patients with positive and negative ltBRAFV600E (P = 0.348 and 0.596, respectively). In addition, after patients were divided into group A (both cfBRAFV600E and ltBRAFV600E positive, n = 56), group B (ltBRAFV600E positive and cfBRAFV600E negative, n = 28), and group C (both cfBRAFV600E and ltBRAFV600E negative, n = 56), there was a significant difference in the 3-year PFS rate and progression/reactivation rate among the three groups (47.1% ± 7.6%, 92.9% ± 6.1%, and 72.2% ± 6.1%, P < 0.001; 44.6%, 3.6%, and 26.8%, P < 0.001, respectively). In the multivariate analysis, cfBRAFV600E and age at diagnosis remained independent prognostic factors for 3-year PFS in childhood LCH. Therefore, cfBRAFV600E was more closely associated with important clinical characteristics, treatment response at week 6, and prognosis than ltBRAFV600E.

Combined analysis of IKZF1 deletions and CRLF2 expression on prognostic impact in pediatric B-cell precursor acute lymphoblastic leukemia.

This study aimed to investigate the combined impact of IKZF1 deletions/high expression of CRLF2 on the prognosis of pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL). IKZF1 deletions and CRLF2 expression were assessed in bone marrow samples from 117 children with newly diagnosed BCP-ALL. Sixteen (13.7%) patients were found to harbor IKZF1 deletions, which was associated with inferior outcomes. The event-free survival (EFS) for patients with high -CRLF2 expression was significantly worse than that for low -CRLF2 expression. Moreover, combined modeling of IKZF1+ /CRLF2high identified 7.8% of cases as the highest risk subgroup (7-year EFS 33.3 ± 15.7%). In a multivariate analysis, IKZF1+ /CRLF2high remained a strong independent prognostic factor for EFS (HR: 14.263, p = 0.019). IKZF1 deletions and high -CRLF2 expression were associated with inferior outcomes, and the coexistence of IKZF1+ /CRLF2high had a significant impact on an integrated prognostic model for high-risk BCP-ALL.

Effectiveness and Safety of Dabrafenib in the Treatment of 20 Chinese Children with BRAFV600E-Mutated Langerhans Cell Histiocytosis.

PURPOSE: We sought to investigate the effectiveness and safety of dabrafenib in children with BRAFV600E-mutated Langerhans cell histiocytosis (LCH). MATERIALS AND METHODS: A retrospective analysis was performed on 20 children with BRAFV600E-mutated LCH who were treated with dabrafenib. RESULTS: The median age at which the patients started taking dabrafenib was 2.3 years old (range, 0.6 to 6.5 years). The ratio of boys to girls was 2.3:1. The median follow-up time was 30.8 months (range, 18.9 to 43.6 months). There were 14 patients (70%) in the risk organ (RO)+ group and six patients (30%) in the RO- group. All patients were initially treated with traditional chemotherapy and then shifted to targeted therapy due to poor control of LCH or intolerance to chemotherapy. The overall objective response rate and the overall disease control rate were 65% and 75%, respectively. During treatment, circulating levels of cell-free BRAFV600E (cfBRAFV600E) became negative in 60% of the patients within a median period of 3.0 months (range, 1.0 to 9.0 months). Grade 2 or 3 adverse effects occurred in five patients. CONCLUSION: Some children with BRAFV600E-mutated LCH may benefit from monotherapy with dabrafenib, especially high-risk patients with concomitant hemophagocytic lymphohistiocytosis and intolerance to chemotherapy. The safety of dabrafenib is notable. A prospective study with a larger sample size is required to determine the optimal dosage and treatment duration.

A pilot study of ruxolitinib as a front-line therapy for 12 children with secondary hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is an immune-regulatory disorder characterized by excessive production of inflammatory cytokines. The treatment recommendations of the HLH-1994 and HLH-2004 protocols have long been used in HLH therapy, but some patients still do not respond well to or have unacceptable side effects from conventional therapies. It is believed that cytokine-targeted strategies that directly target disease-driving pathways will be promising options for HLH. This prospective study aimed to investigate the efficacy and safety of ruxolitinib, a Janus kinase (JAK) 1/2 inhibitor, as a front-line therapy in children with secondary HLH. Twelve newly diagnosed patients without previous treatment were enrolled in this study with a median follow-up of 8.2 (7.1-12.0) months, including 8 cases of Epstein-Barr virus associated HLH (EBV-HLH), 2 cases of autoinflammatory disorder (AID)- associated HLH, and 2 cases of unknown etiology. Patients received oral ruxolitinib dosed on 2.5 mg, 5 mg or 10 mg twice daily depending on the body weight for 28 consecutive days. The overall response rate at the end of treatment (day 28) was 83.3% (10/12), with 66.7% (8/12) in complete response (CR), 8.3% (1/12) in partial response (PR), and 8.3% (1/12) in HLH improvement. Among the patients achieving CR, 87.5% (7/8) maintained CR condition for>6 months, and one patient with EBV-HLH relapsed following CR. For the EBV-HLH subgroup, all 8 patients responded to ruxolitinib, with a CR rate of 75% and a PR rate of 25%. Two patients with AID-associated HLH had quite different responses, with one showing reversal of the HLH abnormalities soon and the other showing no improvement, as did the two cases of unknown etiology. Patients who had no response or discontinued ruxolitinib all responded well to the subsequent HLH-1994 regimen. The expected 6-month event-free survival (EFS) rate was 58.3%±10.2%. No serious adverse effects were reported. Our study provides further support for the possibility of ruxolitinib targeted therapy for secondary HLH in children. This study was registered in the Chinese Clinical Trials Registry Platform (http://www.chictr.org.cn/) as ChiCTR2000029977.

Extremely low dose of 6-mercaptopurine in a Chinese child with acute lymphoblastic leukaemia and multiple pharmacogenetic mutations.

WHAT IS KNOWN AND OBJECTIVES: Thiopurines are cornerstone drugs in the treatment of acute lymphoblastic leukaemia (ALL), but their use can be complicated by the incidence of life-threatening leucopenia. CASE DESCRIPTION: We describe a case of a 6-year-old Chinese boy with B-ALL receiving extremely low dose of 6-mercaptopurine (only 4% of recommended dose) during the ALL maintenance therapy phase. WHAT IS NEW AND CONCLUSION: Complex pharmacogenetic tests and TDM should be recommended in children with complicated ALL to highlight the large individual variability in the responses to 6-MP exposure and the associated adverse effects.

Paediatric drugs trials in China.

OBJECTIVE: Clinical trials of children's drugs are of great significance to rational drug use in children. However, paediatric drugs trials in China are facing complex challenges. At present, the investigation data on registration status of paediatric drug trials in China are still relatively lacking, and relevant research is urgently needed. METHODS: The advanced retrieval function is used to retrieve clinical trials data in the Clinical Trial.gov and Chinese Clinical Trial Registry databases in 22 April 2019. Fifteen key items were analysed to describe trial characteristics, including: registration number, study start date (year), mode of funding, type of disease, medicine type, research stage, research design, sample size, number of experimental groups, placebo group, blind method, implementation centre, child specific, newborn specific and participant age. RESULTS: A total of 1388 clinical trials of paediatric drugs conducted in China were registered. The number of paediatric drug trials grew steadily over time, from less than 20 per year before 2005 to more than 100 per year after 2012. Most clinical trials were postmarketing (n=800, 57.6%), single-centre (n=1045, 75.3%), intervention studies (n=1161, 83.6%) without blinded methods (1169, 84.2%) and funded by non-profit organisations (n=838, 60.4%). The number of clinical trials for antineoplastic agents (n=254, 18.3%), anti-infectives (n=156, 11.2%) and vaccines (n=154, 11.1%) is the largest. CONCLUSION: Paediatric drug trials in China made a significant progress in recent years. Innovative method and trial design optimisation should be encouraged to accelerate paediatric clinical research. Pharmaceutical companies need to be further stimulated to carry out more high-quality paediatric clinical trials with support of paediatric drug legislation.

Associations between PRF1 Ala91Val polymorphism and risk of hemophagocytic lymphohistiocytosis: a meta-analysis based on 1366 subjects.

BACKGROUND: Perforin (PRF1) gene mutation can cause the onset of hemophagocytic lymphohistiocytosis (HLH). It has reported that PRF1 Ala91Val polymorphism was related with HLH risk. In the meta-analysis, we aim to evaluate the association between PRF1 Ala91Val polymorphism and HLH risk. METHODS: We accomplished a meta-analysis of six published case-control studies including 391 patients with HLH and 975 controls. We evaluated the quality of each study through Newcastle-Ottawa Scale (NOS). Data analysis was performed with Stata software. RESULTS: In general, all studies were of high quality (NOS score higher than 7). There were statistically significant between the PRF1 Ala91Val polymorphism and HLH risk though the pooled analysis [for Ala/Val vs. Ala/Ala: pooled odds ratio (OR) = 3.22, 95% confidence interval (CI) 1.08-9.56, P = 0.035, random model; for Ala/Val + Val/Val vs. Ala/Ala: pooled OR = 2.96, 95% CI 1.14-7.69, P = 0.025, random model]. Furthermore, sensitivity analysis also revealed a relationship between PRF1 Ala91Val polymorphism and HLH risk (for Ala/Val vs. Ala/Ala: pooled OR = 5.236, 95% CI 2.72-10.08, P < 0.000, I2 = 12.1%, Pheterogeneity = 0.332; for Ala/Val + Val/Val vs. Ala/Ala, pooled OR = 4.856, 95% CI 2.66-8.85, P < 0.000, I2 = 5.9%, Pheterogeneity = 0.373). Funnel plot and Egger's test did not indicate obvious published bias (P = 0.841 for Ala/Val vs. Ala/Ala; P = 0.284 for Ala/Val + Val/Val vs. Ala/Ala). CONCLUSION: This meta-analysis indicated that PRF1 Ala91Val polymorphism affects the factor for developing HLH and future studies of PRF1 Ala91Val on the onset of HLH will be guaranteed.

Precision therapy of 6-mercaptopurine in Chinese children with acute lymphoblastic leukaemia.

AIMS: Chinese children are more susceptible to the development of thiopurine-induced leukopenia compared with Caucasian populations. The aim of our study was to establish a 6-mercaptopurine (6-MP) dose-concentration-response relationship through exploration of pharmacogenetic factors involved in the thiopurine-induced toxicities in Chinese paediatric patients afflicted by acute lymphoblastic leukaemia (ALL). METHODS: Blood samples were obtained from ALL children treated with 6-MP. We determined the metabolite steady-state concentrations of 6-MP in red blood cells (RBCs) by using high-performance liquid chromatography. Pharmacogenetic analysis was carried out on patients' genomic DNA using the MassArray genotyping platform. RESULTS: Sixty children afflicted by ALL who received 6-MP treatment were enrolled in this study. The median concentration of 6-thioguanine in patients afflicted by leukopenia was 235.83 pmol/8 × 108 RBCs, which was significantly higher than for patients unafflicted by leukopenia (178.90 pmol/8 × 108 RBCs; P = 0.029). We determined the population special target 6-thioguanine threshold to have equalled 197.50 pmol/8 × 108 RBCs to predict leukopenia risk in Chinese paediatric patients afflicted by ALL. Among 36 candidate single nucleotide polymorphisms, our results indicated that NUDT15 (rs116855232) and IMPDH1 (rs2278293) were correlated with a 5.50-fold and 5.80-fold higher risk of leukopenia, respectively. MTHFR rs1801133 variants were found to have had a 4.46-fold significantly higher risk of hepatotoxicity vs wild-type genotype. CONCLUSION: Our findings support the idea that predetermination of genotypes and monitoring of thiopurine metabolism for Chinese paediatric patients afflicted by ALL is necessary to effectively predict the efficacy of treatments and to minimize the adverse effects of 6-MP maintenance therapy.