A phase 3 randomized trial of mavorixafor, a CXCR4 antagonist, for WHIM syndrome.

ABSTRACT: We investigated efficacy and safety of mavorixafor, an oral CXCR4 antagonist, in participants with warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome, a rare immunodeficiency caused by CXCR4 gain-of-function variants. This randomized (1:1), double-blind, placebo-controlled, phase 3 trial enrolled participants aged ≥12 years with WHIM syndrome and absolute neutrophil count (ANC) ≤0.4 × 103/µL. Participants received once-daily mavorixafor or placebo for 52 weeks. The primary end point was time (hours) above ANC threshold ≥0.5 × 103/µL (TATANC; over 24 hours). Secondary end points included TAT absolute lymphocyte count ≥1.0 × 103/µL (TATALC; over 24 hours); absolute changes in white blood cell (WBC), ANC, and absolute lymphocyte count (ALC) from baseline; annualized infection rate; infection duration; and total infection score (combined infection number/severity). In 31 participants (mavorixafor, n = 14; placebo, n = 17), mavorixafor least squares (LS) mean TATANC was 15.0 hours and 2.8 hours for placebo (P < .001). Mavorixafor LS mean TATALC was 15.8 hours and 4.6 hours for placebo (P < .001). Annualized infection rates were 60% lower with mavorixafor vs placebo (LS mean 1.7 vs 4.2; nominal P = .007), and total infection scores were 40% lower (7.4 [95% confidence interval [CI], 1.6-13.2] vs 12.3 [95% CI, 7.2-17.3]). Treatment with mavorixafor reduced infection frequency, severity, duration, and antibiotic use. No discontinuations occurred due to treatment-emergent adverse events (TEAEs); no related serious TEAEs were observed. Overall, mavorixafor treatment demonstrated significant increases in LS mean TATANC and TATALC, reduced infection frequency, severity/duration, and was well tolerated. The trial was registered at www.clinicaltrials.gov as #NCT03995108.

Neutropenia in Barth syndrome: characteristics, risks, and management.

PURPOSE OF REVIEW: Barth syndrome (BTHS) is an X-linked disease characterized by defective remodeling of phospholipid side chains in mitochondrial membranes. Major features include neutropenia, dilated cardiomyopathy, motor delay and proximal myopathy, feeding problems, and constitutional growth delay. We conducted this review of neutropenia in BTHS to aid in the diagnosis of this disease, and to improve understanding of both the consequences of neutropenia and the benefits of treatment with granulocyte colony-stimulating factor (G-CSF). RECENT FINDINGS: In 88 patients with BTHS, neutropenia, that is, at least one count below 1.5 × 10/l, was detected in 74 (84%) and 44% had severe chronic neutropenia, with multiple counts below 0.5 × 10/l. The pattern of neutropenia varied between intermittent and unpredictable, chronic and severe, or cyclical with mathematically regular oscillations. Monocytosis, that is, monocytes more than 1.0 × 10/l, was observed at least once in 64 of 85 (75%) patients. G-CSF was administered to 39 of 88 patients (44%). Weekly average G-CSF doses ranged from 0.12 to 10.92 µg/kg/day (mean 1.16 µg/kg/day, median 1.16 µg/kg/day). Antibiotic prophylaxis was additionally employed in 21 of 26 neutropenic patients. Pretreatment bone marrow evaluations predominantly showed reduced myeloid maturation which normalized on G-CSF therapy in seven of 13 examined. Consistent clinical improvement, with reduced signs and symptoms of infections, was observed in response to prophylactic G-CSF ±â€Šprophylactic antibiotics. However, despite G-CSF and antibiotics, one adult patient died with multiple infections related to indwelling medical devices and gastrostomy site infection after 15.5 years on G-CSF and a pediatric patient required gastrostomy removal for recurrent abdominal wall cellulitis. SUMMARY: BTHS should be considered in any men with neutropenia accompanied by any of the characteristic features of this syndrome. Prophylaxis with G-CSF ±â€Šantibiotics prevents serious bacterial infections in the more severe neutropenic patients although infections remain a threat even in patients who are very compliant with therapy, especially in those with indwelling devices.

Somatic mutations and clonal hematopoiesis in congenital neutropenia.

Severe congenital neutropenia (SCN) and Shwachman-Diamond syndrome (SDS) are congenital neutropenia syndromes with a high rate of leukemic transformation. Hematopoietic stressors may contribute to leukemic transformation by increasing the mutation rate in hematopoietic stem/progenitor cells (HSPCs) and/or by promoting clonal hematopoiesis. We sequenced the exome of individual hematopoietic colonies derived from 13 patients with congenital neutropenia to measure total mutation burden and performed error-corrected sequencing on a panel of 46 genes on 80 patients with congenital neutropenia to assess for clonal hematopoiesis. An average of 3.6 ± 1.2 somatic mutations per exome was identified in HSPCs from patients with SCN compared with 3.9 ± 0.4 for healthy controls (P = NS). Clonal hematopoiesis due to mutations in TP53 was present in 48% (13/27) of patients with SDS but was not seen in healthy controls (0/17, P < .001) or patients with SCN (0/40, P < .001). Our SDS cohort was young (median age 6.3 years), and many of the patients had multiple TP53 mutations. Conversely, clonal hematopoiesis due to mutations of CSF3R was present in patients with SCN but was not detected in healthy controls or patients with SDS. These data show that hematopoietic stress, including granulocyte colony-stimulating factor, do not increase the mutation burden in HSPCs in congenital neutropenia. Rather, distinct hematopoietic stressors result in the selective expansion of HSPCs carrying specific gene mutations. In particular, in SDS there is enormous selective pressure to expand TP53-mutated HSPCs, suggesting that acquisition of TP53 mutations is an early, likely initiating event, in the transformation to myelodysplastic syndrome/acute myeloid leukemia in patients with SDS.

An update on the diagnosis and treatment of chronic idiopathic neutropenia.

PURPOSE OF REVIEW: Neutropenia lasting for at least for 3 months and not attributable to drugs or a specific genetic, infectious, inflammatory, autoimmune or malignant cause is called chronic idiopathic neutropenia (CIN). CIN and autoimmune neutropenia (AIN) are very similar and overlapping conditions. The clinical consequences depend upon the severity of neutropenia, but it is not considered a premalignant condition. RECENT FINDINGS: Long-term observational studies in children indicate that the disease often lasts for 3-5 years in children, then spontaneously remits, but it rarely remits in adult cases. The value of antineutrophil antibody testing in both children and adults is uncertain. Most recent data suggest that CIN and AIN are immune-mediated diseases, but there are no new clinical or genetic tests to aid in diagnosis. Treatment with granulocyte colony stimulating factor (G-CSF) is effective to increase blood neutrophils in almost all cases; this treatment is reserved, however, for patients with both neutropenia and evidence of recurrent fevers, inflammatory symptoms and infections. There is little or no evidence to indicate that G-CSF treatment predisposes to myeloid malignancies in this population. SUMMARY: It is important to recognize CIN and AIN, the most common causes of chronic neutropenia in both children and adults. If the neutropenia is not severe, that is more than 0.5 × 10/l, most patients can be observed and not treated prophylactically with antibiotics or a growth factor. When neutropenia is severe, treatment with G-CSF is often beneficial.

Abnormal circumferential strain measured by echocardiography is present in patients with Shwachman-Diamond syndrome despite normal shortening fraction.

BACKGROUND: Shwachman-Diamond Syndrome (SDS) is an autosomal recessive disorder characterized by bone marrow failure and exocrine pancreatic dysfunction. Heart failure has been described in patients with SDS. Circumferential strain (ε(cc)) is a measure of cardiac performance that may identify dysfunction when standard measures are normal. PROCEDURES: Patients with SDS were identified and the echocardiographic database queried. Cardiac anatomy and function were recorded, and ε(cc) was measured retrospectively. RESULTS: From 1995-2013, 27 patients with biallelic SBDS mutations confirming the diagnosis of SDS were identified at our institution: 14 had at least one echocardiogram available; 10 underwent HSCT, with echocardiograms available in nine. Ejection fraction (EF) was normal in all 14 patients evaluated; however, ε(cc) was decreased in 4/12 studies prior to HSCT. In two patients, ε(cc) was abnormal both before and after HSCT, in one, ε(cc) changed from normal to abnormal after HSCT, and in one, ε(cc) was normal after HSCT despite being abnormal prior. Echocardiogram reports were also available for six patients in the North American SDS registry, all with normal EF. CONCLUSIONS: While EF was normal in all patients with SDS, ε(cc) was abnormal in 33% prior to HSCT and 33% of those who had undergone HSCT. This suggests that SDS is associated with systolic dysfunction. Further studies are needed to define the incidence of dysfunction in this group and the progression to heart failure.

Stable long-term risk of leukaemia in patients with severe congenital neutropenia maintained on G-CSF therapy.

In severe congenital neutropenia (SCN), long-term therapy with granulocyte colony-stimulating factor (G-CSF) has reduced mortality from sepsis, revealing an underlying predisposition to myelodysplastic syndrome and acute myeloid leukaemia (MDS/AML). We have reported the early pattern of evolution to MDS/AML, but the long-term risk remains uncertain. We updated a prospective study of 374 SCN patients on long-term G-CSF enrolled in the Severe Chronic Neutropenia International Registry. Long-term, the annual risk of MDS/AML attained a plateau (2.3%/year after 10 years). This risk now appears similar to, rather than higher than, the risk of AML in Fanconi anaemia and dyskeratosis congenita.

Prevalence of mutations in ELANE, GFI1, HAX1, SBDS, WAS and G6PC3 in patients with severe congenital neutropenia.

Severe congenital neutropenia (SCN) is a genetically heterogeneous syndrome associated with mutations of ELANE (ELA2), HAX1, GFI1, WAS, CSF3R or G6PC3. We investigated the prevalence of mutations of ELANE in a cohort of 162 SCN patients for whom blood or bone marrow samples were submitted to the North American Severe Chronic Neutropenia Tissue Repository. Mutations of ELANE were found in 90 of 162 patients (55.6%). Subsequently, we conducted an analysis of a subset of 73 of these cases utilising a high throughput sequencing approach to determine the prevalence of other mutations associated with SCN. Among the 73 patients, mutations of ELANE were detected in 28. In the remaining 45 patients with wild type ELANE alleles, five patients had mutations: GFI1 (1), SBDS (1), WAS (1) and G6PC3 (2); no mutations of HAX1 were detected. In approximately 40% of our cases, the genetic basis of SCN remains unknown. These data suggest that for genetic diagnosis of SCN, ELANE genotyping should first be performed. In patients without ELANE mutations, other known SCN-associated gene mutations will be found rarely and genotyping can be guided by the clinical features of each patient.

Neutrophil elastase mutations and risk of leukaemia in severe congenital neutropenia.

Severe congenital neutropenia (SCN) is a heterogeneous bone marrow failure syndrome predisposing to myelodysplastic syndrome and acute myeloid leukaemia (MDS/AML). We studied 82 North American and Australian SCN patients enrolled in the Severe Chronic Neutropenia International Registry who were on long-term treatment with granulocyte colony-stimulating factor and for whom the neutrophil elastase (ELA2) gene was sequenced. There was no significant difference in the risk of MDS/AML in patients with mutant versus wild-type ELA2: the respective cumulative incidences at 15 years were 36% and 25% (P = 0.96). Patients with either mutant or wild-type ELA2 should be followed closely for leukaemic transformation.

The incidence of leukemia and mortality from sepsis in patients with severe congenital neutropenia receiving long-term G-CSF therapy.

In patients with severe congenital neutropenia (SCN), sepsis mortality is reduced by treatment with granulocyte colony-stimulating factor (G-CSF), but myelodsyplastic syndrome and acute myeloid leukemia (MDS/AML) have been reported. We studied 374 patients with SCN and 29 patients with Shwachman-Diamond syndrome (SDS) on long-term G-CSF enrolled in the Severe Chronic Neutropenia International Registry. In SCN, sepsis mortality was stable at 0.9% per year. The hazard of MDS/AML increased significantly over time, from 2.9% per year after 6 years to 8.0% per year after 12 years on G-CSF. After 10 years, the cumulative incidence was 8% for sepsis mortality and 21% for MDS/AML. A subgroup of SCN patients (29%) received more than the median dose of G-CSF (> or = 8 microg/kg/d), but achieved less than the median absolute neutrophil count (ANC) response (ANC < 2.188 x 10(9)/L [2188/microL] at 6-18 months). In these less-responsive patients, the cumulative incidence of adverse events was highest: after 10 years, 40% developed MDS/AML and 14% died of sepsis, compared with 11% and 4%, respectively, of more responsive patients whose ANC was above the median on doses of G-CSF below the median. Risk of MDS/AML may be similar in SDS and SCN. In less-responsive SCN patients, early hematopoietic stem cell transplantation may be a rational option.