Combining CRISPR-Cas9 and TCR exchange to generate a safe and efficient cord blood-derived T cell product for pediatric relapsed AML.

BACKGROUND: Hematopoietic cell transplantation (HCT) is an effective treatment for pediatric patients with high-risk, refractory, or relapsed acute myeloid leukemia (AML). However, a large proportion of transplanted patients eventually die due to relapse. To improve overall survival, we propose a combined strategy based on cord blood (CB)-HCT with the application of AML-specific T cell receptor (TCR)-engineered T cell therapy derived from the same CB graft. METHODS: We produced CB-CD8+ T cells expressing a recombinant TCR (rTCR) against Wilms tumor 1 (WT1) while lacking endogenous TCR (eTCR) expression to avoid mispairing and competition. CRISPR-Cas9 multiplexing was used to target the constant region of the endogenous TCRα (TRAC) and TCRß (TRBC) chains. Next, an optimized method for lentiviral transduction was used to introduce recombinant WT1-TCR. The cytotoxic and migration capacity of the product was evaluated in coculture assays for both cell lines and primary pediatric AML blasts. RESULTS: The gene editing and transduction procedures achieved high efficiency, with up to 95% of cells lacking eTCR and over 70% of T cells expressing rWT1-TCR. WT1-TCR-engineered T cells lacking the expression of their eTCR (eTCR-/- WT1-TCR) showed increased cell surface expression of the rTCR and production of cytotoxic cytokines, such as granzyme A and B, perforin, interferon-γ (IFNγ), and tumor necrosis factor-α (TNFα), on antigen recognition when compared with WT1-TCR-engineered T cells still expressing their eTCR (eTCR+/+ WT1-TCR). CRISPR-Cas9 editing did not affect immunophenotypic characteristics or T cell activation and did not induce increased expression of inhibitory molecules. eTCR-/- WT1-TCR CD8+ CB-T cells showed effective migratory and killing capacity in cocultures with neoplastic cell lines and primary AML blasts, but did not show toxicity toward healthy cells. CONCLUSIONS: In summary, we show the feasibility of developing a potent CB-derived CD8+ T cell product targeting WT1, providing an option for post-transplant allogeneic immune cell therapy or as an off-the-shelf product, to prevent relapse and improve the clinical outcome of children with AML.

Treatment-related risk factors for inhibitor development in non-severe hemophilia A after 50 cumulative exposure days: A case-control study.

BACKGROUND: Non-severe hemophilia A patients have a life-long inhibitor risk. Yet, no studies have analyzed risk factors for inhibitor development after 50 factor VIII (FVIII) exposure days (EDs). OBJECTIVES: This case-control study investigated treatment-related risk factors for inhibitor development in non-severe hemophilia A and assessed whether these risk factors were different for early versus late inhibitor development. PATIENTS/METHODS: Non-severe hemophilia A patients (FVIII:C 2%-40%) were selected from the INSIGHT study. Inhibitor-positive patients were defined as early (<50 EDs) or late (>50EDs) cases and matched to 1-4 inhibitor-negative controls by year of birth, cumulative number of EDs, and center/country. We investigated treatment intensity during the last 10 EDs prior to inhibitor development. Intensive treatment was defined as: surgery, peak treatment (10 consecutive EDs), and high mean FVIII dose (>45 IU/kg/ED). Odds ratios (OR) were calculated by logistic regression. RESULTS: Of 2709 patients, we analyzed 63 early and 26 late cases and 195 and 71 respectively matched controls. Peak treatment was associated with early and late inhibitor risk (crude OR 1.8, 95% confidence interval [CI] 1.0-3.4; 4.0, 95%CI 1.1-14.3). This association was slightly less pronounced after adjustment for mean FVIII dose. High mean FVIII dose was also associated with early and late inhibitor risk (crude OR 2.8, 95%CI 1.5-5.1; 4.5, 95%CI 1.2-16.6). Surgery increased inhibitor risk for early cases. This was less pronounced for late cases. CONCLUSIONS: Our findings suggest that intensive FVIII treatment remains a risk factor for inhibitor development in non-severe hemophilia A after more than 50 EDs. Therefore, persistent caution is required throughout the life-time treatment course.

Product type and the risk of inhibitor development in nonsevere haemophilia A patients: a case-control study.

Inhibitor development is a major complication of treatment with factor VIII concentrates in nonsevere haemophilia A. It has been suggested that plasma-derived factor VIII (FVIII) concentrates elicit fewer inhibitors than recombinant FVIII concentrates, but studies in severe haemophilia A patients have shown conflicting results. We designed a case-control study to investigate the clinical and genetic risk factors for inhibitor development in nonsevere haemophilia A patients. We investigated whether the type of FVIII concentrate was associated with inhibitor development in nonsevere haemophilia A patients. This nested case-control study includes 75 inhibitor patients and 223 controls, from a source population of the INSIGHT study, including all nonsevere haemophilia A patients (FVIII:C 2-40%) that were treated with FVIII concentrates in 33 European and one Australian centre. Cases and controls were matched for date of birth and cumulative number of exposure days (CED) to FVIII concentrate. A conditional logistic regression model was used to calculate unadjusted and adjusted odds ratios. No increased risk for inhibitor development was found for any type of FVIII concentrate; either when comparing recombinant FVIII concentrates to plasma-derived FVIII concentrates (adjusted odds ratio 0·96, 95% confidence interval (CI) 0·36-2·52) or for specific types of FVIII concentrates.

Dexamethasone promotes durable factor VIII-specific tolerance in hemophilia A mice via thymic mechanisms.

The development of inhibitory antibodies to factor VIII is the most serious complication of replacement therapy in hemophilia A. Activation of the innate immune system during exposure to this protein contributes to inhibitor development. However, avoidance of factor VIII exposure during innate immune system activation by external stimuli (e.g., vaccines) has not been consistently shown to prevent inhibitors. We hypothesized that dexamethasone, a drug with potent anti-inflammatory effects, could prevent inhibitors by promoting immunologic tolerance to factor VIII in hemophilia A mice. Transient dexamethasone treatment during ainitial factor VIII exposure reduced the incidence of anti-factor VIII immunoglobulin G in both a conventional hemophilia A mouse model (E16KO, 77% vs 100%, P=0.048) and a hemophilia A mouse model with a humanized major histocompatibility complex type II transgene (E17KO/hMHC, 6% vs 33%, P=0.0048). More importantly, among E17KO/hMHC mice that did not develop anti-factor VIII immunoglobulin G after initial exposure, dexamethasone-treated mice were less likely to develop a response after re-exposure six (7% vs 52%, P=0.005) and 16 weeks later (7% vs 50%, P=0.097). Similar results were obtained even when factor VIII re-exposure occurred in the context of lipopolysaccharide (30% vs 100%, P=0.069). The ability of these mice to develop immunoglobulin G to human von Willebrand factor, a structurally unrelated antigen, remained unaffected by treatment. Transient dexamethasone administration therefore promotes antigen-specific immunologic tolerance to factor VIII. This effect is associated with an increase in the percentage of thymic regulatory T cells (12.06% vs 4.73%, P<0.001) and changes in the thymic messenger ribonucleic acid transcription profile.

Desmopressin in moderate hemophilia A patients: a treatment worth considering.

Desmopressin increases endogenous factor VIII levels in hemophilia A. Large inter-individual variation in the response to desmopressin is observed. Patients with a lower baseline factor VIII activity tend to show a reduced response, therefore, desmopressin is less frequently used in moderate hemophilia A patients (baseline factor VIII activity 1-5 international units/deciliter), even though factor VIII levels may rise substantially in some of them. We aim to describe the response to desmopressin in moderate hemophilia A patients and to identify predictors. We selected data on 169 patients with moderate hemophilia from the multicenter Response to DDAVP In non-severe hemophilia A patients: in Search for dEterminants (RISE) cohort study. Adequate response to desmopressin was defined as a peak factor VIII level ≥ 30, and excellent response as ≥ 50 international units/deciliter after desmopressin administration. We used univariate and multiple linear regression techniques to analyze predictors of the peak factor VIII level. Response was considered adequate in 68 patients (40%), of whom 25 showed excellent response (15%). Intravenous administration, age, pre-desmopressin factor VIII activity and von Willebrand factor antigen, peak von Willebrand factor activity and desmopressin-induced rise in von Willebrand factor antigen were significant predictors of peak factor VIII level and explained 65% of the inter-individual variation. In 40% of moderate hemophilia A patients, desmopressin response was adequate, thus it is important not to with-hold this group of patients from desmopressin responsiveness. Among the six predictors that we identified for desmopressin-induced factor VIII rise, factor VIII activity and desmopressin-induced rise in von Willebrand factor antigen had the strongest effect.

To serve and protect: The modulatory role of von Willebrand factor on factor VIII immunogenicity.

Hemophilia A is a bleeding disorder characterized by the absence or dysfunction of blood coagulation factor VIII (FVIII). Patients are treated with regular infusions of FVIII concentrate. In response to treatment, approximately 30% of patients with severe hemophilia A develop inhibitory antibodies targeting FVIII. Both patient and treatment related risk factors for inhibitor development have been described. Multiple studies comparing the immunogenicity of recombinant and plasma-derived FVIII have yielded conflicting results. The randomized controlled SIPPET (Survey of Inhibitors in Plasma-Product Exposed Toddlers) trial demonstrated an increased risk of inhibitor development of recombinant FVIII when compared to von Willebrand factor (VWF)-containing plasma-derived FVIII. Presently, it is unclear which mechanism underlies the reduced immunogenicity of plasma-derived FVIII. In this review we address the potential role of VWF on FVIII immunogenicity and we discuss how VWF affects the immune recognition, processing and presentation of FVIII. We also briefly discuss the potential impact of glycan-composition on FVIII immunogenicity. It is well established that VWF shields the uptake of FVIII by antigen presenting cells. We have recently shown that VWF binds to the surface of dendritic cells. Here, we present a novel model in which surface bound FVIII-VWF complexes regulate the internalization of FVIII. Binding of FVIII to VWF is critically dependent on sulfation of Tyr1699 (HVGS numbering) in the light chain of FVIII. Incomplete sulfation of Tyr1699 has been suggested to occur in several recombinant FVIII products resulting in a loss of VWF binding. We hypothesize that this results in alternative pathways of FVIII internalization by antigen presenting cells which are not regulated by VWF. This hypothetical mechanism may explain the reduced immunogenicity of VWF containing plasma-derived FVIII concentrates as found in the SIPPET study.

Emerging Issues in Diagnosis, Biology, and Inhibitor Risk in Mild Hemophilia A.

Mild hemophilia A (MHA) is an X-linked bleeding disorder defined by factor VIII (FVIII) levels between 5 and 40 U/dL. Diagnosis occurs later in life compared with severe or moderate disease. Although bleeding episodes are especially posttraumatic, their unexpected occurrence may be potentially life threatening if diagnosis is missed or delayed. Desmopressin is the treatment of choice for MHA since it is cheap and safe, but a significant proportion of cases do not attain FVIII postinfusion greater than 50 U/dL, which is considered a safe level for major surgery. Thus, replacement therapy may be needed and is usually successful in MHA, but recent data indicate that this can be associated with the occurrence of inhibitors against FVIII, as for severe hemophilia A. However, in contrast to severe or moderate hemophilia A, patients with MHA have a lifelong risk of inhibitor formation. Inhibitors may change the clinical phenotype dramatically, as the inhibitor frequently cross-reacts with the patient's endogenous FVIII, reducing the endogenous FVIII plasma levels below 1 U/dL. Specific F8 missense mutations predispose to inhibitor development. Inhibitors are frequently provoked by intensive treatment with therapeutic FVIII concentrates (more than 5 consecutive exposure days). Bleeding in inhibitor patients may be treated with desmopressin, high doses of FVIII concentrate or FVIII bypassing agents. Many inhibitors disappear over time when no FVIII concentrate is administered. However, this does not imply that a patient is tolerant and an anamnestic reaction may occur when treatment with FVIII concentrate is again necessary. To eradicate, an inhibitor different strategies may be used: watchful waiting, immunosuppression, or immune tolerance induction regimen.

The incidence and treatment of bleeding episodes in non-severe haemophilia A patients with inhibitors.

The development of an inhibitory antibody in non-severe haemophilia A patients may aggravate the bleeding phenotype considerably. Effective treatment of bleeding episodes may be challenging, with ensuing severe complications. At present, evidence is scarce for optimal treatment of bleeding episodes in this patient group. The aim of this study was to describe the incidence and the treatment of bleeding episodes in inhibitor patients in a population-based unselected cohort of non-severe haemophilia A patients with clinically relevant inhibitors. Data were available for 100 of the 107 non-severe haemophilia A patients (factor VIII (FVIII) baseline, 2-40 IU/dl) from 29 centres in Europe and one centre in Australia who had developed a clinically relevant inhibitor between 1980 and 2011. The majority (89 %) of the patients were treated during the inhibitor period for bleeding episodes or a surgical intervention: 66 % needed treatment for bleeding episodes, at a median annual bleeding rate (ABR) of 1.1 (interquartile range (IQR) 0.1-2.5) and a median total of 2 (IQR 1-6) bleeding episodes. Compared to the median ABR before inhibitor development of 0.095 bleeds per year (IQR 0.02-0.42), the increase in ABR is more than a 10-fold. More than 90 % of the bleeding episodes were treated with only one type of product, most frequently (51 %) FVIII concentrates. This study provides the incidence of bleeding episodes and treatment choices in non-severe haemophilia A patients with inhibitors. The 10-fold increase to a median ABR of 1.1 episodes per year emphasizes the impact of inhibitor development for non-severe haemophilia A patients.

Inhibitors in nonsevere haemophilia A: outcome and eradication strategies.

In nonsevere haemophilia A (HA) patients the presence of an inhibitor may exacerbate the bleeding phenotype dramatically. There are very limited data on the optimal therapeutic approach to eradicate inhibitors in these patients. We aimed to describe inhibitor eradication treatment in a large cohort of unselected nonsevere HA patients with inhibitors. We included 101 inhibitor patients from a source population of 2,709 nonsevere HA patients (factor VIII 2-40 IU/dl), treated in Europe and Australia (median age 37 years, interquartile range (IQR) 15-60; median peak titre 7 BU/ml, IQR 2-30). In the majority of the patients (71 %; 72/101) the inhibitor disappeared; either spontaneously (70 %, 51/73) or after eradication treatment (75 %, 21/28). Eradication treatment strategies varied widely, including both immune tolerance induction and immunosuppression. Sustained success (no inhibitor after rechallenge with factor VIII concentrate after inhibitor disappearance) was achieved in 64 % (30/47) of those patients rechallenged with FVIII concentrate. In high-titre inhibitor patients sustained success was associated with eradication treatment (unadjusted relative risk 2.3, 95 % confidence interval 1.3-4.3), compared to no eradication treatment. In conclusion, in nonsevere HA patients most inhibitors disappear spontaneously. However, in 35 % (25/72) of these patients an anamnestic response still can occur when rechallenged, thus disappearance in these patients does not always equal sustained response. Treatment for those requiring eradication has to be decided case by case, as one single approach is unlikely to be appropriate for all.

Effect of von Willebrand factor on inhibitor eradication in patients with severe haemophilia A: a systematic review.

This systematic review was designed to summarize the reported valid quantitative evidence on the association between use of von Willebrand factor (VWF)-containing Factor VIII (FVIII) concentrates and successful immune tolerance induction (ITI) in patients with severe haemophilia A. The primary outcome was successful ITI; secondary outcomes were time to success, complications of the inhibitor or ITI and relapse of the inhibitor. A systematic literature search identified 26 randomized controlled trials, registries and cohort studies, evaluating a total of 1284 patients. For a pooled meta-analysis, 13 studies evaluating 382 patients were included. Due to incomplete data we were not able to assign pre-ITI risk categories to all patients for risk factor analysis. The meta-analysis did not demonstrate a difference in the proportion of patients with successful inhibitor eradication between those treated with VWF-containing products and those treated with FVIII concentrates devoid of VWF (relative risk [RR] 0·70 (95% confidence interval [CI] 0·52-0·89) and 0·84 (95% CI 0·75-0·93) respectively). Bleeding rate during ITI ranged from 0·00 to 0·85 bleeding episodes per year. The proportion of patients with a relapse of the inhibitor (range 0-20%) was mentioned in four studies that were included in the meta-analysis. The results of this systematic review do not support the idea of a positive effect of VWF-containing products in ITI.

Factor VIII gene (F8) mutation and risk of inhibitor development in nonsevere hemophilia A.

Neutralizing antibodies (inhibitors) toward factor VIII form a severe complication in nonsevere hemophilia A, profoundly aggravating the bleeding pattern. Identification of high-risk patients is hampered by lack of data that take exposure days to therapeutic factor VIII concentrates into account. In the INSIGHT study, we analyzed the association between F8 mutation and inhibitor development in patients with nonsevere hemophilia A (factor VIII 2-40 IU/dL). This analysis included 1112 nonsevere hemophilia A patients from 14 centers in Europe and Australia that had genotyped at least 70% of their patients. Inhibitor risk was calculated as Kaplan-Meier incidence with cumulative number of exposure days as the time variable. During 44 800 exposure days (median, 24 exposure days per patient; interquartile range [IQR], 7-90), 59 of the 1112 patients developed an inhibitor; cumulative incidence of 5.3% (95% confidence interval [CI], 4.0-6.6) after a median of 28 exposure days (IQR, 12-71). The inhibitor risk at 50 exposure days was 6.7% (95% CI, 4.5-8.9) and at 100 exposure days the risk further increased to 13.3% (95% CI, 9.6-17.0). Among a total of 214 different F8 missense mutations 19 were associated with inhibitor development. These results emphasize the importance of F8 genotyping in nonsevere hemophilia A.

Feasibility of weaning and direct extubation from open lung high-frequency ventilation in preterm infants.

OBJECTIVE: High-frequency ventilation (HFV) is increasingly used in preterm infants, but data on weaning and extubation are limited. We aimed to establish if weaning the continuous distending pressure (CDP) below 8 cm H2O and the Fio2 below 0.30 is feasible in preterm infants on open lung HFV and if these settings result in successful extubation. DESIGN: Retrospective cohort study. SETTING: Neonatal intensive care unit in a university hospital. PATIENTS: Preterm infants ventilated and directly extubated from HFV between January 2003 and August 2005. MEASUREMENTS AND MAIN RESULTS: Data on patient characteristics, ventilator settings, gas exchange, respiratory support after extubation and the number of patients failing extubation (i.e., reintubation within 48 hr) were retrospectively collected. Two hundred fourteen infants, accounting for 242 ventilation periods, were included in the study. The CDP, but not the Fio2, decreased significantly in the 24-hr period before extubation, resulting in a mean CDP of 6.8 +/- 1.6 cm H2O and a mean Fio2 of 0.25 at the time of extubation. At these settings, 193 (90%) infants were successfully extubated. Multivariate logistic regression analysis showed that birth weight was the only independent variable positively associated with successful extubation. CONCLUSION: This study shows that weaning the CDP below 8 cm H2O with an Fio2 below 0.30 is feasible during open lung HFV and extubation at these settings can be successful in preterm infants. In our series, a 90% success rate was observed. The value of this approach should be prospectively compared with conventional weaning and extubation strategies.