Long-term outcome after autologous BCR::ABL1-negative peripheral blood stem cell transplantation in adults with Philadelphia-positive acute lymphoblastic leukemia: a comparative study

Not available.

Third Early “Booster” Dose Strategy in France of bnt162b2 SARS-CoV-2 Vaccine in Allogeneic Hematopoietic Stem Cell Transplant Recipients Enhances Neutralizing Antibody Responses

Immunocompromised individuals generally fail to mount efficacious immune humoral responses following vaccination. The emergence of SARS-CoV-2 variants of concern has raised the question as to whether levels of anti-spike protein antibodies achieved after two or three doses of the vaccine efficiently protect against breakthrough infection in the context of immune suppression. We used a fluorescence-based neutralization assay to test the sensitivity of SARS-CoV-2 variants (ancestral variant, Beta, Delta, and Omicron BA.1) to the neutralizing response induced by vaccination in highly immunosuppressed allogeneic HSCT recipients, tested after two and three doses of the BNT162b2 vaccine. We show that neutralizing antibody responses to the Beta and Delta variants in most immunocompromised HSCT recipients increased after three vaccine doses up to values similar to those observed in twice-vaccinated healthy adults and were significantly lower against Omicron BA.1. Overall, neutralization titers correlated with the amount of anti-S-RBD antibodies measured by means of enzyme immunoassay, indicating that commercially available assays can be used to quantify the anti-S-RBD antibody response as a reliable surrogate marker of humoral immune protection in both immunocompetent and immunocompromised individuals. Our findings support the recommendation of additional early vaccine doses as a booster of humoral neutralizing activity against emerging variants, in HSCT immunocompromised patients. In the context of Omicron circulation, it further emphasizes the need for reinforcement of preventive measures including the administration of monoclonal antibodies in this high-risk population.

Immunogenicity and safety of the meningococcal B recombinant (4CMenB) vaccine in allogeneic hematopoietic cell transplantation recipients

OBJECTIVES

Despite a high risk of invasive meningococcal (Men) disease, there is no published data on any MenB vaccine after hematopoietic cell transplantation (HCT). We investigated the immunogenicity and safety of the 4CMenB recombinant vaccine (Bexsero®) in adult HCT recipients.

METHODS

Patients were eligible from 6 months post-HCT to receive 2 4CMenB doses at 2 months interval. Sera were collected at baseline, 1 month after the second dose, and 12 months after enrollment. The serum bactericidal activity (SBA) using human complement (hSBA) was assessed against fHbp, NadA, PorAP1.4 and NHBA antigens. The vaccine response was defined by one criteria for one vaccine antigen: (1) In patients with a hSBA titer < 4 at baseline: a titer > 4; (2) In patients with a hSBA titer > 4 at baseline: at least a x4 increase.

RESULTS

40 patients were included at a median of 2.14 (0.57-13.03) years post-transplant. At baseline, most patients (32/40 80%) had hSBA titers < 4 for all vaccine antigens. After 2 vaccine doses, the proportion of patients with a titer > 4 was significantly increased for fHbp (23/40 57.5%), NadA (25/40 62.5%), and PorA (31/40 77.5%) but not for NHBA for which only 6/40 (15%) patients responded. 36/40 (90%) patients were responders to > 1 antigen. However, 9 months later, only 23/37 (62.2%) patients were still seroprotected. No severe adverse event was observed.

CONCLUSION

The response rate of 90% for >1 vaccine antigen and our safety data supports the 4CMenB vaccination of HCT recipients from 6 months after transplant with 2 doses.

CLINICAL TRIALS REGISTRATION

Clinicaltrials.gov, NCT03509051.

TNFR2 blockade of regulatory T cells unleashes an antitumor immune response after hematopoietic stem-cell transplantation

Background

Targeting immune checkpoints that inhibit antitumor immune responses has emerged as a powerful new approach to treat cancer. We recently showed that blocking the tumor necrosis factor receptor-type 2 (TNFR2) pathway induces the complete loss of the protective function of regulatory T cells (Tregs) in a model of graft-versus-host disease (GVHD) prevention that relies on Treg-based cell therapy. Here, we tested the possibility of amplifying the antitumor response by targeting TNFR2 in a model of tumor relapse following hematopoietic stem-cell transplantation, a clinical situation for which the need for efficient therapeutic options is still unmet.

Method

We developed appropriate experimental conditions that mimic patients that relapsed from their initial hematological malignancy after hematopoietic stem-cell transplantation. This consisted of defining in allogeneic bone marrow transplantation models developed in mice, the maximum number of required tumor cells and T cells to infuse into recipient mice to develop a model of tumor relapse without inducing GVHD. We next evaluated whether anti-TNFR2 treatment could trigger alloreactivity and consequently antitumor immune response. In parallel, we also studied the differential expression of TNFR2 on T cells including Treg from patients in post-transplant leukemia relapse and in patients developing GVHD.

Results

Using experimental conditions in which neither donor T cells nor TNFR2-blocking antibody per se have any effect on tumor relapse, we observed that the coadministration of a suboptimal number of T cells and an anti-TNFR2 treatment can trigger alloreactivity and subsequently induce a significant antitumor effect. This was associated with a reduced percentage of activated CD4⁺ and CD8⁺ Tregs. Importantly, human Tregs over-expressed TNFR2 relative to conventional T cells in healthy donors and in patients experiencing leukemia relapse or cortico-resistant GVHD after hematopoietic stem cell transplantation.

Conclusions

These results highlight TNFR2 as a new target molecule for the development of immunotherapies to treat blood malignancy relapse, used either directly in grafted patients or to enhance donor lymphocyte infusion strategies. More widely, they open the door for new perspectives to amplify antitumor responses against solid cancers by directly targeting Tregs through their TNFR2 expression.

Determinants of SARS-CoV-2 waning immunity in allogeneic hematopoietic stem cell transplant recipients

Hematopoietic stem cell transplant (HSCT) recipients are at high-risk for severe COVID-19 and have altered immune responses to vaccination. We sought to evaluate the dynamics of immune response to BNT162b2 mRNA vaccine in HSCT recipients. We systematically proposed vaccination with BNT162b2 to HSCT recipients and gave a third vaccine dose to those showing titers of IgG(S-RBD) below 4160 AU/mL 1 month following the second dose. We then quantified anti-SARS-CoV-2 antibodies dynamics in 133 of these HSCT recipients (88 after two and 45 after three vaccine doses) 6 months after the first vaccine dose. Mean IgG(S-RBD) titer at 6 months was significantly lower than the peak value measured 1 month after a second (p < 0.001) or third (p < 0.01) vaccine dose. IgG(S-RBD) titers at 6 months were strongly correlated to peak values (p < 0.001) and a peak titer above 10,370 AU/mL predicted persistent protection at 6 months. Seventy-two percent (96/133) of patients retained protective antibody levels at 6 months. Immunosuppressive drugs and low lymphocyte counts in peripheral blood correlated with lower IgG(S-RBD) titers at 6 months. Four patients (3%) developed PCR-documented SARS-CoV-2 infection and one died.

Effective Letermovir Prophylaxis of CMV infection post allogeneic hematopoietic cell transplantation: Results from the French temporary authorization of use compassionate program

We report the results of the French Temporary Authorization of Use (ATU) compassionate program of letermovir for primary prophylaxis conducted in 21 transplant centers. Patients were CMV seropositive allogeneic hematopoietic cell transplantation recipients and at high risk for CMV infection. Primary prophylaxis was defined as initiation of letermovir between day 0 and day +28 post-transplant. Between November 2017 and January 2019, 96 patients with a median age of 56 years received letermovir and follow-up data were available for 78 patients. The median time from transplant to letermovir initiation was 4 days, and the median duration of exposure to letermovir was 78 days, with 57 patients still on treatment at the cutoff date. Letermovir was temporarily discontinued in 4 patients (5.1%) and stopped in 39 patients (50.0%), in most cases due to planned end of treatment (n = 16, 20.5%). Fifteen patients (19.2%) each presented one positive CMV PCR, in median 13 days after letermovir initiation. Clinically significant CMV infection was reported in 5 patients (6.4%). No CMV disease was reported. At least one adverse drug reaction was reported for 12 patients (15.4%). In this early access program, letermovir was effective with comparable results of the phase 3 study with a low rate of clinically significant CMV infection, including in patients who were at high-risk for CMV infection.

Antipneumococcal Seroprotection Years After Vaccination in Allogeneic Hematopoietic Cell Transplant Recipients

Background

International guidelines recommend vaccinating allogeneic hematopoietic cell transplant (HCT) recipients at 3 months after transplant, giving 3 doses of pneumococcal conjugate vaccine (PCV) followed by either a dose of 23-valent pneumococcal polysaccharide vaccine (PSV23) or a fourth PCV dose in the case of graft-versus-host disease (GvHD). However, the long-term immunity after this regimen is unknown, and there is no recommendation from 24 months after transplant regarding boosts. Our objective was to assess the antipneumococcal antibody titers and seroprotection rates of allogeneic HCT recipients years after different schedules of vaccination.

Methods

We assessed 100 adult HCT recipients a median of 9.3 years (range: 1.7–40) after transplant. All patients had received at least one dose of PCV and were assessed for antipneumococcal immunoglobulin G (IgG) antibody titers against the 7 serotypes shared by PCV7, PCV13, and PSV23. Sixty-six percent of the patients had been vaccinated according to the current guidelines.

Results

Considering an IgG titer ≥ 0.35 µg/mL as protective for each serotype, the seroprotection rate was 50% for 7/7 serotypes and 70% for 5/7 serotypes, with no differences between the different vaccination schedules. The lack of seroprotection was associated with a transplant performed not in complete remission or from a cord-blood unit, a relapse after transplant, or chronic GvHD at assessment.

Conclusion

Because only half of the vaccinated patients had long-term protection, pending prospective studies defining the best boost program after the initial one, we recommend the assessment of specific IgG titers starting from 24 months to decide for further doses.

Plasma concentrations of atovaquone given to immunocompromised patients to prevent Pneumocystis jirovecii

Objectives

Atovaquone is one of the alternatives to trimethoprim/sulfamethoxazole for prophylaxis of Pneumocystis jirovecii pneumonia (PCP) in immunocompromised patients. In volunteers, there was wide inter-individual variability in atovaquone bioavailability. The aim of this study was to assess the plasma concentrations of atovaquone in immunocompromised patients under PCP prophylaxis.

Methods

Adult haematology or HIV-positive patients receiving atovaquone (750 mg oral suspension twice a day) for PCP prophylaxis were included. Plasma concentrations were assessed using UV-HPLC, around 12 h after the evening dose (Cmin) and 1-5 h after the morning dose (Cmax).

Results

A total of 82 measurements were performed in 33 patients. This included 19 HSCT recipients, 7 haematology non-transplant patients and 7 HIV-positive patients. The median Cmin (IQR) was 11.3 μg/mL (6.2-27.8) and the median Cmax was 13.4 μg/mL (6.0-28.3). The Cmin and Cmax of atovaquone were not different between HIV-negative and HIV-positive patients, or between HSCT and non-HSCT patients. Atovaquone concentrations were not influenced by the co-administration of valaciclovir (n = 20) or ciclosporin (n = 11), by gut graft-versus-host disease (n = 7) or by the intake of atovaquone with food. Nineteen of the 33 (58%) patients had Cmin <15 μg/mL, a threshold associated with a low rate of clinical response in PCP treatment.

Conclusions

Atovaquone is poorly absorbed in more than half of immunocompromised patients and its bioavailability varies between individuals. These unpredictable variations raise the question of therapeutic drug monitoring, in order to identify patients with low concentrations and those who could benefit from regimen adaptation or from alternatives.

Economic burden of preemptive treatment of CMV infection after allogeneic stem cell transplantation: a retrospective study of 208 consecutive patients

BACKGROUND

Cytomegalovirus (CMV) infection and disease (CMV episodes) are global concerns after allogeneic hematopoietic stem cell transplantation (HSCT). They affect survival, both by direct and indirect effects. Due to safety issues of current anti-CMV antivirals, long-term CMV prophylaxis is poorly tolerated and the most common strategy to decrease the incidence of CMV disease is preemptive. New, less toxic, molecules are currently being assessed for CMV prophylaxis which should replace or considerably decrease the preemptive approach. The aim of this study was to assess the economic burden of CMV episodes after HSCT with a preemptive approach.

METHODS

We analyzed data from 208 consecutive adults transplanted in our institution, between 2008 and 2013. Hospital resource utilization was retrieved via the linked hospital admissions and Diagnostic Related Groups for the period of conditioning to 12 months after transplant.

RESULTS

CMV episodes occurred in 70 patients (34%) over the first 12 months following HSCT, after a mean of 75 days (median: 46 (7-334)). The mean total length of stay was significantly associated with the occurrence of a CMV episode (113.9 vs. 87.5 days, p = 0.0002) but was associated neither with the pre-transplant CMV serology of donors/recipients nor with survival. The mean cost of transplant was €104,016 (SD = €37,281) after 12 months. Bivariate and multivariate analyses indicated that the occurrence of >1 CMV episode increased the costs of allogeneic HSCT by 25-30% (p < 0.0001).

CONCLUSION

Our study, which is the largest, single-institution cost study of allogeneic HSCT in Europe, shows that two or more CMV episodes significantly increased the transplant cost. New prophylactic strategies to prevent CMV infection and disease should decrease transplant costs.

Molecular Demonstration of a Pneumocystis Outbreak in Stem Cell Transplant Patients: Evidence for Transmission in the Daycare Center

Pneumocystis jirovecii pneumonia (PCP) is a life-threatening infection in hematology. Although occasionally reported, the role of interhuman transmission of P. jirovecii in PCP, compared to that of reactivation, remains an unresolved question; the recommendation to isolate PCP patients in the hematology ward are not well evidence-based. Following an unexpected increase in the number of febrile pneumonia patients with P. jirovecii DNA detected in respiratory samples in our hematology ward, we explored 12 consecutive patients from November 2015 to May 2016. Genotyping of P jirovecii was performed using microsatellite markers. The frequency of simultaneous occupancy of these 12 patients in the same unit on the same day from 4 months prior to the first diagnosis was recorded. In three patients, the P. jirovecii genotype could not be determined because DNA was insufficient. One rare single genotype (Gt2) was found in four of the other nine, all allogeneic stem cell transplant recipients. The transmission map showed that these 4 patients had multiple opportunities to meet on the same day (median, 6.5; range, 4–10) at the daycare center. It was much less among the eight non-Gt2 patients (median, 1; range, 0–9; P = 0.048). This study, based on modern molecular technics, strongly suggests that interhuman transmission of P. jirovecii between allogeneic stem cell transplant recipients is possible. P. jirovecii DNA detected in respiratory specimens supports that isolation and respiratory precautions be recommended in such cases in the hematology ward.

Risk factors and scoring system for predicting bacterial resistance to cefepime as used empirically in haematology wards

OBJECTIVES

Bacterial resistance is of growing concern in haematology wards. As the inappropriate administration of empirical antibacterial may alter survival, we studied risk factors for resistance to our usual empirical first-line antibacterial therapy, cefepime.

METHODS

We retrospectively studied 103 first episodes of bacteraemia recorded in our haematology department over 2.5 years. Risk factors for cefepime-resistance were identified by multivariate logistic regression with backward selection (P < 0.05). A scoring system for predicting cefepime-resistance was built on independent factor, with an internal validation by the bootstrap resampling technique.

RESULTS

38 (37%) episodes were due to Gram-negative bacteria. Fifty (49%) were due to bacteria resistant to cefepime. Cefepime resistance was significantly associated with a decreased survival at day 30 (P < 0.05). Three risk factors were independently associated with cefepime-resistance: acute lymphoblastic leukaemia; ≥18 days since hospital admission; and receipt of any β-lactam in the last month. Patients with ≥2 of these risk factors had a probability of 86% (CI 95%, 25 to 100%) to carry a cefepime-resistant strain.

CONCLUSION

Using our scoring system should reduce the indication of very broad antibacterial regimens in the empirical, first-line treatment of febrile hematology patients in more than 80% of the cases.

Allogeneic hematopoietic stem cell transplantation for T-prolymphocytic leukemia: a report from the French society for stem cell transplantation (SFGM-TC)

T-prolymphocytic leukemia (T-PLL), a rare aggressive mature T-cell disorder, remains frequently resistant to conventional chemotherapy. Studies have suggested that allogeneic hematopoietic stem cell transplantation (HSCT) might possibly serve to consolidate the response to initial chemotherapy. The current report summarizes the outcome of 27 T-PLL cases identified in the registry in French Society for stem cell transplantation (SFGM-TC). Prior to HSCT, 14 patients were in complete remission (CR), 10 in partial response, three refractory, or in progression. Following HSCT, 21 patients achieved CR as best response. With a median follow-up for surviving patients of 33 (range, 6-103) months, 10 patients are still alive in continuous CR. Overall survival and progression-free survival estimates at 3 yr were 36% (95% CI: 17-54%) and 26% (95% CI: 14-45%), respectively. The relapse incidence after HSCT was 47% occurring at a median of 11.7 (range, 2-24) months. Overall cumulative incidence of transplant-related mortality was 31% at 3 yr. These results suggest that HSCT may allow long-term survival in patients with T-PLL following induction treatment; however, it is associated with a significant rate of toxicity.