Desensitization Regimen Research Articles

Novel desensitization therapy of mesalamine intolerance in patients with ulcerative colitis.

Mesalamine is the first-line drug for treating mild-to-moderate ulcerative colitis (UC); however, some patients develop symptoms of intolerance. Although several desensitization methods have been reported, these desensitization regimens were rather complicated for physicians to prescribe in daily clinical practice; therefore, it has not yet become a major therapeutic option for intolerance patients. Thus, we developed an alternative desensitization protocol. We performed a single-center, retrospective study of patients with UC, who were intolerant to mesalamine and had undergone desensitization therapy. Desensitization starts with 50 mg of granule mesalamine, with an increase in the dose by 50 mg every week up to 200 mg, followed by incremental doses of 100 mg every week. After patients received dosages of more than 1000 mg, the dose was increased by 200 mg every week up to the target dose. Concomitant medications such as oral prednisolone or budesonide rectal foam were allowed during the protocol but were withdrawn before the end of desensitization. We evaluated the success rate of our mesalamine desensitization method and performed safety assessments during the protocol. Of 115 patients, 17 were intolerant to mesalamine. We excluded six patients who had severe disease or organ disorders. Overall, 11 patients received desensitization therapy without hospitalization. All 11 patients successfully underwent desensitization therapy and received the target dose of mesalamine (3000-4000 mg/day) at the end of the protocol. No serious adverse events were observed during this protocol. This retrospective study reports a successful and safe desensitization method for UC patients with mesalamine intolerance.

Effectiveness of combined plasma cell therapy and costimulation blockade based desensitization regimen in heart transplant candidates.

Desensitization is one of the strategies to reduce antibodies and facilitate heart transplantation in highly sensitized patients. We describe our center's desensitization experience with combination of plasma cell (PC) depletion therapy (with proteasome inhibitor or daratumumab) and costimulation blockade (with belatacept). We reviewed five highly sensitized patients who underwent desensitization therapy with plasma cell depletion and costimulation blockade. We evaluated the response to therapy by measuring the changes in cPRA, average MFI, and number of positive beads>5000MFI. Five patients, mean age of 56 (37-66) years with average cPRA of 98% at 5000 MFI underwent desensitization therapy. After desensitization, mean cPRA decreased from 98% to 70% (p=.09), average number of beads>5000 MFI decreased from 59 to 37 (p=.15), and average MFI of beads>5000 MFI decreased from 16713 to 13074 (p=.26). Combined PC depletion and CoB could be a reasonable strategy for sustained reduction in antibodies in highly sensitized patients being listed for heart transplantation.

Haploidentical Hematopoietic Stem Cell Transplantation with Post-Transplant Cyclophosphamide in the Chilean National Health System. a Single Center Study

Haploidentical peripheral blood stem cell transplantation with post-transplant cyclophosphamide (Haplo-PTCy) is the most common transplantation modality in low-and-middle-income countries (LMIC). Registry data has shown comparable outcomes when using haploidentical donors versus Matched Unrelated Donors (MUD) in patients with acute leukemias. In the Chilean Public Health System Haplo-PTCy was incorporated in 2016 for adults up to 60 years old. We analyzed all adult patients who received an Haplo-PTCy at Hospital del Salvador, in a prospective registry study between 2016 and 2021. The primary outcome was overall survival (OS). Secondary outcomes were event-free survival (EFS), cumulative incidence of relapse, and incidence of grade II-IV acute graft-versus-host disease (aGVHD) at day +100. Overall survival and EFS were estimated using the Kaplan-Meier method. The cumulative incidence of relapse was calculated using relapse as the primary event and death without relapse as a competing event. Acute GVHD is shown as absolute incidence at day +100. All statistical analyses were performed with R. This study was done in compliance with the Helsinki Declaration and was approved by the Institutional Review Board. Eighty-five Haplo-PTCy were performed in 82 patients (Table 1). Three-second Haplo-PTCy were excluded from this analysis. The median age was 25 years (range, 15-51), and 65% were male. Ninety-four percent of patients had a neoplastic disease (77/82), and the most common diagnosis was acute lymphoblastic leukemia (57%). Forty-seven percent proceeded to transplant in the first complete response. Most of the patients (76%) presented a low hematopoietic cell transplantation (HCT)-specific comorbidity index. Conditioning was mostly myeloablative (96%). The median dose of CD34+ cells infused was 8.1 x 106/kg (range, 2.4-10.0). No patient needed a desensitization regimen. Cytokine release syndrome (CRS) was common (86%) but no grade 3 CRS was observed. Primary graft failure was observed in one patient (1.2%). Poor graft function was observed in 11 patients (13%). Five patients (6.1%) died before engraftment. The incidence of grade II-IV aGVHD at day +100 was 29% (grade IV was not observed). With a median follow-up of 33 months (range 0-84), the estimated 3-year OS and EFS were 68.3% (95% CI 59-79%) and 64.6% (95% CI 55-76%), respectively (Figure 1). In patients with neoplastic disease (n=77), the 3-year cumulative incidence of relapse was 23% (95% CI 15-33%). Haplo-PTCy is feasible in LMIC. This cohort of cases, mostly young patients with neoplastic disease, shows encouraging survival with an acceptable aGVHD and relapse incidence.

Management of chemotherapy hypersensitivity reactions and desensitization: An SGO clinical practice statement

ObjectiveThe goal of this practice statement is to help members and their multidisciplinary teams recognize infusion reactions and hypersensitivity reactions in the clinical setting. It will provide recommendations to help guide response to reactions and desensitization when appropriate, to promote safe use of chemotherapeutic agents among all providers in the delivery process. MethodsA multi-disciplinary team of healthcare professionals from the Society of Gynecologic Oncology Education Committee collaborated to review peer reviewed literature and guidelines to develop a practice statement on the management of chemotherapy hypersensitivity reactions and desensitization regimens. ResultsThere is always potential for a patient to have a reaction to any medication, with both infusion reactions and hypersensitivity reactions potentially occurring in the treatment of gynecologic cancers. Premedication to prevent reactions should be given at least prior to infusion for regimens that include the most common agents associated with reactions. At the time when reaction is occurring it might be difficult to distinguish between an infusion reaction versus true hypersensitivity given the similarities in signs and symptoms, therefore it is important that orders to manage reactions be included in every chemotherapy order set so the infusion nurse can provide immediate interventions while waiting for the provider to arrive to assess the patient. Desensitization is a potential option to allow the patient to continue to receive the offending agent. While a variety of desensitization regimens have been presented in the literature, the goal is to minimize steps and variability to decrease opportunity for errors during chemotherapy preparation or administration. ConclusionIncorporating a review of the literature and clinical experience from the SGO Education Committee, this paper provides an overview of current approaches for prevention and management of reactions to commonly used chemotherapy agents for gynecologic cancers.

The First Collective Examination of Immunosuppressive Practices Among American Intestinal Transplant Centers.

Unlike other solid organs, no standardized treatment algorithms exist for intestinal transplantation (ITx). We established a consortium of American ITx centers to evaluate current practices. All American centers performing ITx during the past 3 y were invited to participate. As a consortium, we generated questions to evaluate and collect data from each institution. The data were compiled and analyzed. Ten centers participated, performing 211 ITx during the past 3 y (range, 3-46; mean 21.1). Induction regimens varied widely. Thymoglobulin was the most common, used in the plurality of patients (85/211; 40.3%), but there was no consensus regimen. Similarly, regimens for the treatment of acute cellular rejection, antibody-mediated rejection, and graft-versus-host disease varied significantly between centers. We also evaluated differences in maintenance immunosuppression protocols, desensitization regimens, mammalian target of rapamycin use, antimetabolite use, and posttransplantation surveillance practices. Maintenance tacrolimus levels, stoma presence, and scoping frequency were not associated with differences in rejection events. Definitive association between treatments and outcomes, including graft and patient survival, was not the intention of this initial collaboration and is prevented by the lack of patient-level data and the presence of confounders. However, we identified trends regarding rejection episodes after various induction strategies that require further investigation in our subsequent collaborations. This initial collaboration reveals the extreme heterogeneity of practices among American ITx centers. Future collaboration will explore patient-level data, stratified by age and transplant type (isolated intestine versus multivisceral), to explore the association between treatment regimens and outcomes.

#6402 IMPACT OF DARATUMUMAB AND BELATACEPT ON HLA ANTIBODIES IN KIDNEY TRANSPLANT CANDIDATES WITH 100% CPRA: EARLY RESULTS OF ATTAIN (ITN090ST)

Abstract Background and Aims Despite high allocation priority, <10% of kidney transplant candidates with cPRA 100% can find a compatible donor. Current desensitization strategies are ineffective due to antibody rebound. Adding costimulation blockade to plasma cell (PC) depletion prevents antibody rebound in nonhuman primates by countering nodal B cell and Tfh expansion. Method ATTAIN is a pilot, phase I/II trial of daratumumab, a CD38 mAb used in multiple myeloma, plus belatacept, a high affinity CTLA4-Ig, to desensitize kidney transplant candidates with cPRA ≥99.9%. Enrolled subjects receive daratumumab (6 doses: 8 mg/kg) and belatacept (4 doses: 10 mg/kg) over 10 weeks with bone marrow and blood assessments pre-and post-treatment. The primary efficacy endpoint (PE) is a composite of (1) elimination of ≥1 HLA antibody specificity, (2) ≥50% reduction in the MFI of ≥3 HLA antibody specificities, or (3) kidney transplant from a previously incompatible donor. Target accrual is 15, enrolled in 2 cohorts (5+10). Results Cohort 1 (n = 5, mean age 44, 60% with previous transplant) has been enrolled and treated, with 5-31 weeks follow-up to date. The treatment was tolerated well in all 5 patients who showed a significant reduction in most HLA antibodies after treatment without manifestation of rebound. 3 of 5 participants reached the PE and 5 of 5 had >50% bone marrow (BM) PC depletion. One patient received a kidney transplant from a previously incompatible deceased donor and is doing well at 7 months post-transplant without rejection or rebound of HLA antibody. Treatment was temporarily paused in 3 subjects due to AEs (acute cholecystitis and COVID, upper GI bleed, fevers); no cases of opportunistic infection or malignancy occurred. Conclusion A novel HLA desensitization regimen consisting of PC depletion with Daratumumab and costimulatory blockade with Belatacept appears safe and successful in the ongoing ATTAIN clinical trial. In the initial subject, this regimen led to transplant without HLA antibody rebound or acute rejection. Longer follow-up and additional subjects are needed to confirm these promising results. ATTAIN (NCT04827979) is a trial conducted by the Immune Tolerance Network and sponsored by NIAID (award UM1AI109565).

Effects of invivo CXCR4 blockade and proteasome inhibition on bone marrow plasma cells in HLA-sensitized kidney transplant candidates

To date, plasma cell (PC)–targeted therapies have been limited by suboptimal PC depletion and antibody rebound. We hypothesized this is partly because of PC residence in protective bone marrow (BM) microenvironments. The purpose of this proof-of-concept study was to examine the effects of the CXCR4 antagonist, plerixafor, on PC BM residence; its safety profile (alone and in combination with a proteasome inhibitor, bortezomib); and the transcriptional effect on BMPCs in HLA-sensitized kidney transplant candidates. Participants were enrolled into 3 groups: group A (n = 4), plerixafor monotherapy; and groups B (n = 4) and C (n = 4), plerixafor and bortezomib combinations. CD34+ stem cell and PC levels increased in the blood after plerixafor treatment. PC recovery from BM aspirates varied depending on the dose of plerixafor and bortezomib. Single-cell RNA sequencing on BMPCs from 3 group C participants pretreatment and posttreatment revealed multiple populations of PCs, with a posttreatment enrichment of oxidative phosphorylation, proteasome assembly, cytoplasmic translation, and autophagy-related genes. Murine studies demonstrated dually inhibiting the proteasome and autophagy resulted in greater BMPC death than did monotherapies. In conclusion, this pilot study revealed anticipated effects of combined plerixafor and bortezomib on BMPCs, an acceptable safety profile, and suggests the potential for autophagy inhibitors in desensitization regimens.

Efficacy of bortezomib desensitization among heart transplant candidates.

Allosensitization is prevalent in heart transplant candidates and is associated with prolonged waiting times and poor outcomes following transplantation. We analyzed the efficacy of a desensitization regimen consisting of plasma exchange, intravenous immunoglobulin, and bortezomib among 25 consecutive sensitized waitlisted candidates at our center from 2016 to 2021. Following desensitization therapies, all C1q negative antibodies were removed from a candidate's unacceptable antigen list. There was a significant decrease in the median number of human leukocyte antigen (HLA) class I (21-15, p=.001) but not class II antibodies (7-6.5, p=.07). There was a significant corresponding decrease in median calculated panel reactive antibodies for class I (90%-74%, p=.004) but not class II (74.5%-75.5%, p=.30). Following desensitization, 76% of patients were transplanted at a median of 91 days. One-year survival following transplant was 89% with a 33% rate of antibody-mediated rejection (AMR). In conclusion, a bortezomib desensitization protocol was modestly effective for class I antibodies and allowed successful transplant in most cases when combined with selective crossing of C1q negative antigens.

Tocilizumab Evaluation in HLA-Desensitization before Kidney Transplantation as an Add-On Therapy to Apheresis: The TETRA Study.

Desensitization strategies improve access to transplantation in highly sensitized kidney transplant candidates. Tocilizumab could be a valuable addition to more traditional desensitization regimens. We investigated the effect of tocilizumab as an add-on therapy to our standard of care (SoC) desensitization strategy based on rituximab and apheresis. In this study, we prospectively included highly sensitized patients to receive monthly tocilizumab infusions for 6 months before our SoC regimen (Toci + SoC group). We compared the reductions in the mean fluorescent intensity (MFI) rebound at post-transplantation and kidney function at 1-year post-transplantation to patients treated by SoC (based on apheresis and two doses of rituximab). Twenty-six patients were included in the SoC group; seven in the Toci + SoC group. Reductions in pre-transplantation MFI were similar between groups. At 1-year post-transplantation, there was no absolute difference in overall MFI rebounds, including donor-specific antibodies. Toci + SoC helped lower the rebound of antibodies with more elevated baseline MFIs. Graft function and survival rates were similar at one-year post-transplantation (median eGFR 62.8 vs. 65.6 mL/min/1.73 m2 for SoC and Toci + SoC, respectively). Tocilizumab as an add-on to SoC desensitization may help control the post-transplantation rebound of antibodies with elevated baseline MFIs. However, reductions in pre-transplantation MFIs were similar with or without tocilizumab. Further studies are needed to validate this pilot study.

Heart transplantation across preformed donor-specific antibody barriers using a perioperative desensitization protocol

Heart transplantation across preformed donor-specific HLA-antibody barriers is associated with impaired short- and long-term survival. Therefore, in recipients with preformed anti-HLA antibodies, waiting for crossmatch-negative donors is standard practice. As an alternative strategy, recipients with preformed anti-HLA donor specific antibodies have been managed at our institutions with a perioperative desensitization regimen. A retrospective analysis was performed comparing heart transplant recipients with preformed donor-specific HLA-antibodies to recipients without donor-specific antibodies. Recipients with a positive virtual crossmatch received a perioperative desensitization protocol including tocilizumab intraoperatively, plasma exchange and rituximab followed by a six-month course of IgGAM. Among the 117 heart-transplanted patients, 19 (16%) patients underwent perioperative desensitization, and the remaining 98 (84%) patients did not. Cold ischemic time, posttransplant extracorporeal life support for primary graft dysfunction, and intensive care unit stay time did not differ between groups. At 1-year follow-up, freedom from pulsed steroid therapy for presumed rejection and biopsy-confirmed acute cellular or humoral rejection did not differ between groups. One-year survival amounted to 94.7% in the treated patients and 81.4% in the control group. Therefore, heart transplantation in sensitized recipients undergoing a perioperative desensitization appears safe with comparable postoperative outcomes as patients with a negative crossmatch.

Current Perspectives in ABO-Incompatible Kidney Transplant.

For a long time, ABO incompatible living donor kidney transplantation has been considered contraindicated, due to the presence of isohemagglutinins, natural antibodies reacting with non-self ABO antigens. However, as the demand for kidney transplantation is constantly growing, methods to expand the donor pool have become increasingly important. Thus, in the last decades, specific desensitization strategies for ABOi transplantation have been developed. Nowadays, these regimens consist of transient removal of preformed anti-A or anti-B antibodies by using plasmapheresis or immunoadsorption and B-cell immunity modulation by CD20+ cells depletion with rituximab, in association with maintenance immunosuppression including corticosteroids, tacrolimus and mycophenolate mofetil. The outcome in ABOi kidney transplantation have markedly improved over the years. In fact, although randomized trials are still lacking, recent meta analysis has revealed that there is no difference in terms of graft and patient’s survival between ABOi and ABO compatible kidney transplant, even in the long term. However, many concerns still exist, because ABOi kidney transplantation is associated with an increased risk of bleeding and infectious complications, partly related to the effects of extracorporeal treatments and the strong immunosuppression. Thus, a continuous improvement in desensitization strategies, with the aim of minimize the immunosuppressive burden, on the basis of immune pathogenesis, antibodies titers and/or ABO blood group, is warranted. In this review, we discuss the main immune mechanisms involved in ABOi kidney transplantation, the pathogenesis of tolerance and the desensitization regimens, including immunoadsorption and plasmapheresis and the immunosuppressive protocol. Finally, we provide an overview on outcome and future perspectives in ABOi kidney transplant.

Sex Differences in Desensitization for Patients Awaiting Heart Transplantation: Is There a Difference?

Purpose For patients awaiting heart transplantation (HTx), who have high levels of circulating antibodies (greater than 70% PRA) desensitization therapy may be indicated. This will allow expansion of the donor pool for a compatible donor. As women appear to be more highly sensitized (due to multiple pregnancies), it is not clear as to whether women compared to men can benefit from desensitization therapy. We sought to answer this question with review of our large, single center database. Methods Between 2008 and 2020, we assessed 49 patients awaiting HTx who underwent desensitization therapy. These patients were divided into groups by sex to evaluate their response to desensitization therapy. Our desensitization protocols consist of regimens including intravenous immune globulin, anti-CD20 monoclonal antibody, plasmapheresis, proteosome inhibitors. A response to desensitization therapy was assessed by the decline of the dominant circulating antibody determined by mean fluorescence intensity (MFI). Post-HTx data was assessed for 1-year survival and freedom from rejections (acute cellular rejection [ACR], antibody-mediated rejection [AMR]). Rejection episodes were compared to a control group of non-sensitized patients transplanted during the same period (n=771). Results Desensitization therapy in women appeared to be comparable to men considering similar desensitization protocols. There were no significant differences in waitlist mortality, time on the waitlist, or 1-year post-transplant survival, 1-year freedom ACR or AMR, between the two groups. Compared to non-sensitized patients, freedom from AMR was significantly lower in both sensitized men and women (72.7% men and 78.9% women vs. 96.5% control group). Conclusion Sensitized women awaiting HTx compared to men appear to have similar response to various desensitization regimens. Post-HTx, there was more AMR in both groups, suggesting sensitization may be responsible. For patients awaiting heart transplantation (HTx), who have high levels of circulating antibodies (greater than 70% PRA) desensitization therapy may be indicated. This will allow expansion of the donor pool for a compatible donor. As women appear to be more highly sensitized (due to multiple pregnancies), it is not clear as to whether women compared to men can benefit from desensitization therapy. We sought to answer this question with review of our large, single center database. Between 2008 and 2020, we assessed 49 patients awaiting HTx who underwent desensitization therapy. These patients were divided into groups by sex to evaluate their response to desensitization therapy. Our desensitization protocols consist of regimens including intravenous immune globulin, anti-CD20 monoclonal antibody, plasmapheresis, proteosome inhibitors. A response to desensitization therapy was assessed by the decline of the dominant circulating antibody determined by mean fluorescence intensity (MFI). Post-HTx data was assessed for 1-year survival and freedom from rejections (acute cellular rejection [ACR], antibody-mediated rejection [AMR]). Rejection episodes were compared to a control group of non-sensitized patients transplanted during the same period (n=771). Desensitization therapy in women appeared to be comparable to men considering similar desensitization protocols. There were no significant differences in waitlist mortality, time on the waitlist, or 1-year post-transplant survival, 1-year freedom ACR or AMR, between the two groups. Compared to non-sensitized patients, freedom from AMR was significantly lower in both sensitized men and women (72.7% men and 78.9% women vs. 96.5% control group). Sensitized women awaiting HTx compared to men appear to have similar response to various desensitization regimens. Post-HTx, there was more AMR in both groups, suggesting sensitization may be responsible.

A Systemised Approach to Smart Pump Integration with an Electronic Medical Record System – An Australian Experience

ABSTRACT Background: Smart pump integration with Electronic Medical Record (EMR) systems offers an opportunity to introduce a closed-loop medication management system in hospital settings. Closed-loop medication management systems minimise human errors, improve nursing workflow and efficiency, and optimise patient safety. In this descriptive observational study, we will outline some of the key steps required to successfully integrate a smart pump dataset with EMR computerised provider/physician order entry (CPOE) systems. Methodology: The triple C model of consultation, collaboration and consolidation was used for the development and implementation of a smart infusion pump and EMR integration at a 160-bed specialist Australian hospital. This systemised approach allowed a methodical implementation process and ensured sustainability of the intervention. Key stakeholders were identified and engaged to establish a working group to align medication orders in the EMR and the smart pump library to ensure readiness of pump-EMR integration phase. Validation testing was conducted for each EMR infusion order to check successful auto-programming to a corresponding medication on the smart pump. The steps discussed are applicable to all hospital settings with EMR systems and smart pumps. Results: The smart pump dataset contained a total of 217 unique medications and fluids that were tested for interoperability. A total of 87% (188/217) passed full record testing. The remaining 13 % (29/217) were excluded from interoperability. The 13% of medication and fluids that were excluded was due to the medication being prescribed on paper (i.e. medicines with desensitisation regimen), the medication unable to be prescribed as a medicine in the EMR (i.e. blood products), the smart pump limitations to build safety limits around only one medicine (i.e. multi-additive infusions) or excluded due to specialist hospital formulary. Conclusion: This study using a systemised approach, that described and identified key stages and phases required for integration of smart pump infusions with an EMR system, to create a closed-loop medication management system in an Australian hospital setting. Highlights

Clinical Relevance of Isoagglutinin Rebound in Adult ABO-Incompatible Living Donor Liver Transplantation.

ABO-incompatible (ABO-I) living donor liver transplantation (LDLT) can be performed successfully. However, anti-ABO isoagglutinin rebound may cause antibody-mediated rejection (AMR) and graft loss. The risk threshold of isoagglutinin rebound is still not defined. 76 ABO-I LDLT recipients were divided into group A (n = 56) with low isoagglutinin titers (<1:256), and group B (n = 20) with high isoagglutinin titers (≥1:256), at initial assessment for liver transplantation. The last 12 patients in group B received a modified desensitization regimen by adding bortezomib to deplete plasma cells. Six (10.7%) patients in group A and 10 (50.0%) patients in group B had postoperative isoagglutinin rebound (p < 0.001). Three patients (5.54%) in group A and two patients (10%) in group B developed clinical AMR (p = 0.602). The cutoff value of postoperative isoagglutinin rebound to cause clinical AMR was ≥1:1024. Among the 12 patients in group B with bortezomib administration, isoagglutinin rebounded up to 1:128 only, and no clinical AMR occurred. In conclusion, the patients with high isoagglutinin titers had a higher rate of postoperative isoagglutinin rebound. Isoagglutinin rebound ≥1:1024 is risky for developing clinical AMR. Adding bortezomib into the desensitization regimen may mitigate isoagglutinin rebound, and avoid clinical AMR.

Failure of a single day metronidazole desensitization protocol, and success of a modified two-day protocol in an outpatient setting

BackgroundTrue allergy to metronidazole, a common anti-infective in clinical practice, is rarely reported in the literature. In the case of Trichomonas, there are few alternatives to the nitrimidazole class of drugs, and the alternatives that do exist are associated with worse clinical outcomes. Accordingly, for the rare patients with Type 1 hypersensitivity reactions to metronidazole but compelling need, desensitization protocols have been adapted previously. Reactions during these protocols appear common. Patients in previous regimens have required higher level care for observation, which is costly and resource-intensive.Case presentationWe report here on a successful outpatient two-day regimen for metronidazole desensitization. Our patient had compelling indication for metronidazole, but reacted after receiving the very first dose of a previously described desensitization protocol. Accordingly, the protocol was adapted further. Despite this, she went on to develop objective hives prior to reaching the full intended dose. With appropriate symptom management and pre-medication on the second day in clinic, she was successfully desensitized and able to complete a week of full-dose metronidazole. No acute care resources were needed.ConclusionWe propose this two-day desensitization regimen for patients who react during the previously described desensitization protocols. This regimen was effective and safe, and did not necessitate the use of acute-care resources. Two-day desensitization protocols while relatively uncommon, can be successful.

Long-term outcomes of sensitized lung transplant recipients after peri-operative desensitization

The Toronto Lung Transplant Program has been using a peri-operative desensitization regimen of plasma exchange, intravenous immune globulin, and antithymocyte globulin in order to accept donor-specific antibody (DSA)-positive lung transplants safely since 2008. There are no long-term data on the impact of this practice on allograft survival or the development of chronic lung allograft dysfunction (CLAD). We extended our prior study to include long-term follow-up of 340 patients who received lung transplants between January 1, 2008 and December 31, 2011. We compared allograft survival and CLAD-free survival among patients in three cohorts: DSA-positive, panel reactive antibody (PRA)-positive/DSA-negative, and unsensitized at the time of transplant. The median follow-up time in this extension study was 6.7years. Among DSA-positive, PRA-positive/DSA-negative, and unsensitized patients, the median allograft survival was 8.4, 7.9, and 5.8years, respectively (p=.5908), and the median CLAD-free survival was 6.8, 7.3, and 5.7years, respectively (p=.5448). This follow-up study confirms that long-term allograft survival and CLAD-free survival of patients who undergo DSA-positive lung transplants with the use of our protocol do not differ from other lung transplant recipients. Use of protocols such as ours, therefore, may improve access to transplant for sensitized candidates.

Desensitization Regimen Consisting of High-Dose Intravenous Immunoglobulin, Plasmapheresis, and Rituximab (an Anti-CD20 Antibody), Without Eculizumab and/or Bortezomib, in 41 Highly Sensitized Kidney Transplant Recipients.

Antibody-mediated rejection in patients with positive crossmatches can be severe and result in sudden onset of oliguria, leading to graft loss. In an attempt to prevent posttransplant oliguria, we adopted a preoperative desensitization protocol involving the use of high-dose intravenous immunoglobulin/plasmapheresis and the anti-CD20 antibody, rituximab, in 41 transplant recipients with positive crossmatch test results. We retrospectively examined the clinical courses of the 41 kidney transplant recipients, paying special attention to renal graft function, urine volume, and changes in the titers of donor-specific antibodies. Four grafts were lost during an average of 4.5-year follow-up. Average graft function was excellent, with a serum creatinine level of 1.3 ± 0.4 mg/dL. Sufficient urine output, with no oliguria or anuria, was achieved postoperatively in 40 of the 41 patients. However, among the 34 patients who underwent graft biopsies, the biopsies revealed acute antibody-mediated rejection in 21 patients (62%), and chronic antibodymediated rejection in 10 patients (30%). The high-dose intravenous immunoglobulin treatment included in our desensitization protocol was shown to be safe and effective for achieving successful transplant outcomes and allowed the avoidance of more aggressive B-cell-targeted treatments, such as C5 inhibitors and/or proteosome inhibitors, for preventing posttransplant oliguria and anuria.

Genomic and Biochemical Proteasomal Adaptations in Carfilzomib-Resistant Plasma Cells That Limit HLA-Desensitization in Transplantation Candidates

Bone marrow plasma cells (BMPCs) are the source of long-term humoral immunity including HLA antibodies, which promote organ rejection. End-stage renal disease (ESRD) affects more than 660,000 patients per year in the U.S. and is associated with significant morbidity and mortality. Renal transplantation remains the optimal treatment for a substantial proportion of ESRD patients and dramatically improves patient overall survival and quality-of-life. However, preformed human leukocyte antigen (HLA)-specific antibodies are associated with reduced transplantation rates, graft loss and poorer outcomes. Proteasome inhibitor (PI) therapies that target BMPCs to reduce HLA-antibody levels represent an effective means of enhancing transplantation outcomes but are limited by resistance mechanisms. Single antigen bead assays determined that the spectrum of antibody production by HLA-sensitized patient (BMPCs) was remarkably similar to that detected in matching serum samples, supporting the role of BMPCs as the primary source of circulating HLA antibodies. Desensitization therapy with the irreversible proteasome inhibitor carfilzomib reduced PCs in patient BM by ~70% and was associated with a profound reduction in HLA antibodies. We then used bulk RNA-seq transcriptomics to explore potential drug resistance mechanisms within carfilzomib-resistant BMPCs. Network-based pathway analysis revealed that genes encoding the immunoproteasome, a specialized proteasome variant with unique catalytic subunits, and the proteasome activator PA28 were upregulated in BMPCs that survived carfilzomib therapy. Native gel electrophoresis and in vitro functional studies confirmed that BMPCs isolated after carfilzomib therapy contained greater levels of immunoproteasomes as well as increased immunoproteasome-specific peptide-hydrolyzing activity relative to BMPCs from healthy donors or untreated HLA-sensitized patients. Supervised hierarchical clustering analysis (Fig. 1A) and western blotting (Fig. 1B) indicated that PSMB8, which encodes an immunoproteasome catalytic subunit, and PSME1 and PSME2 which encode the proteasome PA28 activator, were significantly upregulated in BMPCs isolated from patients following carfilzomib therapy. Assays then demonstrated that BMPCs that survived carfilzomib therapy were resistant to the FDA-approved PIs bortezomib, carfilzomib and ixazomib but were sensitive to an immunoproteasome-specific inhibitor KZR-616. Thus, we have uncovered proteasomal adaptations in BMPCs as a resistance mechanism underlying carfilzomib therapy and suggest novel strategies that could improve desensitization regimens and reduce antibody-mediated rejection in organ transplantation. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Continuous Platelet Transfusion As a Potential Desensitization Regimen in HLA Class I Alloimmune-Mediated Platelet Refractoriness

Background: The development of HLA antibodies is responsible for 4-8% of platelet transfusion refractoriness (PTR). The presence of HLA antibodies is a clinical complication that is generally managed by the selection of products that are negative for the antigens cognate to the patient's antibodies. Often, this selection is facilitated by targeted recruitment of donors with known HLA types. However, for very broadly HLA-alloimmunized patients, compatible products may be exceedingly scarce or completely unavailable, precluding the ability to consistently provide products the patient will likely increment to and benefit from. Here we describe a case of a patient with severe aplastic anemia (platelet count chronically <1 K/uL) and platelet transfusion refractoriness secondary to broad HLA-alloimmunization (98% PRA). HLA compatible products were unavailable due to the patient's rare HLA type and breadth of antibodies, and attempts at procuring compatible products via multiple national agency searches were unsuccessful. Thus, the patient could only be supplied with HLA incompatible products, which yielded insufficient post-transfusion platelet corrected-count increments (CCI). Her course was eventually complicated by multifocal intracranial hemorrhages, necessitating ICU admission with aggressive platelet transfusion support, immune-targeting therapy consisting of IVIg, and aminocaproic acid and recombinant activated factor VIIa.Methods: A continuous platelet infusion, or “platelet drip,” was employed in order to provide platelet transfusion support in the face of her severe thrombocytopenia with profound refractoriness. This consisted of consecutive transfusions of 4-6 equivalent unit apheresis platelet products (“doses”) transfused over 4 hours with a 15 minute post-transfusion CBC obtained from Q8 to Q12 hours to assess platelet increments. This ultimately resulted in 24-30 equivalent unit platelet product infusions/day.Results: Two days into the continuous platelet infusion, the patient began incrementing appropriately to occasional platelet products (CCI>>5) and, consequently, the infusions were able to sustain a platelet count >10K/uL, with a range of 20-70 K/uL, over the subsequent week. The improved counts, along with the patient's improved clinical condition and stable imaging findings showing resolving intracranial hemorrhages, allowed the transfusion support to be goal-directed targeting a prophylactic platelet threshhold of 10K/uL. Continued monitoring of the patient's CCIs enabled the identification of permissive antigens (i.e., allogeneic platelets with HLA antigens predicted to be incompatible with the patient's serum by solid-phase testing but were found to result in satisfactory increments); this knowledge allowed progressive widening of her permissive donor pool and enabled continued prophylactic support as needed. After three weeks the patient was able to be discharged from the ICU.Subsequent HLA class I antibody screens using flow-cytometry based single antigen bead (SAB) technology revealed progressive decrease in the patient's mean fluorescence intensity for most of her antibody specificities, with the majority of her class I A antibodies falling to undetectable or near-undetectable levels (while previously >5000 MFI). Simple regression analysis (RStudio 1.0.153, R version 3.4.1) was used to test to how level of exposure to individual HLA platelet antigens (as measured by the number of doses with a given antigen) affected subsequent MFI levels. The results of the regression indicate that pre MFI and exposure explain 70.6% of the variance (R2=0.706, F(2,78)=93.7, p=<2.2e-16). It was found that exposure is a significant predictor of decreased MFI (b=-107.20, p=0.01422). High initial MFI was strongly associated with high subsequent MFI (b=0.75, p= <2.2e-16).Conclusions: This data raises the possibility that large bolus platelet infusions could not only be of immediate therapeutic benefit in patients with HLA-alloimmune-mediated platelet refractoriness, but may also accelerate the evanescence of the responsible antibodies. Further research is warranted to explore this possibility, and to ascertain the potential magnitude of this effect in comparison to competing factors such as natural evanescence and/or B-cell immunosuppressive or immunomodulatory therapies. DisclosuresNo relevant conflicts of interest to declare.

Emerging New Approaches in Desensitization: Targeted Therapies for HLA Sensitization.

There is an urgent need for therapeutic interventions for desensitization and antibody-mediated rejection (AMR) in sensitized patients with preformed or de novo donor-specific HLA antibodies (DSA). The risk of AMR and allograft loss in sensitized patients is increased due to preformed DSA detected at time of transplant or the reactivation of HLA memory after transplantation, causing acute and chronic AMR. Alternatively, de novo DSA that develops post-transplant due to inadequate immunosuppression and again may lead to acute and chronic AMR or even allograft loss. Circulating antibody, the final product of the humoral immune response, has been the primary target of desensitization and AMR treatment. However, in many cases these protocols fail to achieve efficient removal of all DSA and long-term outcomes of patients with persistent DSA are far worse when compared to non-sensitized patients. We believe that targeting multiple components of humoral immunity will lead to improved outcomes for such patients. In this review, we will briefly discuss conventional desensitization methods targeting antibody or B cell removal and then present a mechanistically designed desensitization regimen targeting plasma cells and the humoral response.