Despite the great rise in the rate of annual LDAs Tx, many potential TR with suitable donors have been derived out to the ever-expanding DD W/L
By: Fedaey Abbas (MD)
Abbreviations (to facilitate your reading, read twice please):
o - ve: Negative
o +ve: Positive
o AB: Antibody (s)
o Ac Rj: acute rejection
o Aceta: Acetaminophen
o Ag (s): antigen(s).
o aHUS: atypical hemolytic uremic syndrome
o ALm: alemtuzumab
o AMR: Antibody-mediated rejection.
o ATG: Antithymocyte globulin
o Bort: Bortezomib
o C: Complement
o Carf: Carfilzomib
o CDC: complement-dependent cytotoxicity
o CMV: cytomegalovirus
o CMX: Crossmatch
o CNI: calcineurin inhibitor
o cPRA: Calculated panel reactive antibody
o CTS: Collaborative Transplant Study
o DD: deceased-donor
o DDA: Decreased-donor allograft
o Diphen: Diphenhydramine
o DSAs: donor-specific antibodies
o Dsnz: Desensitization/desensitized
o DX: dialysis
o Ecz: Eculizumab
o EMA: European Medicines Agency
o Fc: flow cytometry
o FcRn: Neonatal Fc receptor
o FDA: Food and Drug Administration
o HAR: Hyperacute rejection
o HF: heart failure
o HLA: Human leukocyte antigen antibodies.
o iABO: ABO-incompatible
o ID: immunodominant
o iHLA: incompatible HLA
o IL: the interleukin
o Im/m: immunosuppression
o Imli: Imlifidase
o IVIG: intravenous immune globulins
o KAS: kidney allocation system
o KPD: kidney paired donation
o KTR: kidney transplant recipients
o KTx: kidney transplant/transplantation
o LD: living donor
o LDAs: Living-donor allografts
o mAB: monoclonal antibody
o MCS: median channel shift
o MFI: mean fluorescence intensity
o MMF: Mycophenolate mofetil
o Mthyprd: Methylprednisolone
o Obinu: Obinutuzumab
o OPTN: The Organ Procurement and Transplantation Network
o PCP: Pneumocystis pneumonia,
o PE: plasmapheresis
o PNH: paroxysmal nocturnal hemoglobinuria
o PRAs: panel reactive antibody
o Pred: prednisone
o Preetx: Preemptive transplantation
o rATG: Rabbit anti-thymocyte globulin.
o RCT: randomized controlled trials
o RIS: Relative intensity score
o Rtx: Rituximab
o SAB: Single antigen bead.
o Snz: Sensitization/sensitized.
o Tac: Tacrolimus
o TG: transplant glomerulopathy
o Tocil: tocilizumab
o TR: Transplant recipients
o Tx: transplant/transplantation
o Un-Ag: "unacceptable antigens"
o UNOS: United Network for Organ Sharing
o W/L: waiting list
Despite the great rise in the rate of annual LDAs Tx, many potential TR with suitable donors have been derived out to the ever-expanding DD W/L due to the pre-formed HLA AB that can be acquired through pregnancy, transfusion, and/or previous Tx. The finding of these anti-HLA AB in a potential TR's serum is called = HLA sensitization (Snz). If not properly suppressed, the finding of these AB is probably inducing AMR with early allograft failure. AMR was identified early in the history of Tx as HAR induced by the finding of preformed AB, mostly seen as AB to donor HLAs. The advent of the pre-Tx CMX technology has originally eliminating the HAR. W/L timing may exceed several years up to decades with disproportionate prolonged waiting for ptns with blood group B or O. The prolonged timing spent on W/L for the proper DDA to whom HLA AB not present has a significantly harmful impact on both quality/quantity of ptn life. Preetx (Tx before DX is required) may provide better ptn and graft outcome in comparison with outcome of ptns on maintenance DX for a prolonged period before Tx.
Considering 2020 database from the OPTN, almost 12 % of ptns on the DDA W/L are highly pre-sensitized to HLA (determined as ≥80 % cPRA). Consequently, these ptns are less likely to be prone for Tx and may spend a prolonged period on the W/L, pending an offer of the appropriate donor. Several ptns having a potential LD may be excluded with no further workup considering the results of the initial +ve CMX with a potential TR candidate that reflecting the finding of the pre-formed HLA AB.
The increasing risk of HA AMR with followed graft failure if transplanted against prior finding of HLA AB has developed a general prohibited attitude to this policy. However, recent reports about successfully performed Tx across an HLA barrier via several Dsnz regimens tailored to limit the magnitude of the pre-existing ABs to an extent permitting a successful engraftment have triggered more interest in utilizing an immunologic incompatible graft in KTx. Willing ptns but with iHLA donor may expect DD organ or receiving a LD organ via Dsnz, KPD, or combining both. Choosing Dsnz or KPD for an individual TR relied primarily upon the availability of a suitable matching via KPD and their chance of successful Dsnz regimen. Several approaches have been utilized in KTR to by-pass the HLA Snz barrier:
NEED FOR DSNZ
The magnitude of HLA Snz of a candidate TR is 1st identified at the timing of initial Tx assessment via testing ptn serum against solubilized HLA Ags attaching solid beads. We 1st perform a multiple-Ag Fc bead testing to screen for the finding of anti-HLA AB; if +ve, a SAB assay (Luminex) is proceeded to recognize the specific HLA Ags to which the candidate TR has formed ABs. At certain centers, Ags with an MFI of ≥15,000 are classified as Un-Ag and introduced into UNet, the computerizing system guided by the UNOS.
If an Un-Ag for certain ptn is listed in UNet, kidney grafts from donors having this Ag will NOT be offered to this ptn. Of note, MFI values may differ by about 20-25 % between various HLA labs and MFI threshold values used for designing an Un-Ag are not universal along Tx centers. Computing cPRA is basically depending on ptn's Un-Ag; and currently reflecting both the widths and depth of the ptns' Snz. All ptns assessed with a cPRA ≥30 % or proceeding to a re-Tx are dealt as sensitized and potentially eligible for Dsnz plans. Once the magnitude of ptn Snz has been assessed, the requirement for Dsnz regimen before Tx can be tailored. The suggested therapeutic options varies according to whether or not the TR has a potential LD.
Potential LD: In a sensitized ptn (i.e., cPRA ≥30 % or willing re-Tx) having one or more potential LD, we 1st prepare a virtual CMX to identify if the TR has DSAs or not. A T/B cell CDC CMX and T/B cell Fc CMX are currently performed if the donor is determined. These data can be utilized to determine the potential risks of AMR occurrence and tailor a Dsnz program, if appropriate, or to disagree against Tx with certain donor. Moreover, all Snz ptns with a potential LD can be listed on a DD Tx lists. A suggested approach that is currently based on the findings of the CDC & flow CMX:
o +ve CDC CMX: A +ve CDC CMX is dealt as a contraindication for Tx for certain donor, despite considered in certain centers. Large, multicenter study: 22 Tx US centers performing iHLA KTx, incidence of all-cause allograft loss at 1 & 5 ys: 19 & 40 %, resp, with +ve cytotoxic CMX. This higher risk of AMR & allograft loss with +ve CDC CMX, these ptns should not Dsnz. Rather assess other potential LD or be enrolled in a KPD regimen.
o -ve CDC CMX & +ve Fc CMX: For these ptns we should assess the strength of the flow CMX via MCS assessment:
· MCS is ≤250: HLA Dsnz can be offer according to the total specificity & strength of DSAs. We calculate RIS, with 10 points for each DSA in the strong-binding level (MFI ≥10,000), 5 points for each moderately intense DSA (MFI 5000-9999), & 2 points for every weak DSA (MFI <5000). If RIS is < 17 points -> proceed to standardized Dsnz plan & Tx.
· Rarely, MCS ≤250 with RIS >17 points (most ptns with RIS >17 having MCS >250), NO Dsnz advised and consider other potential donor(s) or KPD.
· MCS >250, NO Dsnz and consider KPD OR other potential donor(s).
o -ve CDC CMX & -ve Fc CMX: These ptns can be DSA-ve, CMX -ve or DSA +ve, CMX -ve. Ptns in either classes still at risk of acute/chronic AMR development, so -> Dsnz + Tx can be proceeded.
Ptns with no potential LD: Ptns Snz (cPRA ≥30 %) and not having a potential LD, should be listed for DD Tx with a pre-Tx Dsnz regimen offered once the ptn became within an accepted range for the offered DD kidney Tx. This can be recognized according to the number of ys on W/L and the quantity of points allotted via the KAS for the magnitude of allo-Snz.
Overview of Dsnz: HLA-mismatched KTx can be complicated by a greater rejection rates with lowered allograft longevity in comparison with HLA-matched Tx. HLA Snz is also associated with lowered allograft longevity, and ptns with higher PRAs are commonly characterizing as being of greater immunological risk. However, some reports suggest that this description may be confined to TR with pre-existing DSAs, as Snz TR with NO DSAs show outcomes that are simulating those of non-sensitized TR.
A higher degree of HLA Snz may lead to an increased possibility of a +ve CMX to a potential DD kidney allograft that usually not accepted as Tx with an iHLA donor can be complicated with:
1) An increased rate of rejection,
2) An increased rate of post-Tx re-hospitalization, &
3) An increased rate of post-Tx allograft loss & death.
However, it seems to be of a survival benefit with Tx from an iHLA donor as compared to ptns still remaining on the Tx W/L, and many Snz ptns either incurring a more timing on DX while on W/L or became unlikely to be offered a compatible donor.
The overall target of HLA Dsnz is 2 folds:
o To abort AMR evolution in these ptns after Tx
o To augment the chance of a successful KTR in TR with broad HLA AB Snz
Dsnz may be proceeded in ptns awaiting either LD or DD Tx. Goals of Dsnz are similar in both settings with approach of therapy is little different considering the unpredicted timing of DD Tx in relation to the given Dsnz plans. The offered HLA Dsnz protocols are not universal, however, the most commonly applied regimens are employing a combination of the following approaches:
o Immunomodulation of the TR immune system, ideally via IVIG
o Removing the circulating anti-HLA AB, via extracorporeal techniques e.g., PE
o Depleting B cell, the source of anti-HLA AB, mostly via Rtx (anti-CD20 agent).
HLA Dsnz protocols: HLA Dsnz regimens are variable at various Tx centers according to the current experience and ptns preference. Unfortunately, there is no RCT comparing the current Dsnz regimens, and the optimal therapeutic approach still uncertain. Pre-Tx HLA Dsnz via a combined IVIG (high-dose) + Rtx has been suggested for most ptns. Dsnz with this regimen will offer:
1) Reducing the mean PRAs,
2) Decreasing Fc CMX MCS, &
3) Shortened timing to Tx, allowing Tx in 75-80 % of ptns.
LD Tx: Ptns offered potential LD who’re mostly qualified for Dsnz, we can perform pre-Tx Dsnz with high-dose IVIG + Rtx. Dsnz protocol for LD Tx can be proceeded as follows:
o Rtx 375 mg/m2 on days 0 & 14 with pre-medication for every Rtx dose with IV Mthyprd 40 mg, oral Aceta 650 mg, and oral Diphen 50 mg.
o IVIG 2 g/kg (max 140 g/dose) on d. 28 & 42 with same pre-medicating
With completed Dsnz regimen, a donor-specific CDC T/B cell CMX & Fc T/B cell CMX can be currently repeated. The Fc CMX is usually proceeded after pronase digestion, so that removing CD20 from B cells and non-HLA Ags from T/B cells that enables more distinct identification of HLA-specific AB and eliminating the impact of Rtx. Dsnz regimen can be considered successful if the ptn shows an accepted CMX that is defined as:
o -ve CDC CMX in ≥1:2 diluted serum,
o -ve Fc CMX, or
o +ve Fc CMX + MCS ≤ 250.
If the findings of the CMX are accepted, Tx surgery can be proceeded within one wk. If the findings of the CMX are NOT accepted, we either:
o Consider alternate Dsnz plan or
o TR enrolled in a KPD program.
Combining high-dose (2 g/kg/dose) IVIG + Rtx has been shown to be safe and efficacious in limiting the anti-HLA AB values and enhancing the rates of Tx among highly sensitized TR offered either a LD or DD Tx.
Open-label study: 20 highly sensitized KTR receiving IVIG (2 g/kg on ds 0 & 30) + Rtx (1 g on ds 7 & 22)à ptns can be eligible for KTx from either a LD or DD. This approach enables 16 of 20 ptns to receive a KTx. Treating with IVIG & Rtx diminished the mean PRA levels from 77 % before therapy to 44 % after treating the ptns, lowering the mean timing to Tx from 144 to 5 mo. The Ac Rj rate was 50 %; however, they were mostly reversible, and, at one y., the mean SCr = 1.5 mg/dL (133 micromol/L), with ptn & graft survival were 100 & 94 %, resp.
Follow-up study: 76 highly sensitized ptns (75 % with PRA ≥80 %), Dsnz with the same regimen decreased class I & II Fc PRA levels & Fc CMX MCS, allowing Tx in ALL candidates. Adding Rtx to IVIG seems to be superior to high-dose IVIG alone for the Dsnz of highly sensitized TR. The following reports showed the range of results:
One RCT: comparing IVIG + Rtx with IVIG + placebo for Dsnz among highly sensitized KTR awaiting DD Tx. Ptns were randomly receiving IVIG 2 g/kg (maximum 140 g) on d. 1 & 20 with either Rtx (1 g) or placebo on d. 15. The study was enrolling 90 ptns but held early after only 15 ptns were enrolled because of 3 serious untoward events, (3 episodes of AMR). Of the 15 enrolled ptns, 13 received Tx (6 in the IVIG + Rtx & 7 in the IVIG + placebo arms). With un-blinding, it was evident that all AMR episodes were observed among ptns receiving IVIG + placebo; with No DSA rebounding was observed in those receiving IVIG + Rtx. Moreover, there were 2 cases of allograft failure in the IVIG + placebo arm in comparison with NILL in the IVIG + Rtx arm.
Study: 54 DD kidney TR with preformed DSA during Tx, 36 received IVIG 2 g/kg on the day of Tx and on d. 21, 42, & 63 post-Tx, and 18 received similar IVIG dose schedule conjugated with one dose of Rtx on d. 4 post-Tx + PE 3 times/wk/1st 3 wks post- Tx. Despite absence of difference in AMR incidence between the 2 g.s, ptns treated with IVIG/Rtx/PE showed greater GFR; 54 vs 43 mL/min/1.73 m2) with less proteinuria (0.1 vs 0.5 g/L) at one y. post-Tx as compared to those received IVIG alone.
Protocol biopsy: at one y. showed few subclinical AMR and TG with lowered degree of peritubular capillaritis among ptns received IVIG/Rtx/PE. Moreover, fewer ptns treated with IVIG/Rtx/PE remained +ve for DSA at one y. (29 vs 75 %).
DD Tx: Ptns on W/L for a DD Tx and qualifying for Dsnz plan, the target of Dsnz is similar to those waiting for a LD, but with little difference due to unpredicted timing of DD Tx in relation to the administrated Dsnz regimen. As the date of Tx is not precisely distinct, Dsnz protocol may be offered to the ptn if a DD graft can be likely offered within one y. This consideration is based on the ptn's kidney allocation points, recognized by the magnitude of waiting time as well as the allocation priority given by the ptn's cPRA. With a DD organ is NOT likely expected within one y., ptn can be kept on the DD W/L with NO specific Dsnz therapy. All ptns must be authorized from their insurance company for all treatments related to Dsnz as well as for the Tx surgery prior to Dsnz can be commenced.
Ptns on W/L for DD Tx, we offer pre-Tx Dsnz via high-dose IVIG + Rtx with similar regimen to that applied in ptns waiting for LD Tx. After completed the Dsnz protocol, we do the Luminex single-Ag test on a monthly bases for currently maintaining sera for CMX testing. The cPRA is rarely required to be adjusted as Dsnz regimen usually doesn’t entirely eliminating HLA AB but commonly limiting their MFI.
If the ptn cannot receive a DD KTx within 6 mo of the initial Dsnz course, we may provide a 2nd course of Dsnz consisting of PE followed by high-dose IVIG + Rtx. PE is provided to decrease the circulating anti-HLA AB levels.
1) Alternate-d. PE for 5 sessions, via 1.5 volume exchanges with 5 % replacing albumin for every PE session.
2) One dose of IVIG 2 g/kg (max. 140 g) immediately after the last PE session. Pre-medicate IVIG with IV Mthyprd 40 mg, oral Aceta 650 mg, & oral Diphen 50 mg.
3) Rtx 375 mg/m2 one wk after the last PE session with same pre-medication.
Rtx is usually given one wk after PE sessions and IVIG infusion to limit the impact of FcRn saturation by IVIG. FcRn that is greatly expressed on the vascular endothelial cell and the myeloid cell, can bind under acidic states to the IgG inhibiting its metabolism, so, extending the ½-life of AB. Saturated FcRn by a higher-dose of IVIG overwhelming FcRn ability to abort IgG degradation and it is one suggested mechanism, the IVIG facilitate clearing the pathogenic auto-AB in autoimmune disorders. However, IVIG can decrease the ½ -life & effectiveness of other therapeutic IgG AB given closely to IVIG therapy.
One study: ptns with multifocal motor neuropathy, ptns receiving Ecz (monoclonal AB) in conjunction with IVIG showed lowered serum levels of Ecz as compared with ptns receiving Ecz alone. Similar observations have been shown in ptns receiving the anti-C5 monoclonal AB tesidolumab in conjunction with IVIG.
So, we should wait 7-10 ds at least after the infused IVIG before providing any chimeric/humanized mAB. Dsnz can be proceeded with PE, high-dose IVIG, and Rtx every 6 mo until the ptn can receive a DD Tx. Luminex single-Ag testing can be performed on monthly bases to maintain current sera for CMX assay.
As an alternate, if the ptn is not receiving a KTx within 6 mo after the 2nd round of Dsnz, we can offer treating the ptn with the combined high-dose IVIG (2 g/kg on d. 0 & 30) + Tocil (8 mg/kg on d. 15, then monthly repeated), a monoclonal AB against IL-6 receptor that is currently administrated for rheumatoid arthritis as well as systemic juvenile idiopathic arthritis therapy.
Using IVIG + Tocil was assessed in a pilot study of 10 highly sensitized Tx ptns and not responding to Dsnz with high-dose IVIG + Rtx (with/without PE). Of the 8 ptns completing the trial (2 were eliminated from the trial due to non-adherence), 5 can be Tx with a mean timing to Tx of 8.1 mo from commencing Tocil (25 mo from initial Dsnz regimen). The mean RIS, a measure of DSA strength & quantity, declined from 7.8 before therapy to 3.2 at the timing of Tx. A wide RCT may be currently warranted to validate this Dsnz regimen.
Other Dsnz regimens:
Lower-dose IVIG + PE: For Dsnz before LDTx, other Tx centers may apply regimen consisting of low-dose IVIG combined with alternative day PE. In this protocol, alternate-d. PE is commenced before Tx, and IVIG (or CMV AB Ig, according to the institutional policy) is provided with dosing of 100 mg/kg following each session. The quantity of pre-Tx sessions can be assessed according to the basal DSA titer. Tac & MMF are typically commenced with the start of PE session, despite this policy may differ from center to another. Once DSA values and pre-Tx CMX are evidently accepted, Tx can be proceeded. In certain centers PE may be routinely continued after Tx for a pre-planned number of therapies, other centers, however, only performing post-Tx PE for the therapeutic purposes of acute AMR.
Long-term assessment of ptns Dsnz with alternative day PE + low-dose IVIG may suggest significant longevity benefit following this approach.
One study: ptn survival in 211 HLA-Snz ptns Tx after Dsnz with PE + low-dose IVIG compared to that in 2 matched control g.s of ptns on W/L for KTx who continued to undergo DX (DX-only g.) or who underwent either DX or HLA-compatible Tx (DX -or- Tx g.). Ptn longevity in Dsnz ptns was greater at 3, 5, & 8 ys (86, 81, & 81 %, resp.), compared with that in ptns in the DX-only g (67, 52, & 31 %, resp) and ptns in the DX -or- Tx g. (77, 66, & 49 %, resp).
Disadvantages of this regimen may include its higher financial costs & resources supplements. Several pre-Tx therapeutic sessions may be mandated to achieve adequate lowered DSA titer permitting successful Tx, and numerous post-Tx therapeutic sessions usually required to manage any rise of DSA titer, preventing any suspected AMR. With the timing of the proceeded Tx surgery must be monitored to permit an accepted AB titer, however, this regimen is only accepted for candidate TR of a LD Tx.
Lowered-dose vs higher-dose IVIG: There’re no RCT comparing utilization of lowered-dose IVIG + PE with high-dose IVIG for Dsnz. Retrospective study: comparing 3 different Dsnz protocol in LD TR with a +ve T cell CDC CMX: high-dose IVIG (2 g/kg) given 1-3 d.s before Tx; PE, low-dose IVIG (100 mg/kg), and Rtx 375 mg/m2; and PE, low-dose IVIG (100 mg/kg), and Rtx 375 mg/m2 with pre-Tx rATG-Thymoglobulin with robust post-Tx DSA monitoring.
All TR with a basal CMX titer <1:4 get a -ve CMX regardless of Dsnz protocol, compared with only 1 of 10 ptns with a basal CMX titer >1:32. Among ptns with a basal titer of 1:18 & 1:16, only 33 % receiving high-dosing IVIG achieved -ve CDC CMX, as compared to 87 % in the 2 g.s receiving PE/low-dose IVIG/Rtx. In ptns Tx, rates of AMR were 80, 37, & 29 % for ptns received higher-dose IVIG, PE/IVIG/Rtx, and PE/IVIG/Rtx/rATG-Thymoglobulin, resp. These findings suggest that:
o High-dose IVIG & PE/low-dose IVIG/Rtx are similarly efficacious for Dsnz if the T cell CDC CMX is +ve with lowered titer (<1:4).
o No one of the Dsnz regimens can be effective if the T cell CDC CMX is +ve at a higher titer (>1:32).
o PE/lower-dose IVIG/Rtx may be more efficacious than higher-dose IVIG if T cell CDC CMX is +ve with intermediate titer (1:8-1:16). However, it should be noted that ptns Dsnz with higher-dosing IVIG and NOT receiving Rtx, they are frequently vulnerable for a higher rates of AMR.
Considering the high rates of AMR within all the 3 Dsnz regimens, it is recommended to be cautious in proceeding to a Tx with a +ve CDC CMX. As mentioned before, we should NOT proceed with Dsnz or Tx in ptns with a baseline +ve CDC CMX.
Less commonly protocols:
Bortezomib (Bort): a robust, reversible proteasome inhibitor targeting terminal differentiation of plasma cell that’re responsible for AB production. Bort has been to be successful in AMR therapy. In certain centers, Bort did not routinely used in HLA Dsnz regimens considering its non-obvious efficacy and untoward effects.
Prospective trial of Bort-based Dsnz: 44 Snz ptns (current/peak cytotoxic PRA or cPRA >20 %), proceeded in 5 phases along 3 y.s. All ptns received LD with +ve CDC or Fc CMX with DSAs. Therapeutic protocol in every phase composed of Bort (1.3 mg/m2/dose/6-8 doses), one dose of Rtx 375 mg/m2, and PE; phases are varying in the Bort doses and quantity of PE sessions.
Almost 19 out of 44 (43 %) ptns received Tx during the study. 6 of 15 (40 %) ptns with DSAs and a +ve T cell Fc CMX against a LD achieved a -ve CMX; 4 were Tx, while 2 were not Tx due to a persistent DSA with an MFI >3500. 6 out of 44 (13.5 %) showed a 50 % decline in the cytotoxic PRA by 50 %; ptns with higher titer DSAs were less likely to respond. In responding ptns, the decline in DSAs can be durable with minimal short-term rebounding, despite later rebounding at 3 mo and after that was seen according to the given protocol. At 6 mo post-Tx, the rate of Ac Rj & AMR were 18.8 & 12.5 %, resp. Generally, Bort was well tolerated medication with currently given doses in this trial.
However, study: 10 highly senz KTx ptns with DSAs against their candidate LD, using 32 doses of Bort (1.3 mg/m2) as monotherapy only induced a moderate decline in DSAs without changing the cPRA. Moreover, Bort therapy was Not tolerated owing to untoward effects. So, although a Bort-based Dsnz regimen permits some Tx candidates to get a -ve CMX, this benefit was only limited to a minority of TR; ptns did not mostly achieved a satisfactory decline in DSAs nor were Tx, and many ptns have shown many adverse effects.
Ecz: a humanized mAB directed to the terminal C component C5. It has received an US FDA approval for therapy of PNH & aHUS and has been utilized as salvage therapy in the management of refractory acute AMR, however, it is not routinely utilized as a part of any HLA Dsnz regimens regarding its cost and unclear impact. There’re limited data about using Ecz for HLA Dsnz.
One study assessed the administration of Ecz among 30 LD TR with an initial +ve B cell Fc CMX MCS between 200-450. TR with a pre-Tx MCS ≥300 provided PE before Tx to get an MCS <300 by the d. of Tx. Ecz was provided as follows: 1200 mg immediately before Tx, 600 mg on day 1 after surgery, and 600 mg weekly thereafter/4 wks. At wk 4 post-Tx, ptns with a B cell Fc CMX MCS >200 received another Ecz (1200 mg on wk 5, then biweekly thereafter until the MCS reached <200). Outcome were compared with TR of a historical control g. of 48 LD TR of a +ve CMX Tx who were Dsnz with the same regimen with no Ecz.
Ptns receiving Ecz had a lowered incidence of acute AMR along 38 mo. As compared to historical controls along 73 mo (7 vs 44 %, resp.). However, Ecz-treated ptns showed a higher incidence of TG due to persisting DSAs (45 vs 64 % in controls) that suggest an impact of other mechanisms inducing allograft injury besides C complement activation. The % of ptns showed a B cell Fc CMX MCS >200 at 6 mo among Ecz-treated ptns was simulating controls (46 vs 41 %) suggesting no further benefits of Ecz on reducing DSA as compared to the standard regimens. Among these ptns, NO difference can be detected in TG at one y (50 vs 36 %). By contrast, ptns showed improving MCS <200 at 6 mo, none of the Ecz-treated ptns had TG at one y, as compared to 42 % in controls. Despite non-conclusive, this observation may suggest Ecz-treated ptns and having reduced DSA along 6 mo may be less vulnerable to develop chronic AMR as compared with those not treated with Ecz.
Investigational agents: Several investigational agents have been assessed as Dsnz strategies:
 Imlifidase (Imli): An IgG-degrading enzyme extracted from Streptococcus pyogenes (Imli; IdeS) is a recombinant cysteine protease cleaving all 4 subclasses of human IgG into F (ab') 2 and Fc fragment (s), inhibiting CDC and AB-related cellular cytotoxicity. Imli efficacy as a Dsnz regimen was assessed in 2 independent phase I/II studies from the US & Sweden including 25 greatly HLA-Snz ptns (average cPRA of 96 & 81 % in the US & Swedish trials, resp.).
Among these ptns, 92 % had a DD Tx, 92 % showed anti-HLA DSAs at the timing of Tx (mean class I & II MFI of 5660 & 8199, resp.), and 80 % showed +ve Fc CMX at the timing of Tx. All ptns receiving Imli (0.24 mg/kg in the US trial and 0.25 mg/kg or 0.50 mg/kg in the Swedish trial) provided IV 4-6 hs prior to Tx.
Ptns included in the US study was receiving an ALm induction (30 mg given on d. 4 after Tx), while ptns in the Swedish trial were receiving induction via horse ATG, ALL ptns were receiving maintenance Im/m composed of Tac, MMF, & Pred. Moreover, ptns in the US trial were receiving IVIG 2 g/kg (maximum 140 g) on ds 7-14 after Tx and Rtx 375 mg/m2 on d. 14-21 post- Tx.
The following findings were observed:
o Imli therapy induced total cleavage of IgG into F (ab')2 & Fc fragments within 6 h.s. Intact IgG still absent in all ptns for minimal 7 d., moreover, there was persistent decline in IgG values for 28 d. after infusing Imli.
o Ptns in the Swedish trial, not receiving IVIG + Rtx after Imli, showed DSA rebounding at 7-14 d. post-Tx; median MFI of the ID DSA was about 11,000 at one mo. In contrary, US trial ptns receiving IVIG + Rtx after Imli, showed less DSA rebounding, with median MFI of the ID DSA showed to be 0 at one mo.
o 3 of 11 ptns (27 %) in the Swedish trial showed AMR at 2 wks post-Tx. 2 of 14 ptns (14 %) in the US trial met Banff 2013 criteria of AMR at 2 & 5 mo after Tx; and more 5 ptns showed microvascular inflammatory states with no DSA.
o One ptn in the US trial had immediate HAR after revascularization that can be attributed to an IgM AB as ptn has no detected DSA after Imli therapy.
o Mean eGFR at 1-6 mo after Tx = 49 mL/min/1.73 m2 in the Swedish trial & 70 mL/min/1.73 m2 in the US trial.
Following up, multinational trial investigating the criteria of Imli converting a +ve CMX testing into -ve in 19 highly Snz kidney TR (average cPRA 99 %). 13 of them have received a DD KTx, 5 received LD Tx, and one ptn did not Tx after having an infusion-induced reaction to Imli. Imli induced -ve CMX in 17 of 19 ptns (89 %) along 24 hs after therapy. DSA rebound observed in most ptns between 3 & 14 ds after Imli administration, despite MFI still lower than pre-therapeutic values.
At 6 mo.s post-Tx, ptn & graft survival were 100 & 89 %, resp, and the average eGFR among the 16 ptns with a functioning graft was 47 mL/min/1.73 m2. Rejected Tx was observed in 9 of 18 TR (50 %); of them, 7 have developed AMR. Generally, the early interpretation with Imli is promising indicating the permition of use in incompatible Tx. However, long-term outcome has to be assessed, particularly with the commonly observed DSA rebound after Dsnz with Imli. Imli has been approved by the EMA for Dsnz in KTR in the European Union. However, Imli is not yet received an approval from the US FDA in the US.
 Obinutuzumab (Obinu): is a 3rd generation anti-CD20 mAB. In contrary to Rtx, B cell death with Obinu is less reliable on CDC and is mediated mainly via AB-related cellular cytotoxicity. Both Rtx & Obinu show robust deplete of B cells in peripheral circulation; however, Obinu is more effectively depleting B cells in the secondary lymphoid system and may show more remote actions on the memory B cells and plasma cells owing to its particular mechanism of action.
Using Obinu for Dsnz has been assessed in a trial of 25 highly sensitized KTR, receiving either a single dose of Obinu 1000 mg followed by IVIG 2 g/kg (maximum 140 g) at wks 3 & 6 (n = 5) or Obinu 1000 mg on ds 1 & 15 and an optional 1000 mg dose at wk 24 with added IVIG 2 g/kg at wks 3 & 6 (n = 20). From 25 ptns enrolled, 8 proceeded to KTx (7 were Dsnz with the frequent-dosing protocol), receiving more Obinu infusions at Tx & 24 wks after Tx. Only 4 of 25 ptns (16 %) had statistically significant decline in total mean MFI from base line, and MFI declining in individual ptns were not consistent across allele (s).
However, 14 of 24 ptns (one ptn was not involved in efficacy analyses as he was receiving a Tx 6 d.s after Obinu infusion) had a decline in the quantity of Un-Ag, and 12 of 24 showed a decrease in their cPRA enabled by moderate decline in MFI. These results may suggest that Obinu can be included as a Dsnz agent, despite its impact on HLA AB decline is currently mild.
 Carfilzomib (Carf): Carf is a 2nd generation, irreversible proteasome inhibitor showing durable impact on the plasma cell as compared with the 1st generation, reversible proteasome inhibitor, Bort. Moreover, it shows a more accepted toxicity profile than Bort with remarkable less associated peripheral neuropathy. Utilizing Carf in Dsnz protocols was shown in a small trial of 13 highly Snz TR tailored to evaluate its safety and efficacy conjugated with PE.
All ptns were receiving escalating dosing of Carf from 20-36 mg/m2 along 12 doses followed by 3 sessions of PE on d. 47, 49, & 51. Further subgroup receiving PE along the Dsnz plan before Carf dosages. Therapy impact was well tolerated with no reported peripheral neuropathy or HF cases. MFI decline with Carf alone was mostly moderate and can be more triggered after PE. AB rebounding to baseline values seen in all ptns within 5 mo after completing Dsnz. Further investigations are currently warranted for better evaluation of the safety/ efficacy of Carf as a Dsnz tool in KTR.
Im/m in Dsnz ptns, Induction therapy:
A suggested approach to induction therapy in iHLA KTR varies from that given in most HLA-compatible Tx. Whilst most HLA-compatible KTR who’re considered at higher risk for rejection typically receiving rATG-Thymoglobulin as an induction therapy, ALm administration is preferable in iHLA TR. Moreover, immunomodula-ting therapy with IVIG & Rtx can be provided near the timing of Tx.
●For LD TR, pre-Tx IVIG + Rtx Dsnz plan can be completed within one week of Tx. We can give ALm 30 mg SC on the d. of Tx, then a course of IVIG 2 g/kg (maximum 140 g) within 7-14 d. after Tx can be added.
●In DD TR, we can provide ALm 30 mg SC + IVIG 2 g/kg (maximum 140 g) at the timing of Tx. A subsequent additional dosing of IVIG 2 g/kg within 7-14 days after Tx. Rtx 375 mg/m2 is also provided within 7-14 ds after Tx if it has not been given within 6 mo of the Tx.
There’re no high-quality accepted data that compare various induction protocols among iHLA kidney TR. ALm is preferred based mainly upon clinical experience in this ptn cohort. IVIG & Rtx are provided in addition to ALm to limit or remove anti-HLA AB rebound in the early post-Tx timing. The impact of this protocol has been shown in a report of 2 different trials assessing utilization of a streptococcal IgG endopeptidase (Imli) in iHLA KTR. All ptns receiving Imli just before Tx; in one trial, ptns were given horse ATG as induction therapy, whereas in the 2nd trial, ptns were given ALm as an induction but also was receiving IVIG & Rtx prior to and after Tx. After one mo. after Tx, few ptns receiving IVIG & Rtx have developed DSA rebound as compared to TR who did not.
Maintenance Im/m: In TR of an iHLA KTx, we may provide a triple-therapy maintenance im/m strategy starting on the day of Tx including the Tac, MMF, & Pred. This regimen is simulating the initial maintenance im/m utilized in most HLA-compatible kidney TR in the US.
POS-TX MONITORING: After HLA Dsnz & Tx, ptns can be monitored via an approach simulating that used in TR of HLA-compatible Tx. We may check SCr + urinalysis twice weekly for the 1st mo post- Tx, then weekly for one mo, then every 2 wks for one mo, and then every 1-2 mo for the 1st y after Tx. Given the higher risk for AMR in iHLA TR, we perform a kidney graft biopsy in all ptns developing graft dysfunction if rejection is suspected. Moreover, routine monitoring of DSA values on monthly bases for the 1st 3 mo post-Tx; then at mo. 6, 9, & 12; and annually thereafter. Ptns showing persistent or de novo DSAs should be assessed with a kidney graft biopsy to exclude an impending AMR. DSA assessment in the early post-Tx timing may not be totally reliable, however, as recent IVIG can induce false +ve results related to non-specific binding of AB to single-Ag (Luminex) beadings. This impact of IVIG will be negligible by mostly 2 mo post-Tx.
Infection: Despite there’re major variabilities between iABO & iHLA Tx, both show many similarities in their pre-Tx Dsnz. In view of the data sparsity regarding infectious sequelae in iHLA TR, data from the iABO cohort can be reflected on the iHLA population. The documented infectious complications may vary by ptns populations, however, certain reports showed that the rate of infection episodes is not generally higher than that in other TR groups.
Retrospective study: 361 kidney TR comparing infectious outcome between ptns receiving Rtx + high-dose IVIG for Dsnz before iHLA- or iABO Tx and another group of non-Snz ABO-compatible TR.
All ptns receiving similar antibiotic and viral prophylaxis. After almost 18 mo, there were no clear differences in episodic bacterial, viral, fungal, and other opportunistic infection between the 2 populations. However, infectious episodes still a crucial cause of mortality in the Dsnz cohort:
o Cohort study: Korean Organ Tx Registry reporting the clinical outcome for 1964 LD TR, including 248 iABO TR, 144 iHLA TR, and 31 ABO- & iHLA TR. TR with an incompatible Tx, infectious episodes were the most common cause of mortalities (8 of 9 deaths [89 %]). On the other hand, only 3 of 11 (27 %) deaths in the compatible TR can be related to infection.
o Analysis:1420 iABO LD kidney TR in 101 European Tx centers (2005-2012), significant high rate of death-related infection in the 1st y after Tx in TR with iABO vs ABO-compatible Tx. However, the absolute risk difference was little, about 1 %. Moreover, adjusted analysis for variability in basal criteria between g.s was not introduced, so, it cannot be deduced if the difference in infection-induced deaths between iABO & ABO-compatible TR can be attributed to Dsnz vs other agents. Moreover, there was no variability in the rate of infection-related hospitalization along 1st Tx y. between iABO & ABO-compatible TR.
For all TR of an iHLA Tx, we give antibiotic and antiviral prophylaxis with a regimen that is similar to that given to TR of an HLA-compatible Tx including the prophylaxis against PCP, CMV, and herpes simplex disease (in ptns who’re at low CMV risk). Moreover, may provide antifungal prophylaxis, despite this policy may differ from center to another.
Malignancy: Scanty of studies that evaluate the risk of cancer among TR of an iHLA KTx, and data from the iABO Tx cohort are usually extrapolating to the iHLA Tx cohort. Most reports have found that iABO TR do NOT show a higher risk of cancer in comparison with ABO-compatible Tx ptns. Single-center report: 69 iABO, 27 iHLA, & 10 ABO- & iHLA LD kidney TR, malignancies were entirely NOT common, and their incidence was NOT showing a significant difference between the 3 groups.
It is usually difficult to decide to proceed to an iHLA KTx rather than waiting a longer time for a more appropriate donor, particularly considering the higher MR seen among ptns on DX as compared with TR proceeding to a KTx. In almost all ptn cohorts, the long-term risk of mortality is lowered with a KTx compared with DX. Large multicenter study: 1025 TR of an iHLA LD KTx, there was greater short- & long-term (8 ys) ptns’ survival among TR of an iHLA Tx in comparison with ptn on W/L matched controls.
These results were persistent among TR having a +ve Luminex assay/-ve flow cytometric CMX, +ve flow cytometric CMX, or +ve cytotoxic CMX. Of note, ptn & graft survival were comparable between highly Snz TR given Dsnz prior to Tx and less sensitized TR have no pre-Tx Dsnz.
Analysis: of 910 DD & LD TR (372 receiving pre-Tx Dsnz due to HLA Snz or iABO Tx): no difference in graft or ptn longevity up to 60 mo between HLA-Snz TR of pre-Tx Dsnz and lowered immunological risk TR. Generally, the greater intensity of incompatibility the higher the risk of allograft loss & mortality. Ptns with DSA but a -ve CMX have been reported to have a similar risk of mortality or graft loss as compared to compatible TR; in contrary, a +ve flow or cytotoxic CMX was complicated with a 1.65- & 1.80-fold greater risk of allograft loss and a 1.32- & 1.51-fold greater risk of mortality as compared to the compatible TR.
In this trial, 5-y. unadjusted allograft failure was 17, 20, 29, & 40 % for compatible TR, TR with DSA but a -ve flow CMX, TR having a +ve flow CMX but -ve cytotoxic CMX, and TR of a +ve cytotoxic CMX KTx, resp. 5-y unadjusted MR was 9, 10, 13, & 19 % for compatible TR, TR with DSA but a -ve flow CMX, TR with a +ve flow CMX but -ve cytotoxic CMX, and TR of a +ve cytotoxic CMX KTx, resp..
Cost of iHLA Tx: Costs of iHLA KTR are currently greater than those with compatible KTR, not only for the administration of injectable agents with or without PE for the Dsnz plans, but also due to prolonged hospitalization, more frequent allograft biopsies, and frequent rejection episodes. The mean organ acquisition cost of an iHLA LD KTx was reported to be USD $151,024 compared with USD $106,306 for matched TR; higher levels of incompatibilities (DSA with -ve flow CMX, +ve flow but -ve cytotoxic CMX, and +ve cytotoxic CMX) were accompanied with currently higher unadjusted costings. With adjusting the difference (s) in baseline TR & donor criteria between the incompatible and matched controls, however, there was no significance in in cost difference with Tx with DSA & -ve flow CMX and Tx with +ve flow but -ve cytotoxic CMX. Tx across a +ve cytotoxic CMX was associated with a greater cost as compared to Tx with DSA & -ve flow CMX and Tx with +ve flow but -ve cytotoxic CMX.