Co Stimulation Blockade and The Allograft

Co- Stiumulation Blockadeand the allograft

Iti Yadav, MD

HOFSTRA NORTH SHORE LIJ SCHOOL OF MEDICINE

Main Causes of Renal Allograft Loss

ACUTE RENAL ALLOGRAFT REJECTION

• A process by which the immune system of the recipient of a transplant attacks the transplanted organ or tissue

• This is the normal response of the healthy human immune system, which can distinguish foreign tissues and attempts to destroy them

• Mediated by activated T lymphocytes

• Activation occurs following recognition of graft Ag directly or after being processed & presented by APC

• At least one episode of acute rejection occurs in 62% of patients t/t with CsA, AZA and Steroids

• Less common with newer immunosuppressants

High Risk For AMR

•Desensitization protocols

•HLA incompatible•ABO incompatible •High preexisting DSA

•History of •Pregnancy•Transfusion •Transplant

• Types

• Without Vascular

involvement • C4d +

• Classic Vascular

involvement

Classic Vascular

• Uncommon

• Severe Necrotizing arteritis

• Arterial mural fibrinoid necrosis

• Variable inflammation( Neutr/Lymp/Mono)

• Monocyte infiltration of GC & PTC ( detected by CD68 staining) more sensitive

• Severely damaged endothelial cells

• Luminal thrombosis common

• Typically cortical infarction +focal interstitial hemorrhage rather than tubulitis

Neutrophil infiltrates in peritubular capillaries

Histology not a sensitive/specific diagnostic tool for acute humoral rejection as are methods to detect DSA/C4d

Non Vascular

• More frequent form

• C4d is covalently bound to peritubular capillary endothelium/BM collagen

• C4d can be +ve in glomerular mesangium,glomerular BM,tubular BM & arterioles in both native and transplanted kidney

• Diffuse peritubular capillary (PTC) C4d has only been described in renal allografts (Cause of this specificity ?)

• Diagnosis by immunostaining for C4d,Best seen on Frozen sections

• Despite association of C4d with IC deposition ,IG has not been detectable in same areas (endothelial cells might be dislodging surface Ab, C4d resists modulation d/t covalent binding to tissue)

• Scattered glomerular ,peritubular capillary and TI neutrophils ,ATN +/-

• C4d catalytically inactive• Does interact with C4d receptors on B & follicular dendritic cells

C3 convertase are controlled by various mechanismsE.g. cleavage of C4b by factor I C4d

• C4b2a catalyzes cleavage of C3, C5

• C4b covalently bonds with C2a C4b2a ( classical pathway C3 convertase)

• C1qrs • Cleaves & Activates C4, C2

• Complement fixing Ab binds to cell surface recruit C1qrs complexes

• C4d -footprint of humoral rejection

• Can be evident within one hr of transplantation

• Marker of complement activation generated by presence of Ab-Ag complexes

• Strong linear widespread peritubular capillary staining to be called a positive

• N Kidneys detectable in glomerular mesangium, vascular pole

C4d in peritubular capillaries

Correlation b/w +C4d staining, DSA & h/p findings

• Indication allograft biopsies pts with circulating DSA & H/p findings of neutrophils in PTC/fibrinoid necrosis - diffuse PTC C4d + seen in 100% biopsies

• 37% with steroid resistant rejection had DSA and 95% of these had C4d in PTC

• C4d -95% Sensitive & 96% specific for presence of DSA

• Graft loss higher in Ab mediated rejection(~40%) esp if associated with arteritis than with cellular rejection(~7%)

• Inferior graft survival with circulating DSA and C4d +ve as compared to positive DSA alone

• Focal C4d positivity

• High circulating DSA

• WORSE TRANSPLANT

SURVIVAL

c4d

• Unclear duration of persistence

• Disappearance has been reported on repeat biopsies 2-3 weeks after DSA no longer detectable

• Perfect correlation b/w positive staining and DSA does not occur• Non HLA Ab (AG II receptor A/Antiendothelial

Ab) can l/t C4d deposition• Circulating DSA can be below level of detection • Positive DSA >sensitive assays with –ve C4d

staining d/t DSA which is non complement activating (clinically insignificant)

Differential Diagnosis AMR

• Systemic necrotizing arteritis( recurrence of vascular lesions in transplant rare)

• Arterial occlusion from surgical causes- ligation of artery or embolization

• C4d staining in renal allograft other causes

• Simultaneous occurrence of Ab mediated & Cellular (Mixed) may be common

Therapeutic options

• IVIG

• Plasmapheresis

• Selective Immunoadsorption

• Antilymphocyte Therapy

• Altered Maintenance Immunosuppressants

• Combination of above

• Addition of t/t targeting simultaneous Cellular rejection (Steroids/Anti-lymphocyte) as they may down regulate B cell response via decrease in activity of helper T cells

IVIG

• Optimal Quantities and MOA poorly defined

• Proposed mechanisms-Suppression of IG synthesis-Altered Complement binding -Inhibition of Complement

activation

PLasmapheresis

• Removes Ab present in circulation

• No effect on further AB production

• Alone may stimulate a rebound IG production

• Need determined based on -preexisting Ab titer -affinity of Ab to

Ag -quantity of IVIG given

-use of adjunct agents

• Initial t/t 1-1.5 volume exchange

• Alternate day exchange protocol preferable as allows for interval recovery PT/PTT & fibrinogen to acceptable levels w/o need for FFP thereby minimizing sensitization

• Usually carried until S Cr is within 20-30% of previous baseline for min 4 t/t sessions

• Switch to MMF & Tacrolimus regimen

• If already on above, augment dose

• Methylprednisolone for 3-5 days with rapid taper to maintenance dosing

• Monitor DSA: 50% reduction associated with improved graft survival

• CNI’s affect broad range of non immunologic targets

• Associated with worsening HTN,DM & DYSLIPIDEMIA

• Contributing to increased CV morbidity & mortality

• MC cause death among transplant recipients 1yr post transplant

Investigational Immunosuppression

• Belatacept(LEA29Y)-Fusion Protein with mutated high affinity receptor for B7-1& B7-2 and LEA29Y portion of IG molecule

• Eculizimab-Complement inhibitory monoclonal Ab inhibits assembly of MAC

• Alefacept-Humanized LFA-3-Ig targeting T memory cells

• Voclosporine-Isomeric Cyclosporine ( >potent)

• Sotrastaurin-Protein kinase C inhibitor targeting T cell activation

• Tasocitinib-Jak 3 inhibitor selective reduction NK and T cell subsets

• Bortozemib-inhibitor of 26S proteosome

• Photopheresis-Peripheral Lymphocytes collected exposed to UV light to down regulate T cell clones

T-Cells Require Co stimulation for Full Activation

BelataceptFirst in class Selective costimulation blocker

• Fusion protein composed of Fc fragment of human IgG1 linked to extracellular domain of CTLA-4 which is molecule crucial for T-cell costimulation

• Binds surface ligands CD80 & CD86 of APC & blocks costimulatory pathway for T cell activation

• Blockade of signal 2 inhibits T-cell activation, promoting anergy,apoptosis

• Derived from Abatacept (Orencia) but Differs by only 2 AA

• Conferring greater binding avidity to CD80 & CD86, more potent inhibition of T-cell activation, effective rejection prophylaxis

• Rejection prophylaxis in transplantation

• Designed to avoid nephrotoxicity & increased cardiovascular and metabolic risks associated w CNI

Bristol-Myers Squibb

Belatacept blocks T-cell activation

• Phase II ,Randomized, multicenter Trial,22 centers US, Canada & Europe

• Compared Belatacept to Cyclosporine for prevention of Acute rejection and protection of renal function

• N=218(74 MI B,71 LI B,73 CsA)

• Acute rejection defined as Histologic evidence + at least 0.5 mg/dl rise in S. Cr above baseline

• All received Basiliximab,MMF, Steroids as induction agents

Vincenti,Larsen NEJM 2005 353:770

• Most (N193) Low-risk patients (89%)

Patients receiving 1st renal transplant

Patients with a history of panel reactive Ab titer ≤20%

Patients at low risk for acute rejection (investigator determined)

• At 6mo Acute rejection rates similar(7%MI ,6% LI ,8% CsA) Biopsy proven!

• Investigator treated rejection 26%-LI 29%-MI Belatacept 16%-Cyclosporine

• At 12mo GFR significantly higher with both Belatacept groups

• Lipid levels/BP lower in Belatacept despite greater use of hypolipidemic therapy in CsA t/t gp

• CAN less common with both Belatacept groups

• Incidence of infection similar ( UTI, CMV)

• Target trough levels CsA high(150-300ng/ml)contributed to development of CAN in CsA group

Vincenti,Larsen NEJM 2005 353:770

• PTLD Incidence 6% MI 0%LI & Cyclosporine groups

• Cancer occurrence

N=2 MI Belatacept (one breast cancer, one PTLD)

N=0 LI Belatacept( ? dose related occurrence)

N=2 CsA(one skin cancer,one thyroid cancer)

• PTLD developed in 2 additional patients t/t with MI regimen @ 2 &13 mo after belatacept had been replaced with conventional immunosuppression

• 2/3 patients PTLD primary EBV infection

• The 3rd pt received OKT3 for acute rejection, belatacept had been discontinued before this therapy with PTLD developing >12 mo later

• Rate of cancer with belatacept consistent with estimated incidence(3.3%) for non dermatologic cancers at 1Yr in transplant population

• Not inferior to CsA in preventing AR

• May preserve GFR

• May reduce rate of CAN

• Results of Extension of this trial for another 4 years (voluntary enrollment of ~ 50% patients)

• GFR remained stable with Belatacept

• PTLD in one pt t/t with CsA, none with Belatacept

• Serious GI disorders more common with Belatacept (12 Vs. 8%)

Vincenti,Larsen NEJM 2005 353:770

CONCLUSIONS

• Included adult(>18yrs) recipients of a living/deceased-donor kidney

• Cold ischemia time < 24hrs

• 3-yr, randomized, controlled, parallel-group, multicenter Phase III study conducted at 100 centers worldwide (N 686)

• Assessed MI or LI regimen of Belatacept Vs.CsA (Trough levels 100-250ng/ml)

• Excluded: -Recipients of ECD kidneys -Prior/concurrent non renal solid organ transplants -First-time patients with PRA>50%/Retransplants with PRA>30%

• Each patient treated with Basiliximab induction, MMF & CS

Vincenti, Am J Transplantation 2010:535

• 3 primary outcomes composite patient & graft survival composite renal impairment endpoint incidence of acute rejection

• Overall patient and graft survival with a functioning kidney were similar across the treatment groups-86% MI, 88% LI,85% CsA

• GFR better with Belatacept(65 vs. 63 vs. 50ml/min)

• Despite Belatacept gp higher incidence & grade of acute rejection episode (22% MI,17% LI,7% CsA)

• Presence of T reg cells in acute rejection infiltrates has been proposed to impart improved outcomes

• Graft biopsies in Belatacept t/t patients have significantly greater number FOXP3(+) T reg cells during acute rejection compared with CNI t/t patients

• First 12 mo malignancy incidence MI (5) LI(4) CsA(1) (excluding non melanoma skin cancer)

• First 12 mo PTLD MI(1) LI(2) CsA(1)

• 2 additional in MI gp after 12 mo (both involved CNS)

• More common with Belatacept 5 vs. 1 CsA gp

• 4 of total 6 PTLD cases had risk factors EBV negative serology

• Similar frequency of bacterial, viral ,fungal, CMV & BKV infections

• 6% in Belatacept MI gp, N 4% in LI gp experienced corticosteroid-resistant acute rejection,N 0 in CsA

• Observed rates of donor-specific anti-HLA Ab production were lower in Belatacept-treated patients vs. CsA

• In ECD recipients renal function was better, pt/graft survival & acute rejection similar with immunosuppression regimen based on Belatacept vs. CsA

• No additional efficacy gained using MI regimen

• Second Phase III randomized multicenter(79 worldwide) trial

• Similar design as BENEFIT

• 543 adult recipients of ECD kidney as defined by UNOS but also other high risk transplants (cold ischemia time>24hrs & donors with cardiac death) randomized to receive

MI (N 184),LI regimen of Belatacept (N 175) or CsA (N184)

• All patients received Basiliximab induction, MMF & CS

2 co primary endpoints composite of pt/graft survival at 12 mo composite renal function (measured GFR >60 at mo 12/decrease in GFR of 10 or more

from mo 3-12)

Secondary Endpoint Incidence of acute rejection (AR)

Durrbach Am J Transplantation 2010:547

• Graft & Patient survival similar

• Fewer Belatacept t/t pts reached composite renal impairment endpoint vs. CsA

• Mean GFR 4-7ml/min higher in Belatacept gp

• Incidence of DGF similar

• Unlike BENEFIT, the incidence of acute rejection comparable across all three arms of BENEFIT-EXT, between 14% and 18%

• Severity of rejection higher with Belatacept

• Recipients of these ECD kidneys were old patients with low immunologic risk

• Infection & malignancy rates similar

• CV & Metabolic outcomes superior with Belatacept

• More cases of PTLD in Belatacept gp (4/5 were PTLD of CNS -lethal)

• During first 12 mo PTLD MI(N 1) LI(N 2) and none in the CsA gp

• After 12 mo PTLD MI(N1) LI(1)

• Most cases PTLD in recipients with known risk factors

“Article in REVIEW”

• Extension of the Phase II trial

• Comparing beyond 1 Yr Belatacept with CsA for prevention of ACUTE REJECTION

&

PRESERVATION OF RENAL FUNCTION

• Assess long term safety & efficacy of Belatacept

Trough concentrations of Belatacept

Amount of free CD86 (HA5 binding) on

Monocytes from whole blood

• 7 Belatacept receiving pts switched to Tacrolimus(5 in yr 2)

• 1 Belatacept receiving pt switched from MMF to Sirolimus

• 3 Belatacept recipients switched MMF to low dose MMF& Sirolimus

• Switched pts were included in final analysis

• Data cut off date 6yrs and 7 mo after initiation original trial

• At end of study all were >5Yrs post transplant (76% Belatacept & 62% CsA recipients remained in study)

Stable renal function in belatacept-treated patients over timeCalculated GFR (MDRD) assessed at 6-mo intervals in t/t patients who

reached indicated time points Data as means SD

GFR decreased from 74.4 to 59.3 at mo 60

• No substantial differences in GFR observed between patients on 4/8 wk dosing

Kaplan-Meier plot for all randomly assigned & transplant recipients in ITT population w/o cancer >60 mo

Patients with skin/organ cancer/PTLD were excluded

• Cause of Death Belatacept (N 3)MI, Cardiopulmonary arrest,

PNA CsA (N2) PNA,PTLD

• Graft Loss Belatacept (N 1) CAN CsA (N 0)

• All BPAR mild/moderate severity: Banff grade IB/IIA

• Treated Acute Rejection (CSAR+BPAR) Belatacept (N 11)

4 wk dosing (n 4) 8 wk dosing (n 7) CsA (N 3)

• Biopsy Proven Acute Rejection Belatacept (N 6)

4 wk dosing (n 2), 8 wk dosing (n 4) CsA (N 0)

Cardiovascular risk factors in the LTE

Frequencies & incidence rates of SAEs occurred in 2/more pts in any group by category

Neoplasms in the LTE

In original study 3 cases PTLD b/w 3-13 mo after transplantation Belatacept (all in those receiving more intensive regimen)

(LATE)

• Selection Bias : Self selected cohort

• CsA gp small allowing only limited conclusions from direct comparisons

• Included patients had fared well during first phase of study

• Both gps higher average GFR’s as compared to gps in original study

• Baseline characteristics (Age, Cr, Co morbidities contributing to allograft dysfunction) at study entry not published

• Study underpowered to detect meaningful differences especially when pts withdrew during long term follow up

• Study compared CsA with Tacrolimus being most widely used CNI