regardless of genetic relationship and HLA mismatch. Pre-emptive transplants (i.e. pre-dialysis) have the best outcome of all. \200 Time on di alysis is associated with poorer transplant outcomes. \200 7 35% of live donor transplant s in the UK are pre-emptive. Live donor transplantation is elective surgery and easier to organize. \200 Laparoscopic donor techniques have helped acceptability ( b p. 378). \200 Closer HLA matching may be p ossible. \200 Live donor transplantation expands the overall donor pool \200\224 leaving deceased donor kidneys for those with no other options. There is minimal ischaemic damage to graft ( 6 d DGF). \200 Less potent immunosuppression (possibly). \200 Psychological bene \201 ts (better compliance, sense of well-being, et c.). Disadvantages \200 Perioperative donor mortality is 7 1 in 3,000 (causes: occult cardiac disease, venous thromboembolism). Major complications occur in 7 2% (intraoperative bleeding, wound problems, DVT). Minor complications occur in 7 20%. \200 Stress to donor (and family). \200 X Later dev elopment of donor i BP, proteinuria, or CKD (mean donor GFR after 25 years is 7 70% of that prior to donor nephrectomy). Dif \201 cult to guarantee \200\230 freely given \200\231 consent \200\224 has the dono r been coerced? Potential donors should be assessed in isolation from recipients and allowe d to withdraw (without explanation) at any stage. Assessment of a potential live donor This is subject to several comprehensive guidelines, e .g. M http://www. bts.org.uk . LIVE DONOR TRANSPLANTATION 373 A successful live donor program requires a multidisciplinary team approach. \200 Willing to donate? Information and discussion are of paramount importance. This should be delivered through a mixture of culturally appropriate written an d visual material as well as face-to-face consultations. A dedicated live donor team, separ ate from the potential recipient \200\231s nephrologist, would usually undertake this. The risks of the live donor process, how the pathway works, and the nature of the necessary inv estigations should all be clearly explained. ABO compatibility ( b p. 360). \200 HLA typing and donor-speci \201 c HLA antibodies ( b pp. 360 \200\2233). The impact of HLA matching is much less powerful in live donor transpl antation: a 1 haplotype mismatched live related graft 1-1-1 (e.g. parent to child) has simi lar outcomes to a 2-2-2 mismatched live unrelated graft (e.g. from a spouse) \200\224 and, in all cases, the outcomes are as good as for a 0-0-0 mismatched deceased donor kidney. Ho wever, HLA matching can help to select between multiple potential donors: 0-0-0 mismatched grafts still have the best outcomes, and poorly HLA-matched grafts risk the subsequent deve lopment of DSA, with potential implications for subsequent repeat transplantation in younge r patients. Medical evaluation: the goals are to protect the health of the donor and to prevent transmissible disease (malignancy and infection) to the recipient. \200 Hi story, clinical examination. \200 BP. \200 Urinalysis (at least x 2 on separate occasio ns), MSU, and uPCR. \200 U&E, SCr, eGFR. \200 FBC, clotting, LFTs, bone 9 Hb electropho resis (? sickle cell trait). \200 Fasting glucose 9 glucose tolerance test (if fasting va lue 6 \200\223 7mmol/L, i BMI, or family history of T2DM). PSA ( 4 > age 60). \200 Estimation of GFR ( b p. 374). \200 ECG 9 ECHO if i BP 9 stress testing if age >60. \200 CXR. \200 HIV, Hep serology, CMV, EBV, syphilis and HTLV-1 an d 2. \200 Age appropriate cancer screen. Psychosocial evaluation. This is a complex area, and many live donor programs will have considerable expertise within their multidisciplinary team. Many d onors \201 nd donation a positive act, associated with increased self-esteem. However, th is is not universal. Psychosocial assessment and support may be required (including formal psychiatric review in some cases). Support may need to continue post-donation. Formal menta l health assessment is recommended for all non-directed altruistic donors in the UK. Donor anatomy: Renal USS: to check there are two normal-sized kidneys. \200 Isotope renography (e.g. DMS A): for split renal function. If there is a difference, the kidney with less function would generally be selected for transplantation. CHAPTER 5 Transplantation 374 Arterial and venous anatomy: CTA is now generally favored over the more invasive, but less revealing, angiography (CT also yields additional anatomical information; e.g. the IVU phas e will identify a duplex ureter). Some centers may prefer MRA. How many arteries and veins? Multiple arteries usually require bench reconstruction prior to transplantation. Will laparoscopic surgery be possible? The l eft kidney is generally favored as the renal vein is longer. Informed consent. The donor should meet the donor surgeon. \200 In the UK, it is a mandat ory requirement of the Human Tissue Authority (HTA) that all potential live donor transplants undergo evaluation by an \200 \230 independent assessor \200\231 . The assessor must be satis \201 ed that adequate inf ormation has been provided (and understood), that consent has been freely given (no coercio n or rewards), and that the relationship between the pair is as described. The transplant m ust then proceed within a certain time frame (usually 6 months). If a donor is unsuitable, it is important that the reasons why are clearly explained (and that any necessary follow-up is organized). Donor nephrectomy. For techniques, see b p. 378. \200 Donors should be seen 4 \200\223 6 weeks post-surgery and then reviewed annually (check eGFR, BP, and urinalysis 9 uPCR). Thi s could be undertaken in primary care (but it is important that outcome data are collected by the transplant center). Renal outcomes Following the initial decline in GFR (as half the donor \200\231s nephron ma ss is removed at the time of surgery), the rate of loss of renal function is no faster than expected with normal ageing, in fact, residual hyper \201 ltration leads to an increase i n GFR to 770% of pre-donation level. There is a small increased risk of low-grade proteinuria ( s to hyper \201 l- tration in t he remaining kidney) and i BP. However, donation increases the absolute cumulative risk of ESRD by <1%. There are data that suggest improved life expectancy for individu- als who have donated, pr esumably re \202 ecting their evident \201 tness at the time of donation and perhaps mot ivation to stay \201 t post-donation. However, this may not continue to hold true as more patients are accepted to donate and their long-term follow-up improves. LIVE DONOR TRANSPLANTATION 375 Assessment of GFR for live donation In many countries (including the USA), GFR is estimated using creatinine clearance (CrCl) on a 24h urine collection. eGFR, using equations, such a s MDRD, are not acceptable, as they are not suf \201 ciently accurate when renal function is normal or near normal ( b p. 34). GFR may also be measured using radioisotopes, such as 51 Cr-EDTA (recommended in the UK). A suitable GFR for donation should be age-adjusted (see Fig. 5.16 and Table 5.5). 120 100 GFR (mL/min/1.73m2) 80 Mean GFR 60 Safe to donate 40 20 0 10 20 30 40 50 60 70 80 Age (years) Fig. 5.16 Diagram showing the variation of GFR with age. The lower line shows the safety li mit of 80mL/min/1.73m 2 for adults up the age of 46 years, declining to 50mL/ min/1.73m 2 a t age 80. For donors with a preoperative GFR above the lower line, the GFR of the remaining kidney will still be greater than 37.5mL/min/1.73m 2 at age 80. The upper line is based on an analysis of 7 425 living renal transplant donors who had 51 Cr-ETDA GFR measurements. R eproduced from the British Transplant Society Guidelines for Living Donor Kidney Transplant ation ( M www.bts.org.uk ), with permission. Table 5.5 Acceptable GFR by donor age prior to donation Acceptable corrected GFR prior to donation (mL/min/1.73m 2 ) Donor age Up to 46 80 50 77 60 68 70 59 80 Reproduced, with permission, from the British Transplant Society Guidelines for Living D onor Kidney Transplantation. 50 CHAPTER 5 Transplantation 376 Potential contraindications to live kidney donation \200 Age <18 (except in exceptional c ircumstances). \200 There is no upper age limit, but donors >60 will require particularly diligent assessment. Inadequately controlled i BP ( b p. 377). \200 CV disease (including strong family histor y) ( b p. 377). \200 i BMI ( b p. 377). \200 Diabetes mellitus or high risk of future d iabetes ( \201 rst-degree relative with T2DM + abnormal glucose tolerance, previous gestat ional DM). Other signi \201 cant comorbidity, e.g. respiratory disease. \200 Malignancy (localized skin malignancy is an exception). Ensure breast and cervical screening has been undertaken. Urinary tract infection. \200 Structural urinary tract abnormalities. \200 Nephrolithia sis. \200 Renal disease. Any primary GN or other renal disease. Proteinuria >150mg/24h precludes donation. \200 Microscopic haematuria: donation may stil l be possible ( b p. 377). \200 If family history of renal disease, exclude in the donor, e.g. Alport syndrome. Thromboembolic disease. \200 Transmissible infection (HIV, HBV, HCV, TB history, or recen t contact). Previous extensive abdominal surgery. \200 Smoking and alcohol excess. \200 Recreationa l drug use or dependence on prescribed medication. \200 Social issues: what will be the i mpact on employment, dependants, etc. \200 Active mental health issues. LIVE DONOR TRANSPLANTATION 377 Common concerns during live donor work-up \200 i BP Only a relative contraindication. \200 i BP precludes donation if: \200\224 Evidence of target organ damage ( b p. 462). \200\224 >2 antihypertensives are n ecessary to maintain BP <140/90mmHg. \200\224 10-year CV risk <20% ( b p. 470). CV disease: CV assessment of potential donors is not always straightforward. As a general rule, there s hould be a low threshold for screening potential donors for CV disease. Coronary artery disease is the most common concern, but valvular disease, cardiac dysfunction, and other vascular disease (e.g. peripheral, carotid ) also require consideration. Potential donors with exercise capacity >10 METs are at very low cardiac risk. METs are metabolic equivalents \200\224 based on the resting oxygen consumption of a 70kg 40-year-old 4 (3.5mL/kg/min or 1 MET). They can be calculated from activity scores, derived from questionnaire responses. In the UK, it is suggested that potential donors with an exercise capacity of <4 METs (acti vities that require >4 METs include moderate cycling, skiing, tennis, and jogging) or who h ave >10% estimated risk of signi \201 cant coronary disease ( b p. 470) should undergo car diological assessment (essentially dynamic stress testing of some type). Obesity: A risk factor for perioperative complications, such as VTE, wound infection, chest infection. Potential association with subsequent CKD, proteinuria, and T2DM. Potential donors with a BMI >35 should be discouraged, but given lifestyle advice and, if a ppropriate, weight loss goals. Moderately obese patients (BMI 30 \200\223 35kg/m 2 ) shoul d be counseled carefully concerning the additional perioperative and long-term risks and ad vised to lose weight prior to donation (and maintain this post-donation). Persistent microscopic haematuria: A relatively common \201 nding ( 7 5%). \200 Requires urological assessment, with urina ry tract imaging and cystoscopy. X If urological investigations prove normal, many centers perform a renal biopsy to exclude signi \201 cant (and potentially progressive) glomerular disease; for example, IgA nephropathy would be a contraindication to donation, whereas thi n membrane disease ( b p. 568), assuming appropriate assessment and counseling, might not. CHAPTER 5 Transplantation 378 Live donor nephrectomy General issues The most important early complications are bleeding, venous thrombo- embolism, renal impairment, chest infection/post-op atelectasis, and inad- equate pain relief (see Box 5.3). Ensure adequate hydration (e.g. IV crystalloid 1L over 6 \200\223 8h, beginning pre-op), V TE prophylaxis (LMWH and compression stockings), adequate analgesia (see Box 5.3), early mo bilization, and physiotherapy, as needed. Live donor transplant recipients are often commen ced on ciclosporin or tacrolimus a few days prior to the date of transplant, allowing thera peutic plasma levels to be reached and reducing the risk of early rejection. Open vs laparoscopic nephrectomy Laparoscopic donor nephrectomy is replacing open nephrecto my as the procedure of choice for live donor nephrectomy and has helped to increase donor r ates. The kidney is usually removed through a 6cm Pfannenstiel or a lower midline incision. Open nephrectomy involves a larger, more painful wound (often requiring rib resection) and a longer recovery time. Although overall complication rates are similar, laparoscopic nephrec- tomy is associated w ith less pain, a smaller wound (and several smaller scars), a shorter hospital stay, and sw ifter resumption of normal activities. Disadvantages: laparoscopic techniques are more dif \201 cult to learn; there is less intraoperative control of bleeding, and warm ischaemic t ime is increased by a few minutes over open techniques. laparoscopic nephrectomy, hand-assisted laparoscopic nephrectomy (HALDN) and retroperitonea l donor nephrectomy (in the latter, the peritoneal cavity is not entered, so there is less risk of bowel injury and fewer subsequent adhesions). There are several variations: total LIVE DONOR TRANSPLANTATION 379 Box 5.3 Pain relief in live donors With post-operative attention often focused on the recip ient, pain in the donor may be overlooked. Live donation is an unsel \201 sh act \200\224 it is inexcusable to leave a donor in pain because of insuf \201 cient analgesia. \200 Consider a fentanyl PCA (to be set up in theater), e.g. bolus 15 micrograms with a 5min loc k-out and background infusion of 15 micrograms/h. \200 On the ward: Paracetamol 1g qds PO/IV ( (cid:2) if donor is <50kg, IV dose is 15mg/ kg/dose). NSAID, e.g. ibuprofen 400mg tds PO (unless patient intolerant/ allergic). Ensure adequate hydration, and monitor renal function. PPI, e.g. omeprazole 20mg od PO (to cover NSAID). Antiemetic: Ondansetron 8mg tds PO/IV (regularly). \200 Cyclizine 50mg tds PO/IV prn. If pain is inadequately controlled, ensure the PCA is set up correctly and being used appro priately. Then consider increasing bolus and back- ground to 20 micrograms (ensure the pati ent is alert and respiratory rate is >12). Review regularly. Depending on patient progress, the PCA will hopefully only be nec- essary for 24 \200\223 48h. However, adequate step-down analgesia, based on preceding PCA use, is essential. \200 If fentanyl use <400 micrograms in previous 24h, prescribe regular oxycodone 5mg qds as w ell as prn oxycodone 5 \200\223 10mg 2-hourly. \200 If fentanyl use >400micrograms in pr evious 24h, prescribe regular oxycodone 10mg qds and prn oxycodone 5 \200\223 10mg 2-hourly. Assess pain every 2h after step-down. If uncontrolled, consider restarting PCA. CHAPTER 5 Transplantation 380 Immunosuppression: overview Introduction Successful transplantation between non-identical i ndividuals became pos- sible with the combined used of corticosteroids and azathioprine in the 1960s. However, severe rejection, often with graft loss, remained com- mon. Solid organ transplantation was transformed by the introduction of ciclosporin in the 1980s, with a si gni \201 cant reduction in acute rejection rates and improved long-term graft outcomes. The number of immune suppressive agents has grown considerably over the last two decades. R andomized trials have attempted to de \201 ne the ideal cocktail of drugs, but have genera lly been pharmaceutical company-driven, too short-term (often leading to the use of acute r ejection, rather than graft outcomes as the primary endpoint), and too small to convincingl y demonstrate any differences. This means there is no universal regimen \200\224 each transplant center will develop its own protocol, based on their interpretation of the available evidence, their local experien ce, and their local population. General principles \200 To match the amount of immune suppression with the perceived degree of immunological risk. To use higher doses in the early part of transplantation when the risk of rejection is high est ( induction ), with gradual reduction, even withdrawal, of some agents over time ( main tenance ). To try to tailor immune suppression to the individual where possible. \200 The use of cic losporin with corticosteroids and azathioprine became known as triple therapy . Similar such regimens are still the cornerstone of many protocols \200\224 modern triple therapy often comprises tacrolimus, corticosteroids, and MMF. Acute rejection is treated with an (immediate) escalation in immune suppression, often with a subsequent increase in maintenance therapy. Each immunosuppressive agent has a particular side effect pro \201 le. However, the entire group is associated with an increased risk of infection (bacterial, viral, and fungal) and malignancy. 2 The more potent the immune suppression, the less chance of rejection and the greater chance of these side effects. As acute rejection rates have fallen and graft outcomes improved, both the short-term ( (ci d:2) infection) and long-term ( (cid:2) CV disease, malignancy, nephrotoxicity) side effect s of immune suppression have become increasingly familiar. Immune suppression is only effective if taken consistently and as prescribed. The stakes are high in non-compliant patients, but such non-adherence remains s urprisingly common. It should be recognized that regimens are often burdensome, involving m ultiple tablets, with multiple side effects, taken at multiple times of day. IMMUNOSUPPRESSION: OVERVIEW 381 Key questions to ask of a transplant center \200\231s immune suppression protocols \200 I s immune suppression the same for each patient or modi \201 ed, according to perceived immunological risk (see Box 5.4)? \200 What antibody ( \200\230 b iological \200\231 agent), if any, is used at induction? \200 If a depleting antibody is used, what are the protocols surrounding its safe administration? Is maintenance immune suppression based on ciclosporin or tacrolimus? What are the desired therapeutic ranges of these agents at each stage post-tran splantation? Does maintenance immunosuppression include azathioprine or MMF? Are corticosteroids used from the outset? Under what circumstances are they withdrawn? What are the local policies concerning prophylaxis against infections, such as CMV and TB? What clinical trials are being undertaken at the center? What protocols apply to these patients? What are the protocols for ABO- or HLA-incompatible transplantation if they are performed? \200 How is T cell-mediated rejection treated? \200 How is acute antibody-mediated rejection treated? Box 5.4 Estimating immunological risk X Many transplant centers aim to tailor immune suppre ssion according to a strati \201 cation of immunological risk. Criteria vary but, as an ex ample: \200 Low immunological risk: Recipients without HLA antibodies, or \200 Recipients receiving a \201 rst transplant k idney from a HLA-identical sibling. Standard immunological risk: Recipients with HLA antibodies. \200 Any of the following groups, regardless of presence or absence of HLA antibodies: \200 Husband to wife, or child to mother. \200 Second or subsequent kid ney transplant. \200 Black recipient. \200 High immunological risk: Recipients who are FC-XM-negative but who have a current, or historic, antibody directed ag ainst the transplant organ (usually arises in a live donor transplant context, as such orga ns would not be allocated to a recipient via deceased donor schemes). HLA-incompatible transplants require individualized immunosuppression regimens. CHAPTER 5 Transplantation 382 Immunosuppression: induction Introduction Induction therapy is an initial period of intense immune suppression, given at the time of transplantation, to reduce the incidence of early acute rejec- tion. It has two components: \200 Higher initial doses of agents that will subsequently be used for maintenance, e.g. pulsed IV and high-dose oral corticosteroids and ciclosporin or tacrolimu s, with higher early target therapeutic levels. \200 Antibody induction with a \200\230 biological \200\231 agent; this will be with either a depleting or non-depleting antibody. \200 Depleting antibodies: ATG, OKT3, alemtuzumab. \200 Non-depleting antibodies: basiliximab. Antibody induction is used for >80% of transplants. In broad terms, depleting antibodies ar e favored in the USA, whilst non-depleting antibodies are more widely used in the UK and Eu rope. X While the evidence that antibody induction reduces acute rejection is good (depleting ant ibody > non-depleting antibody), the effects on long-term graft outcome are less clear. Other potential advantages (depleting antibody > non-depleting antibody): lower baseline ma intenance immune suppression (esp. steroids), allows gradual introduction of CNI to assist recovery from DGF, facilitates higher immunological risk transplants ( b p. 381). Potential disadvantages (depleting antibody >> non-depleting antibody): higher infection rates, greater long-term risk of malignancy. Non-depleting antibodies Basiliximab \200 A monoclonal antibody directed against CD25, a component of the IL-2 receptor on activated T cells. Binding prevents IL-2-induced T cell proliferation and clonal expansion. Basiliximab is a chimeric mouse-human monoclonal antibody that does not evoke an immune res ponse. It consequently has a long half-life. Used for transplant induction only, not the treatment of rejection (there are many other T cell mitogens besides IL-2, it is ineffective in this context). Demonstrably reduces acute rejection in the \201 rst year post-transplant ( 7 33%). \200 Basiliximab: 20 mg IVI on day 0 and day 4. The \201 rst infusion is usually started immediately pre-theater. \200 SE: surprisingly few. Infusion reactions are rare. Does not appear to signi \201 cantly increase the risk of infection or malignancy. IMMUNOSUPPRESSION: INDUCTION 383 Depleting antibodies Anti-thymocyte globulin (ATG) \200 Polyclonal T cell-depleting antib odies are produced by immunizing animals with human thymic lymphocytes. Several are available, e.g. Thymoglobulin (produced in rabbits). \200 Among the polycl onal antibodies are antibodies speci \201 c for components of the TCR (CD3, CD4, CD8) and cytokine receptors (including CD25) as well as ad hesion molecules. Numerous effects on T cells: cytokine release, d proliferation, d adherence, and i clearance ( l lysis or reticuloendothelial uptake). (cid:2) T cell depletion may persist for months (even years). \200 They also have anti-B cell effects ( d T cell help). \200 SE: 3 Anaphylaxis. \200 Cytokine release syndrome (fever, rigors, pruritus, erythema, dyspnoea, i HR, i / d BP). Generally limited to 1st or 2nd dose. \200 Serum sickness ( s to anti-rabbit antibodies and immune complex formation) after 7 7 days \200\231 treatment. Features: fever, rash, arthralgia, myalgia. Requires treatment cessation. d WCC, d Plt. \200 i infections (PCP, adenovirus, invasive fungal infections, CMV, toxopl asma, HSV, VZV are all concerns during this therapy). i PTLD (risk x 2) ( b p. 441). Used for both induction therapy and treatment of rejection ( b p. 408). \200 Anti-rabbit antibodies may develop and impair ef \201 cacy (especially with repeat courses). Alemtuzumab \200 Developed in the Cambridge Pathology Laboratories (hence Campath ). Licensed for the treatment of CLL but used extensively in transplantation. It is a humanized anti-CD52 antibody: CD52 is a highly expressed glycoprotein antigen on th e surface of T and B cells (as well as thymocytes, monocytes, macrophages, and NK cells). Binding does not cause cell activation, instead cells are rapidly cleared from the circulation. Profound lymphopenia persists for 6 months (B cells reconstitute before T cells). Dose: 2 x 30mg doses administered by SC injection (can be IV) 24h apart (day 0 and day 1 po st-transplant). Initial dose generally administered intraoperatively prior to organ reperfu sion (if the patient is age >60, some centers administer only one dose). Infusion reactions (SC < IV) are less severe than other depleting antibodies (as not associated with cytokine release) but still occur. Premedication and prophylaxis as for thymoglobulin in Box 5.5. \200 SE: d Hb, d Plt ( (ci d:2) weeks 2 \200\223 4), d WCC ( (cid:2) weeks 4 \200\223 8), i infection; autoimmune ph enomena, such as ITP and haemolytic anemia, may be seen as lymphocytes reconstitute. (cid:2) Beware late rejection, as T cells reconstitute at 7 6 months. CHAPTER 5 Transplantation 384 There are no randomized studies that directly compare against other agents for induction. I t had been used to treat acute rejection, but experience and evidence are currently lacking . Box 5.5 Administration of thymoglobulin Dose 1.5mg/kg (ideal body weight), rounded up to nearest 25mg in 500mL normal saline or 5% glucose. Premedication Chlorphenamine 10mg IV and hydrocortisone 100mg IV 1h before each infusion. A ntipyretic agents (e.g. paracetamol) may also increase tolerability. If reactions occur, tr eat with additional steroid, antihistamine, nebu- lized salbutamol, and IV hydration. Administration \200 (cid:2) ATG should be given via a central line. \200 Administration through a 0.22 micron in-line \201 lter is recommended. \200 Administer \201 rst dos e at 10mL/h for the \201 rst hour. \200 If no adverse effects, i infusion rate so that total duration is \211 6h. \200 Subsequent infusions should be administered over \211 6h. \200 Treatment with ATG should not usually exceed 14 days. \200 Vials batch number s should be recorded (it is a blood product). Monitoring CD3 monitoring \200 X Not universally undertaken (or accepted). \200 CD3 count should b e measured before the \201 rst dose as a reference. \200 Daily CD3 counts thereafter. A djust daily doses according to result (reference range 1 \200\223 30 cells/ L). Guide ( local protocols will vary): \200 <10 cells/ L: no dose. \200 10 \200\223 20 cells/ L: half dose. \200 >20 cells/ L: full dose. Other monitoring \200 Monitor general appearance, BP, HR, and temp every 15min during ini tial hour of \201 rst infusion. Hourly monitoring for remainder of \201 rst and subsequ ent infusions. \200 Check infusion rate regularly. \200 Daily FBC. Other considerations Prophylaxis against opportunistic infections \200 Oral candidiasis: nystatin 1mL qds. Continue 1 month after course. \200 CMV ( b p. 432), PCP ( b p. 428), a nd TB prophylaxis ( b p. 395). Other immunosuppressive therapy Stop MMF or azathioprine dur ing therapy to reduce neutropenia risk. Restart 2 \200\223 3 days before the end of the co urse. IMMUNOSUPPRESSION: INDUCTION 385 OKT3 \200 OKT3 is a mouse mAb speci \201 c for CD3 (a component of the TCR on all T cells). On binding, CD3 +ve cells release cytokines, internalize the CD3-TCR complex, and are rapidly cleared from the circulation. T cell rebound is more rapid than for ATG. \200 Premedication and prophylaxis as for thym oglobulin, except a larger dose of corticosteroid is often given, e.g. 250 \200\223 500mg IV methylprednisolone. Given as a 5mg IV bolus (can be administered peripherally). \200 Anaphylaxis is more comm on and cytokine release syndromes almost universal and more severe (particularly on repeat dosing). These serious (sometimes very serious: non-cardiogenic pulmonary oedema, aseptic meningitis , and encephalopathy) side effects mean that OKT3 is now generally reserved for the treatme nt of refractory rejection, rather than for induction therapy. (cid:2) Do not administer to volume-overloaded patients (diurese or ultra \201 ltrate the patient, as necessary, \201 rst). i infection and PTLD risk, as for other depleting agents. \200 A 10-day course is usual. CD3 monitoring can be undertaken, as for thymoglobulin. Neutralizing antibodies may limit ef \201 cacy. Rituximab \200 A chimeric (mouse/human) mAb directed against CD20 (expressed on B cells but not plasma cells \200\224 so it rarely causes hypogammaglobulina emia). Binding induces apoptosis and complement-dependent cytotoxicity. \200 Causes rapid and su stained depletion (6 \200\223 9 months) of both circulating and tissue-based B lymphocytes. Repeat administration of rituximab is sometimes based on measurement of circulating CD19 +ve B cells. Main role (in transplantation), to date, has been to prevent resynthesis of HLA or ABO anti bodies, following plasma exchange in ABO- or HLA-incompatible transplants (see b p. 444). Premedication and prophylaxis, as for thymoglobulin. \200 Infusion reactions and cytokine release syndrome are well recognized. \200 A single dose of 375mg/m 2 is given IV 2 \200\223 4 weeks prior to transplantation (50 \200\223 400mg/h). (cid:2) Rituximab bound to B lymphocytes may lead to a false positive B cell cross-match. Role as induction therapy or in the treatment of antibody-mediated rejection remains to be de \201 ned. CHAPTER 5 Transplantation 386 Immunosuppression: maintenance Introduction Maintenance immune suppression is given for the lifetime of the graft to prevent rejection. These agents are administered orally, and regi mens usu- ally involve several agents. Standard \200\230 triple therapy \200\231 consists of a calcineu- rin inhibitor (CNI), an antimetabolite and corticosteroids. Calcineurin inhibitors: ciclosporin, tacrolimus \200 The cornerstone of maintenance thera py over the last few decades. \200 Ciclosporin (CIC) is a lipid-soluble peptide, derived from the fungus Tolyplacadium in \202 atum . Tacrolimus (TAC, previously known as FK506) is a macrolide antibiotic, isolated from the bacterium Streptomyces tsukubaensis . Both disrupt T cell signal 1 through binding intracytosolic immunophylins (cyclophylin or FKBP12). These complexes then bind calcineurin (a protein pho sphatase), preventing its interaction with substrates, such as NFAT, and reducing the trans cription of T cell activation genes (including IL-2 and IL-2R). \200 Therapeutic drug mon itoring is mandatory: Both have a narrow therapeutic index: too little l inadequate immune suppression; too much l side effects ( (cid:2) particularly nephrotoxicity). There is also signi \201 cant interpatient variation in drug metabolism. Drug concentrations are measured in whole blood, as much is red blood cell or plasma protein-bound. 12h \200\230 trough \200\231 levels (C 0 ) are generally measured. \200 The use of TAC is growing at the expense of CIC: Head-to-head comparisons have generally been confounded by inadequate power and variable dosing regimens. However, there has been a signi \201 cant d in acute rejection in many studies (including d steroid-resistant rejection), and a large meta-analysis has sugge sted d early graft loss. Ciclosporin \200 Neoral , a microemulsion preparation, has been the main CIC formulation over recent years, but several generic preparations are now available. (cid:2) There are important differences in bioavailability between formulations, so it is crucial that the patient is consistently prescribed the same brand. Dose: 7mg/kg in two divided doses (PO), with subsequent adjustment, according to levels. Target ranges (12-hour trough). (cid:2) Depends on local practice, immunological risk, and evidence of nephrotoxicity. For guidance: \200 0 \200\223 6 mont hs: 200 \200\223 250ng/mL. \200 6 \200\223 12 months: 150 \200\223 200ng/mL. \200 >1 2 months: 75 \200\223 150ng/mL. X There has been much interest in using 2h post-dose levels (C 2 ) for therapeutic monitori ng, as these provide a better estimate of drug IMMUNOSUPPRESSION: MAINTENANCE 387 exposure (and have been associated with d acute rejection in some studies). However, perhap s because it is a less practical, it has not been widely adopted. CIC is metabolized in the GI tract and liver by the cytochrome P450 system (CYP3A4) \200\224 with implications for drug interactions (see Table 5.6, Box 5.6 ) . If required IV, administer 1/3 of the oral dose. Tacrolimus \200 Prograf has been the main formulation over recent years. Advagraf i s a once-daily formulation. (cid:2) Several generic preparations are now available, with potentially signi \201 cant differences in bioavailability between brands. Dose: 0.1mg/kg in two divided doses (or as a single dose for once-daily formulations), with subsequent adjustment, according to level. Typical target ranges (12-hour trough). (cid:2) Depends on immunological risk and evidence of nephrotoxicity. Check local protocols: \200 Low immunological risk: trough level 3 \200\223 7 micrograms/L. \200 Standard immunological risk: trough level 1 0 \200\223 12 micrograms/L for \201 rst 2 months, then 8 \200\223 10 micrograms/L. High immunological risk: trough level 10 \200\223 12 micrograms/L for \201 rst 2 months, then 8 \200\223 10 micrograms/L. C 0 (trough) levels correlate well with drug exposure (a signi \201 cant advantage over CIC). Metabolized by the cytochrome P450 (CYP3A4) system \200\224 with implications for drug interactions (see Table 5.6, Box 5.6 ). If required IV, the dose is 0.03 \200\223 0.05mg/kg as an infusion over 24h. CHAPTER 5 Transplantation 388 CNI side effects \200 Nephrotoxicity: initially reversible renal vasoconstriction l d GFR, but irreversible interstitial \201 brosis supervenes. Some degree is common on trans plant biopsies (and a particular problem in recipients of other solid organ transplants, wi th 7 5% l ESRD after 10 years). i BP. \200 Headache (rarely, more severe neuropsychiatric issues). \200 Tremor. \200 Liver dysfunction. \200 Post-transplant DM \200\224 NODAT (esp. TAC) ( b p. 424). \200 May potentiate DGF. \200 i K + (similar to a type IV RTA) ( b p. 825). \200 i urate (+ gout), d Mg 2+ , d PO 4 . \200 Thrombotic microangiopathy (TMA) ( b p. 412). \200 Cosm etic: hirsutism (esp. dark-haired, darker-skinned patients), gum hypertrophy (CIC > TAC), hair loss (TAC > CIC). Dyslipidaemia (CIC > TAC). \200 Diarrhea (TAC > CIC). (cid:2) Severe diarrhea may signi \201 cantly i TAC levels (enterocytes that normally secrete TAC into the gut lumen via P-gl ycoprotein are destroyed, causing less TAC elimination via this route). Table 5.6 Induction and inhibition of CYP3A4 i CNI levels Grapefruit juice d CNI levels Rifampicin Erythromycin Caspofungin Clarithromycin Griseofulvin Fluconazole Phenobarbital Ketoconazole Phenytoin Itraconazole Carbamazepine Verapamil St John \200\231s wort Diltiazem Lercanidipine Ritonavir Nel \201 navir IMMUNOSUPPRESSION: MAINTENANCE 389 Box 5.6 CNI drug interactions \200 Statin levels are signi \201 cantly increased by CNIs (CIC > TAC). May l i CK and rhabdomyolysis. \200 Statins should be introduced at low dose and titrated cautiously. \200 The co-prescription of simvastatin and CIC is contraindicated by the MHRA in the UK. CIC inhibits the enterohepatic recirculation of MPA, meaning that higher MMF doses are requ ired in recipients treated with CIC. These drugs increase the nephrotoxicity of CNIs: NSAIDs. \200 Aminoglycosides. \200 Amphotericin. These drugs increase the incidence of i K + : ACE-I/ARB. \200 K + -sparing diuretics. Mycophenolic acid \200 Mycophenolate mofetil (MMF) and mycophenolate sodium (MPS) are the ester and sodium salt pro-drugs of the active compound mycophenolic acid (MPA). MPA is a reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), a critical en zyme for de novo purine nucleotide synthesis. \200 Lymphocytes are dependent on the de no vo pathway (other cell types have a salvage pathway), so inhibition l d proliferation of ac tivated T and B lymphocytes. MMF has been shown to d acute rejection, more than azathioprine, as part of triple therapy with CIC. Limited evidence for additional bene \201 t in TAC-based regimens. However, ther e has been a massive shift toward MMF, such that it is now the staple at most centers. Note that AZA may remain a good option in TAC-treated patients with MMF-related GI side effects . SE: gastrointestinal side effects can be problematic. Diarrhea in 7 30%, gastritis in 7 20%, nausea, vomiting, constipation, dyspepsia. Bone marrow suppressi on is relatively common. Infective side effects (e.g. CMV) are more common than with AZA. Relatively few important drug interactions. CIC d enterohepatic recirculation of MPA, so hi gher doses of MMF are required than with TAC. MPA sodium is available as an enteric-coated, slow-release formulation, designed to d GI side effects (Myfortic ). This is not demonstrably the cas e in practice, although some patients seem to bene \201 t from a change in tablet. Initial dose: MMF 1g bd (or 500mg qds) \200\224 some centers use 1.5g bd for black recipie nts; MPA 720mg bd. Subsequent dosing will depend on local protocols, CNI levels, and side e ffects (including bone marrow tolerability). X There is very marked interpatient variability in plasma MPA levels. Therapeutic monitorin g of MPA levels is available, but its role has not CHAPTER 5 Transplantation 390 yet been established. May be measured in those with severe GI side effects. Azathioprine \200 Metabolized to a purine analog (6-thioguanine), which competitively inhibits purine synthesis (for RNA and DNA). This inhibits all cell replication, including d T cell proliferation. An old friend: in use in transplantation for >40 years. \200 Dose: usual starting dose is 1.5 \200\223 2mg/kg once daily. Reduce if WCC <4.0 x 10 9 /L and stop if <2.0 x 10 9 /L. SE: myelosuppression, hepatitis, cholestasis. \200 Interactions: (cid:2) allopurinol shou ld be used with great caution with azathioprine, as AZA is also metabolized by xanthine oxi dase ( l potentiates bone marrow toxicity). Consider transfer to MMF. \200 Patients with an inherited de \201 ciency of the enzyme thiopurine methytransferase (TPMT) metabolize AZA slowly, resulting in drug accumulation (and bone mar row suppression). If necessary, patients can be screened for TPMT levels (and the presence of the genetic abnormality). Sirolimus (rapamycin) \200 Derived from a macrolide antibiotic identi \201 ed on Rapa Nu i (Easter Island). Inhibits mammalian target of rapamycin (mTOR), a key regulatory kinase in cell division. Like TAC, it binds FKBP12, but the resulting complex binds and inhibits mTOR l d lymphocyte proliferation in response to cytokines. A long half-life allows once-daily dosing. \200 Dose: typical loading dose of 6mg for two doses, followed by maintenance dose of 2 \200\223 4mg. Trough C 0 levels correlate well with overall drug exposure. Aim level 5 \200\223 10ng/mL.