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Protective antibody levels and dose requirements for IV 5% Nabi Hepatitis B immune globulin combined with lamivudine in liver transplantation for hepatitis B-induced end stage liver disease
Article first published online: 28 DEC 2005
Copyright © 2005 American Association for the Study of Liver Diseases
Volume 12, Issue 1, pages 124–133, January 2006
How to Cite
Dickson, R. C., Terrault, N. A., Ishitani, M., Reddy, K. R., Sheiner, P., Luketic, V., Soldevila-Pico, C., Fried, M., Jensen, D., Brown, R. S., Horwith, G., Brundage, R. and Lok, A. (2006), Protective antibody levels and dose requirements for IV 5% Nabi Hepatitis B immune globulin combined with lamivudine in liver transplantation for hepatitis B-induced end stage liver disease. Liver Transpl, 12: 124–133. doi: 10.1002/lt.20582
- Issue published online: 28 DEC 2005
- Article first published online: 28 DEC 2005
- Manuscript Accepted: 2 AUG 2005
- Manuscript Received: 14 FEB 2005
- Nabi Biopharmaceuticals
Lamivudine combined with Hepatitis B immune globulin (HBIg) prevents post liver transplant (LT) HBV recurrence. The study was designed to assess the impact of lamivudine on hepatitis B antibody (anti-HBs) and dosage requirements of intravenous 5% HBIg (Nabi-HB®) in the first 36 weeks post LT. Adults undergoing LT for chronic HBV received lamivudine prior to or at LT, and IV HBIg 20,000 IU on day of LT, 10,000 on days 1-7, weeks 4 and 8, and 5,000 every 4 weeks thereafter. Replicative status based on serum HBV DNA (> 5 pg/mL = replicator (R) or ≤ 5 pg/mL = nonreplicator (N) was determined at initiation of lamivudine (R or N) and within 2 weeks of LT (r or n), resulting in 3 groups: Nn, Rn, and Rr. Between December 1999 and May 2001, 30 patients (10 Nn, 13 Rn, 6 Rr, and 1 unknown), mean age of 52 years underwent LT. HBsAg neutralization was achieved with anti-HBs > 300 IU/L during week 1 and > 200 IU/L during weeks 2-12. All but one patient were HBsAg-negative on last follow-up. Pre-LT suppression of HBV replication resulted in similar dose requirements and pK in the Rn and Nn groups within 1 week after LT. Comparatively, the Rr group had greater HBIg requirements during weeks 1-12 due to greater anti-HBs clearance and shortened t1/2 during the entire 36-week follow-up. In conclusion, this study provides a rationale for the use of lower HBIg doses in HBV patients with suppressed replication undergoing LT. Liver Transpl 12:124–133, 2006. © 2005 AASLD.
Hepatitis B virus (HBV) associated liver disease was previously considered a contraindication to liver transplantation (LT) due to poor graft and patient survival.1 The poor outcomes were directly related to HBV infection of the hepatic allograft in the absence of effective antiviral prophylaxis.2–5
A major advance in LT was the demonstration that high dose, peri-operative intravenous (IV) Hepatitis B Immune Globulin (HBIg) could prevent or delay HBV reinfection.6 This was confirmed in a large European series where patients receiving IV HBIg to keep levels above 100 IU/L for at least 6 months had a 3-year actuarial recurrence rate of about 36%, far less than those receiving no HBIg or those receiving HBIg less than 2 months. Patients transplanted with detectable serum HBV DNA had a significantly higher actuarial recurrence rate at 2 years than those without serum HBV DNA (96% vs. 29%).7
Two major US centers, using aggressive high dose IV HBIg, decreased recurrence to < 20%. This led to improved post LT outcomes and acceptance of HBV-liver disease as an indication for LT.8, 9 However, even using intensive monitoring during the first week post LT and additional HBIg infusions to keep anti-HBs titers above 500 IU/L, patients with active replication still had a rate of HBV recurrence of 16%.9
Lamivudine is an orally administered nucleoside analogue that effectively suppresses HBV replication via inhibition of the HBV reverse transcriptase Lamivudine therapy of chronic HBV infection,10 and prophylaxis in LT patients has been limited by development of resistant mutations in the YMDD motif of the HBV polymerase. HBV recurred in 10-20% of patients without, and 60-70% of patients with active virus replication at LT.11, 12 Lamivudine-resistant mutations, once thought to be less virulent, have recently been shown to lead to progressive liver disease in post-LT patients and patients with chronic liver disease.12–15 Lamivudine monotherapy is now generally considered inadequate for HBV prophylaxis post LT.
Combination parenteral HBIg and lamivudine has been shown to prevent recurrence in over 90% of chronic HBV patients undergoing LT including a low recurrence rate in patients with active replication at the time of nucleoside/nucleotide initiation16–23 and is currently considered the standard of care for prevention of HBV recurrence after LT. However, the high cost and inconvenience of parenteral HBIg has led to attempts to utilize lower doses of HBIg and provide more convenient dosing regimens. Multiple intramuscular (IM) or intravenous (IV) regimens of HBIg have been used in combination with lamivudine,24 but most are empiric.
We performed a prospective multi-center trial of HBV prophylaxis in LT using IV 5% HBIg (Nabi-HB®) in combination with lamivudine to determine anti-HBs titers required to neutralize HBsAg to determine whether suppression of HBV replication by lamivudine prior to LT affects HBIg pharmacokinetics and to evaluate the efficacy of lower dose HBIg from 12 to 36 weeks post-LT.
PATIENTS AND METHODS
Patients ≥ 18 years of age with HBV-induced chronic liver disease (serum HBsAg-positive and documented cirrhosis or hepatocellular carcinoma (HCC) with characteristics suitable for LT,25 UNOS Status 2 or 3 considered to be within 3 months of LT were included (presence or absence of anti-HDV, HBeAg, and HBV DNA were not considered for eligibility). Patients were excluded if they required re-LT for recurrent hepatitis B, had a history of a known lamivudine-resistant HBV infection, had concurrent causes of liver disease (including chronic hepatitis C), required systemic chemotherapy for HCC, were seropositive for HIV, or received any investigational drug or device within 30 days prior to LT. Data to calculate MELD scores, history of significant alcohol abuse, and history of HCC was collected retrospectively. MELD scores were calculated without additional points for HCC.
All subjects provided written informed consent. The study protocol was approved by the institutional review board of each study center and the study was conducted in accordance with the principles delineated in the Declaration of Helsinki and in accordance with U.S. Federal Regulations (21 CFR 312, 50 and 56).
This was a prospective, multi-center study using IV 5% HBIg (Nabi-HB®) preparation in combination with lamivudine in adult patients undergoing LT for HBV-induced liver disease. The projected enrollment among 15 centers was 30 patients. Patients not receiving lamivudine at enrollment were to start daily oral lamivudine pre-LT. All patients were to continue lamivudine for the duration of the 36 week study. There were two phases of the study. Phase one was from the day of LT until the beginning of post-LT week 12. The second continued from weeks 12 to 36 post-LT. During the first phase a total of 11 IV doses (10,000 IU/dose) were to be administered: 20,000 IU during the LT surgery (10,000 IU while the subject was anhepatic and 10,000 IU following reperfusion), 10,000 IU daily on days 1 through 7, and 10,000 IU once weekly during weeks 4 and 8. The target trough serum anti-HBs level during phase 1 was ≥ 500 IU/L (enzyme immunoassay, EIA; Abbott Laboratories, Diagnostics Division, Chicago, IL).
Because of individual variability in pharmacokinetics (pK) of HBIg seen early after LT, intensive monitoring of the anti-HBs titers was performed in week 1. An additional dose of 5,000 IU was to be given if the serum anti-HBs level was projected to be < 500 IU/L.
During the second phase, 5,000 IU HBIg IV was administered every 4 weeks if, without additional doses, the serum anti-HBs trough titer was ≥ 500 IU/L in week 8. Patients whose 8-week serum trough level was < 500 IU/L received 10,000 IU HBIg every 4 weeks for the remainder of the study. Furthermore, an additional 5,000 IU was to be given between scheduled doses if the projected trough anti-HBs level was < 250 IU/L. Four week projected trough levels were calculated using a one compartment linear regression model utilizing the half hour and 2-week post infusion antibody titers, the patient's body weight, and dose of HBIg.
Patients were observed for adverse events during the entire 36 weeks of the study. After the trial was terminated, the protocol was amended and follow-up data was retrospectively collected for a minimum of 2 years post-LT.
Blood samples were collected for serum HBsAg during screening, at the time of LT and following LT on days 2 and 7 and weeks 2, 3, 4, 8, 12, 16, 20, 24, 28, 32, and 36. ALT, AST, total bilirubin, BUN, and creatinine were measured daily for the first 7 days after LT, at weeks 2, 3, and 4, and then every 4 weeks. Quantitative HBV DNA levels were determined prior to initiation of lamivudine and at the time of LT. HBV DNA levels were performed through the individual sites. The majority in this time period were performed by the Hybrid Capture II HBV DNA Test (Digene Corp., Gaithersburg, MD). Results reported in copies/mL were converted to pg/mL (copies/ml divided by 280,000). Patients who were started on lamivudine prior to being seen at the transplant center for replicative disease without a documented value were listed as having a positive DNA result. Serum HBeAg and anti-HBe were measured at screening, at the time of LT, and at 12, 24, and 36 weeks.
Serum HBsAg was obtained 30 minutes before each infusion. Serum anti-HBs trough and peak levels were obtained 30 minutes before and after each dose, respectively, beginning on day 1. Additional anti-HBs levels were obtained 4 hours after the infusion on days 2, 3, 4, and 5 and after additional infusions. Random anti-HBs levels were obtained during Weeks 2, 3, 6, and 10 and then every 4 weeks thereafter.
Anti-HBs levels were determined by EIA (Abbott Laboratories, Diagnostics Division, Chicago, IL) at the University of Virginia Medical Center, Charlottesville VA.
Study Drugs and Administration
Nabi-HB® is a sterile 5% protein solution of immunoglobulin containing a minimum of 312 IU anti-HBs per mL. It is prepared from the pooled plasma of healthy donors with high titers of anti-HBs. The solution for intravenous use is formulated in 0.075 M NaCl, 0.15 M glycine, and 0.01% polysorbate 80, at pH 6.2 and contains no thimerosal. Nabi-HB® is manufactured by Nabi Biopharmaceuticals, Boca Raton, FL. Nabi-HB® (intramuscular) was approved by FDA for use in post hepatitis B exposure prophylaxis. Intravenous administration of Nabi-HB® in this clinical study was permitted under FDA IND BB-IND 8442.
Lamivudine was obtained from commercial sources and administered as tablets or as an oral solution as an off label indication. Lamividine (100 to 150 mg) was to be administered, with dose adjustment for patients with renal insufficiency according to calculated creatinine clearance (CrCl) using the Cockcroft-Gault equation.26 The initial dose of lamivudine for patients with a CrCl ≥ 15 mL/min was 100 mg, while the initial dose for patients with a CrCl < 15 mL/min the initial dose was 35 mg. Maintenance doses were adjusted based on CrCl as follows: 100 mg for CrCl > 50 mL/min, 50 mg for CrCl 30-49 mL/min, 25 mg for CrCl 15-29 mL/min, 15 mg for CrCl 5-14 mL/min, and 10 mg for CrCl < 5 mL/min.
Immunosuppression, CMV prophylaxis, and monitoring and treatment of rejection were done as per protocol of each individual institution.
All data were analyzed using the nonlinear mixed effects modeling program NONMEM version V, level 1.1.27 A one-compartment model with first-order elimination and intermittent infusion input was specified and used to determine the half-life (T1/2), volume of distribution (VD), and clearance for each patient during specified time periods.
For the purpose of analysis, a replicator was defined as either HBV DNA ≥ 5 pg/mL or presence of HBeAg with a positive qualitative HBV DNA result. A non-replicator was defined as a serum HBV DNA < 5 pg/mL. Patients were divided into three groups based on the HBV replication status at the time of lamivudine initiation and the time of LT. The Nn Group consisted of patients who were non-replicators at the time of lamivudine initiation and at the time of LT, the Rn Group consisted of patients who were replicators at the time of lamivudine initiation but non-replicators at the time of, or within 2 weeks prior to LT, and the Rr Group consisted of patients who were replicators at both evaluations.
Statistical significance of serum trough levels was calculated by the Cochran-Mantel-Haenszel test (SAS/STAT PROC FREQ). A compartmental pharmacokinetics model was used to give one estimate per subject during each study period. Comparisons of log-transformed values were done using one-way ANOVA test with Bonferri correction.
Thirty (27 male) subjects enrolled at 10 study centers underwent LT between 12/19/1999 and 5/14/2001. The mean age was 52 (range 31-71) years; the mean MELD score was 23. Fifty percent were White, 40% Asian, 6.7% Black, and 3.3% of Hispanic ethnicity. All patients had end stage HBV-induced liver disease and were HBsAg-positive prior to LT. Anti-HDV antibody was undetectable for 16 patients, present for 1 patient, and status not known for 13 patients. Sixteen patients (53.3%) were HBeAg-positive, 13 (43%) were HBeAg-negative, and for 1 patient the HBeAg status was unknown at the time of LT. Three HBeAg-positive patients at the time of lamivudine initiation were HBeAg-negative at the time of LT. No HBeAg-negative patient at lamivudine initiation became HBeAg-positive at the time of LT or during the study period. Replication status at the time of lamivudine initiation (R or N) and at the time of LT (r or n) was as follows: Nn (10 patients), Rn (13 patients), Rr (6 patients), and status unknown (1 patient). The mean MELD score at the time of LT did not differ between groups: 26 vs. 22 vs. 21, respectively.
The mean time from start of lamivudine administration to transplantation was 17 (range 0-41) days, 515 days (91-1140), and 116 days (1 day after LT to 447 prior) in the Rr, Rn, and Nn groups, respectively (see Table 1). Two patients in the actively replicating group received the first dose of lamivudine on the day of LT. Two patients in the Nn group also received the first dose of lamivudine on the day of LT and 1 received lamivudine on the first day after. The initial intent was to have all patients suppressed at the time of transplantation, but given the delay in obtaining HBV DNA levels, the need to use organs for patients when organs became available and the different philosophies at different transplant centers this did not occur in all cases.
|Replication status||Sex||Race||Age||MELD||HBV DNA level ETOH||HBV DNA level HCC||PreLam (pg/ml)||PreLT pg/ml||eAg preLam||EAg PreLT||Interval lam-LT days||F/U weeks||Alive||Ex-clude phase I/2||Reason|
|F||W||71.6||21||No||Yes||539.04||539.04||Yes||Yes||0||6||No||No/yes||Death due to sepsis|
|M||W||69.4||17||No||Yes||74.3||83||Yes||Yes||41||4||No||No/yes||Death due to GI bleed|
|Rn||M||W||45.9||41||No||No||303||UD||Yes||Yes||980||36||Yes||Yes/no||ReLT Day 2|
|M||A||48.6||44||No||No||Positive||UD||Yes||Yes||374||6||Yes||No/yes||Dropout at 6 weeks|
|Nn||M||W||51.9||14||Yes||No||UD||UD||UK||No||0||8||No||No/yes||Death due to gastric ulcer bleed|
|M||A||56.1||36||No||Yes||UD||UD||No||No||20||26||Yes||No/no||reLT Week 28|
|M||A||46.1||35||No||No||4.2||UD||No||No||205||0.29||No||No/yes||Death (Day 3) intracranial bleed|
|M||I||47.3||16||No||No||1||UD||No||no||219||30||Yes||No/no||Relocated; lost to follow|
|Other||M||A||56.5||17||No||No||13.3 pg/ml||UD||No||no||6||36||Yes||Yes/yes||HBsAb + LT|
Overall Study Outcomes
All patients received at least four infusions of HBIg. Two patients completed the 36-week trial but were excluded from PK analysis [one patient was HBsAg-negative (with measurable anti-HBs) at the time of LT, and the replication status was unknown for one patient]. Four patients died within the first 8 weeks (day 3 to week 8). Two patients withdrew consent. One withdrew for personal but otherwise not specified reasons (week 4), one believed that nausea, anorexia, and malaise were related to study drug (week 6); however this patient did allow retrospective data collection following completion of the trial. One patient relocated (week 30) and was lost to follow-up. One Rn patient underwent repeat liver transplantation (re-LT) at day 2 and was censored from the remainder of the phase 1 analysis but was included in the phase 2 analysis. A second patient underwent re-LT at week 28. This patient completed the 36-week follow-up but data were censored from the trial after week 28. Thus, 27 patients were included for the Phase 1 analysis and 24 were included for analysis of phase 2. Follow-up data were collected for 23 patients alive at the end of phase 2 (Fig. 1 Flow Diagram).
HBsAg was present on last follow-up in one of 30 patients during the 36-week trial period, a Rr patient who died at week 4. This patient had persistently low anti-HBs titers during the entire 4 weeks of post-LT and was the only patient without a decrease in HBV DNA from the time of lamivudine initiation to the time of LT (41 days), raising the possibility of a lamivudine mutation. However, the presence or absence of a mutation was not determined due to death early in the study. No other patient had clinical evidence of lamivudine resistance prior to or following LT.
The overall patient and graft recurrence-free survival was 87% and 93%, respectively. The mean follow-up time during the 36-week trial was 29 weeks, 26 weeks for the Rr group, 34 weeks for the Rn, and 25 weeks for the Nn groups (P = NS).
Twenty-four patients had retrospective follow-up after completion of the trial (weeks 36-239): All 24 patients were initially treated with 5,000 IU HBIg every 4 weeks. HBIg was subsequently discontinued in 7 (4 Nn and 3 Rn) patients 36 to 73 weeks after LT. Two of 3 Rn patients became HBsAg-positive, 383 and 518 days, after discontinuation of Nabi-HB. The remaining 22 patients remained HBsAg negative for the duration of the follow-up period (mean 165 weeks).
HBIg Administration and HBsAg
Phase I (Day 0 to Week 12)
All patients received scheduled HBIg doses as per protocol. In the first 7 days, 7/10 Nn, 9/11 Rn, 6/6 Rr had at least 1 anti-HBs level < 500 IU/L. Although the protocol allowed for additional doses of HBIg to be administered when the anti-HBs titer was less than the target level of 500 IU/L, a delay in reporting anti-HBs levels prevented implementation of the additional doses in a timely fashion in all cases during the first 7 days. Between weeks 2 through 12, 4/6 Rr patients, 2/12 Rn patients and 1/9 Nn patients had at least 1 titer < 500 IU/L.
During the first 12 weeks, the 10 Nn patients received a total of 2 additional 5,000 IU doses of HBIg (total 10,000 IU/L), the 11 Rn patients received no additional doses, and the 6 Rr patients received a total of 11 additional doses (total 95,000 IU/L).
Phase 2 (Weeks 12-36)
Twenty-two of the patients entered phase 2 and had the dose of HBIg reduced to 5,000 IU every 4 weeks. During phase 2, 2/4 Rr, 2/11 Rn, and 2/7 Nn patients had titers < 250 IU/L (the target anti-HBs level). Single additional HBIg doses were given to 1/4 Rr, 2/11 Rn, and 0/7 Nn.
Because of persistently low titers for one Rn patient during weeks 12-28, the monthly dose was increased to 10,000 IU beginning at week 28, which resulted in anti-HBs titers of 171 IU/L at week 32 and 200 IU/L at week 36.
Neutralizing Anti-HBs Titers During HBIg Treatment
Paired serum HBsAg and anti-HBs titers were analyzed to determine the lowest anti-HBs titers at which HBsAg was not detected for three time intervals. During week 1, HBsAg was present in 9/11 (82%) with anti-HBs < 300 IU/L vs. 1/44 (2%) with anti-HBs > 300 IU/L. In weeks 2-12, HBsAg was present in 4/7 (57%) with anti-HBs < 200 IU/L. vs. 2/112 (2%) with levels > 200 IU/L (P < 0.001 for both comparisons). In weeks 12-36, HBsAg was not detected in 131 samples despite 4 anti-HBs titers < 100 IU/L and 16 titers < 300 IU/L. Based on these and historical data, threshold trough titers of 300, 200, and 100 IU/L for each respective time period were used for further analysis.
In the first 12 weeks following LT, there was a significant difference between HBV replicative groups and the percentage of patients with titers less than the threshold titers outlined above (Tables 2, 3). The difference remained significant between the Rr vs. (combined Rn + Nn) groups at all time points within the first 12 weeks. During the first 4 days post LT there was a trend towards a greater percentage of Rn compared to Nn patients to have titers below the threshold level. After day 6, no patient from either the Rn or the Nn group had any titers below the designated threshold levels.
|Day 1-2||<300||6/40 (15%)||5/10 (50%)||18/44 (41%)||8/11 (73%)||21/23 (91%)||6/6 (100%)||0.004|
|Day 3-4||<300||1/36 (3%)||1/9 (11%)||8/43 (19%)||3/11 (27%)||13/22 (59%)||6/6 (100%)||0.001|
|Day 5||<300||0/18 (0%)||0/9 (0%)||1/22 (5%)||1/11 (9%)||2/10 (20%)||1/5 (20%)||NS|
|Day 6-7||<300||0/34 (0%)||0/9 (0%)||0/44 (0%)||0/11 (0%)||5/22 (23%)||2/6 (33%)||0.032|
|Day 8-30||<200||0/18 (0%)||0/9 (0%)||0/22 (0%)||0/11 (0%)||2/11 (18%)||2/5 (40%)||0.022|
|Day 31-week 12||<200||0/26 (0%)||0/8 (0%)||0/37 (0%)||0/11 (0%)||5/23 (22%)||2/4 (50%)||0.015|
|Weeks 13-24||<100||0/40 (0%)||0/7 (0%)||0/56 (0%)||0/10 (0%)||2/22 (9%)||1/4 (25%)||NS|
|Weeks 25-36||<100||0/52 (0%)||0/7 (0%)||0/68 (0%)||0/10 (0%)||2/28 (7%)||1/4 (25%)||NS|
|Study Period||Number of patients||GM Anti-HBs titer|
|Nn||Rn||Rr||Nn||Rn||Rr||Nn vs. Rn||Nn vs. Rr||Rn vs. Rr||Nn+Rn vs. Rr|
After week 12, one of the four Rr patients had a single titer less than the threshold level. There were no significant differences in percentages of patients in any of the three groups with anti-HBs titers less than the threshold level during this time period.
Anti-HBs Peak and Troughs
Anti-HBs peak and trough values varied markedly between patients within the different replicative groups at the different time periods (data not shown). Mean peak values well above that required for HBsAg neutralization were achieved by nonreplicative patients at the time of LT (Nn and Rn) within the first few days after LT and by the end of the first week for the Rr group (Table 3). The geometric mean (GM) peak levels were similar for the Rn and Nn groups toward the end of the first week after LT, but it was not until week 8 that the Rr patients began to achieve comparable peak anti-HBs levels. The GM trough levels for the nonreplicative groups (Rn and Nn) were likewise similar starting in week 2 (Table 4). The Rr group GM trough anti-HBs levels were always less than those for the other two groups and were significantly less during the first 12 weeks.
|Study Period||Number of patients||GM Anti-HBs titer|
|Nn||Rn||Rr||Nn||Rn||Rr||Nn vs. Rn||Nn vs. Rr||Rn vs. Rr||Nn+Rn vs. Rr|
A one-compartment pharmacokinetic model was adequate to describe the HBIg concentrations obtained in this study. For each group (Rr, Rn, and Nn), the volume of distribution (Vd), half-life (t1/2), and clearance (CL) were determined for four periods following transplantation: days 1-2, days 3-7, days 8-30, and for the period beyond 30 days. Adjusted pair-wise comparisons using the Tukey-Kramer method for multiple comparisons were performed. The Vd did not change significantly over time and there were no significant differences between the different replicative groups. In contrast, the clearance decreased and the t1/2 increased with time from LT for all patient groups. The clearance and the t1/2 became similar for the Rn and Nn groups by the end of the first post-operative week. However, the clearance was greater, and half-life was shorter at all time points during the trial among patients with quantifiable virus replication at the time of LT. Pair wise comparisons are shown in Table 5.
|pK Parameter||Period||GM||ANOVA P-values|
|Rn + Nn vs. Rr*||Nn vs. Rn||Nn vs. Rr||Rn vs. Rr|
|Volume of distribution (liters)||1–2||5.99||5.29||3.31||0.25||0.11||0.91||0.24||0.39|
Clinical Laboratory Tests
Liver and kidney function were monitored regularly throughout the trial. ALT and total bilirubin were elevated at baseline in 67% (20/30) and 83% (25/30) but were in the normal ranges in 78% (18/23) and 91% (21/23), respectively, by the end of the trial. A total of 37% (11/27) subjects had decreased creatinine clearance at baseline and 35% (8/22) at the end of study (P = NS).
A total of 58 adverse events were recorded in 16 of 30 (53%) patients. The majority of the adverse events was mild to moderate in severity, required no intervention, and resolved without sequelae. Only five of the events (three episodes of nausea, one of malaise, and one of anorexia) reported by three subjects were judged to be related to treatment with HBIg. Seven patients (23%) experienced 15 serious adverse events, all of which were considered unrelated to treatment with HBIg. Three deaths resulted from sepsis (days 37, 58, and 628), one on day 3 from intracranial hemorrhage, and one on day 24 from gastrointestinal hemorrhage and peritonitis. No death was considered related to treatment with the study medication.
This prospective multi-center trial was designed to determine the anti-HBs titers required to neutralize HBsAg and the effect of lamivudine suppression of HBV replication on IV HBIg dose requirements during the first 36 weeks post-LT. The study is limited by the lack of sensitivity of the DNA assays available at the time and the lack of stored serum to perform retrospective analysis. Although future studies should utilize these more sensitive assays, this study nevertheless provides valuable information for management of HBV-infected LT patients.
First, there are minimum anti-HBs titers required for HBsAg neutralization in the initial post LT period, corresponding to > 300 IU/L in the first week post LT and > 200 IU/L during weeks 2-12. These levels are similar to those described by McGory using HBIg monotherapy (> 500 IU/L and > 250 IU/L, respectively).9 These data suggest that lamivudine does not affect the titer of anti-HBs required to neutralize HBsAg within the first 12 weeks. After week 12, a minimum neutralizing titer could not be determined in this study as HBsAg was never detected despite 4 anti-HBs titers < 100 IU/L and 16 titers < 300 IU/L. For this reason, we used a target trough titer of > 100 IU/L based on data from McGory et al. in their HBIg monotherapy study for the week 12 to 36 period.9
Second, lamivudine suppression of HBV replication (even with the limitations of our assay) does affect the dose required to achieve HBsAG neutralization and pharmacokinetics of HBIg. The suppression of HBV replication prior to LT, either naturally or with pre-LT lamivudine (91-1140 days) led to rapid achievement of neutralizing anti-HBs titers within the first week following LT using the current dosing regimen. Patients with active replication and more limited exposure to lamivudine (0-41 days) prior to LT had detectable HBV DNA (> 5pgs/ml) at the time of LT, higher HBIg requirements and a more prolonged period with HBsAg in the serum in the first 12 weeks post LT. In fact, even larger quantities of HBIg than given in our protocol (90,000 IU or more in the first week post LT) may be required to provide adequate anti-HBs neutralization titers for patients with HBV replication at LT.
After the first 12 weeks, all patients without active replication at the time of transplant (Nn and Rn groups) maintained anti-HBs titers > 100 IU/mL when administered 5,000 IU HBIg IV monthly. One of four Rr patients continued to have anti-HBs 4-week trough levels > 100 IU/L requiring reversion to 10,000 IU HBIg IV monthly. This suggests that the potential benefit of early HBV suppression may extend even after the initial 12 weeks post LT period.
The pharmacokinetics supported the clinical observations. During the first 7 days, half-life and clearance for the Rn group became similar to those for the Nn group. After the first week, pharmacokinetics of HBIg for the two groups was indistinguishable. During the 36 weeks post LT, there was a modest decrease in HBIg clearance and an increase in half-life in the Rr group. However, there was consistently greater clearance and shorter T1/2 than those in the Nn and Rn groups.
Suppression of HBV replication prior to LT has been supported by other studies. Patients with HBV replication at the time of LT are at higher risk for HBV recurrence using high dose IV HBIg or lamivudine monotherapy.7, 9, 11, 12 Partovi et al. recently suggested that patients with HBV DNA levels > 100,000 copies/mL (3.5 × 10−1 pg/mL) have an increased risk of HBV recurrence after LT. Though the majority of patients were treated with HBIg monotherapy rather than in combination with lamivudine, the authors suggested the importance of suppression of HBV DNA below this level.28 Patients in our study with quantifiable amounts of HBV DNA at the time of LT (DNA ≥ 5 pg/mL) had higher HBIg requirements and a more prolonged period with HBsAg in the serum in the first 12 weeks post LT. This finding suggests an increased risk for HBV recurrence during this time period, particularly in light of lamivudine failure due to antiviral resistance. Other authors as well have reported potential clinical benefits of suppression of HBV replication in patients with ESLD due to HBV, leading to improvement in clinical status and delay in LT in these patients.29–31
Combination therapy using high dose IV 5% HBIg was well tolerated with minimal associated adverse events. The majority of recorded adverse events were likely unrelated to treatment and only one patient withdrew from the study related to potential adverse effects of the therapy (nausea, anorexia, and malaise). Symptoms commonly associated with 12.5-15% protein HBIg infusions, such as myalgias, predominantly back pain (90%), headache (20%), and flushing (5%),32 were rarely reported in our study, which may be due to the lower protein concentration. Though, our trial was not specifically designed to evaluate efficacy, the therapy was effective in preventing recurrent HBV infection over a 36 week period. Only one of the thirty patients (a patient in the Rr group) had evidence of HBV infection at last follow-up during the study period. Of interest, after completion of the 36-week trial, two of three Rn patients in whom HBIg was discontinued developed recurrent HBsAg, suggesting that patients with active replication at the time of lamivudine initiation may require indefinite HBIg therapy.
The ideal method of dosing HBIg would be through individualized dosing utilizing anti-HBs levels obtained in a timely fashion, given the significant interpatient variability in response to HBIg. However, the majority of LT programs are unable to obtain immediate anti-HBs titers and thus for the majority of centers fixed dose protocols are required. The results from this study can be used to refine a recently proposed HBV prophylaxis strategy utilizing fixed doses of IV HBIg in combination with nucleoside analogue therapy.33
All Nn and Rn patients obtained neutralizing trough titers > 300 IU/L by day 6. Since the PK parameters do not significantly improve until after the first week, high doses of HBIg are required (20,000 IU intra op and 10,000 IU/day for 7 days) if early HBsAg neutralization is to be achieved. Patients with quantifiable HBV DNA at the time of LT (those with active pre-LT replication and less lamivudine exposure) have the highest HBIg dose requirements in the early post LT period. Large doses of HBIg or when clinically permitted, delaying transplantation to achieve suppression of HBV replication should be considered. After the first 12 weeks, the mean trough titers obtained from the Rn and Nn groups remained well above 100 IU/L using monthly IV doses of 5,000 IU HBIg. The prolonged half-life and decreased clearance in these groups suggests that further reductions in doses are possible with maintenance of adequate neutralizing titers. The use of 5,000 IU per month should achieve neutralization titers in the majority of but not all Rr patients. The prophylactic strategy supported by our data is provided in Figure 2.
The role of IM HBIg in this prophylactic strategy cannot be adequately assessed as the pK are different than when used IV.28 The data do provide a rationale for the use of low dose IM HBIg. However, the pK and dose requirements of IM HBIg need to be adequately studied in the context of combination therapy.
In summary, high dose IV HBIg in combination with lamivudine was well tolerated and prevented HBV recurrence during an extended follow-up of over 3 years post transplantation. Lamivudine suppression of HBV replication prior to LT decreased HBIg requirements and allowed early HBsAg neutralization using the high dose IV HBIg regimen in our protocol. Our study supports the further reduction of HBIg doses and exploration of low dose IM HBIg in patients without active replication at the time of transplantation.
- 16An efficacy and cost-effectiveness analysis of combination hepatitis B immune globulin and lamivudine to prevent recurrent hepatitis B after orthotopic liver transplantation compared with hepatitis B immune globulin monotherapy. Liver Transpl 2000; 6: 741–748., , , , , , et al.
- 17Lamivudine and low-dose hepatitis B immune globulin for prophylaxis of hepatitis B reinfection after liver transplantation possible role of mutations in the YMDD motif prior to transplantation as a risk factor for reinfection. J Hepatol 2001; 34: 895–902., , , , , , .
- 27Group NP. NONMEM users guides 1992. BoeckmannAJ, SheinerLB, eds. San Francisco: University of California at San Francisco, 1992.
- 29Lamivudine treatment is beneficial in patients with severely decompensated cirrhosis and actively replicating hepatitis B infection awaiting liver transplantation: a comparative study using a matched, untreated cohort. Hepatology 2001; 34: 411–416., , , , .