estudio de rituximad para tratamiento de neuromielitis optica

1. A 5-Year Follow-up of Rituximab Treatment in Patients
With Neuromyelitis Optica Spectrum Disorder
Su-Hyun Kim, MD; So-Young Huh, MD; Sun Ju Lee, MS; AeRan Joung, RN; Ho Jin Kim, MD, PhD
N
euromyelitis optica (NMO) is an autoimmune inflam-
matory disease of the central nervous system charac-
terized by severe attacks of optic neuritis and longi-
tudinally extensive transverse myelitis. Recently, the
demonstration of a pathogenic role for the anti–aquaporin 4
(AQP4) antibody in NMO has marked a major advance in the
understanding of the disease.1
The critical role of B cells in the
pathogenesis of NMO previously has been suggested by an as-
sociation with the anti-AQP4 antibody.2
Rituximab, a monoclonal antibody that selectively tar-
gets CD20+
B cells, has exhibited promising clinical efficacy for
the prevention of relapses in patients with NMO. In 2005, Cree
and colleagues3
reported the first open-label study evaluat-
ing rituximab therapy in patients with NMO; their study in-
cluded 8 patients. In 2008, the beneficial effects of rituximab
were reported in a retrospective multicenter study4
of 25 pa-
tients with NMO (median duration of treatment, 19 months).
In 2011, favorable outcomes of repeated treatment with ritux-
imab were reported in 2 studies5,6
of patients with NMO, in-
cluding 23 and 10 patients.
To date, it has generally been accepted that repeated treat-
ment with rituximab is necessary to prevent NMO relapse, but
questions remain as to how and when patients with NMO
should receive further treatment. Common practice includes
the repeated administration of a single course (375 mg/
m2
/wk for 4 weeks or 1000 mg infused twice, with 2 weeks be-
IMPORTANCE A previous 2-year analysis of repeated rituximab treatment in patients with
neuromyelitis optica (NMO) revealed significant improvements in relapse rates and disability.
We report the findings from the longest follow-up of rituximab treatment in NMO, which
provide reassurance regarding the long-term efficacy and safety of rituximab in NMO.
OBJECTIVE To report the results of rituximab treatment in patients with relapsing NMO or
NMO spectrum disorder (NMOSD) for a median of 60 months.
DESIGN, SETTING, AND PARTICIPANTS Retrospective case series in an institutional referral
center for multiple sclerosis, including 30 patients with relapsing NMO or NMOSD.
INTERVENTIONS After induction therapy, a single infusion of rituximab (375 mg/m2
) as
maintenance therapy was administered whenever the frequency of reemerging CD27+
memory B cells in peripheral blood mononuclear cells, as measured with flow cytometry,
exceeded 0.05% in the first 2 years and 0.1% thereafter.
MAIN OUTCOMES AND MEASURES Annualized relapse rate (ARR), disability (Expanded
Disability Status Scale score), change in anti–aquaporin 4 antibody, and safety of rituximab
treatment.
RESULTS Of 30 patients, 26 (87%) exhibited a marked reduction in ARR over 5 years (mean
[SD] pretreatment vs posttreatment ARR, 2.4 [1.5] vs 0.3 [1.0]). Eighteen patients (60%)
became relapse free after rituximab treatment. In 28 patients (93%), the disability was either
improved or stabilized after rituximab treatment. No serious adverse events leading to
discontinuation were observed during follow-up.
CONCLUSIONS AND RELEVANCE Repeated treatment with rituximab in patients with NMOSD
over a 5-period, using an individualized dosing schedule according to the frequency of
reemerging CD27+
memory B cells, leads to a sustained clinical response with no new adverse
events.
JAMA Neurol. 2013;70(9):1110-1117. doi:10.1001/jamaneurol.2013.3071
Published online July 29, 2013.
Editorial page 1102
Author Affiliations: Department of
Neurology, Research Institute and
Hospital of National Cancer Center,
Gyeonggi, Korea.
Corresponding Author: Ho Jin Kim,
MD, PhD, Department of Neurology,
Research Institute and Hospital of
National Cancer Center, 323 Ilsan St,
Ilsandong-gu, Goyang-si,
Gyeonggi-do, Korea (hojinkim@ncc
.re.kr).
Research
Original Investigation
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2. tween doses) every 6 to 12 months.3-7
We reported elsewhere8
a significant clinical effect of repeated rituximab treatment in
30 patients with NMO spectrum disorder (NMOSD). Patients
received a single additional infusion of rituximab (375 mg/
m2
) as maintenance therapy on the reappearance of periph-
eral CD27+
memory B cells.8
During a 2-year period, the re-
lapse rate was reduced by 88%, and, overall, 70% of patients
became relapse free.8
Our strategy could achieve effective dis-
ease control with a much lower cumulative dose than used in
prior studies.3-6
Moreover, memory B-cell depletion in periph-
eral blood was shown to be associated with the clinical re-
sponse to rituximab.8
Although available clinical data regarding treatment with
repeated cycles of rituximab show clinical efficacy and an ac-
ceptable safety profile, the long-term efficacy and safety of ri-
tuximab in patients with NMO has yet to be determined. Of 30
patients enrolled in a previous 2-year study,8
27 have contin-
ued rituximab treatment for up to 7 years. We present here the
updated results of long-term rituximab treatment in the same
cohort.
Methods
Patients
The original study cohort included 30 patients with NMOSD;
inclusion criteria have been described in detail elsewhere.8
In
brief, patients were required to have (1) a diagnosis of NMO (ac-
cording to the 2006 diagnostic criteria9
) or NMOSD10
and (2)
at least 1 relapse during the 12 months before the start of ri-
tuximab therapy. Treatment protocols were approved by the
institutional review board of the National Cancer Center.
Treatment Protocol
The treatment protocol of the initial 2-year study included in-
duction and maintenance phases. Two regimens were used as
induction treatment: (1) 375 mg/m2
infused once weekly for 4
weeks (n = 16) and (2) 1000 mg infused twice at a 2-week in-
terval (n = 14). Peripheral blood samples were obtained every
6 weeks throughout the first year and every 8 weeks through-
out the second year to evaluate lymphocyte subsets, includ-
ing CD27+
memory B cells and anti-AQP4 antibody levels. The
therapeutic target for CD27+
memory B-cell depletion was de-
fined as less than 0.05% in peripheral blood mononuclear cells
(PBMCs), and patients were given 1 additional infusion of ri-
tuximab (375 mg/m2
) when the memory B-cell frequency was
at least 0.05% in PBMCs. After completion of the initial 2-year
study, the interval for monitoring memory B cells was ex-
tended to 10 weeks, and patients received 1 additional infu-
sion of rituximab (375 mg/m2
) as maintenance therapy when-
ever the frequency of reemerging memory B cells in PBMCs
exceeded 0.1%, as determined by flow cytometry (Figure 1).
No patient was given concomitant immunosuppressants while
receiving rituximab.
Clinical Assessment
The primary end point was the annualized relapse rate
(ARR) for each patient, and the secondary end points were
neurological status, as indicated by the Expanded Disability
Status Scale (EDSS) score, and the safety of rituximab.
Relapses were defined as the objective worsening of new
neurological symptoms lasting at least 24 hours that
increased the EDSS score by at least half a step (0.5). Acute
relapses were treated with high-dose intravenous methyl-
prednisolone sodium succinate. If a severe disability per-
sisted after corticosteroid therapy, plasma exchange was
performed. Clinical adverse events were recorded through-
out the study. Serum levels of IgG were evaluated at base-
line and every year thereafter. Serum levels of IgM and IgA
were measured every year after 3 years of treatment.
Flow Cytometric Analysis and Measurement of Serum
Anti-AQP4 Antibody Levels
Simple whole-blood staining was used to characterize leuko-
cyte and B-cell subsets directly from the circulation. Triple-
colorimmunofluorescentstainingofwhole-bloodsampleswas
performed within 60 minutes after blood was collected, using
antibodies directed against CD14/CD3/CD19 and CD27/CD19
with isotype controls. This was followed by red blood cell ly-
sis and immediate acquisition and analysis with flow cytom-
etry. The quantitative change in anti-AQP4 antibody levels was
measured by using an enzyme-linked immunosorbent assay.11
Statistical Analysis
The ARR, EDSS score, and serum anti-AQP4 antibody levels
were compared before and after rituximab treatment using the
Wilcoxon signed rank test and the 2-sided sign test. Univari-
ate linear regression analyses were used to test for associa-
tions among values. All statistical analyses were performed
using GraphPad Prism software, version 4.0 (GraphPad), and
differences were considered statistically significant at P < .05.
Figure 1. Treatment Protocol
30 Patients with NMO or NMOSD started
rituximab treatment
After induction treatment, single IV
reinfusion of 375 mg/m2
whenever
frequency of CD27+
memory B cells in
peripheral blood is ≥0.05% based on
evaluation of peripheral circulating
B-cell subsets every 6-8 wk
1 Stopped rituximab treatment
before year 2 owing to
insufficient response
29 Patients eligible for follow-up at 2 y
2 Dropped out of treatment
1
1
Switched to other treatment
because too-frequent
readministration was required
Lost to follow-up
27 Continued rituximab treatment
Single IV reinfusion of 375 mg/m2
whenever frequency of CD27+
memory B cells in peripheral blood is
≥0.1% based on evaluation of
peripheral circulating B-cell subsets
every 10 wk
Flowchart shows treatment protocol in the current study. IV indicates
intravenous; NMO, neuromyelitis optica; NMOSD, NMO spectrum disorder.
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3. Results
Patient Characteristics and Follow-up
Thirty patients (27 women and 3 men) were initially
enrolled and treated. The median duration of treatment
with rituximab was 60 months (range, 9-82 months). The
mean age for starting rituximab therapy was 38 years
(range, 23-58 years), and the median interval from the onset
of NMO to treatment with rituximab was 4.5 years (range,
0.5-12.9 years). At last review, 27 patients continued
re-treatment with rituximab, with a median duration of 61
months (range, 49-82 months). Three patients discontinued
rituximab treatment; patient 18 moved to a distant location
2 years after treatment and was unable to visit the clinic,
patient 20 switched to mitoxantrone 2 years after starting
rituximab because she required too-frequent readministra-
tion to maintain therapeutic B-cell depletion, and patient 26
switched to mitoxantrone 9 months after starting rituximab
because of sustained relapses during treatment.
Treatment Efficacy
Of the 30 patients, 26 showed a marked reduction in ARR over
5 years (Figure 2). The mean (SD) pretreatment ARR was 2.4
(1.5), and the mean (SD) posttreatment ARR over 5 years was
0.3 (1.0) (P < .001). Eighteen patients (60%) were relapse free
during rituximab treatment. Among all patients, the EDSS
scores improved in 24 patients and stabilized in 4. The me-
dian EDSS score was 4.0 (range, 1.0-8.5) before rituximab treat-
ment and 3.0 (range, 1.0-7.5) after treatment (P < .001).
Rituximab Treatment
Over 5 years, the median interval between treatments was 27
weeks (range, 6-68 weeks), and the mean time to re-treatment
variedbetweenindividualsfrom10to39weeks.Subgroupanaly-
seswereperformedtoassessthefrequencyofre-treatmentover
5 years and compare the interval to re-treatment between the
first 2 years and thereafter. With the 3 patients who discontin-
ued rituximab excluded from analysis, the mean number of re-
treatments after induction was 8 (range, 6-11). The interval un-
til re-treatment with rituximab after 2 years (mean, 36 weeks)
wasextendedcomparedwiththatduringtheinitial2-yearstudy
(mean, 23 weeks; P < .001).
Relapses During Treatment
During 5 years, a total of 21 relapses occurred in 11 patients
(Table), with 14 occurring in 9 of 30 patients during the initial
2 years and 7 in 4 of 27 patients during the next 3 years. Re-
lapses during the initial 2 years were described in the previ-
ous report.8
Five relapses in 5 patients (patients 10, 16, 20, 25,
and 27) occurred after induction therapy but before therapeu-
tic depletion, and 3 relapses in 2 patients (patients 11 and 16)
occurred in conjunction with delayed re-treatment. Two re-
lapses in 2 patients (patients 9 and 13) occurred despite adher-
ence to the treatment protocol, and 4 relapses in 1 patient (pa-
tient 26) occurred with incomplete CD27+
memory B-cell
depletion despite several re-treatments.8
Among the 7 relapses occurring after the initial 2 years, 2
relapses in 2 patients (patients 7 and 11) occurred in conjunc-
tion with delayed re-treatment. Patient 7 missed a scheduled
rituximab reinfusion, despite significant reconstitution of
memory B cells (0.27%), and experienced relapse 10 weeks af-
ter the last memory B-cell assessment. Patient 11 missed a
scheduledmemoryB-cellassessment,whichshouldhavebeen
performed 10 weeks after the last assessment, and had a re-
lapse 12 weeks after the last memory B-cell assessment
(Figure 3). Five relapses in 2 patients (patients 9 and 29) oc-
curred despite adherence to the treatment protocol. Of note,
Figure 2. Neuromyelitis Optica Relapses Before and After Start of Rituximab Treatment
–160 –120 –100 –80 –60 –40 –20 0 20 40 60 80
Patients
Time Relative to Start of Rituximab Treatment, mo
–140
Relapse
Last follow-up
Charts depict occurrence of relapses
in patients with neuromyelitis optica
before and after the start of
rituximab treatment. On the x-axis, 0
indicates the start of treatment. Each
row of symbols on the y-axis
represents a patient.
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4. during the third year of treatment, patient 9 had 3 relapses dur-
ing a 6-month period during which the memory B cells were
belowthe0.05%cutoff.Afterthefourthrelapseduringthethird
year of treatment, a switch in treatment was considered, but
the patient refused other immunosuppressants and decided
to continue rituximab treatment. No further relapses were ob-
served in the following 2 years of treatment.
Anti-AQP4 Antibody
Twenty-three patients (77%) were seropositive for the anti-
AQP4 antibody. Anti-AQP4 antibody levels were generally re-
duced or maintained at levels consistent with the initial 2 years
of treatment during the follow-up phase. Anti-AQP4 anti-
body levels gradually increased after 4 years of treatment in
conjunction with a prolonged re-treatment interval in 6 pa-
tients, but no clinical relapse was observed. Six patients who
were initially seropositive were later seronegative at the last
follow-up. Seven patients maintained a seronegative status
throughout rituximab treatment; 6 were relapse free but 1 (pa-
tient 13) had a relapse during the first 2 years. Most relapses
were accompanied by an elevation of anti-AQP4 antibody lev-
els, but rising anti-AQP4 antibody levels were not always as-
sociated with clinical relapse (Figure 3).
Flow Cytometric Analysis
Withasinglereadministrationofrituximab(375mg/m2
),CD27+
memory B-cell frequency decreased to the therapeutic target
value in 27 patients. Reconstitution of B cells involves mainly
CD27−
-naive B cells. The median percentage of CD27−
-naive B
cells in the reconstitution of B cells was 86.2% (range, 0.04%-
99.6%). Reconstitution of B cells is not necessarily propor-
tional to CD27+
memory B cells, and the reemergence of
memory B cells above the therapeutic target occurred even in
CD19+
B cells at less than 0.1% of PBMCs (Figure 4). No re-
lapses occurred in patients with CD27+
memory B-cell fre-
quency below the therapeutic target except in patient 9, but
12 (60%) and 13 (65%) of 20 relapses occurred in patients with
CD19+
B-cell counts less than 0.01 × 109
/L or less than 0.5% of
PBMCs, respectively, which was considered B-cell depletion
in prior studies6,12
(Table).
Safety
Over the 5 years, no case of progressive multifocal leukoen-
cephalopathy or malignancy was observed, and there were no
serious adverse events leading to discontinuation of treat-
ment. At last follow-up, serum IgM levels were below the lower
limit of normal in 11 (37%) of the patients, IgA levels were low
Table. Characteristics of 21 Relapses in 11 Patients During Rituximab Treatment
Patient No.
Relapse
No.
Interval to Relapse, wk
Frequency of
CD27+
Memory
B Cells in
PBMCs at Last
Analysis Before
Relapse, %
Frequency of
CD19+
B Cells in
PBMCs at
Relapse, %
CD19+
B-Cell
Count in
Peripheral
Blood at
Relapse,
×109
/L
Frequency of
CD27+
Memory B
Cells in PBMCs
at Relapse, %
Anti-AQP4
Antibody
Level at
Relapse, SU
From
Initiation of
Rituximab
Treatment
From Last
Reinfusion
of
Rituximab
From Last
Flow
Cytometric
Analysis
7 1 108 42 10 0.27a
3.43 0.082 0.44 1.185
9 1 102 28 4 0.01 4.44 0.095 0.07 0.345
2 108 4 6 0.07 0 0 0 1.267
3 118 14 10 0.00 0 0 0 0.978
4 130 1 2 0.01 0.01 0.003 0.01 1.213
5 155 24 4 0.01 0.69 0.015 0.25 1.011
10 1 24 3 0.03 0.17 0.004 0.14 0.260
11 1 77 43 7 0.12a
6.60 0.141 0.06 0.540
2 122 38 12 NA 11.66 0.387 0.11 0.804
13 1 70 23 7 0.02 3.36 0.089 0.06 0.366
16 1 12 4 0.04 0.09 0.002 0.06 1.208
2 43 21 6 0.05a
NA NA NA NA
3 99 2 2 0.40b
0.08 0.002 0.07 1.237
20 1 8 1 1 0.58c
0.57 0.011 0.36 0.718
25 1 3 0.09 0.001 0.08 0.382
26 1 6 0.16 0.019 0.16 0.313
2 21 6 6 0.04 0.15 0.002 0.1 0.415
3 25 4 4 0.10c
0.07 0.001 0.06 0.432
4 39 6 7 0.07c
0.1 0.002 0.07 0.482
27 1 6 0.06 0.001 0.05 0.649
29 1 175 10 10 0.19 0.20 0.002 0.12 0.380
Abbreviations: AQP4, aquaporin 4; NA, not available; PBMCs, peripheral blood
mononuclear cells; SU, standard unit.
a
The patient missed a scheduled reinfusion despite reconstitution of memory B
cells.
b
Significant reconstitution of memory B cells because the patient missed a
scheduled memory B-cell assessment.
c
Incomplete depletion of memory B cells despite induction treatment or
reinfusion of rituximab.
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5. Figure 3. Clinical Response, CD27+
Memory B Cells, and Anti–Aquaporin 4 Antibody Levels During Rituximab Treatment
0.0
0 100 150 200 250 300
1.0 0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.6
0.8
FrequencyofMemoryBCells,%
Anti-AQP4AntibodyLevels,SU
Anti-AQP4AntibodyLevels,SU
Duration of Treatment, wk
0.4
0.2
50
0.0
0 100 150 200 250
2.5 1.6
1.2
0.8
1.4
1.0
0.6
0.4
0.2
0.0
1.5
2.0
FrequencyofMemoryBCells,%
Anti-AQP4AntibodyLevels,SUAnti-AQP4AntibodyLevels,SU
Duration of Treatment, wk
0.4
0.2
50
0.0
0 100 150 200 250 300
3.0 1.8
1.4
1.0
0.6
1.6
1.2
0.8
0.4
0.2
0.0
2.0
2.5
FrequencyofMemoryBCells,%
Duration of Treatment, wk
1.5
1.0
0.5
50
0.0
0 100 150 200 250
1.4 0.8
0.6
0.4
0.2
0.0
1.0
1.2
1.1
1.3
FrequencyofMemoryBCells,%
Anti-AQP4AntibodyLevels,SU
Duration of Treatment, wk
0.6
0.4
0.2
50
0.0
0 100 150 200 250
1.2 1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.8
1.0
FrequencyofMemoryBCells,%
FrequencyofMemoryBCells,%
Duration of Treatment, wk
0.4
0.2
5025 125 175 22575
Memory B cells
Anti-AQP4 antibody
Cutoff level of anti-AQP4 antibody
Reinfusion of rituximab
Clinical relapse
Missed schedule for reinfusion
Missed schedule for memory B-cell
assessment
Patient 3
Patient 9
Patient 11
Patient 29
Patient 10
0.0
0 100 150 200 250
4 0.8
0.6
0.4
0.2
0.0
2
3
FrequencyofMemoryBCells,%
Anti-AQP4AntibodyLevels,SU
Duration of Treatment, wk
0.6
0.4
0.2
50
0.00
0 100 150 200
4 0.8
0.6
0.4
0.2
0.0
2
3
Anti-AQP4AntibodyLevels,SU
Duration of Treatment, wk
0.50
0.25
50
Patient 17
Patient 7
Graphs display relationships among clinical response, frequency of CD27+
memory B cells, and anti–aquaporin 4 (AQP4) antibody levels during rituximab treatment.
SU indicates standard unit.
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6. in 9 (30%), and IgG levels were low in 4 (13%). The most com-
monlyreportedinfectionswererespiratorytractinfections,uri-
nary tract infections, and a single case of herpes zoster infec-
tion,butnoseriousinfectionsoccurredthatrequiredtreatment
with intravenous anti-infective agents. Infusion-related ad-
verse events were noted in 40% of patients during the year af-
ter first rituximab exposure but declined in the second year
and generally remained stable thereafter.
Discussion
The current study demonstrates the sustained clinical effi-
cacy of repeated rituximab treatment, with no new adverse
events during a median 5-year follow-up in patients with
NMOSD. Of the 30 patients, 26 (87%) maintained a marked re-
duction in ARR, and the disability either improved or stabi-
lizedin93%ofpatients.Over5years,60%ofpatientswerecom-
pletely free from relapse.
Rituximab is very expensive, and the long-term safety of
repeated rituximab treatment is unclear. Any effective treat-
mentstrategythatminimizesunnecessaryexposuretothedrug
and allows significant cost savings and safety would be ben-
eficial. We postulated that after the disease activity stabi-
lized, less frequent re-treatment than during the early stage
of treatment might be sufficient to prevent a relapse in NMO.
Based on our hypothesis, we extended the testing interval and
increased the therapeutic threshold of CD27+
memory B cells
after completion of the initial 2-year treatment. This might en-
courage patients to adhere to our strategy during their long-
term treatment. Control of disease activity was maintained in
allbut2patients,withlongerre-treatmentintervalsafter2years
than during the initial 2-year study (about 8 vs 5 months, re-
spectively).
Long-term B-cell depletion after repeated rituximab treat-
ment did not give rise to any increased safety risk. Decreases
in immunoglobulin levels were observed in some patients af-
ter rituximab treatment, but the clinical consequences of these
decreases are unclear. The safety profile in the current analy-
sis was consistent with that reported in the patients with rheu-
matoid arthritis (RA). A recent long-term safety analysis13
of
all clinical trials in patients with RA (3194 patients with 11 962
patient-years of observation) found no evidence of an in-
creased safety risk over time or increased reporting rates of any
types of adverse events with prolonged exposure to ritux-
imab during up to 9½ years of observation.
To date, the clinical challenges associated with the use of
rituximab in patients with NMO are based on developing a re-
treatment strategy. In the current study, CD27+
memory B cells
in PBMCs were regularly monitored, and re-treatments were
adjusted to sustain the therapeutic depletion of these cells.
Consequently, a median of 8 single infusions of rituximab (375
mg/m2
) after induction were required to prevent exacerba-
tionofdisabilityover5years.Thecumulativedoseinthisgroup
is much lower than achieved with the common practice of 4
infusions (375 mg/m2
) or 2 infusions (1000 mg) of rituximab
at a fixed interval of every 6 to 9 months.4-6
This has consid-
erable economic implications. For example, in Korea, the av-
erage annual cost of maintenance rituximab therapy for this
protocol is lower than the annual cost of the immunosuppres-
santmycophenolatemofetil.Alowercumulativedosemayalso
decrease the risk of serious adverse effects, such as infection
and malignancy. Our findings suggest that tighter control of
disease activity by sustaining a predefined therapeutic target
before disease activity flares up can enable control of the dis-
ease activity with a lower dose. However, confirmation of our
observations will require study of a larger cohort using a ran-
domized clinical design to compare our tighter control strat-
egy based on memory B-cell frequencies and fixed 1000-mg
dose re-treatment every 6 to 12 months.
The current rituximab protocol with a therapeutic target
for memory B-cell depletion is consistent with a recently
changed strategy for rituximab treatment in RA. In initial stud-
ies with RA, subsequent cycles of rituximab treatment were
administered based on clinical disease activity, as needed.14
However, recent guidelines for RA treatment have advocated
a treatment-to-target approach, a treatment strategy tailored
to the individual patient whereby patients are regularly moni-
tored and treatment is adjusted to achieve a predefined level
of disease activity.15-17
In NMO, the symptoms of relapse do not
present gradually as in RA and there is no defined tool to moni-
tor disease activity. We defined depletion of memory B cells
asatherapeutictargetrepresentinglowdiseaseactivityorclini-
cal remission, and treatment was adjusted to achieve a pre-
definedtherapeutictarget.Thus,ourstrategyandrecentguide-
lines for treating RA emphasize the importance of keeping
diseaseactivitylowbyapplyingpreemptivere-treatmentbased
on a quantitative therapeutic target.
PreviousstudiesmonitoredCD19+
BcellsinPBMCstoguide
treatment decisions, but no specific threshold value was used
to determine the timing of re-treatment.4-6,18,19
In the cur-
rent study, more than half of relapses occurred at CD19+
B-
cell counts below 0.01 × 109
/L or less than 0.5% of PBMCs but
above the therapeutic threshold for CD27+
memory B cells,
Figure 4. Reconstitution of B Cells at Re-treatment
0
0.0 0.80.6 1.2 1.6
14
10
FrequencyofCD19+
BCellsinPBMCs,%
Frequency of CD19+
CD27+
Memory B Cells in PBMCs, %
6
2
1
0.1 0.2 1.0 1.4
Reconstitution of CD19+
B cells is not necessarily proportional to repopulation
of CD27+
memory B cells at the time of re-treatment. PBMCs indicates
peripheral blood mononuclear cells.
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7. whereas no relapses occurred below the therapeutic thresh-
old except in 1 patient. Most important, the reemergence of
CD27+
memory B cells above the therapeutic target could oc-
cur even with a very small reconstitution of CD19+
B cells
(Figure 4). Memory B cells, precursors of autoantibody-
producing plasma cells, can elicit rapid and robust responses
compared with corresponding antigen-inexperienced naive B
cells.20
Thus, it seems likely that targeting CD27+
memory B
cells rather than CD19+
B cells provides a better measure of ri-
tuximabefficacy.Over5yearsofrituximabtreatment,theover-
all level of anti-AQP4 antibody was decreased or maintained,
buttherelationshipbetweenclinicaloutcomeandlevelofanti-
AQP4 antibody is less clear than with memory B cells.
The therapeutic target value of 0.05% CD27+
memory B
cells in PBMCs was arbitrary, based on our experience before
this study. Nevertheless, our current results suggest the rel-
evance of this value as a quantitative threshold to determine
re-treatment.
All but 1 patient experienced relapses after the reemer-
gence of memory B cells above the defined therapeutic deple-
tion status. In addition, re-treatment after significant reple-
tionofCD27+
memoryBcellscouldnotpreventaclinicalrelapse
in patient 16 (Table). This result suggests that additional deple-
tion of CD27+
memory B cells must occur before disease activ-
ity increases. Nevertheless, 1 patient (patient 9) had 3 relapses
before the proportion of CD27+
memory B cells in PBMCs
reached 0.05%. The explanation for this observation is un-
clear.AlthoughtheCD27markerhasbeenusedtorepresenthu-
man memory B cells, recently appearing memory B cells could
befurtherfractionatedbasedontheexpressionofIgD,IgM,and
CD27 as IgM+
IgD+
CD27+
memory B cells, IgM-only memory B
cells, IgD-only memory B cells, IgM−
IgD−
CD27+
memory B cells
(class-switched CD27+
memory B cells), and IgM−
IgD−
CD27−
memory B cells (class-switched CD27−
memory B cells).21
Re-
centstudiesinpatientswithRAsuggestthatbaselinebloodlev-
els of the molecular marker for late-stage B-cell lineage plas-
mablasts identify patients who are unlikely to gain substantial
clinical benefit from rituximab therapy.22
The re-treatment de-
cision based on more segmented memory B-cell and plasma-
blast monitoring may elevate the therapeutic efficacy of ritux-
imab in patients with NMO.
Our study was limited by its retrospective analysis, the
small number of patients, and the absence of a control group.
Moreover, the improvement in EDSS scores may be attribut-
able to recovery from a relapse because the pretreatment EDSS
score may have been determined before complete recovery.
These limitations notwithstanding, considering the rarity of
the disease, the limited evidence of rituximab treatment in
NMO, and the ethical difficulties in conducting randomized
clinical trials, our results are encouraging and should reas-
sure clinicians regarding the long-term efficacy and safety of
rituximab in NMO. Furthermore, this treatment-to-target ap-
proach with monitoring of blood memory B cells may enable
cost-effective and personalized therapy.
ARTICLE INFORMATION
Accepted for Publication: April 2, 2013.
Published Online: July 29, 2013.
doi:10.1001/jamaneurol.2013.3071.
Author Contributions: Drs S.-H. Kim and H. J. Kim
had full access to all the data in the study and take
responsibility for the integrity of the data and the
accuracy of the data analysis.
Study concept and design: S.-H. Kim, H. J. Kim.
Acquisition of data: All authors.
Analysis and interpretation data: All authors.
Drafting of the manuscript: S.-H. Kim, H. J. Kim.
Critical revision of the manuscript for important
intellectual content: All authors.
Statistical analysis: S.-H. Kim, H. J. Kim.
Administrative, technical, and material support: Lee,
Joung, H. J. Kim.
Study supervision: H. J. Kim.
Conflict of Interest Disclosures: Dr H. J. Kim
reported having received a research grant from the
Ministry for Health and Welfare and honoraria for
speaking or consulting from Bayer Schering
Pharma, Merck Serono, Novartis, Biogen Idec, and
Genzyme.
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