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Schiffmann R, Kopp JB, Austin III HA, et al. Enzyme Replacement Therapy in Fabry Disease: A Randomized Controlled Trial. JAMA. 2001;285(21):2743–2749. doi:10.1001/jama.285.21.2743
Context Fabry disease is a metabolic disorder without a specific treatment,
caused by a deficiency of the lysosomal enzyme α-galactosidase A (α-gal
A). Most patients experience debilitating neuropathic pain and premature mortality
because of renal failure, cardiovascular disease, or cerebrovascular disease.
Objective To evaluate the safety and efficacy of intravenous α-gal A for
Design and Setting Double-blind placebo-controlled trial conducted from December 1998 to
August 1999 at the Clinical Research Center of the National Institutes of
Patients Twenty-six hemizygous male patients, aged 18 years or older, with Fabry
disease that was confirmed by α-gal A assay.
Intervention A dosage of 0.2 mg/kg of α-gal A, administered intravenously every
other week (12 doses total).
Main Outcome Measure Effect of therapy on neuropathic pain while without neuropathic pain
medications measured by question 3 of the Brief Pain Inventory (BPI).
Results Mean (SE) BPI neuropathic pain severity score declined from 6.2 (0.46)
to 4.3 (0.73) in patients treated with α-gal A vs no significant change
in the placebo group (P = .02). Pain-related quality
of life declined from 3.2 (0.55) to 2.1 (0.56) for patients receiving α-gal
A vs 4.8 (0.59) to 4.2 (0.74) for placebo (P = .05).
In the kidney, glomeruli with mesangial widening decreased by a mean of 12.5%
for patients receiving α-gal vs a 16.5% increase for placebo (P = .01). Mean inulin clearance decreased by 6.2 mL/min
for patients receiving α-gal A vs 19.5 mL/min for placebo (P = .19). Mean creatinine clearance increased by 2.1 mL/min (0.4 mL/s)
for patients receiving α-gal A vs a decrease of 16.1 mL/min (0.3 mL/s)
for placebo (P = .02). In patients treated with α-gal
A, there was an approximately 50% reduction in plasma glycosphingolipid levels,
a significant improvement in cardiac conduction, and a significant increase
in body weight.
Conclusion Intravenous infusions of α-gal A are safe and have widespread
therapeutic efficacy in Fabry disease.
Fabry disease is a rare X-linked recessive glycosphingolipid storage
disorder that is caused by a deficiency of the lysosomal enzyme α-gal
A (α-galactosidase A).1 Its incidence
has been estimated to be 1:117 000 births.2
Globotriaosylceramide (Gb3), the glycosphingolipid substrate of
this enzyme, accumulates within vulnerable cells, tissues, and organs of affected
patients. Affected cell types include endothelial cells, pericytes, smooth
muscle cells of the vascular system, renal epithelial cells, myocardial cells,
and dorsal root ganglia neuronal cells.3-5
Clinical onset of the disease typically occurs during childhood or adolescence
with recurrent episodes of severe, debilitating neuropathic pain in the extremities.
The neuropathic pain syndrome is thought to be secondary to a small-fiber
peripheral neuropathy caused by destruction of dorsal root ganglion cells
by progressive deposition of Gb3.3
With increasing age, Gb3 progressively accumulates throughout the
body. Deposition of Gb3 occurs within multiple sites throughout
the nephrons and renal vasculature. Progressive glomerular injury is associated
with mesangial widening and ultimately with segmental and global glomerulosclerosis.6 Patients often also develop hypertrophic cardiomyopathy,7 coronary artery disease, valvular abnormalities,8,9 dysrhythmias, and conduction disturbances.10
Death usually occurs during the fourth or fifth decade of life secondary
to renal, cardiac, or cerebrovascular complications.11
To date, there has been no definitive therapy for Fabry disease.
Previous studies have demonstrated that partially purified preparations
of α-gal A are metabolically active.12,13
Recently, 10 patients with Fabry disease were each treated with a single intravenous
infusion of 5 escalating doses of highly purified α-gal A.14
This study showed that α-gal A significantly reduced Gb3
levels in the liver and in shed renal tubular epithelial cells in urine sediment.
Immunohistochemical staining of liver tissue approximately 2 days after enzyme
infusion identified α-gal A in every cell type, suggesting diffuse uptake
via the mannose-6-phosphate receptor. The tissue half-life in the liver was
greater than 24 hours, consistent with that of other lysosomal enzymes.15-17
The goal of this study was to assess the safety and clinical efficacy
of repeated intravenous administrations of α-gal A for the treatment
of patients with Fabry disease.
Twenty-six hemizygous men 18 years of age or older, with Fabry disease
confirmed by α-gal A assay, participated in this study (Figure 1). All patients had neuropathic pain. The institutional
review board of the National Institute of Neurological Disorders and Stroke
approved the study. All the patients who participated in this study gave their
written informed consent prior to their inclusion in this trial.
α-Gal A was produced in a genetically engineered continuous human
cell line (Transkaryotic Therapies, Inc, Cambridge, Mass). α-Gal A in
the cell culture supernatant was harvested, and the enzyme was purified by
a series of conventional chromatographic steps in facilities compliant with
Good Manufacturing Practices. Purified α-gal A was formulated and placed
in vials containing sodium phosphate as a buffering agent (pH 5.8-6.2 at 4°C),
polysorbate 20 as a stabilizing agent, and sodium chloride as an isotonic
agent. The drug was diluted in 100 mL of normal saline for administration.
The specific activity of the enzyme was 3.4 × 106 nmol/h
per milligram of protein and it was more than 99.5% pure.
α-Gal A (0.2 mg/kg) was administered by intravenous infusion initially
over a period of 20 minutes. Approximately midway into the trial, the infusion
time was increased to 40 minutes to diminish the likelihood of mild infusion
reactions (see "Safety," below). Doses were administered every other week
for 6 months (12 doses total). The placebo infusions, aside from the absence
of α-gal A, were identical to the enzyme infusions in composition, appearance,
and method of administration.
A randomization schedule was prepared prior to the start of the study
and was provided to an unblinded pharmacist in the research pharmacy at the
National Institutes of Health. No other medical or sponsor personnel had access
to the randomization code until the study was completed. Patients were randomized
after the first evaluation was completed and the eligibility criteria were
confirmed. Randomization was blocked to minimize imbalances between study
Neuropathic Pain. The Brief Pain Inventory (BPI) short form contains 9 pain-related questions,
each answered by circling a number on a 0 to 10 scale.18
The BPI was completed by the patients at baseline, during each visit to the
National Institutes of Health for enzyme infusion, and at the end of the study.
At baseline and at weeks 8, 16, and 23, patients discontinued taking any neuropathic
pain medications and completed the BPI within the following week, with the
precise timing based on individual patient analgesic requirements. This procedure
allowed the severity of the pain without pain medications to be assessed accurately
while minimizing patients' discomfort. Following pain medication withdrawal
and BPI scoring, patients were able to remain without their chronic neuropathic
pain medication regimens if they felt able to do so.
The primary efficacy end point was the effect of therapy on neuropathic
pain while without pain medications, as measured by the "pain at its worst"
item (question 3) from the BPI ("Please rate your pain by circling the one
number that best describes your pain at its worst in the last week"). Other
pain end points included the mean score of the BPI severity items (questions
3 through 6: "please rate your pain by circling the one number that best describes
your pain at its least in the last week; please rate your pain by circling
the one number that best describes your pain on the average; please rate your
pain by circling the one number that tells how much pain you have right now"),
and the BPI interference items, question 9 ("Circle the one number that describes
how, during the past week, pain has interfered with your: A, general activity;
B, mood; C, walking ability; D, normal work [includes both work outside the
home and housework]; E, relations with other people; F, sleep; G, enjoyment
of life"). Patients' use of pain medication was recorded throughout the study.
Neuropathic pain medications were defined to include carbamazepine, gabapentin,
phenytoin, lamotrigine, nortriptyline, and amitriptyline.
Renal Outcome Measures. At baseline and at week 24, inulin clearance and creatinine clearance
were used to estimate glomerular filtration rate, and renal biopsies were
All biopsy specimens were coded so that the analysis would be blinded
to treatment assignment, patient number, and order of biopsy. Two renal pathologists
assessed renal biopsies and a consensus score was reached. Glomerular numbers
were counted in paraffin and plastic sections and the total number of glomeruli
was recorded. The mean glomerular number was 24, with a range of 2 to 52;
only 1 biopsy specimen had fewer than 8 glomeruli. The morphology of each
glomerulus was classified as normal (without mesangial changes); with mesangial
widening (mesangial widening observed to an equal extent throughout the capillary
tuft); with segmental glomerulosclerosis (a portion of the capillary tuft
exhibited marked solidification or matrix expansion out of proportion to the
remainder of the tuft, often accompanied by mesangial widening); or obsolescent
(a globally sclerotic glomerulus with no patent capillary loops). The numerical
fraction of glomeruli in these 4 categories was determined. The tubulointerstitial
pathology score was determined as a sum of the following parameter scores,
each rated on a scale of 0 to 3: tubular atrophy, interstitial inflammation,
interstitial fibrosis, vascular hyalinosis, and vascular medial thickening.
Glycolipid inclusions were assessed by examination of toluidine blue–stained
semi-thin sections and a total score was calculated as a sum of scores for
the following cellular compartments, each rated on a scale of 0 to 3: glomerular
epithelial cells, glomerular endothelial/mesangial cells, proximal tubular
epithelial cells, distal tubular epithelial cells, vascular endothelial cells,
and vascular medial cells.
Gb3 Analysis. Levels of Gb3 were determined in plasma, 24-hour urine sediment,
and in renal biopsy tissue. The analysis was performed essentially as previously
was added as an internal standard to calculate Gb3 recovery.
Antibody Analyses. Serum specimens were collected at baseline and weeks 9, 17, and 24 following
the initial treatment. Anti–α-gal A antibodies were assayed using
a plate enzyme-linked immunosorbent assay technique based on a goat anti–human
IgG secondary antibody. For the immunoprecipitation assays, serum was diluted
1:2 and preincubated with purified α-gal A. Complexes were precipitated
Data were summarized by treatment group with respect to demographics,
baseline characteristics, and safety and efficacy variables. One patient randomized
to the placebo group did not complete the study for personal reasons. All
statistical tests were 2-sided and were performed at a significance level
of <.05. All pain analyses were performed on an intent-to-treat basis.
Missing data (4/104 BPI measurements) were imputed by the method of last observation
carried forward. A second patient (randomized to α-gal A) had protracted
bleeding as the result of the baseline kidney biopsy, requiring 2 vascular
occlusive procedures. Because this complication likely affected renal function,
it was prospectively determined that the patient be excluded from the renal
analyses. A third patient (randomized to placebo) had entered end-stage renal
disease at week 24 and had creatinine clearance measured as 7 mL/min (0.12
mL/s), but due to low urine output did not undergo inulin clearance measurement
or renal biopsy at week 24. Based on the ratio of creatinine clearance to
inulin clearance at baseline, the week 24 inulin clearance was imputed as
4 mL/min for this patient. Renal pathologic analysis was conducted on all
samples for which adequate tissue was available from the baseline and week
For the analysis of efficacy, a 1-way analysis of covariance (ANCOVA)
model was used for the treatment effect of the primary efficacy variable with
the baseline value for the variable of interest as the only covariate. In
addition, a repeated measures analysis on raw data scores was used. Other
continuous variables were analyzed similarly to the primary efficacy variable.
The log-rank test was used in Kaplan-Meier analysis for the assessment of
the time to permanent discontinuation of neuropathic pain medications. The
total number of days with and without pain medications in each treatment group
was compared using the t test. All results are given
as mean (SE).
The age distribution, race, weight, duration and severity of illness,
and residual α-gal A activity were comparable in the 2 groups (Table 1). Mean pain score at baseline was
higher in the placebo group compared with the α-gal A group. Twenty-five
of the patients completed the study and 1 (randomized to placebo) withdrew
for personal reasons at week 22. Random differences between the groups for
the various parameters at baseline were not systematic and were taken into
account by ANCOVA.
Figure 2 presents the mean
BPI short-form results (question 3, "pain at its worst") for the measurements
without pain medication for the 2 treatment groups of the intent-to-treat
population. There was a consistent and progressive decline in the pain scores
in the α-gal A treatment group and essentially no change in the placebo
group. There was a significant difference for the change from baseline in
pain scores between the 2 treatment groups favoring the α-gal A treatment
group (P = .02). A subgroup analysis showed no significant
difference in pain response between patients with and without infusion reactions
(data not shown). There was also a significant decline in overall pain severity
in the α-gal A treatment group (Table
2, P = .02). Treatment with α-gal
A also improved pain-related quality of life (Table 2, P = .05).
In the α-gal A treatment group, 11 of 14 were taking neuropathic
pain medication(s) at the time of the first infusion of study drug, as were
11 of 12 in the placebo group. Four patients in the α-gal A treatment
group of the 11 who were taking neuropathic pain medication(s) at the start
of the study were able to discontinue these pain medications for the duration
of the trial. Discontinuation of pain medication occurred between weeks 1
and 8 of the study with a mean time to discontinuation for these responders
of 30.5 days. In contrast, no patient in the placebo group of 11 taking neuropathic
pain medication(s) was able to discontinue these pain medications (P = .03).
For those patients who were taking neuropathic pain medications, the
mean (SE) number of days that patients in the α-gal A treatment group
were able to remain without pain medications during the study was 74.5 (22.5)
days, compared with 12.9 (6.11) days for the placebo group (P = .02). The days that patients in the placebo group were able to
remain without pain medications were largely accounted for by the 3 periods
of pain medication withdrawal required by the protocol.
Therapy with α-gal A was associated with improvement in glomerular
histology (Table 3). There was
a 21% increase in the fraction of normal glomeruli (glomeruli without mesangial
widening or sclerosis) in patients treated with α-gal A and a 27% decrease
in the fraction of normal glomeruli in patients randomized to placebo (P = .01). Furthermore, in the α-gal A treatment group,
the fraction of glomeruli with mesangial widening exhibited a significant
decrease compared with an increase in the placebo population (P = .01). Although there was a significant increase in the fraction
of glomeruli with segmental sclerosis in the α-gal A treatment group,
the relative increases were small compared with the changes in normal glomeruli
and glomeruli with mesangial widening. There was no significant difference
in the fraction of obsolescent glomeruli between the 2 groups. No significant
change in total score for tubulointerstitial pathology or for the total Fabry
inclusion score was seen in this 6-month trial. When the individual inclusion
scores were examined, there was a decrease in glycolipid inclusions within
the vascular endothelium in the enzyme group and an increase in the placebo
group (P = .002).
Glomerular filtration rate was assessed in 2 ways. First, analysis of
inulin clearance showed a trend in favor of enzyme treatment, with the placebo
group experiencing a 3-fold greater decline than the α-gal A treatment
group (P = .19, Table 4). The range of changes was broader in the placebo group
(−70 to 8 mL/min/1.73 m2) than in the α-gal A treatment
group (range −28 to 15 mL/min/1.73 m2). In general, patients
in the placebo group with a normal inulin clearance at baseline experienced
a greater decrease in renal function than patients with depressed renal function
Second, analysis of creatinine clearance showed an improvement in renal
function with α-gal A therapy compared with a decline with placebo treatment
(P = .02, Table
4). Although there is no standard definition of undercollection
or overcollection of a 24-hour urine sample, to confirm the robustness of
the data we performed a subset analysis in which we prospectively determined
that 24-hour urine collections must have less than 35% deviation from the
mean creatinine appearance for each patient. This resulted in the elimination
of 3 of 97 urine collections. Even with these exclusions, the α-gal
A group gained 1.9 mL/min/1.73m2 and the placebo group lost 10.5
(19.9) mL/min/1.73m2 (P = .06).
Five patients in the enzyme group and 3 receiving placebo had a urinary
protein excretion greater than 1 g/24 h, while the other patients had protein
excretion below that level. The degree of proteinuria was evenly distributed
between the 2 treatment groups. There was no consistent change in proteinuria
seen in either group, but there was a large individual variability in the
amount of protein excreted over 24 hours. One patient in the placebo group
progressed to end-stage renal disease during the course of the study and began
There was a significant decrease in QRS-complex duration as measured
by electrocardiography, with a decrease of 2.4 (3.90) milliseconds (94.1 [4.85]
to 91.7 [2.14] milliseconds) in the treatment group vs an increase of 3.6
(1.17) milliseconds (94.0 [3.39] to 97.6 [3.37] milliseconds) in the placebo
group (P = .047). Furthermore, 1 patient in the α-gal
A treatment group began the study with a right bundle-branch block pattern
that completely resolved during α-gal A therapy.
Patients treated with α-gal A had a greater than 50% decrease
in their plasma Gb3 levels, whereas patients receiving placebo
had a small mean decrease in their plasma Gb3 levels (Table 5, P = .005).
Similarly, treatment with α-gal A resulted in a decrease of renal tubular
glycosphingolipid levels as detected in 24-hour urine sediments (Table 5). α-Gal A recipients showed
a mean decrease in urine sediment Gb3 levels of 30%, while patients
in the placebo group had a mean increase of 15% (P
= .05). The patients treated with α-gal A had a 21% decrease from baseline
in their kidney Gb3 levels, while patients in the placebo group
had a 4% decrease (Table 5, P = .27).
Patients treated with α-gal A gained an average (SD) of 1.5 (0.6)
kg (73.4 [3.3] to 75.0 [3.5] kg), compared with an average loss of 1.4 (1.3)
kg in the placebo group (73.8 [4.8] to 72.4 [0.8 kg]) (P = .02).
α-Gal A was well tolerated. The vast majority of adverse events
(eg, constipation, abdominal pain crisis, and hearing loss) were symptoms
that are typically observed in patients with Fabry disease and were not thought
to be related to the study drug. The 1 patient in the placebo group who developed
renal failure requiring peritoneal dialysis continued in the study and was
receiving peritoneal dialysis at the time of his final visit.
Eight of 14 patients receiving α-gal A experienced mild infusion
reactions, generally consisting of rigors within 45 minutes following the
infusion. These reactions were readily controlled with regimens of antihistamines
and low-dose corticosteroids, which were subsequently tapered. All patients
who experienced these reactions were able to continue with α-gal A infusions
at a reduced infusion rate, and subsequent reactions were generally milder
than the initial reaction.
No patient developed an IgE, IgA, or IgM antibody to α-gal A.
Three of the 14 patients who received α-gal A developed a low-titer
(approximately 1:10) IgG antibody. Nine patients were positive by the immunoprecipitation
assay with titers of approximately 1:2. Patients who developed an immune response
to α-gal A subsequently became desensitized with reductions in antibody
levels over time. Subset analyses demonstrated that the low-titer antibodies
appeared to have no clinically significant effect on the safety or efficacy
of the α-gal A. In addition, the presence of antibodies did not correlate
with the incidence of infusion reactions.
This study has demonstrated widespread effects of α-gal A enzyme
replacement therapy on a number of clinically significant aspects of Fabry
disease. Compared with placebo, α-gal A reduced the level of severe
incapacitating neuropathic pain; improved pain-related quality of life, renal
pathology, and cardiac function; may have improved renal function; and partially
corrected the underlying metabolic defect as reflected by significant Gb3 reductions and weight gain.
The level of neuropathic pain decreased approximately 2 units on the
BPI, where a 1-unit decrease is considered clinically significant (Charles
Cleeland, MD, M. D. Anderson Cancer Center, Houston, Tex, oral communication,
November 1998). In addition, the decrease in pain passed through level 5 on
This level is most clinically sensitive to the effects of changes in patients'
levels of pain.23 Consistent with the marked
decrease in pain, most patients receiving α-gal A were either able to
discontinue their chronic neuropathic pain medication regimens for the duration
of the trial or to markedly decrease their use of pain medications. The placebo
effect may have been mitigated in the placebo group by the exacerbations of
neuropathic pain that they incurred during periodic withdrawals of pain medications.
The lack of a difference between patients with and without infusion reactions
argues against the possibility that study blinding was compromised by adverse
effects from the active drug.
These changes were corroborated by changes in all of the other questions
on the BPI. The severity items revealed a significant decrease in the level
of pain in the α-gal A group and the analysis of the interference items
that measure pain-related quality of life also revealed a significant decrease
in the level of pain in the α-gal A group. Taken together, these data
suggest that there is a time-dependent and sustained effect of α-gal
A therapy on pain in Fabry disease. The improvement in neuropathic pain seen
in this study may reflect the initial mobilization of Gb3 from
damaged dorsal root ganglion cells by α-gal A.26
The measurements of glomerular filtration rate showed differences between
placebo and α-gal A groups that favored the treatment group, although
there was insufficient statistical power to prove a treatment effect in this
relatively short-duration study. All the patients who completed this study
were subsequently enrolled into an open-label maintenance study in which they
received α-gal A for 1 year. We found that the decline in renal function
associated with the placebo group was halted, and at 1 year a statistically
significant improvement in renal function in the placebo patients was observed.
An additional year of therapy in the patients originally treated with α-gal
A demonstrated that renal function remained stable after 18 months of α-gal
A therapy (R. S. et al, unpublished data, 2001). These results strongly suggest
that the findings of the current study are representative of the effect of α-gal
A on renal function.
The pathologic hallmark of Fabry renal disease is accumulation of glycosphingolipid
within the glomerular epithelial, mesangial, distal tubular epithelial, vascular
endothelial, and vascular smooth muscle cells. Progression of disease is associated
with mesangial expansion and ultimately glomerulosclerosis.27-29
Therapy with α-gal A was associated with improved glomerular histology
and with reduced mesangial widening. Lipid deposition in the kidney affects
predominately glomerular epithelial cells but also endothelial, tubular, mesangial,
and interstitial cells. It has been suggested that in Fabry renal disease,
degenerative glomerular changes are not related to glomerular lipid deposition
and instead may be due to ischemic damage.27
Importantly, the overall glomerular architecture was improved by therapy with α-gal
A, and, in addition, treatment with α-gal A also reduced the extent
of glycolipid storage deposits within renal vascular endothelial cells.
Glomerular diseases associated with metabolic disorders have rarely
been found to reverse with therapy. In the case of diabetic nephropathy in
patients who undergo pancreatic transplantation, reversal of basement membrane
thickening and mesangial expansion occurs; this effect is seen only after
5 to 10 years following normalization of blood glucose levels.30
Thus, α-gal A administration in Fabry disease may represent the first
metabolic disease affecting the glomerulus that improves with medical therapy,
even with a relatively short duration of treatment.
The beneficial clinical effects of α-gal A were associated with
a significant reduction in the total glycosphingolipid burden in the treated
patients. The reduction of neuropathic pain and improvement in renal pathology
occurred despite incomplete clearance of accumulated Gb3. It is
possible that with further clearance of stored material there will be further
clinical improvements including pain reduction and further preservation of
renal function. The many organ systems and cell types affected by these improvements
suggest that the enzyme is taken up diffusely throughout the body by mannose-6-phosphate
Repeated administration of this α-gal A preparation was demonstrated
to be safe and well tolerated. Drug reactions were mild, easily treated, and
could be prevented with anti-inflammatory premedication. Lengthening of the
infusion time in subsequent studies from 20 minutes to 40 minutes has markedly
reduced the incidence of these reactions. Currently, with the lengthening
of the infusion time, less than 10% of patients who have received α-gal
A for the first time have experienced infusion reactions. The development
of antibodies is not surprising given the fact that the majority of patients
with Fabry disease do not synthesize a full-length enzyme.26
Even these low-titer antibodies decreased over time, indicating the induction
of tolerance. Patients with and without the low-titer antibodies responded
to α-gal A similarly, and accordingly it appears that the antibodies
were of no clinical significance.
The clinical efficacy data from this study suggest that this fully human α-gal
A preparation is delivered to multiple different tissues throughout the body
including those of nerves, kidneys, heart, blood vessels, and liver. Based
on the improvement of multiple functional, metabolic, and pathologic parameters,
repeated administration of α-gal A is expected to improve the overall
prognosis of patients with Fabry disease.
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