Protocol AGAL-017-01: Multi-centre, Open-Label Study of Low Dose Maintenance Treatment of Fabrazyme^®(Recombinant Human α-Galactosidase A (r-hαGAL)) Replacement Therapy in Patients With Fabry Disease

Fabrazyme^® (agalsidase beta)

Drug Name	Generic Name	Studied Indications or Disease	Approved U.S. Drug Label
Fabrazyme®	agalsidase beta	Fabry disease	Prescribing Info

NAME OF SPONSOR/COMPANY

Genzyme LLC, 500 Kendall Street, Cambridge, Massachusetts, 02142

Investigators and Study Center(s)

Four (4) study centres in Europe participated in this clinical trial.

Publication (Reference)

Publications

Studied Period

29 June 2003 (first patient enrolled) to
20 April 2006 (last patient exited the study)

Phase of Development

Phase 2

Objectives

The primary objective was to evaluate the efficacy of 0.3 mg/kg Fabrazyme every 2 weeks after having received 1mg/kg Fabrazyme every 2 weeks for approximately 6 months to clear and maintain clearance of globotriaosylceramide (GL-3) from the interstitial capillary endothelium of the kidney in patients with Fabry disease. Additional objectives of the study were to evaluate the efficacy of Fabrazyme at the proposed dosing regimen to clear and maintain clearance of GL-3 from the superficial capillary endothelium of the skin and from other cell types in the kidney, to decrease and maintain plasma clearance of GL-3, and to evaluate clinical stabilisation of the disease by means of cardiac, renal and cerebrovascular disease measures, as well as pain.

Methodology

This was a multi-centre, open-label study of patients with Fabry disease who had no prior treatment with Fabrazyme. Following the Baseline assessments, patients who met the selection criteria and gave written informed consent, received 1.0 mg/kg Fabrazyme every two weeks for approximately six months followed by 0.3 mg/kg Fabrazyme every two weeks for approximately 18 months. Following the first infusion, clinical and/or laboratory evaluations were performed at regular intervals with a final safety assessment two weeks after the final follow-up procedures were completed. Kidney biopsies were performed at Baseline, Week 24 (after approximately 6 months of initial treatment) and Week 96 (after 18 months of treatment with 0.3mg/kg of Fabrazyme). Skin biopsies were performed at Baseline and repeated every 24 weeks. During the 1.0 mg/kg Fabrazyme treatment period, blood for pharmacokinetic (PK) measurements was drawn at Infusion 1 (Day 0) and Infusion 12 (Week 22). During the subsequent 18 months (0.3 mg/kg Fabrazyme) blood for PK measurements was drawn at Infusions 13, 25, 37, and 49 (Weeks 24, 48, 72, and 96).

If a patient relapsed while receiving the lower dosing regimen, the patient was to be changed back to the 1.0 mg/kg dose. Relapse was pre-defined as a combination of significant clinical deterioration and evidence of GL-3 re-accumulation in the tissue as evidenced by a significant increase of plasma GL-3 level or skin GL-3 histology score.

Number of Patients (Planned and Analyzed)

PLANNED: Approximately 20 male patients were to be enrolled.

ANALYZED: 21male patients were enrolled and treated with Fabrazyme. No patients discontinued participation in the study.

Diagnosis and Main Criteria for Inclusion

Patients had to meet the following criteria to be enrolled in this study:

The patient or patient’s parent/guardian had to provide written informed consent prior to any study-related procedures being performed. The patient had to be male and ≥ 16 years of age, have clinical presentations consistent with Fabry disease (e.g., angiokeratoma, Fabry pain, decreased sweating, etc.), and have documented plasma α-galactosidase A (αGAL) activity of <1.5 nmol/hr/mL or a documented leukocyte αGAL activity of <4 nmol/hr/mg.

Patients were excluded from this study if they were suffering from renal insufficiency, as defined by serum creatinine ≥2.2 mg/dL (194.7 µmol/L) and/or an estimated glomerular filtration rate (eGFR) of <80 mL/min (using the equation derived from the Modification of Diet in Renal Disease Study (MDRD)¹), had undergone kidney transplantation or were currently on dialysis or in an unstable condition, had a clinically significant organic disease or an unstable condition (with the exception of symptoms relating to Fabry disease) that – in the opinion of the Investigator –precluded participation in this trial, had participated in a study employing an investigational drug within 30 days of the start of their participation in this trial, had received prior treatment with enzyme replacement therapy as therapy for Fabry disease, or were unable to comply with the requirements of the protocol.

Test Product, Dose, and Mode of Administration

Patients received 1.0 mg/kg Fabrazyme intravenously every 2 weeks for approximately 6 months (12 infusions) followed by 0.3 mg/kg of Fabrazyme intravenously every 2 weeks for approximately 18 additional months (37 infusions). The 1.0 mg/kg Fabrazyme infusions were administered at an initial rate of 0.25 mg/min (15 mg/hr). If the treatment was tolerated (i.e., only mild reactions were observed), the infusion rate could have been increased with subsequent infusions but the total infusion time was not to be less than 90 minutes unless authorisation was given by the Genzyme medical monitor. The first 0.3 mg/kg Fabrazyme infusion (Week 24; Infusion 13) was administered at the same protein load (mg/hr) as the last 1.0 mg/kg Fabrazyme dose was administered at Week 22 (Infusion 12). The infusion rate could be increased with subsequent infusions, but the total infusion time was not to be less than 30 minutes for the 0.3mg/kg dose.

Duration of Treatment

After a treatment period of approximately 6 months (12 infusions; until Week 24) with 1.0 mg/kg Fabrazyme, patients were treated for approximately 18 additional months (37 infusions; through Week 96) with 0.3 mg/kg Fabrazyme.

Reference Therapy, Dose and Mode of Administration

Not applicable.

Criteria for Evaluation:
EFFICACY: The primary efficacy response was determined by the proportion of patients who achieved a normal to trace score (0-score) of GL-3 in the interstitial capillary endothelium of the kidney at Week 24, and maintained this score at Week 96 compared to Week 24, as evaluated by a group of independent pathologists using quantitative light microscopy (LM). Kidney biopsies were re-scored using another system (2-step scoring method) to be consistent with the Phase 3 study (AGAL-1-002-98). The primary analysis is based on the quantitative scoring method described in the protocol. This analysis is supported by an analysis of scores derived by the 2-step scoring method.

Additional efficacy response assessments included the change from Baseline in severity of GL-3 inclusions in the capillary endothelium of the skin at Weeks 24, 48, 72, and 96. The kidney biopsies were also evaluated for clearance of GL-3 inclusions in other cell types, including glomerular endothelial cells, mesangial cells, podocytes, interstitial cells, non-capillary endothelial cells, non-capillary smooth muscle cells, distal convoluted tubules and collecting ducts cells. Change in clinical efficacy parameters evaluated over time included: cardiac status, cerebrovascular status, pain, renal function measured by GFR (inulin clearance), serum creatinine, urinary protein excretion, creatinine clearance, and estimated GFR. In addition, change in urine GL-3 and plasma GL-3 compared to Baseline was assessed.

SAFETY: Safety was assessed in terms of adverse events (AEs) and regular physical exams, serial measurements of vital signs, laboratory parameters, electrocardiograms (ECGs) and review of concomitant medications. Serum was collected throughout the study to determine the development of IgG antibodies against recombinant human α-galactosidase A (r-haGAL; agalsidase beta). In case of IgG antibody development the serum was also tested for circulating immune complexes. An independent Data and Safety Monitoring Board (DSMB) continuously monitored the trial and could potentially recommend to stop the trial if deemed necessary.

Pharmacokinetic: PK profiles were carried out at Weeks 0, 22, 24, 48, 72, and 96.

Statistical Methods

EFFICACY: Summary tables show the n, mean, standard deviation, median, and range for each continuous variable and its change score. Graphs show how each of these endpoints change over time. An Exact Binomial Matched Pairs Procedure was used to compare the proportion of patients with a LM majority score of zero at Baseline to the proportion of patients with a score of zero at Week 24. This test also compared Week 24 to Week 96 for kidney, and Baseline to Week 24 and Week 24 to Weeks 48, 72, and 96 for skin..

SAFETY: AEs were coded using the Medical Dictionary of Regulatory Activities (MedDRA; Version 8.1). All AEs were summarised by System Organ Class and Preferred Term. A detailed listing of patients who experienced AEs and serious adverse events (SAEs) is presented. Vital signs and laboratory evaluations were summarised at each time point. Additionally, the change from Baseline was summarised.

Summary – Conclusions

Efficacy

The objective of the study was to evaluate the efficacy of 0.3 mg/kg Fabrazyme every 2 weeks after having received 1mg/kg Fabrazyme every 2 weeks for approximately 6 months to clear and maintain clearance of globotriaosylceramide (GL-3) in the various physiological compartments (kidney and skin tissue, plasma) of patients with Fabry disease, and to evaluate clinical stabilisation of the disease by means of cardiac, renal and cerebrovascular disease measures, as well as pain.

The 21 patients who were treated had a mean age of 34.0 ± 10.0 years. The age of onset of Fabry symptoms ranged from 6 to 14 years and the age of diagnosis with Fabry disease from 7 to 49 years. At Baseline, a majority of the patients presented with typical symptomatology of Fabry disease such as angiokeratoma, acroparaesthesia, left ventricular hypertrophy, proteinuria, and pain. Nine patients had eGFR < 90 mL/min, and 6 patients had a urinary protein/creatinine ratio > 1. All patients completed the 12 infusions of 1.0 mg/kg and 20 patients completed at least 80% of the infusions with 0.3mg/kg.

In the interstitial capillary endothelium of the kidney, a majority of the patients (18/21; 86%) had accumulation of GL-3 at Baseline (using the quantitative light microscopy scoring method). After 24 weeks of 1.0 mg/kg Fabrazyme treatment, GL-3 was cleared in all patients (p< 0.001). At Week 96, after 72 weeks of treatment with 0.3 mg/kg, 18 of the 20 patients (90%) with available data had maintained clearance, while the 2 remaining patients showed a non-zero score (mild GL-3 accumulation) and 1 patient had no assessment. There was no statistically significant difference in terms of GL-3 clearance in this cell type between Week 24 and Week 96. However, this does not prove that the two treatment regimens were equivalent, as the design of this small study did not allow for testing this hypothesis.

In 5 of the 7 other kidney cell types, a statistically significant decrease from Baseline to Week 24 in GL-3 scores was seen, but not for podocytes and non-capillary smooth muscle cells. Complete clearance was achieved at Week 24 in glomerular endothelial, mesangial, non-capillary endothelial cells and was maintained at Week 96. In interstitial, non capillary smooth muscle, and distal convoluted tubules and collecting duct cells, a reduction was observed from Baseline to Week 24, but a secondary accumulation in some of these cell types occurred in 5 of the 20 patients at Week 96. The accumulation in podocytes was reduced in 3 of the 19 patients (16%) at Week 24 and continued at Week 96 with 9 of the 17 patients (53%) having lower scores compared to Baseline. To assess more globally the kidney GL-3 burden, a composite endpoint that takes into consideration quantitative variations of GL-3 scores of each individual kidney cell type was calculated by adding the scores of all cell types. After 24 weeks of treatment with 1.0 mg/kg Fabrazyme every 2 weeks, a reduction of the mean composite score from 13.7 (range 3 to 20) at Baseline to 4.5 (range 2 to 8) was observed, and a slight further reduction from 4.5 to 3.4 (range 2 to 7) was observed during the lower dose period with 0.3 mg/kg Fabrazyme every 2 weeks. However, 3 of the 17 patients (18%) showed a slight increase in composite kidney score at Week 96 compared to Week 24. Of note, for one patient no composite kidney score could be calculated, but increases in GL-3 in some cell types were observed.

In skin capillary endothelium, mild to severe GL-3 accumulation was observed at Baseline in 16 of the 21 patients (76%). All patients showed clearance at Week 24, except one patient who had mild accumulation after having moderate accumulation at Baseline. During the lower dose period with 0.3mg/kg, 7 patients presented with a skin capillary endothelium GL-3 score higher (for at least one time point) than the score at Week 24.

At Baseline, 19 of the 21 patients (90%) had abnormal plasma GL-3 levels (i.e., > 7.03 µg/mL), while at Week 24 all patients, except one, had normalised. During the 72-weeks at 0.3mg/kg, 10 patients had abnormal GL-3 levels at at least one time point and 5 of these patients had abnormal GL-3 levels at Week 96, however, the mean remained within normal range.

Urinary GL-3 data for each patient were very variable from one time point to the other. Mean GL-3 concentrations in first morning void urine and 24-hour urine were above normal in almost all patients at Baseline, and showed a decrease at Week 12; a mean secondary increase was observed at the end of the 1.0 mg/kg dosing regimen (Week 24), but there was still a statistically significant decrease compared to Baseline; mean urinary GL-3 levels remained above normal in most patients during the lower dose period with 0.3mg/kg.

Renal function was monitored by measuring serum creatinine, creatinine clearance, eGFR, GFR_inulin, 24-hour urinary protein, and microalbuminuria. Urinary protein/creatinine ratio was also calculated. There was no clinically relevant change in median serum creatinine during the study. However, two patients had renal disease progression as they showed a >50% increase in serum creatinine from Baseline and a serum creatinine value >1.4 mg/dL together with significantly decreased eGFR values. They also presented with clinically significant proteinuria (protein/creatinine 3.4 and 5.0 g/g) at Baseline which remained high during the study. One patient had 43% sclerotic glomeruli at Baseline (no data was available for the other patient), and also had a low eGFR value at Baseline (75 mL/min/1.73 m²). These two patients were, therefore, at high risk of kidney deterioration, since elevated proteinuria and extensive glomerulosclerosis have already been identified as risk factors for Fabry kidney disease progression despite ERT treatment (Banikazemi, 2007; Germain, 2007). No statistically significant changes in mean eGFR were observed from Baseline to Week 24 or from Week 24 to Week 96.

Median urinary protein values remained stable throughout the trial. A majority (70 %) of the patients had urinary albumin ≥ 30 mg/24hr at Baseline, and no significant change was observed during the trial.

A treatment relapse algorithm was defined for the purpose of the protocol, so that in case a patient was deteriorating clinically, and had an obvious concomitant re-accumulation of GL-3 during the lower dose period with 0.3mg/kg, the patient would be switched back to 1.0 mg/kg. Per the protocol definition, no patient relapsed. However, upon request of an investigator, the treatment of one patient who showed progression of renal disease was switched back to 1.0 mg/kg Fabrazyme at Week 76, despite the fact that no concomitant re-accumulation of GL-3 had been documented.

Altogether, during the 1.0 mg/kg dose regimen from Baseline to Week 24, GL-3 clearance in kidney and skin tissues, as well as in plasma, was very effective and consistent with what was observed in previous studies. During the lower dose period from Week 24 to Week 96, tissue clearance was maintained in many patients, but GL-3 re-accumulation was observed in some patients. Urine GL-3 reduction was very variable between patients ranging from transient in some patients to a sustained reduction in others. Overall these results may indicate a lower efficacy of the 0.3 mg/kg every 2 weeks Fabrazyme regimen to maintain GL-3 clearance in some patients, as compared to 1.0 mg/kg every 2 weeks.

Because secondary accumulation occurred in some but not all patients while receiving the lower dose, a post hoc analysis explored the possibility that the presence of anti-r-hαGAL IgG antibodies could have impacted the efficacy of the 0.3 mg/kg every 2 weeks dose maintenance regimen. The IgG peak titre and trend over time were assessed for each patient. As an approximation of the average titre of anti-r-hαGAL IgG antibodies during the lower dose period only (Week 24 to Week 96), the time-weighted AUC of IgG antibody titre (AUC/time) could be calculated for all except one patient. When receiving the lower dose regimen, patients with high antibody titres appeared to be at greater risk of cellular GL-3 re-accumulation. Urinary GL-3 values were generally decreased and stabilised in patients with low IgG antibody titres. Urinary GL-3 showed a secondary increase by Week 24 in several patients, who tended to have higher IgG antibody titres.

Pharmacokinetic Results:

The PK analysis revealed that r-hαGAL clearance varied over time as a result of changes in IgG antibody titres, but Vss, V1, V2, α-half-life, and β-half-life did not. As a result of the change in clearance, exposure varied over the course of therapy, but with the concurrent change in dose at Week 24, the resulting pharmacokinetic profiles were relatively stable over time with a slightly higher exposure at Week 22. AUC(0-∞) and Cmax both increased from Week 0 to Week 22, decreased at Week 24 when the administered dose was changed from 1.0 to 0.3 mg/kg. By Week 96, Cmax values were similar to Baseline despite the lower dosing regimen.

Safety Results

Overall, the safety profile of Fabrazyme remains favourable. Twenty patients received at least 80% of their infusions. The mean infusion time of 1.0 mg/kg decreased gradually over time from 271.3 min (range 23-342 min) for the first infusion at Week 0 to 238.8 min (range 117-350 min) at Week 22. The mean infusion time of 0.3 mg/kg decreased from 115.3 min (range 58-245 min) at Week 24 to 81.1 min (range 60-118 min) at Week 96.

Fifteen of the 21 patients who participated in the trial experienced a total of 123 treatment-emergent AEs. The most frequently involved System Organ Classes were General Disorders and Administration Site Conditions, Nervous System Disorders, Gastrointestinal Disorders, Skin and Subcutaneous Tissue Disorders, and Cardiac Disorders. The most frequently occurring AEs in >10% of patients without regard to causality included diarrhoea (19%), chills (14%), pyrexia (14%), dizziness (14%), paraesthesia (14%), cough (14%), and angiokeratoma (14%). One patient, who had a history of syncope prior to the start of Fabrazyme therapy, experienced 27 events of syncope. No differences were observed with regard to the types of AEs (i.e., reported Preferred Terms) that were experienced during either the 1.0 mg/kg or the 0.3 mg/kg treatment period except that diarrhoea, paraesthesia, cough, and angiokeratoma.were reported during the lower dose period at 0.3mg/kg and not during the 1.0 mg/kg treatment period. The majority of AEs were mild or moderate in intensity. A total of 19 AEs in 6 patients were considered by the Investigators to be related to Fabrazyme treatment.

There were no patient deaths during the study. Five patients experienced a total of 9 SAEs which were not related to Fabrazyme treatment. Eight of these 9 SAEs occurred during the 0.3 mg/kg treatment period, and one SAE occurred after the patient’s dose was switched from 0.3 mg/kg to 1.0 mg/kg. Four of 8 SAEs (atrioventricular block complete, dehydration, cerebral ischaemia, and syncope), which occurred during the 0.3 mg/kg treatment period, were assessed as severe in intensity.

Eighteen (18) of the 19 related treatment-emergent AEs experienced by 6 patients were assessed as IARs. The most commonly occurring IARs were chills (14%) and pyrexia (14%). All IARs were mild or moderate in intensity. The IARs were managed by infusion rate adjustments and/or medications (e.g., anti-pyretics, antihistamines and/or steroids). All patients recovered from the IARs with the exception of one patient who had not yet recovered from paraesthesias at the time of completion of the study.

Eighteen (86%) patients IgG seroconverted in a mean time of 60.0 days since first infusion. Three patients tolerised, 2 patients had a low response, 8 patients had a downward trend, and 5 patients plateaued.

Mean values for all laboratory and vital signs parameters were within normal ranges and there were no clinically meaningful changes overall or trends in changes over time.

No new safety concerns were identified based upon evaluation of AEs, vital signs, physical examination findings, laboratory values, ECGs, and concomitant medication use.

Conclusion:

The results of this study show that transfer to a lower dose of 0.3 mg/kg Fabrazyme every 2 weeks after an initial debulking dose of 1.0 mg/kg Fabrazyme every 2 weeks for 24 weeks (approximately 6 months) was well tolerated.

With regards to efficacy:

- The dose of 1.0 mg/kg Fabrazyme every 2 weeks cleared GL-3 from the capillary endothelium of the kidney (primary endpoint) and multiple other cell types in kidney and skin at Week 24, which is consistent with the data from the Fabrazyme Phase 3 study (AGAL-1-002-98). Plasma GL-3 levels normalised rapidly, but the initial decrease in the abnormally high urinary GL-3 levels was only transiently maintained in some patients.

- After 6 months of treatment with 1.0 mg/kg every 2 weeks, treatment with 0.3 mg/kg Fabrazyme every 2 weeks maintained the clearance of GL-3 from the capillary endothelium of the kidney and skin and several other cell types of the kidney, as well as the normalisation of plasma GL-3 levels in some, but not all, of the patients. This indicates that 0.3 mg/kg every 2 weeks is overall less efficacious in terms of maintaining cellular GL-3 clearance than 1 mg/kg every 2 weeks.

- A post hoc analysis revealed that cellular re-accumulation of GL-3 in several kidney cell types and skin during the lower dose period at 0.3mg/kg occurred in some of the patients with relatively high IgG antibody response to r-hαGAL. Importantly, cellular clearance was seen at the 1.0 mg/kg dose in these same patients, indicating that even in the presence of IgG antibodies to r-hαGAL, the 1.0 mg/kg dose of Fabrazyme was able to achieve cellular clearance.

- No statistically significant difference in renal function outcomes was demonstrated between the two dosing periods, but the trial was relatively small and rather short in duration to be conclusive. Furthermore, other key clinical organ systems, such as cardiac and cerebrovascular, were not studied extensively, therefore, no conclusion can be drawn with regard to clinical efficacy of the lower dose regimen for these organs.

In summary, following treatment with the approved dose of 1.0 mg/kg of Fabrazyme for 24 weeks, a dose of 0.3 mg/kg Fabrazyme every 2 weeks maintained cellular GL-3 clearance in the capillary endothelium of the kidney and skin and other kidney cell types in some but not all patients, indicating a dose-dependent maintenance effect. Due to the limitations of the study design, no definitive conclusion regarding the lower dose regimen can be drawn, but these findings suggest that, after an initial debulking dose of 1.0 mg/kg every 2 weeks for 24 weeks (approximately 6 months), 0.3 mg/kg every 2 weeks may be sufficient in some patients to maintain clearance of GL-3 in some cell types. However, at the lower dose, IgG antibodies to r-hαGAL may play a role with respect to efficacy (GL-3 clearance) in some patients, which would warrant reversion to the higher dose to maintain adequate cellular clearance.