A chaperone enhances blood α-glucosidase activity in Pompe disease patients treated with enzyme replacement therapy

Abstract

Enzyme replacement therapy is currently the only approved treatment for Pompe disease, due to acid α-glucosidase deficiency. Clinical efficacy of this approach is variable, and more effective therapies are needed. We showed in preclinical studies that chaperones stabilize the recombinant enzyme used for enzyme replacement therapy. Here, we evaluated the effects of a combination of enzyme therapy and a chaperone on α-glucosidase activity in Pompe disease patients. α-Glucosidase activity was analyzed by tandem-mass spectrometry in dried blood spots from patients treated with enzyme replacement therapy, either alone or in combination with the chaperone N-butyldeoxynojirimycin given at the time of the enzyme infusion. Thirteen patients with different presentations (3 infantile-onset, 10 late-onset) were enrolled. In 11 patients, the combination treatment resulted in α-glucosidase activities greater than 1.85-fold the activities with enzyme replacement therapy alone. In the whole patient population, α-glucosidase activity was significantly increased at 12 hours (2.19-fold, P = 0.002), 24 hours (6.07-fold, P = 0.001), and 36 hours (3.95-fold, P = 0.003). The areas under the curve were also significantly increased (6.78-fold, P = 0.002). These results suggest improved stability of recombinant α-glucosidase in blood in the presence of the chaperone.

Figure 1

Protocol of ERT and NB-DNJ administration and DBS sampling. (a) The overall duration of the study was 16 months. The patients were subjected to a baseline assessment for two months with rhGAA alone (ERT1), then were treated for 12 months with the combination of rhGAA and NB-DNJ (ERT-CHAP), and subsequently were re-evaluated for two months with rhGAA alone (ERT2). GAA profiling in DBS was performed three times at baseline (ERT1) and three times in the first ERT cycles of ERT+CHAP, and again three times at the end of ERT+CHAP, and three times in ERT2. (b) Patients were treated with rhGAA at standard doses of 20 or 40 mg/kg/infusion (day 0). rhGAA was reconstituted according to the manufacturer's instructions and given intravenously, in 5–7 hours. NB-DNJ was given in four doses of 80 mg/m² each, one on the evening before ERT (day -1), and three on the day of the infusion (day 0). The sampling for GAA activity in DBS was performed before each ERT infusion (day −1), and on days 1, 3, 5, 7, 9, and 11, (DBS sampling 1) at the beginning of the study (protocol ERT1, months 1–2, and first round of sampling in ERT-CHAP, months 3–4). To better evaluate the GAA profile in the first 72 hours following ERT, at the end of the ERT+CHAP period (months 13–14) and during ERT2 (months 15–16), GAA activities were assayed in DBS every 12 hours for three days (DBS sampling 2).

Figure 2

GAA activity profiles in DBS. (a) The combination of ERT and NB-DNJ (protocol ERT+CHAP) resulted in increases of GAA activity peak areas greater than 1.85-fold, compared to ERT alone in patients 0101, 0103, 0201,0202, 0203, 0204, 0301, 0302, 0303, 0401, 0402). (b) In the whole population, the average GAA activities were significantly increased compared to ERT alone at 12 hours (P = 0.002), 24 hours (P = 0.001), 36 hours (P = 0.003), and remained significantly higher up to 72 hours (inset). The increase in the areas under the curve ranged between 1.90 and 3.42-fold, with an average increase of 6.78, and was also highly statistically significant (P = 0.002).

Figure 3

GAA activities in the Pompe diseasemouse. Pompe disease mice received a single retro-orbital injection of rhGAA with or without an oral administration of NB-DNJ by gavage, and GAA activity was measured in DBS and tissues (liver, quadriceps and gastrocnemius) at 24, 48, and 72 hours. For each time point the average and SD of the activities in three to five animals is shown. The DBS GAA profile in mice showed a maximum peak at 24 hours after the injection and a rapid decrease of activity over the following days (dotted line). A parallel increase in GAA activity was detectable in liver, gastrocnemius and quadriceps, where the GAA activity persisted up to 72 hours (dotted lines). In the animals treated with the combination of ERT and NB-DNJ a significantly higher peak (approximately fivefold compared to ERT alone; P = 0.01 at 24 and 48 hours) was observed in DBS (continuous line). At 48 hours, a statistically significant increase in GAA activity with the combination protocol was observed in liver (P = 0.02), and in quadriceps (P = 0.04). The activities obtained in tissues from the Pompe disease mice treated with ERT alone or with the combination protocol were compared using the Student's t-test.