LB.P.3 First-in-Human Study of ATB200/AT2221 in Patients With Pompe Disease: Interim Results From the ATB200-02 Trial Roberts M1, Sitaraman S2, Barth JA2, Sathe S2, on behalf of the ATB200-02 Clinical Trial Investigators (Drago Bratkovic, Barry J. Byrne, Paula Clemens, Tarekegn Geberhiwot, Ozlem Goker-Alpan, Priya Kishnani, Xue Ming, Tahseen Mozaffar, Peter Schwenkreis, Kumaraswamy Sivakumar, Ans T. van der Ploeg, Benedikt Schoser) 1Salford Royal NHS Foundation Trust, Salford, UK; 2Amicus Therapeutics, Inc., Cranbury, NJ, USA • Improvement in motor function tests, along with 6MWT, were consistent with an overall improvement in muscle function for both ambulatory ERT-switch and ERT-naive patients (Table 3) INTRODUCTION Pompe disease is an inherited metabolic disease of impaired lysosomal glycogen clearance due to acid -glucosidase (GAA) deficiency, which leads to accumulation of the substrate most prominently in the heart, skeletal muscle, and smooth muscle1,2 Progressive accumulation of glycogen results in a spectrum of disease severity, often leading to organ failure and/or death. Skeletal muscle weakness and progressive respiratory involvement are predominant manifestations of late-onset Pompe disease (LOPD)1,2 Enzyme replacement therapy (ERT) with recombinant human GAA (rhGAA) is the definitive therapy for LOPD1 ATB200 is a next-generation rhGAA ERT designed with optimized glycosylation and high levels of mannose 6-phosphate residues for better uptake in target muscle tissues (Figure 1). The pharmacological chaperone AT2221 is co-administered with ATB200 to minimize denaturation of the enzyme in blood and maintain catalytic activity to deliver active ERT to lysosomes3,4 Preclinical studies were conducted in Gaa knockout mice to evaluate the pharmacokinetics (PK) and efficiency of glycogen reduction at varying ATB200 ERT and AT2221 chaperone doses. These data were used to estimate the comparable AT2221 chaperone doses in humans5 Study ATB200-02 (NCT02675465) was designed to evaluate the safety, tolerability, PK, pharmacodynamics (PD), and efficacy of ATB200 co-administered with AT2221 RESULTS Sixteen clinical sites in 5 countries participated in the ATB200-02 clinical study Patients were representative of the overall LOPD population (Table 1) Table 3. Other Motor Function Tests • • • Table 1. Baseline Characteristics (N=20) • • • 4 Stair Climb 4.1 (2.7) -1.0 (1.2) -0.9 (1.3) Sex, M:F 9:2 3:1 1:4 Gowers a 7.9 (2.8) -2.2 (2.0) -2.1 (1.3) • 6MWT, meters, mean (SD) 392.0 (93.4) NA 399.5 (83.5) • NA=not applicable; SD=standard deviation. aCohort 1 patients were required to have been on alglucosidase alfa for 2-6 years at baseline. Figure 1. Representative Schematic of ATB200/AT2221 and Go 4 Stair Climb 4.2 (1.5) -0.6 (0.3) -0.8 (0.3) Safety • AEs were generally mild and transient (Chaperone) Activity/Stability  Most common AEs reported as treatment related were nausea (3/20), tremor (3/20), headache (3/20), fatigue (3/20), diarrhea (2/20), muscle spasm (2/20), and joint swelling (2/20) Gowers 13.9 (11.0) 7.9b (21) -1.3 (0.0) • One serious AE was reported, which was unrelated to the study drug (hospitalization for lower respiratory tract infection) No patients discontinued the study due to an AE There were 3 incidents of infusion-associated reactions (IARs) in 400+ infusions, which were controlled by standard premedication aN=9; one patient refused to perform test. bMedian change from baseline was -0.8, and 4/5 patients had a decrease. • • • Consistent and substantial increases were observed in upper extremity strength in all nonambulatory ERT-switch patients at month 6 (Table 4)   One IAR event in a nonambulatory ERT-switch patient (skin discoloration) Two IAR events in an ERT-naive patient (localized pruritus, erythema and burning sensation) Table 4. Muscle Strength Testing in Nonambulatory ERT-Switch Patients (cohort 2) • Longest duration of treatment was 72 weeks Markers of Muscle Injury • Muscle damage markers (creatine kinase enzyme, alanine aminotransferase, and aspartate aminotransferase): Mean reductions from baseline were approximately 30-35%, 5-20%, and 40-55% for ambulatory ERT-switch (n=9), nonambulatory ERT-switch (n=4), and ERT-naive (n=5) patients, respectively (Figure 4) Glycogen accumulation marker (urine hexose tetrasaccharide [Hex4]): Mean reductions from baseline were approximately 39%, 32%, and 55% for ambulatory ERT-switch (n=9), nonambulatory ERT-switch (n=4), and ERT-naive (n=5) patients, respectively (Figure 4) ERT=enzyme replacement therapy; M6P=mannose 6-phosphate. • OBJECTIVE To evaluate the preliminary safety, PK, PD, and efficacy of ATB200/AT2221 in patients with Pompe disease enrolled in the phase 1/2 ATB200-02 study Shoulder Adductiona Shoulder Abductionc Elbow Flex Elbow Extension 1.0 (1.0) 1.3 (1.2) 2.0 (2.0) 2.0 (2.0) 1.3 (1.2) 1.3 (1.2) 2.3 (2.5) 2.0 (2.0) +0.7 (1.2) 0.0 (0.0) +1.0 (1.0) +1.0 (1.0) +0.7 (1.2) +0.5 (0.7) +0.7 (0.6) +0.7 (0.6) • Figure 4. Mean Percentage Change From Baseline in Markers of Muscle Injury and Disease Substrate in (A) Ambulatory ERT-Switch Patients; (B) Nonambulatory ERT-Switch Patients; and (C) ERT-Naive Patients Manual Muscle Testing, manual scoreb METHODS Study Design an=3 due to assessment not being performed at some visits for some patients. bScoring: (1) Visible muscle movement, but no movement at the joint; (2) Movement at the joint, but not against gravity; (3) Movement against gravity, but not against added resistance; (4) Movement against resistance, but less than normal; (5) Normal strength. cn=2 due to assessment not being performed at some visits for some patients. • ATB200-02 is an open-label, fixed-sequence, ascending-dose, first-in-human, phase 1/2 study to assess the safety, tolerability, PK, PD, and efficacy of intravenous infusions of ATB200 co-administered with oral AT2221 in adults with LOPD (Figure 2) • FVC was generally stable in ambulatory ERT-switch patients and increased in ERT-naive patients (Table 5)   Figure 2. ATB200-02 Study Design FVC was stable or increased in 5/8 and 5/7 ERT-switch patients at months 6 and 9, respectively FVC increased in 4/5 and 2/2 ERT-naive patients at months 6 and 9, respectively • Maximal inspiratory pressure (MIP) was stable and maximal expiratory pressure (MEP) increased in ambulatory ERT-switch patients; MIP increased and MEP was stable in ERT-naive patients (Table 5) Table 5. Forced Vital Capacity and Other Pulmonary Function Tests Baseline to Month 9, ERT-Switch MIP 35.7 (11.0) +0.9 (4.5) -1.4 (2.7) ATB200 20 mg/kg Fixed-Dose ATB200 + AT2221 QOW + high-dose AT2221 1 dose: 20 mg/kg + high-dose AT2221 MIP 32.6 (18.5) +11.0 (5.0) +1.5 (0.7) aFVC not available for 1 patient. QOW=every other week. aSafety data from 2 sentinel patients from Cohort 1 were reviewed at each dose level before dosing in Cohorts 2 and 3. bDuring stages 2 and 3, AT2221 was orally administered prior to the start of ATB200 intravenous infusion. For all doses, ATB200 was intravenously infused for a 4-hour duration. cThe first 2 patients in Cohorts 2 and 3 served as sentinel patients for their respective cohorts. SUMMARY AND CONCLUSIONS Key Inclusion Criteria • Males and females aged 18–65 years who were diagnosed with Pompe disease based on documented deficiency of GAA enzyme activity or by GAA genotyping Received ERT with alglucosidase alfa for 2-6 years (or >2 years for Cohort 2) prior to trial initiation (Cohort 1) Currently receiving alglucosidase alfa at a frequency of every other week and having completed the last 2 infusions without a drug-related adverse event (AE) resulting in dose interruption (Cohorts 1 and 2) Must be able to walk between 200 and 500 meters on the 6-Minute Walk Test (6MWT) (Cohorts 1 and 3) Upright forced vital capacity (FVC) must be 30-80% of predicted normal value (Cohorts 1 and 3) Must be wheelchair-bound and unable to walk unassisted (Cohort 2) • • • • • Analyses • Data are from interim analysis 4 (Figure 3) REFERENCES Kishnani PS et al. Genet Med. 2006;8(5):267-288. Bijvoet AGA et al. Hum Mol Gen. 1998;7(1):53-62. Gotschall R et al. Mol Genet Metab. 2015;114(2):S49. Khanna R et al. Presented at the 12th Annual WORLDSymposium™; February 29-March 4, 2016; San Diego, CA, USA. Data on file. Amicus Therapeutics, Inc. Figure 3. Summary of Analyses and Available Data 1. 2. 3. 4. 5. Cohort 1 (ERT-Switch Ambulatory, N=11) Cohort 2 (ERT-Switch Nonambulatory, N=4) Cohort 3 (ERT-Naive, N=5) Data are reported through an interim data analysis (maximum 58 weeks, 24 weeks, and 36 weeks for cohorts 1, 2, and 3, respectively). Missing values were either unable to be analyzed or not yet analyzed. BL=baseline; SE=standard error; WK=week. ACKNOWLEDGEMENTS The authors acknowledge the patients, their families, and Pompe disease patient organizations, as well as the study investigators. The authors would also like to thank Jacquelyn Wright and Franklin K Johnson (employees of Amicus Therapeutics, Inc.) for their contributions to this work. Third-party medical editing assistance was provided by ApotheCom and was supported by Amicus Therapeutics, Inc. • Safety and tolerability (n=11) • Biomarkers (n=11) • Functional assessments at • Safety and tolerability (n=4) • Biomarkers (n=4) • Functional assessments at Month 6 (n=4) • Functional assessments: – Muscle Strength Tests • Safety and tolerability (n=5) • Biomarkers (n=5) • Functional assessments at – Month 6 (n=5) – Month 9 (n=2) • Functional assessments: – 6MWT – Other motor function tests (time tests and GSGC) – Pulmonary function (FVC, MIP/MEP) Efficacy • 6MWT improved for both ambulatory ERT-switch and ERT-naive patients at month 6, with continued benefit to month 9 (Table 2) – Month 6 (n=9) – Month 9 (n=8) a  6MWT distance increased in 7/9 and 8/8 ERT-switch patients at months 6 and 9, respectively – Two patients were stable at month 6; 1 of them reached month 9 and had increased 6MWT • Functional assessments: – 6MWT – Other motor function tests (time tests and GSGC) – Pulmonary function (FVC, MIP/MEP) DISCLOSURES  6MWT distance increased in 5/5 and 2/2 ERT-naive patients at months 6 and 9, respectively Table 2. 6-Minute Walk Test Conflicts of Interest M. Roberts has no conflicts of interest to disclose. S. Sitaraman, J.A. Barth, and S. Sathe are employees of and own stock in Amicus Therapeutics. Baseline, Mean (SD) Change From Baseline to Month 6, Mean (SD) Change From Baseline to Month 9, Mean (SD) Cohort 1 ERT-Switch n=10 n=9 n=8 For questions, please contact Mark Roberts at markrob@doctors.org.uk. 397.2 (96.8) +35.3 (40.1) +37.2 (33.8) Cohort 3 ERT-Naive n=5 n=5 n=2 6MWT=6-minute walk test; FVC=forced vital capacity; GSGC=Gait, Stair, Gower, Chair; MEP=maximal expiratory pressure; MIP=maximal inspiratory pressure. aOne patient discontinued after completing stage 1 (week 18) due to travel burden and family considerations, and 1 patient’s month 6 data are pending. 399.5 (83.5) +41.8 (29.4) +74.9 (4.0) Results are given in meters. Supported by Amicus Therapeutics, Inc. Presented at the 22nd International Congress of the World Muscle Society; October 3-7, 2017; St. Malo, France Percent Change From Baseline (Mean ± SE) Percent Change From Baseline (Mean ± SE) Percent Change From Baseline (Mean ± SE) Percent Change From Baseline (Mean ± SE) Percent Change From Baseline (Mean ± SE) Percent Change From Baseline (Mean ± SE) •There is concordance in the data showing a parallel improvement in markers of muscle injury and substrate accumulation, motor function (endurance, timed tests, and muscle strength), and stabilization and/or improvement in respiratory function tests across the different cohorts •Muscle function improved in 16/18 and 10/10 patients at months 6 and 9, respectively •Increases in 6MWT distance were consistent and durable out to month 9 as were the improvements in other motor function tests in ambulatory ERT-switch and ERT-naive patients •Qualitative and quantitative measures showed increases in upper extremity strength in nonambulatory ERT-switch patients at month 6 •FVC was generally stable in ambulatory ERT-switch patients and increased in ERT-naive patients •The multi-dimensional impact of the therapy is suggestive that the combination regimen of ATB200/AT2221 has the potential to be an important treatment option for patients with Pompe disease. Further study of this regimen is ongoing MEP60.6 (8.3)-0.4 (12.4)-1.0 (19.8) MEP72.6 (32.6)+20.3 (42.4)+31.1 (39.3) Cohort 3 ERT-naiven=5n=5 n=2 FVC, % predicted53.4 (20.3)+4.2 (5.6)+5.0 (1.4) AssessmentBaseline,Change From Mean (SD)Baseline to Month 6, Mean (SD) Change From Mean (SD) Cohort 1n=10n=9 n=8 FVC, % predicteda 52.6 (14.7)-1.0 (4.2)-2.0 (3.6) Cohort 1Cohort 1 ERT-switch ambulatory patients (n=11)ERT-switch ambulatory patients (n=11) Stage 1Stage 2a,b Cohort 2 ERT-switch nonambulatory Fixed-SequenceFixed-Sequencepatients (n=4) Single Ascending DoseMultiple Ascending DosesCohort 3 ATB200 QOWATB200 + AT2221 QOWERT-naive ambulatory patients (n=5) 1 dose: 5 mg/kg3 doses:Stage 3b,c + low-dose AT2221 1 dose: 10 mg/kg 3 doses: Multiple doses: ATB200 20 mg/kgATB200 20 mg/kg A ATB200 doseATB200 dose escalation ATB200 20 mg/kgATB200 20 mg/kg +escalation ATB200 20 mg/kgATB200 20 mg/kg + (5>10>20) + low dose AT2221high dose AT2221(5>10>20) + low dose AT2221high dose AT2221 2525 1515 55 00 -5-5 -15-15 -25-25 -35-35 -45-45 -55-55 -65-65 B ATB200 20 mg/kg + high dose AT2221ATB200 20 mg/kg + high dose AT2221 2525 1515 55 00 -5-5 -15-15 -25-25 -35-35 -45-45 -55-55 -65-65 C ATB200 20 mg/kg + high dose AT2221ATB200 20 mg/kg + high dose AT2221 2525 1515 55 00 -5-5 -15-15 -25-25 -35-35 -45-45 -55-55 -65-65 VisitBLWK 2WK 4WK 12WK 24WK 36 N554-5552 VisitBLWK 2WK 4WK 12WK 24WK 36 N554-5552 Urine Hexose Tetrasaccharide (mmol/mol/creatinine) Alanine Aminotransferase (U/L) Aspartate Aminotransferase (U/L) Creatine Kinase (IU/L) VisitBLWK 2WK 4WK 12WK 24 N44434 VisitBLWK 2WK 4WK 12WK 24 N44434 Urine Hexose Tetrasaccharide (mmol/mol/creatinine) Alanine Aminotransferase (U/L) Aspartate Aminotransferase (U/L) Creatine Kinase (IU/L) Visit BL WK 2 WK 4 WK 6 WK 8 WK 10 WK 12 WK 14 WK 16 WK 18 WK 34 WK 46 WK 58 N 11 11 10 9-10 11 11 8-11 11 11 11 9 8 3 Visit BL WK 2 WK 4 WK 6 WK 8 WK 10 WK 12 WK 14 WK 16 WK 18 WK 34 WK 46 WK 58 N 11 11 10 9-10 11 11 8-11 11 11 11 9 8 3 Urine Hexose Tetrasaccharide (mmol/mol/creatinine) Alanine Aminotransferase (U/L) Aspartate Aminotransferase (U/L) Creatine Kinase (IU/L) AssessmentMuscle Group Tested Baseline,Change From Baseline to Mean (SD)Month 6, Mean (SD) Right Left Right Left Quantitative Muscle Testing—Dynamometer, pounds force Shoulder Adductiona1.5 (1.9)4.2 (6.8)+5.8 (8.4)+2.3 (4.4) Shoulder Abduction6.9 (7.6)9.8 (10.9)+0.8 (1.5)+0.3 (5.1) Elbow Flex4.9 (5.1)7.8 (8.7)+2.4 (6.1)-0.1 (10.0) Elbow Extension5.0 (5.9)7.3 (8.1)+4.1 (2.1)+1.5 (3.4) GSGC Score12.2 (3.6)-1.8 (3.8)-4.0 (1.4) 10M Walk7.9 (3.0)-0.7 (1.1)-1.0 (0.1) AT2221 Tolerability/Immunogenicity ATB200 (Novel ERT) Optimized mixture of glycans Uptake/Targeting High levels of M6P and bis-M6P FVC upright, % predicted, mean (SD)52.3 (13.2)NA53.4 (20.3) GSGC Score12.6 (4.8)-0.8 (3.0)-0.9 (3.5) Cohort 3 ERT-Naiven=5n=5n=2 Timed Up 9.4 (2.9)-1.0 (1.1)-1.6 (1.0) Time on alglucosidase alfa, years, mean (SD)4.77 (1.42)a 8.9 (3.8)NA 10M Walk7.4 (3.0)-0.3 (1.6)0.1 (1.3) Cohort 1Cohort 2Cohort 3 ERT-SwitchERT-SwitchERT-Naive AmbulatoryNonambulatory(n=5) (n=11)(n=4) Age, years, mean (range)49.4 (28-66)36.0 (18-56)49.4 (24-65) Assessment,Baseline,Change From Baseline toChange From Baseline to secMean (SD)Month 6, Mean (SD)Month 9, Mean (SD) Cohort 1n=10n=9n=8 ERT-Switch Timed Up and Go10.5 (6.6)-2.2 (3.4)-0.6 (2.5)

Positive Pompe Phase 1/2 Data at World Muscle Society Conference Call & Webcast October 4, 2017

Safe Harbor This presentation contains "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995, including statements relating to encouraging preliminary data from a global Phase 1/2 study to investigate ATB200/AT2221 for the treatment of Pompe and the potential implications on these data for the future advancement and development of ATB200/AT2221. Words such as, but not limited to, “look forward to,” “believe,” “expect,” “anticipate,” “estimate,” “intend,” "confidence," "encouraged," “potential,” “plan,” “targets,” “likely,” “may,” “will,” “would,” “should” and “could,” and similar expressions or words identify forward-looking statements. The forward looking statements included in this presentation are based on management's current expectations and beliefs which are subject to a number of risks, uncertainties and factors, including that the preliminary data based on a small patient sample and reported before completion of the study will not be predictive of future results, that results of additional preliminary data or data from the completed study or any future study will not yield results that are consistent with the preliminary data presented, that the Company will not be able to demonstrate the safety and efficacy of ATB200/AT2221, that later study results will not support further development, or even if such later results are favorable, that the Company will not be able to successfully complete the development of, obtain regulatory approval for, or successfully commercialize ATB200/AT2221. In addition, all forward looking statements are subject to the other risks and uncertainties detailed in our Annual Report on Form 10-K for the year ended December 31, 2016 and Quarterly Report on 10-Q for the Quarter ended June 30, 2017. As a consequence, actual results may differ materially from those set forth in this press release. You are cautioned not to place undue reliance on these forward looking statements, which speak only of the date hereof. All forward looking statements are qualified in their entirety by this cautionary statement and we undertake no obligation to revise this press release to reflect events or circumstances after the date hereof. Introduction

Novel Pompe Treatment Paradigm with Three Key Differentiators Novel ERT for Pompe Disease – ATB200 + Chaperone Chaperone addition Optimized mixture of glycans ATB200 + Chaperone: A Highly Differentiated Approach ATB200 (Novel ERT) High levels of M6P and bis M6P *Artist rendering, not actual product image

Phase 1/2 ATB200-02 Study Design Pompe Phase 1/2 Study ATB200-02 Data at WMS Phase 1/2 Clinical Study to Evaluate Safety, Tolerability, Pharmacokinetics (PK), and Pharmacodynamics (PD) of ATB200 + Chaperone (ATB200/AT2221) at 16 Sites in 5 Countries 18-Week Primary Treatment Period with Long-Term Extension (n=20) ATB200 5mg/kg (wk 2) 10mg/kg (wk 4) 20mg/kg (wk 6) ATB200 20mg/kg + AT2221 (Low Dose) wks 8,10,12 ATB200 20mg/kg + AT2221 (High Dose) wk 14+ Cohort 1 (Ambulatory ERT-Switch, n=11) Cohort 2 (Non-Ambulatory ERT-Switch, n=4) & Cohort 3 (ERT-Naïve, n=5) ATB200 20mg/kg + AT2221 (High Dose) wk 2+ Safety/Tolerability Plasma PK Infusion-Associated Reactions Antibody & Cytokine Levels Pharmacodynamics Efficacy (Long-Term Extension) Assessments:

Baseline Characteristics (N=20) Cohort 1: Ambulatory ERT-Switch* (N=11) Cohort 2: Non-Ambulatory ERT-Switch (N=4) Cohort 3: ERT-Naïve (N=5) Time on Standard of Care – mean years (SD) 4.77 (1.4)* 8.9 (3.8) N/A Age – mean years (range) 49.4 (28, 66) 36.0 (18, 56) 49.4 (24, 65) Sex M:F 9:2 3:1 1:4 6MWT – mean meters (SD) 392.0 (93.4) N/A 399.5 (83.5) FVC Upright – mean % predicted (SD) 52.3 (13.2) N/A 53.4 (20.3) Baseline Characteristics Patients Across Three Cohorts Representative of Overall Late-Onset Pompe Population with Impairment at Baseline Pompe Phase 1/2 Study ATB200-02 Data at WMS Baseline Characteristics of Patients in Phase 1/2 ATB200-02 Study (n=20) *Cohort 1 patients required to have been on ERT Standard of Care for 2-6 years at baseline

Summary of Available Data Pompe Phase 1/2 Study ATB200-02 Data at WMS *One patient discontinued after completing Stage 1 (week 18) due to travel burden/family considerations and one patient’s month 6 assessments pending due to an incomplete visit Cohort 1 (ERT-Switch, n=11) Cohort 2 (Non-ambulatory ERT-Switch, n=4) Cohort 3 (ERT-Naive, n=5) Safety and tolerability n=11 n=4 n=5 Biomarkers n=11 n=4 n=5 Functional assessments at month Month 6 (n=9)* Month 9 (n=8) Month 6 (n=4) Month 6 (n=5) Month 9 (n=2) Functional assessments 6MWT Other motor function tests Pulmonary function (FVC, MIP/MEP) Muscle Strength Tests 6MWT Other motor function tests Pulmonary function (FVC, MIP/MEP)

Safety Summary (n=20)* AEs were generally mild and transient Very low number (<1%) of infusion-associated reactions (IARs) after 400+ total infusions One IAR event in one ERT-switch patient (skin discoloration) Two IAR events in one ERT-naïve patient (localized pruritus, erythema and burning sensation) Longest duration of treatment is 72 weeks AEs Generally Mild and Transient with Very Low (<1%) Rate of Infusion-Associated Reactions After 400+ Total Infusions of ATB200/AT2221 Across All Cohorts Pompe Phase 1/2 Study ATB200-02 Data at WMS *Reported through interim data analysis (maximum 72 weeks)

Persistent and Durable Improvement in Biomarkers of Muscle Damage (CK, ALT, AST) and Disease Substrate (Hex4) for up to 58 Weeks on ATB200/AT2221 Pompe Phase 1/2 Study ATB200-02 Data at WMS Cohort 1 (ERT-Switch): Biomarkers up to Week 58 (N=11)* *Reported through interim data analysis (maximum 58 weeks); Missing values either unable to be analyzed or not yet analyzed Mean Percent Change From Baseline (Mean ± SE) ATB200 dose escalation (5>10>20) ATB200 20 mg/kg + low dose AT2221 ATB200 20 mg/kg + high dose AT2221 Visit BL WK 2 WK 4 WK 6 WK 8 WK 10 WK 12 WK 14 WK 16 WK 18 WK 34 WK 46 WK 58 N 11 11 10 9-10 11 11 8-11 11 11 11 9 8 3 Mean Percent Change From Baseline (Mean ± SE) ATB200 dose escalation (5>10>20) ATB200 20 mg/kg + low dose AT2221 ATB200 20 mg/kg + high dose AT2221 Visit BL WK 2 WK 4 WK 6 WK 8 WK 10 WK 12 WK 14 WK 16 WK 18 WK 34 WK 46 WK 58 N 11 11 10 9-10 11 11 8-11 11 11 11 9 8 3 Muscle Damage Biomarkers (% Change from Baseline for CK, ALT, and AST) Disease Substrate Biomarker (% Change from Baseline for Hex 4)

Improvement in Biomarkers of Muscle Damage (CK) and Disease Substrate for up to 24 Weeks on ATB200/AT2221 Pompe Phase 1/2 Study ATB200-02 Data at WMS Cohort 2 (Non-Ambulatory ERT-Switch): Biomarkers up to Week 24 (N=4)* *Reported through interim data analysis (maximum 24 weeks); Missing values either unable to be analyzed or not yet analyzed Muscle Damage Biomarkers (% Change from Baseline for CK, ALT, and AST) Disease Substrate Biomarker (% Change from Baseline for Hex 4) Mean Percent Change From Baseline (Mean ± SE) ATB200 20 mg/kg + high dose AT2221 Visit BL WK 2 WK 4 WK 12 WK 24 N 4 4 4 3 4 ATB200 20 mg/kg + high dose AT2221 Mean Percent Change From Baseline (Mean ± SE) Visit BL WK 2 WK 4 WK 12 WK 24 N 4 4 4 3 4

Cohort 3 (ERT-Naïve): Biomarkers up to Week 36 (N=6)* Improvement in Biomarkers of Muscle Damage and Disease Substrate for up to 36 Weeks on ATB200/AT2221 Pompe Phase 1/2 Study ATB200-02 Data at WMS *Reported through interim data analysis (maximum 36 weeks); Missing values either unable to be analyzed or not yet analyzed Mean Percent Change From Baseline (Mean ± SE) Mean Percent Change From Baseline (Mean ± SE) ATB200 20 mg/kg + high dose AT2221 ATB200 20 mg/kg + high dose AT2221 Visit BL WK 2 WK 4 WK 12 WK 24 WK 36 N 5 5 4-5 5 5 2 Visit BL WK 2 WK 4 WK 12 WK 24 WK 36 N 5 5 4-5 5 5 2 Muscle Damage Biomarkers (% Change from Baseline for CK, ALT, and AST) Disease Substrate Biomarker (% Change from Baseline for Hex 4)

Cohort 1 and 3: 6-Minute Walk Test (6MWT) (n=14) Pompe Phase 1/2 Study ATB200-02 Data at WMS Mean 6MWT Distance Improved for Both ERT-Naïve Patients (+41.8 Meters) and ERT-Switch Patients (+35.3 Meters) at Month 6 with Continued Benefit Out to Month 9 6-Minute Walk Test (m): Month 6 and 9 6MWT distance increased in 7/9 and 8/8 ERT-switch patients at Month 6 and 9, respectively Two patients stable at Month 6, one of these patients reached Month 9 and had increased walking distance 6MWT Increased in 5/5 and 2/2 ERT-Naïve Patients at Month 6 and Month 9, Respectively Cohort Baseline (n=10) Mean (SD) Change at Month 6 (n=9) Mean (SD) Change at Month 9 (n=8) Mean (SD) Cohort 1 ERT-Switch 397.2 (96.8) +35.3 (40.1) +37.2 (33.8) Cohort Baseline (n=5) Mean (SD) Change at Month 6 (n=5) Mean (SD) Change at Month 9 (n=2) Mean (SD) Cohort 3 ERT-Naïve 399.5 (83.5) +41.8 (29.4) +74.9 (4.0)

Cohort 1 and 3: Other Motor Function Tests (n=14) Pompe Phase 1/2 Study ATB200-02 Data at WMS Improvement in Nearly All Motor Function Tests with 6MWT Consistent with Overall Improvement in Motor Performance for Both ERT-Switch and ERT-Naïve Patients at Month 6 and 9 Other Motor Function Tests: Month 6 and 9 Notes: * Median change from baseline was -0.8 and 4/5 had decrease; # N=9 Missing values not obtained due to patient refusal to perform test Cohort Assessment (sec) Baseline (n=10) Mean (SD) Change at Month 6 (n=9) Mean (SD) Change at Month 9 (n=8) Mean (SD) Cohort 1: ERT-Switch Timed up and Go 10.5 (6.6) -2.2 (3.4) -0.6 (2.5) 4 Stair Climb 4.1 (2.7) -1.0 (1.2) -0.9 (1.3) 10M walk 7.4 (3.0) -0.3 (1.6) 0.1 (1.3) Gowers# 7.9 (2.8) -2.2 (2.0) -2.1 (1.3) GSGC Score 12.6 (4.8) -0.8 (3.0) -0.9 (3.5) Cohort Assessment (sec) Baseline (n=5) Mean (SD) Change at Month 6 (n=5) Mean (SD) Change at Month 9 (n=2) Mean (SD) Cohort 3: ERT-Naïve Timed up and Go 9.4 (2.9) -1.0 (1.1) -1.6 (1.0) 4 Stair Climb 4.2 (1.5) -0.6 (0.3) -0.8 (0.3) 10M walk 7.9 (3.0) -0.7 (1.1) -1.0 (0.1) Gowers 13.9 (11.0) 7.9* (21.0) -1.3 (0.0) GSGC Score 12.2 (3.6) -1.8 (3.8) -4.0 (1.4)

Cohort 2: Muscle Strength Testing at Month 6 (n=4) Pompe Phase 1/2 Study ATB200-02 Data at WMS Substantial and Consistent Improvement in Upper Extremity Strength in Non-Ambulatory ERT-Switch Patients in Nearly All Quantitative and Qualitative Measures at Month 6 Assessment Muscle Group Tested Baseline Change to Month 6 Left Mean (SD) Right Mean (SD) Left Mean (SD) Right Mean (SD) QMT- Quantitative Muscle Testing - Dynamometer (pounds force) Shoulder Adduction* 4.2 (6.8) 1.5 (1.9) +2.3 (4.4) +5.8 (8.4) Shoulder Abduction 9.8 (10.9) 6.9 (7.6) +0.3 (5.1) +0.8 (1.5) Elbow Flex 7.8 (8.7) 4.9 (5.1) -0.1 (10.0) +2.4 (6.1) Elbow Extension 7.3 (8.1) 5.0 (5.9) +1.5 (3.4) +4.1 (2.1) MMT - Manual Muscle Testing (manual score) Shoulder Adduction* 1.3 (1.2) 1.0 (1.0) +0.7 (1.2) +0.7 (1.2) Shoulder Abduction** 1.3 (1.2) 1.3 (1.2) +0.5 (0.7) 0.0 (0.0) Elbow Flex 2.3 (2.5) 2.0 (2.0) +0.7 (0.6) +1.0 (1.0) Elbow Extension 2.0 (2.0) 2.0 (2.0) +0.7 (0.6) +1.0 (1.0) Note: MMT Scoring: 1) Visible muscle movement, but no movement at the joint, 2) Movement at the joint, but not against gravity, 3) Movement against gravity, but not against added resistance, 4) Movement against resistance, but less than normal, 5) Normal strength *N=3 or **N=2 due to assessment not being performed at some visits for some patients

Forced Vital Capacity (FVC) Summary (n=13)* Pompe Phase 1/2 Study ATB200-02 Data at WMS FVC Increased in ERT-Naïve Patients and was Generally Stable in ERT-Switch Patients FVC (% Predicted): Month 6 and 9 *FVC results not available for 1 subject at Month 6 and 9 FVC stable or increased in 5/8 and 5/7 ERT-switch patients at Month 6 and Month 9 respectively FVC increased in 4/5 and 2/2 ERT-naïve patients at Month 6 and Month 9 respectively Cohort Baseline (n=9) Mean (SD) Change at Month 6 (n=8) Mean (SD) Change at Month 9 (n=7) Mean (SD) Cohort 1 ERT-Switch Ambulatory* 52.6 (14.7) -1.0 (4.2) -2.0 (3.6) Cohort Baseline (n=5) Mean (SD) Change at Month 6 (n=5) Mean (SD) Change at Month 9 (n=2) Mean (SD) Cohort 3 ERT-Naïve 53.4 (20.3) +4.2 (5.6) +5.0 (1.4)

Other Pulmonary Function Tests at Month 6 (n=14) Pompe Phase 1/2 Study ATB200-02 Data at WMS MIP and MEP Generally Stable or Increased in Both ERT-Naïve and ERT-Switch Patients Other Pulmonary Function Tests: MIP and MEP Patients Assessment Baseline (n=10) Mean (SD) Change at Month 6 (n=9) Mean (SD) Change at Month 9 (n=8) Mean (SD) Cohort 1: ERT-Switch MIP 35.7 (11.0) +0.9 (4.5) -1.4 (2.7) MEP 72.6 (32.6) +20.3 (42.4) +31.1 (39.3) Patients Assessment Baseline (n=5) Mean (SD) Change at Month 6 (n=5) Mean (SD) Change at Month 9 (n=2) Mean (SD) Cohort 3: ERT-Naive MIP 32.6 (18.5) +11.0 (5.0) +1.5 (0.7) MEP 60.6 (8.3) -0.4 (12.4) -1.0 (19.8)

Study ATB200-02 Data Summary Pompe Phase 1/2 Study ATB200-02 Data at WMS MIP Increased and MEP was Stable in ERT-Naïve Patients, MIP was Stable and MEP Increased in ERT-Switch Patients Consistent and Durable Improvement in Key Biomarkers and Muscle Function as well as Stabilization or Improvement in Respiratory Function Muscle function improved in 16/18 and 10/10 patients at Month 6 and 9, respectively 6MWT distance increased to Month 9 ERT-naïve: mean increases of +42m (Month 6) and +75m (Month 9) ERT-switch: mean increases of +35m (Month 6), +37m (Month 9) Improvement in other motor function tests consistent with 6MWT for both ERT-naïve and ERT-switch patients 4/4 non-ambulatory ERT-switch patients showed significant increase in muscle strength tests at Month 6 FVC generally stable in ERT-switch patients FVC increased in a majority of ERT-naïve patients MIP and MEP generally stable or improved in both ERT-switch and ERT-naïve patients Muscle Function (All Cohorts) Pulmonary Function (Cohorts 1 and 3)

Pompe Phase 1/2 Study ATB200-02 Data Cascade Novel ERT for Pompe Disease – ATB200 + Chaperone Continuing Collaborative Discussions with Regulators in the U.S. and EU Update Anticipated in the First Half of 2018 Pompe Milestones in 2017 Discussionswith U.S. and EU regulators 18-WEEK DATA Safety / tolerability Pharmacokinetics (PK) EXTENSION DATA Motor/pulmonary function 18-Week & Extension Data Presentation at World Muscle Society Additional 18-Week & Initial Extension Data Preliminary 18-Week Data at WORLDSymposium Biomarkers Immunogenicity

Thank you

Appendix

Pompe Disease Overview Pompe Disease is Heterogeneous Across a Broad Spectrum of Patients Pompe Overview Deficiency of GAA leading to glycogen accumulation Age of onset ranges from infancy to adulthood Symptoms include muscle weakness, respiratory failure, and cardiomyopathy Respiratory and cardiac failure are leading causes of morbidity and mortality 5,000 – 10,000 patients diagnosed WW1 ~$800M+ Global Pompe ERT sales in FY152 1. National Institute of Neurological Disorders and Stroke (NIH). 2. Sanofi Press Release & 10-K