Pharmacological Chaperone Therapy: Preclinical Development, Clinical Translation, and Prospects for the Treatment of Lysosomal Storage Disorders
Authors: Giancarlo Parenti, Generoso Andria, Kenneth J Valenzano
Journal: Molecular Therapy (2015)

Lysosomal storage disorders (LSDs) are a group of inborn metabolic diseases caused by mutations in genes that encode proteins involved in different lysosomal functions, in most instances acidic hydrolases. Different therapeutic approaches have been developed to treat these disorders. Pharmacological chaperone therapy (PCT) is an emerging approach based on small-molecule ligands that selectively bind and stabilize mutant enzymes, increase their cellular levels, and improve lysosomal trafficking and activity. Compared to other approaches, PCT shows advantages, particularly in terms of oral administration, broad biodistribution, and positive impact on patients' quality of life. After preclinical in vitro and in vivo studies, PCT is now being translated in the first clinical trials, either as monotherapy or in combination with enzyme replacement therapy, for some of the most prevalent LSDs. For some LSDs, the results of the first clinical trials are encouraging and warrant further development. Future research in the field of PCT will be directed toward the identification of novel chaperones, including new allosteric drugs, and the exploitation of synergies between chaperone treatment and other therapeutic approaches. Lysosomal storage disorders (LSDs) are a group of inborn metabolic diseases caused by mutations in genes that encode proteins involved in different lysosomal functions, in most instances acidic hydrolases. Different therapeutic approaches have been developed to treat these disorders. Pharmacological chaperone therapy (PCT) is an emerging approach based on small-molecule ligands that selectively bind and stabilize mutant enzymes, increase their cellular levels, and improve lysosomal trafficking and activity. Compared to other approaches, PCT shows advantages, particularly in terms of oral administration, broad biodistribution, and positive impact on patients' quality of life. After preclinical in vitro and in vivo studies, PCT is now being translated in the first clinical trials, either as monotherapy or in combination with enzyme replacement therapy, for some of the most prevalent LSDs. For some LSDs, the results of the first clinical trials are encouraging and warrant further development. Future research in the field of PCT will be directed toward the identification of novel chaperones, including new allosteric drugs, and the exploitation of synergies between chaperone treatment and other therapeutic approaches. Lysosomal storage disorders (LSDs) represent a heterogeneous group of more than 50 distinct diseases, each of which results from functional deficiency of a particular lysosomal protein. For the majority of LSDs, the defective protein is a soluble acidic hydrolase, while several others are caused by deficiency of integral membrane, activator, transporter, or nonlysosomal proteins that are necessary for lysosomal function. Deficiency of a lysosomal function invariably leads to the accumulation of a wide range of complex substrates, which may include various glycosphingolipids, glycosaminoglycans, glycogen, oligosaccharides, cholesterol, peptides, and/or glycoproteins,1Karageorgos LE Isaac EL Brooks DA Ravenscroft EM Davey R Hopwood JJ et al.Lysosomal biogenesis in lysosomal storage disorders.Exp Cell Res. 1997; 234: 85-97Crossref PubMed Scopus (64) Google Scholar,2Parkinson-Lawrence EJ Shandala T Prodoehl M Plew R Borlace GN Brooks DA Lysosomal storage disease: revealing lysosomal function and physiology.Physiology (Bethesda). 2010; 25: 102-115Crossref PubMed Scopus (164) Google Scholar and in secondary impairment of lysosome-related pathways.3Ballabio A Gieselmann V Lysosomal disorders: from storage to cellular damage.Biochim Biophys Acta. 2009; 1793: 684-696Crossref PubMed Scopus (428) Google Scholar Storage of different substrates in multiple organs and systems results in the variable association of visceral, ocular, hematologic, skeletal, and neurological manifestations. Severity of clinical manifestations, age at onset, and disease course often vary among individuals with the same LSD, resulting in broad clinical presentation. In general, LSDs substantially impact patients' health, quality of life, life expectancy, and physical and intellectual performances. While each LSD is quite rare, collectively they affect a large number of individuals, with an estimated incidence rate of 1:5,000 to 1:7,000 live births.4Fuller M Meikle, PJ Hopwood JJ. Epidemiology of lysosomal storage diseases: an overview.in: Mehta A Beck M Sunder-Plassmann G Fabry Disease: Perspectives from 5 Years of FOS. Oxford PharmaGenesis, Oxford2006http://www.ncbi.nlm.nih.gov/books/NBK11586/?report=readerGoogle Scholar For their impact on patients' health and for their cumulative frequency, LSDs represent a heavy burden in terms of public health and economical costs. Even though LSDs are rare, their biological and clinical interest is high. These diseases represent models to understand lysosomal function and its role in cellular biology. Furthermore, over the past 25 years, intensive and continuous advancements have been made to develop therapies that are specifically aimed at correcting the metabolic defect(s) of LSDs.5Parenti G Andria G Ballabio A Lysosomal storage diseases: from pathophysiology to therapy.Annu Rev Med. 2015; 66: 471-486Crossref PubMed Scopus (263) Google Scholar The majority of these therapeutic approaches are directed toward increasing the cellular activity or level of the defective enzyme or protein, with the ultimate goal of lowering the accumulated substrate in key cell types and tissues. Given that the underlying cause of most LSDs is deficiency of a particular enzyme activity, the primary therapeutic approach that has been most successful and broadly reached to date is enzyme replacement therapy (ERT). ERT is based on the periodic intravenous administration of a manufactured enzyme that can be taken up into cells, be delivered to lysosomes, and reduce substrate storage.6Brady RO Enzyme replacement for lysosomal diseases.Annu Rev Med. 2006; 57: 283-296Crossref PubMed Scopus (239) Google Scholar To date, seven LSDs have marketed ERT products, and in some cases, multiple products exist for a single LSD. Similar to ERT, normal enzyme also may be provided as a precursor that is secreted into the circulation by allograft of transplanted cells (hematopoietic stem cell transplantation (HSCT))7Boelens JJ Prasad VK Tolar J Wynn RF Peters C Current international perspectives on hematopoietic stem cell transplantation for inherited metabolic disorders.Pediatr Clin North Am. 2010; 57: 123-145Abstract Full Text Full Text PDF PubMed Scopus (94) Google Scholar or by a patient's own engineered cells.8Biffi A Genetically-modified hematopoietic stem cells and their progeny for widespread and efficient protein delivery to diseased sites: the case of lysosomal storage disorders.Curr Gene Ther. 2012; 12: 381-388Crossref PubMed Scopus (11) Google Scholar Similarly, the gene mutation may potentially be corrected by delivering a wild-type copy that will direct the synthesis of the normal enzyme in the patient's cells.9Sands MS Davidson BL Gene therapy for lysosomal storage diseases.Mol Ther. 2006; 13: 839-849Abstract Full Text Full Text PDF PubMed Scopus (207) Google Scholar Alternative strategies also exist and are directed toward reducing the synthesis of substrates (i.e., substrate reduction therapy, for which two drugs currently exist),10Platt FM Jeyakumar M Substrate reduction therapy.Acta Paediatr Suppl. 2008; 97: 88-93Crossref PubMed Scopus (123) Google Scholar by enhancing clearance of substrates from cells and tissues, or by manipulating specific cellular pathways (such as those involved in vesicle trafficking).11Spampanato C Feeney E Li L Cardone M Lim JA Annunziata F et al.Transcription factor EB (TFEB) is a new therapeutic target for Pompe disease.EMBO Mol Med. 2013; 5: 691-706Crossref PubMed Scopus (232) Google Scholar The focus of this paper, however, is pharmacological chaperones, small molecules that can selectively bind and stabilize mutant enzymes, protecting them from premature denaturation and degradation, and ultimately increasing their lysosomal levels and activity.12Parenti G Treating lysosomal storage diseases with pharmacological chaperones: from concept to clinics.EMBO Mol Med. 2009; 1: 268-279Crossref PubMed Scopus (217) Google Scholar,13Valenzano KJ Khanna R Powe AC Boyd R Lee G Flanagan JJ et al.Identification and characterization of pharmacological chaperones to correct enzyme deficiencies in lysosomal storage disorders.Assay Drug Dev Technol. 2011; 9: 213-235Crossref PubMed Scopus (125) Google Scholar,14Boyd RE Lee G Rybczynski P Benjamin ER Khanna R Wustman BA et al.Pharmacological chaperones as therapeutics for lysosomal storage diseases.J Med Chem. 2013; 56: 2705-2725Crossref PubMed Scopus (163) Google Scholar Recently, pharmacological chaperone therapy (PCT) for a number of LSDs has been evaluated in the clinic, with some molecules showing therapeutic promise. The balance between protein synthesis, folding, and degradation is a closely monitored and highly dynamic process that is critical to maintain cellular protein homeostasis, i.e., proteostasis (Figure 1).15Balch WE Morimoto RI Dillin A Kelly JW Adapting proteostasis for disease intervention.Science. 2008; 319: 916-919Crossref PubMed Scopus (1748) Google Scholar,16Muntau AC Leandro J Staudigl M Mayer F Gersting SW Innovative strategies to treat protein misfolding in inborn errors of metabolism: pharmacological chaperones and proteostasis regulators.J Inherit Metab Dis. 2014; 37: 505-523Crossref PubMed Scopus (89) Google Scholar Cells have evolved complex quality control systems that function in various organelles, including the endoplasmic reticulum (ER), to aid in these processes.16Muntau AC Leandro J Staudigl M Mayer F Gersting SW Innovative strategies to treat protein misfolding in inborn errors of metabolism: pharmacological chaperones and proteostasis regulators.J Inherit Metab Dis. 2014; 37: 505-523Crossref PubMed Scopus (89) Google Scholar,17Ellgaard L Helenius A Quality control in the endoplasmic reticulum.Nat Rev Mol Cell Biol. 2003; 4: 181-191Crossref PubMed Scopus (1672) Google Scholar These mechanisms rely on multiple classes of proteinaceous molecular chaperones and folding factors (e.g., heat-shock proteins) that recognize and cotranslationally interact with various partially folded, aggregation-prone structural motifs of nascent proteins during synthesis, such as exposed hydrophobic regions, regions of unstructured polypeptide sequence, or unpaired cysteine residues, to distinguish stable, native conformations from unstable, misfolded conformations.16Muntau AC Leandro J Staudigl M Mayer F Gersting SW Innovative strategies to treat protein misfolding in inborn errors of metabolism: pharmacological chaperones and proteostasis regulators.J Inherit Metab Dis. 2014; 37: 505-523Crossref PubMed Scopus (89) Google Scholar Upon recognition and binding to the nascent polypeptide, molecular chaperones can stabilize protein conformation, inhibit premature misfolding, and prevent aggregation.18Gregersen N Protein misfolding disorders: pathogenesis and intervention.J Inherit Metab Dis. 2006; 29: 456-470Crossref PubMed Scopus (71) Google Scholar,19Hartl FU Hayer-Hartl M Converging concepts of protein folding in vitro and in vivo.Nat Struct Mol Biol. 2009; 16: 574-581Crossref PubMed Scopus (841) Google Scholar,20Vabulas RM Proteasome function and protein biosynthesis.Curr Opin Clin Nutr Metab Care. 2007; 10: 24-31Crossref PubMed Scopus (17) Google Scholar Only those proteins that are correctly folded and stable can exit the ER efficiently and traffic to the lysosome. If folding of the nascent protein fails despite the action of molecular chaperones, the protein may be recognized by the ER quality control system as aberrant and targeted for degradation either by the lysosome or by the proteasome.21Anelli T Sitia R Protein quality control in the early secretory pathway.EMBO J. 2008; 27: 315-327Crossref PubMed Scopus (475) Google Scholar,22Hebert DN Molinari M In and out of the ER: protein folding, quality control, degradation, and related human diseases.Physiol Rev. 2007; 87: 1377-1408Crossref PubMed Scopus (492) Google Scholar For the latter, ER-associated degradation involves polyubiquination, translocation to the cytosol, and proteasomal degradation. In the case of LSDs, the ER quality control often recognizes mutant forms of lysosomal enzymes that retain catalytic activity or that have only modestly compromised function, due to slight modifications in their stability or conformation. This recognition may prevent trafficking through the secretory pathway and result in loss of function due to premature degradation or ER aggregation. Based on an evolving understanding of these mechanisms, several small-molecule approaches to correct deficiencies that result from mutations in lysosomal enzymes have emerged over the past 15 years.16Muntau AC Leandro J Staudigl M Mayer F Gersting SW Innovative strategies to treat protein misfolding in inborn errors of metabolism: pharmacological chaperones and proteostasis regulators.J Inherit Metab Dis. 2014; 37: 505-523Crossref PubMed Scopus (89) Google Scholar One of the more promising and advanced approaches utilizes pharmacological chaperones: small-molecule ligands that selectively bind and stabilize otherwise unstable enzymes to increase total cellular levels and improve lysosomal trafficking and activity (Figure 2). Lysosomal enzyme synthesis occurs in the neutral pH environment of the ER. As these enzymes are acidic hydrolases, many tend to be thermodynamically less stable at neutral pH compared to the low-pH environment of lysosomes.23Lieberman RL D'aquino JA Ringe D Petsko GA Effects of pH and iminosugar pharmacological chaperones on lysosomal glycosidase structure and stability.Biochemistry. 2009; 48: 4816-4827Crossref PubMed Scopus (121) Google Scholar For some mutant lysosomal enzymes, this thermodynamic instability can be exacerbated, with consequently even less of the properly folded enzyme able to exit the ER. In this context, pharmacological chaperones selectively bind and stabilize a specific target enzyme, resulting in increased total cellular levels, and passage through the quality control mechanisms of the ER, with subsequent delivery to lysosomes.12Parenti G Treating lysosomal storage diseases with pharmacological chaperones: from concept to clinics.EMBO Mol Med. 2009; 1: 268-279Crossref PubMed Scopus (217) Google Scholar,13Valenzano KJ Khanna R Powe AC Boyd R Lee G Flanagan JJ et al.Identification and characterization of pharmacological chaperones to correct enzyme deficiencies in lysosomal storage disorders.Assay Drug Dev Technol. 2011; 9: 213-235Crossref PubMed Scopus (125) Google Scholar For a number of reasons, LSDs can be considered excellent candidates for PCT. While many types of mutations have been identified in LSDs, including large deletions, insertions, premature stop codons, and splicing mutations, missense mutations tend to be more common.13Valenzano KJ Khanna R Powe AC Boyd R Lee G Flanagan JJ et al.Identification and characterization of pharmacological chaperones to correct enzyme deficiencies in lysosomal storage disorders.Assay Drug Dev Technol. 2011; 9: 213-235Crossref PubMed Scopus (125) Google Scholar In most cases, missense mutations occur outside the enzyme's active site and have negative effects on protein folding efficiency, thermodynamic stability, and lysosomal trafficking, although the mutant enzymes retain their catalytic properties.16Muntau AC Leandro J Staudigl M Mayer F Gersting SW Innovative strategies to treat protein misfolding in inborn errors of metabolism: pharmacological chaperones and proteostasis regulators.J Inherit Metab Dis. 2014; 37: 505-523Crossref PubMed Scopus (89) Google Scholar This concept has been characterized in detail for several LSDs. For example, Gaucher disease, generally thought to be the most prevalent LSD, is caused by mutations in the GBA1 gene that encodes glucocerebrosidase (GCase; EC 3.2.1.45),24Beutler E Gaucher disease: multiple lessons from a single gene disorder.Acta Paediatr Suppl. 2006; 95: 103-109Crossref PubMed Scopus (57) Google Scholar and is characterized by progressive accumulation of glucosylceramide primarily within macrophages of the liver, bone marrow, and spleen. Among more than 200 mutations identified in GBA1, the 2 most prevalent missense mutations are N370S and L444P,24Beutler E Gaucher disease: multiple lessons from a single gene disorder.Acta Paediatr Suppl. 2006; 95: 103-109Crossref PubMed Scopus (57) Google Scholar retaining ~30 and 10–12% residual cellular activity, respectively.25Sawkar AR Adamski-Werner SL Cheng WC Wong CH Beutler E Zimmer KP et al.Gaucher disease-associated glucocerebrosidases show mutation-dependent chemical chaperoning profiles.Chem Biol. 2005; 12: 1235-1244Abstract Full Text Full Text PDF PubMed Scopus (168) Google Scholar These mutations result in deleterious changes in the three-dimensional structure and in variable levels of ER retention and ER-associated degradation.26Ron I Horowitz M ER retention and degradation as the molecular basis underlying Gaucher disease heterogeneity.Hum Mol Genet. 2005; 14: 2387-2398Crossref PubMed Scopus (240) Google Scholar Evidence that mutations in the genes encoding different lysosomal enzymes result in protein misfolding, retention in the ER/Golgi, degradation, lack of appropriate protein processing, and/or defective transport to lysosomes has also been reported for many other LSDs.27Parenti G Moracci M Fecarotta S Andria G Pharmacological chaperone therapy for lysosomal storage diseases.Future Med Chem. 2014; 6: 1031-1045Crossref PubMed Scopus (43) Google Scholar Since the mutations that cause misfolding are relatively prevalent in some LSDs, like Gaucher disease and Fabry disease, PCT has the potential to be a suitable strategy for the treatment of a substantial fraction of affected patients. For most LSDs, it has been speculated that substrate storage occurs if residual enzyme activity falls below a certain threshold (Figure 3) and that above a certain level, accumulation of clinically relevant quantities of substrate would require a duration that exceeds the human life span.28Suzuki Y Emerging novel concept of chaperone therapies for protein misfolding diseases.Proc Jpn Acad Ser B Phys Biol Sci. 2014; 90: 145-162Crossref PubMed Scopus (52) Google Scholar It has been assumed that a threshold activity of ~10% is sufficient to prevent storage in several LSDs, with restoration of 3–5% activity often cited as sufficient to slow down the disease progress.29Hopwood JJ Muller V Biochemical discrimination of Hurler and Scheie syndromes.Clin Sci (Lond). 1979; 57: 265-272Crossref PubMed Scopus (39) Google Scholar,30Leinekugel P Michel S Conzelmann E Sandhoff K Quantitative correlation between the residual activity of beta-hexosaminidase A and arylsulfatase A and the severity of the resulting lysosomal storage disease.Hum Genet. 1992; 88: 513-523Crossref PubMed Scopus (260) Google Scholar,31Desnick RJ Fan JQ Pharmacological chaperone therapy for lysosomal disease.in: Futerman AH Zimran A Gaucher Disease. CRC Press, Boca Raton, FL2006: 377-396Crossref Google Scholar This suggests that enhancement of the residual cellular activity by PCT may attenuate disease progression and translate into benefit for patients. However, the residual activity known to be associated with attenuated phenotypes and required to prevent massive storage seems to vary among different disorders and may depend, in part, on various factors such as the severity of the enzymatic defect, the rate of substrate accumulation/turnover, the stage of disease progression, sex, etc. For example, while 1–2% of normal GCase and α-iduronidase activity have been reported for some mild cases of Gaucher disease and mucopolysaccharidosis I, respectively, higher activities (6%) have been reported in late-onset GM1 gangliosidosis.13Valenzano KJ Khanna R Powe AC Boyd R Lee G Flanagan JJ et al.Identification and characterization of pharmacological chaperones to correct enzyme deficiencies in lysosomal storage disorders.Assay Drug Dev Technol. 2011; 9: 213-235Crossref PubMed Scopus (125) Google Scholar ERT is currently considered the standard of care for several LSDs. While some of the underlying pathologies and affected organ systems are treated well by ERT, others are not. This is often due to poor tissue access, as well as inefficient cellular uptake and lysosomal delivery. In particular, the ability to target the central nervous system has not been achieved, given the inability of large proteins to cross the blood–brain barrier.32Beck M Emerging drugs for lysosomal storage diseases.Expert Opin Emerg Drugs. 2010; 15: 495-507Crossref PubMed Scopus (32) Google Scholar,33Lim-Melia ER Kronn DF Current enzyme replacement therapy for the treatment of lysosomal storage diseases.Pediatr Ann. 2009; 38: 448-455Crossref PubMed Scopus (36) Google Scholar Furthermore, most of the current ERTs are immunogenic, eliciting immune responses that can limit tolerability and efficacy.34Bodensteiner D Scott CR Sims KB Shepherd GM Cintron RD Germain DP Successful reinstitution of agalsidase beta therapy in Fabry disease patients with previous IgE-antibody or skin-test reactivity to the recombinant enzyme.Genet Med. 2008; 10: 353-358Abstract Full Text Full Text PDF PubMed Scopus (43) Google Scholar,35Banugaria SG Patel TT Kishnani PS Immune modulation in Pompe disease treated with enzyme replacement therapy.Expert Rev Clin Immunol. 2012; 8: 497-499Crossref PubMed Scopus (22) Google Scholar,36Beck M Alglucosidase alfa: long term use in the treatment of patients with Pompe disease.Ther Clin Risk Manag. 2009; 5: 767-772Crossref PubMed Google Scholar,37de Vries JM van der Beek NA Kroos MA Ozkan L van Doorn PA Richards SM et al.High antibody titer in an adult with Pompe disease affects treatment with alglucosidase alfa.Mol Genet Metab. 2010; 101: 338-345Abstract Full Text Full Text PDF PubMed Scopus (80) Google Scholar In addition, ERT requires lifelong intravenous infusion, with frequent hospital admissions, need for central venous devices (and related risk of infections), and high costs.38Wyatt K Henley W Anderson L Anderson R Nikolaou V Stein K et al.The effectiveness and cost-effectiveness of enzyme and substrate replacement therapies: a longitudinal cohort study of people with lysosomal storage disorders.Health Technol Assess. 2012; 16: 1-543Crossref PubMed Scopus (90) Google Scholar The other therapeutic approaches mentioned above (e.g., substrate reduction therapy, HSCT, gene therapy) are either restricted to a few LSDs or are in early stages of clinical development. In principle, PCT has the potential to address at least some of the limitations of existing therapies. Pharmacological chaperones are small molecules with published data indicating, as a class, good oral bioavailability, broad tissue distribution to key cell types and tissues including the brain, and the ability to diffuse across membranes, achieving therapeutic concentrations in specific cellular compartments. Enhancement of enzyme activity by PCT also may lead to sustained and stable enzyme levels, more closely mimicking the natural production of these endogenous enzymes as compared to weekly or biweekly ERT administration that leads to intermittent and fluctuating cellular activity. In addition, unlike the manufactured enzymes used for ERT, pharmacological chaperones are nonimmunogenic and would not be expected to have tolerability issues similar to those described for a number of different ERTs. In fact, the safety profiles of some pharmacological chaperones have been evaluated clinically and appear to be acceptable. Since 1999, PCT has been evaluated in preclinical studies for a number of LSDs. Table 1 provides a list of selected chaperones that have shown the greatest potential for clinical studies.Table 1Current stage of development of select pharmacological chaperonesDiseaseTherapeutic agent (route of administration, as applicable)Orphan drug designationDevelopment status/clinical trial study IDCompany, sponsorReferencesFabryGalactose (intravenous)N/AMonotherapy Pilot clinical studyUniversita Cattolica del Sacro Cuore, Roma, Italy84Frustaci A Chimenti C Ricci R Natale L Russo MA Pieroni M et al.Improvement in cardiac function in the cardiac variant of Fabry's disease with galactose-infusion therapy.N Engl J Med. 2001; 345: 25-32Crossref PubMed Scopus (295) Google ScholarMigalastat H Cl/AT1001/1- deoxygalactonojirimycin/DGJ (oral)US: 02/25/2004 EU: 05/22/2006 Monotherapyphase 2:NCT00214500 (FAB-CL-201)NCT00283959 (FAB-CL-202)NCT00283933 (FAB-CL-203)NCT003045120 (FAB-CL-204)NCT00526071 (FAB-CL-205)phase 3:NCT00925301 (AT1001-011)NCT01218659 (AT1001-012)NCT01458119 (AT1001-041)NCT02194985 (AT1001-042)Amicus Therapeutics88,91 Combination therapy (phase 2)+ intravenous agalsidase alfa or beta: NCT01196871 (AT1001-013)Amicus Therapeutics109Warnock D Bichet D Holida M Goker-Alpan O Nicholls K Thomas M et al.A phase 2A study to investigate the effect of a single dose of migalastat HCl, a pharmacological chaperone, on agalsidase activity in subjects with Fabry disease.Mol Genet Metab. 2013; 108 (S(abstract 248)): 96Abstract Full Text Full Text PDF Google ScholarGaucher, type IAfegostat tartrate/AT2101/isofagomine/IFG (oral)US: 01/10/2006 EU: 10/23/2007 Monotherapy (phase 2)NCT00875160 (GAU-CL-104)NCT00433147 (GAU-CL-201)NCT00446550 (GAU-CL-202)NCT00813865 (GAU-CL-202X)Amicus TherapeuticsAmbroxol (oral)US: 06/29/2011 EU: N/AMonotherapy (phase 1/2) NCT01463215ExSAR Corp.103Zimran A Altarescu G Elstein D Pilot study using ambroxol as a pharmacological chaperone in type 1 Gaucher disease.Blood Cells Mol Dis. 2013; 50: 134-137Crossref PubMed Scopus (105) Google ScholarPompeDuvoglustat HCl/AT2220/1- deoxynojirimycin/DNJ (oral)US: 06/18/2007 EU: N/AMonotherapy (phase 2) NCT00688597 (POM-CL-201)Amicus TherapeuticsCombination therapy (phase 2) + intravenous alglucosidase alfa: NCT01380743 (AT2220- 010)Amicus Therapeutics107Kishnani P Tarnopolsky M Sivakumar K Roberts M Byrne B Goker-Alpan O et al.A phase 2a study to investigate drug–drug interactions between escalating doses of AT2220 (duvoglustat hydrochloride) and acid alfa-glucosidase in subjects with Pompe disease.Mol Genet Metab. 2013; 108: S54Abstract Full Text Full Text PDF Google ScholarMiglustat (oral)N/ACombination therapy (phase 2) + intravenous alglucosidase alfa: EudraCT n. 2010-024647-32Universita degli Studi di Napoli Federico II, Italy106Parenti G Fecarotta S la Marca G Rossi B Ascione S Donati MA et al.A chaperone enhances blood α-glucosidase activity in Pompe disease patients treated with enzyme replacement therapy.Mol Ther. 2014; 22: 2004-2012Abstract Full Text Full Text PDF PubMed Scopus (55) Google ScholarCombination therapy (phase 1/2) + intravenous alglucosidase alfa: NCT02185651University of Florida/Amicus TherapeuticsGM1 gangliosidosisNOEV (oral)N/A MonotherapyPreclinical cell-based and in vivo studiesN/A64Suzuki Y Ichinomiya S Kurosawa M Matsuda J Ogawa S Iida M et al.Therapeutic chaperone effect of N-octyl 4-epi-β-valienamine on murine G(M1)-gangliosidosis.Mol Genet Metab. 2012; 106: 92-98Abstract Full Text Full Text PDF PubMed Scopus (34) Google ScholarGM2 gangliosidosisN-acetylglucosamine thiazoline (NGT)N/A MonotherapyPreclinical cell-based studies onlyN/A110Tropak MB Reid SP Guiral M Withers SG Mahuran D Pharmacological enhancement of beta-hexosaminidase activity in fibroblasts from adult Tay-Sachs and Sandhoff Patients.J Biol Chem. 2004; 279: 13478-13487Crossref PubMed Scopus (179) Google Scholar,111Tropak MB Mahuran D Lending a helping hand, screening chemical libraries for compounds that enhance beta-hexosaminidase A activity in GM2 gangliosidosis cells.FEBS J. 2007; 274: 4951-4961Crossref PubMed Scopus (58) Google ScholarAdNDJ/OT1001 (oral)N/A MonotherapyPreclinical cell-based and in vivo studiesN/A110Tropak MB Reid SP Guiral M Withers SG Mahuran D Pharmacological enhancement of beta-hexosaminidase activity in fibroblasts from adult Tay-Sachs and Sandhoff Patients.J Biol Chem. 2004; 279: 13478-13487Crossref PubMed Scopus (179) Google Scholar,112Knight EM Williams HN Stevens AC Kim SH Kottwitz JC Morant AD et al.Evidence that small molecule enhancement of β-hexosaminidase activity corrects the behavioral phenotype in Dutch APP(E693Q) mice through reduction of ganglioside-bound Aβ.Mol Psychiatry. 2015; 20: 109-117Crossref PubMed Scopus (22) Google ScholarPyrimethamine (oral)US: 08/16/2011 EU: N/AMonotherapy (phase 1/2) NCT01102686The Hospital for Sick Children, Canada105,112MPS IIICGlucosamineN/A MonotherapyPreclinical cell-based studies onlyN/A113Feldhammer M Durand S Pshezhetsky AV Protein misfolding as an underlying molecular defect in mucopolysaccharidosis III type C.PLoS One. 2009; 13: e7434Crossref Scopus (62) Google ScholarBattenCS38N/A MonotherapyPreclinical cell-based studies onlyN/A114Dawson G Schroeder C Dawson PE Palmitoyl:protein thioesterase (PPT1) inhibitors can act as pharmacological chaperones in infantile Batten disease.Biochem Biophys Res Commun. 2010; 395: 66-69Crossref PubMed Scopus (33) Google ScholarEU, European Union; N/A, not applicable; US, United States. Open table in a new tab EU, European Union; N/A, not applicable; US, United States. The first studies on PCT in an LSD were done for Fabry disease, an X-linked disorder caused by mutations in the GLA gene that encodes α-galactosidase A (α-Gal A; EC 3.2.1.22).39Germain DP Fabry disease.Orphanet J Rare Dis. 2010; 5: 30Crossref PubMed Scopus (739) Google Scholar Deficiency of α-Gal A activity results in accumulation of glycosphingolipids, prima