This document discusses enzyme replacement therapy (ERT) for lysosomal storage disorders. It provides details on ERT including its development, mechanisms, available products, dosing and costs. Challenges with ERT include limited blood-brain barrier penetration and immunogenicity. Alternative therapies discussed include substrate reduction therapy, pharmacological chaperones, and direct delivery of enzymes into the cerebrospinal fluid. ERT remains the standard treatment but has limitations for treating neurological manifestations of lysosomal storage disorders.

1. Dr Ravi Goyal
SR Neurology
GMC KOTA

2.  Enzyme replacement therapy (ERT) is a medical treatment which
replaces an enzyme that is deficient or absent in the body .
 ERT was developed in 1964 by Christian de Duve and Roscoe Brady.
 ERT was used in clinical practice after 1991 and the FDA
gave orphan drug approval for the treatment of Gaucher disease
with Alglucerase.
 Initially manufactured by isolating the therapeutic enzyme from
human placent but now derived from other human cells, animal
cells (i.e. Chinese hamster ovary cells, or CHO cells) and plant cells.

3.  The first publication of ERT in india was from BARC Hospital,
Mumbai which described a 5-year-old boy who started receiving
human placenta-derived alglucerase (Ceredase®) since 1999.
 Limited production because of limited availability of human
placenta .
 Later in 2002 , the development of a DNA recombinant product
analog of human β-glucocerebrosidase, imiglucerase replaced
the alglucerase .

5.  ERT is currently available for some lysosomal storage diseases
with neurologic involement :-
 Gaucher disease
 Fabry disease
 Pompe disease
 MPS I (Hurler‘s syndrome)
 MPS II (Hunter syndrome)
 MPS III
 MPS VII
 Neuronal Ceroid Lipofuscinosis II

6.  ERT does not correct the underlying genetic defect, but it
increases the concentration of the enzyme that the patient is
lacking .
 It is administered by IV infusion.
 Typically, infusions occur every week or every two weeks.
 For some types of ERT, these infusions can occur as
infrequently as every four weeks.

7.  Lysosmal storage AR Disorder
 Due to mutations in the gene glucocerebrosidase1 (GBA1), located
on chromosome 1q21 .
 deficiency of a lysosomal enzyme gluco cerebrosidase ( also known
as glucosyl ceramidase or acid beta- glucosidase, GCase)
 Three types
 Type1 GD (non neuronopathic form)
 Type2 GD (Acute Neuronopathic form)
 Type3 GD(subacute or chronic neuronopathic form)

9.  Guidelines for the use of ERT in patients with neuronopathic GD are
less well established.
 The recombinant enzyme does not cross the blood-brain barrier so
has limited ability to impact central nervous system (CNS) disease.
 In some studies, ERT was found to reverse almost all of the systemic
manifestations and appeared to stabilize or slow progression of
central neurologic disease (except progressive myoclonic epilepsy)
in some patients
 This was illustrated in a series of 21 patients, ages 8 months to 35
years, with GD3 who were treated with individually adjusted doses.

11. Disease Product Company US FDA*
approval/E
U
EMA† appro
val
Treatment
in India
Dose/frequ
ency (IV
infusion)
Approximate
annual cost
(INR) - 10 kg
child
Gaucher Imiglucerase Sanofi-
Genzyme
1994/1997 2002 60
units/kg/EO
W‡
40 lakhs
Velagluceras
e α
Shire HGT 2010/2010 2014 60
units/kg/EO
W
70 lakhs
Taliglucera
se α
Protalix 2012/not
approved
No
information
60 units/kg
q EOW
No
information

12.  Fabry disease is an X-linked glycolipid storage disease.
 Caused by deficient activity of the lysosomal enzyme alpha-
galactosidase A,
 which causes progressive accumulation of α-D galactosyl
moieties, such as globo triaosyl ceramide (the glycolipid
substrate for alpha galactosidase A)
 within multiple cell types and tissues of affected patients .

13.  Neurologic manifestations of the disease includes :-
 A small-fiber peripheral neuropathy (short term complication)
 An increased propensity for ischemic stroke in affected males
and female heterozygotes (long term complication) .

14.  The effects of enzyme replacement therapy on short-term
neurologic complications in the phase II/III clinical trials:
 The National Institutes of Health (NIH) trial involved 26
hemizygous males treated with agalsidase alfa (0.2 mg/kg) infusion
or placebo, which was administered every two weeks for 12 doses
(24 weeks) .
 Active treatment significantly decreased plasma and urine Gb3
levels.
 The primary outcome measure, neuropathic pain assessed by
questionnaire, was significantly improved with active treatment,
but not placebo.

15.  Reports of long-term neurologic outcomes following enzyme
replacement therapy are limited .
 A longitudinal cohort study of over 200 adults and 7 children
with Fabry disease found no association between time on
enzyme replacement therapy and the risk of stroke or TIA.
 Thus , these data suggest that enzyme replacement therapy for
Fabry disease decreases neuropathic pain, but does not reduce
the risk of stroke .
 Some studies even suggest that enzyme replacement is
associated with an increased stroke risk compared with the
natural history data from the Fabry Registry .

16. Fabry Agalsidas
e β
Sanofi-
Genzyme
2003/200
1
2005 1 mg/kg
EOW
20 lakhs
Agalsidas
e α
Shire HGT Not
approved
/2001
2014 0.2 mg/kg
EOW
20 lakhs

17.  Autosomal recessive disorder.
 Due to Acid alpha-glucosidase (GAA, also called acid maltase)
deficiency.
 First identified lysosomal storage disease. (GSD II)
 Two form :
 1 The classic infantile form is characterized by cardiomyopathy
and severe, generalized muscular hypotonia
 2 The juvenile and adult form, the primary clinical finding is
skeletal myopathy with a more protracted course leading to
respiratory failure.

18.  Early-onset disease — Several small studies in patients with
infantile GAA deficiency have found short- and long-term
improvements in cardiac and skeletal muscle function, need for
ventilatory support and survival by enzyme replacement therapy.
 Late-onset disease — Intravenous ERT with alglucosidase alfa has
also shown efficacy for late onset GAA deficiency.
 The international Pompe survey has demonstrated a positive effect
of ERT on survival and on fatigue, quality of life, and participation
in daily life in patients with late-onset disease.

19. Pompe Alglucosi
dase α
Sanofi-
Genzyme
2006/20
06
2008 20 mg/kg
EOW
49 lakhs

20.  Treatment outcome in infantile GAA deficiency is affected by cross-
reactive immunologic material (CRIM) status.
 CRIM-negative status (lacking any residual GAA expression) was
associated with an increased risk of death or invasive ventilation
after 52 weeks of therapy. ( 54.5 versus 4.8 percent in CRIM positive
patients)
 (a retrospective analysis of 32 patients who were treated with
alglucosidase alfa)
 Induction of immune tolerance by using a combination of rituximab
and methotrexate with or without intravenous immune globulin
(IVIG) that neutralizes antibody effect.

21.  Lysosomal enzyme deficiency in the different muco
polysaccharidosis (MPS) disorders leads to progressive
glycosaminoglycan (GAG) accumulation and a variety of somatic
and neurological manifestations.
 Despite existing treatments for some MPS disorders, it remains
challenging to effectively treat neurocognitive deterioration and
behavioral problems in patients with MPS I, II, III, and VII .

22.  Irreversible damage of the Central nervous system (CNS)
 Selective permeability of the blood-brain barrier damage (BBB)
 Mainly structural information by neuroimaging
 Limited biomarkers reflecting CNS disease
 Limits the use of ERT in mucopolysaccharidosis.

23.  MPS I (Hurler syndrome)- Alpha-L iduronidase deficient
 MPS II (Hunter syndrome)- X linked, Iduronate sulfatase
 MPS III (Sanflippo syndrome) –
III A Heparan N-sulfatase
III B Alpha-N acetyl glucosaminidase
III C Heparan sulfate acetyl-CoA ,
alpha - glucosaminide N- acetyltransferase
III D N-acetylglucosamine-6-sulfatase
 MPS VII (Sly syndrome) - Beta-glucuronidase

24.  These Muco polysacchioridosis have common clinical feature
 Aggressive behavior
 Developmental delay with
 Early age of presentation.

25. MPS I Laroni
dase
Sanofi
-
Genzy
me
2003/
2003
2006 0.58
mg/k
g
weekl
y
46
lakhs
MPS II Idursu
lfase
Shire
HGT
2006/
2007
2014 0.5
mg/kg
weekl
y
1
crore
MPS VII Vestr
onida
se α
Ultrag
enyx
Nove
mber
2017
Not
availa
ble
4
mg/k
g
EOW
No
infor
matio
n

26.  Penetration of BBB :-
 Trojan horse strategy
 Nano-enabled therapy
 Bypassing of BBB :-
 Intracerebroventricular approach
 Intrathecal approach

27.  Fusion of recombinant enzyme with a genetically engineered
molecule, usually an antibody, that can bind to a receptor
present on the
 BBB which allows entry in the CNS through receptor-mediated
transcytosis referred to as the ‘Trojan horse’ strategy.
 The fusion protein can be administered directly, or through
expression mediated by a vector that contains the fusion gene.
 Phase 1 clinical trials in MPS I and MPS II patients with
human insulin receptor monoclonal antibody-enzyme fusion
proteins are currently ongoing ,

28.  A second strategy to facilitate CNS access is the use of coated
nanoparticles as a carrier to transport recombinant enzyme across
the BBB .
 More recently it was shown that high molecular weight molecules,
such as the recombinant enzymes for MPS disorders, can be
efficiently encapsulated by or linked to nanoparticles like
Arylsulfatase B-loaded poly (butyl cyanoacrylate) .
 Recently, Mayer et al. synthesized laronidase surface-
functionalized multiple-wall lipid-core nanocapsules, which were
able to improve bio distribution of laronidase in MPS I mice .
 The findings of these studies open up the opportunity for further
development of nanoenabled therapies for the MPS disorders.

31.  A possible way to circumvent the BBB is direct delivery of
the enzyme in the cerebrospinal fluid (CSF) through
 either intra cerebro ventricular (ICV) injection into the lateral
ventricle (via a catheter/reservoir)
 or intrathecal (IT) injection into the lumbar spine or
subarachnoid space at the cisterna magna .
 (via lumbar puncture or an IT drug delivery device [IDDD]).

32.  Studies in small (mice and rats) and large (cats, dogs, and monkeys)
MPS animal models suggest
 IT and ICV-administered recombinant enzyme is safe, distributes
within the brain parenchyma, throughout the neuraxis (including the
spinal cord) and deeper brain structures.
 Reduce GAG levels in the CSF and storage material in the brain.
 Diminish inflammation , reduce neurological damage (i.e.
ventricular enlargement and cortical atrophy) and normalize
behavior .
 These results triggered clinical studies with IT ERT in patients with
MPS and on trials now .

33.  A rare genetic disorder, belongs to a group of progressive
degenerative neuro metabolic disorders known as the neuronal
ceroid lipofuscinoses (NCL) .
 That is characterized by abnormal accumulation of certain fatty,
granular substances (i.e., pigmented lipids [lipo pigments] ceroid
and lipofuscin) within neurons of the brain as well as
 other tissues of the body that may result in progressive
deterioration (atrophy) of certain areas of the brain and
neurological impairment.

34.  CLN2 normally directs production of a lysosomal enzyme
called tri peptidyl peptidase 1 or TPP1.
 A deficiency of TPP1 results in abnormal storage of proteins
and lipids in neurons and other cells that impair cellular
function .
 Age of presentation usually between 2 and 4 years of age
with
 progressive loss of vision, seizures, progressive neurological
decline and ataxia .

35. Neuronal
ceroidlipofuscinos
is type 2
Cerlip
onase
α
BioM
arin
2017/
2017
Not
availa
ble
300
mg
EOW
Intrav
entric
ular
4.7
crores

36.  This therapy is expensive , may cost over $200,000 annually.
 The distribution of the therapeutic enzyme in the body (bio
distribution) after these IV infusions is not uniform.
 The enzyme in less available to certain areas in the body, like the
bones, lungs, brain.
 For these reasons, many features of lysosomal storage diseases
remain untreated by ERT, especially neurological .

37.  Additionally, the efficacy of ERT is often reduced due to an
unwanted immune response against the enzyme, which
prevents metabolic function.
 The side effects are usually related to the intravenous
infusion and include fever, chills, and flu-like symptoms .

38.  Substrate Reduction therapy -:
 Based on the concept that the inhibition of specific steps of the
biosynthetic pathways of substrates may reduce their flux to
lysosome.
 by using small-molecule inhibitors of enzymes involved in the
biosynthesis of substrates.
 Approved for clinical use for the treatment of type 1 Gaucher
disease, (Miglustat) , Niemann-Pick disease type C (NPC).
 A novel substrate inhibitor, eliglustat tartrate, was recently
introduced and evaluated in a multisite, open-label, single-arm
phase II clinical trial .

39.  Preclinical and clinical studies on the use of non-specific
inhibitors of glycosaminoglycan synthesis, the isoflavone
genistein and the chemical dye rhodamine B are under trial
for muco polysaccharidosis (type III) .
 A few preclinical studies for the treatment of Sandhoff
disease, Fabry disease and Pompe disease are also going
on.

40.  Small-molecule ligands (pharmacological chaperones) can interact
with the mutant protein, favor its correct conformation and
enhance its stability.
 As a result, the enzymatic activity of the mutant protein is
partially rescued .
 Advantages (compared to ERT) -
 orally administered allowing for a non-invasive treatment.
 Non-immunogenic and not need to be delivered to cells through
the mannose-6-phosphate pathway, which may be secondarily
impaired in some of these disorders .

41.  Phase I/II clinical trials are being conducted for Fabry,
Gaucher and Pompe disease.
 For Fabry disease, a phase II/III clinical trial has been
performed and has shown encouraging results in terms of
enhancement is there .

42.  Combination of chaperones and ERT
 Gene Therapy
 Hematopoietic stem cell transplantation

43.  ERT is currently the standard of care for selected LSDs and
proceeds in parallel with supportive multidisciplinary medical
and surgical interventions. The foremost prerequisite is a
confirmed diagnosis .
 But high cost, invasive administration and less Blood Brain
Barrier Penetration limits its use in neurological disorders.
 Intra thecal and Intra cerebro ventricular route for direct delivery
of ERT is under trial with good results .

44.  The possibility to combine different approaches in order to
obtain the highest therapeutic efficacy
 and to personalize treatment protocols for each disorder and
for each individual patient must be explored.

45. THANK YOU

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disease in the mucopolysaccharidoses.(2017 ) .
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recognition and comprehensive care. J Pediatr. 2004
 Beck M. New therapeutic options for lysosomal storage disorders:
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 Up to date