IVIg for Small Fiber Neuropathy With Autoantibodies TS-HDS and FGFR3

Small fiber neuropathies, and mixed small and large fiber neuropathies, have many potential
causes including diabetes, vitamin deficiencies, environmental and toxic exposures, HIV,
autoimmune and paraproteinemias.

However, despite this broad differential at least 30% of cases of small fiber neuropathies
remain idiopathic. There is therefore a growing interest in the potential for using IVIG in
small fiber neuropathy without direct proof that the disorder is caused by immune reactions.
We have recently uncovered two novel autoantibodies, TS-HDS and FGFR-3, that are targeted
again peripheral neural structure. TS-HDS is a disaccharide component of glycosylation of
heparin and heparin sulfate.

Patients with elevated levels of IgM against TS-HDS display clear small fiber loss with IgM
deposits around the outside of medium- & larger-sized capillaries with C5b-9 complement
deposits. FGFR-3 is a secreted cell surface receptor; genetic defects of FGFR-3 are linked to
achrondroplasia and other bony abnormalities.

The antibodies to TS-HDS and FGFR-3 are detected in up to 20% of patients with otherwise
idiopathic small fiber neuropathy, but are rare in patients without small fiber neuropathy.

Dr. Levine (a co-investigator on this project) recently presented 3 cases of small fiber
associated with elevated levels of auto-antibodies to TS-HDS or FGFR-3 who were treated with
IVIG at 2 gm/kg/month for 6 months. He examined skin biopsies for intra-epidermal nerve fiber
density and patient self-reported pain scores at baseline and after six months of therapy.
All 3 cases showed marked improvement in pain scores. The average reduction in pain was 54%.
In addition there was a clear increase in the intra-epidermal nerve fiber density (IENFD)
after 6 months of therapy. Pre-treatment IENFD was 1.6, 1.7, and 2.4 at the calf. After 6
months of therapy the IENFD was 8.4, 5.7, 3.3 respectively (these are clinically significant
improvement in nerve fiber density.

The investigators believe these anecdotal cases suggest that TS-HDS and FGFR-3 antibodies may
be a marker for a group of SFN patients that are immune mediated and may respond to IVIG.
(This case series was presented as a poster at the American Academy of Neurology meeting in
2017)

Inclusion Criteria:

1. Patient with clinically evident and biopsy proven pure small fiber neuropathy as
evidenced by reduced intra-epidermal nerve fiber density seen on skin biopsy using PGP
9.5 as the immunostain.

2. Patients must have a baseline pain score on a VAS scale of Greater or equal to 4/10

3. Patients must have elevated titers of autoantibodies to TS-HDS or FFR3 as measured in
Dr Alan Pestronk's lab at Washington University in St Louis.

Exclusion Criteria:

1. Any other known cause for small fiber neuropathy other than the presence of the
elevated titers of auto-antibodies. For example patients with diabetes, HIV, Sjogrens,
Vitamin deficiency etc.

2. Patients with generalized, severe musculoskeletal conditions other than SFN that
prevent a sufficient assessment of the patient by the physician

3. Cardiac insufficiency (New York Heart Association III/IV), cardiomyopathy, significant
cardiac dysrhythmia requiring treatment, unstable or advanced ischemic heart disease).

4. Severe liver disease (ALAT 3x > normal value).

5. Severe kidney disease (creatinine 1.5x > normal value).

6. Known hepatitis B, hepatitis C or HIV infection.

7. Patients with a history of deep vein thrombosis (DVT) within the last year prior to
baseline visit or pulmonary embolism ever; patients with susceptibility to embolism or
deep vein thrombosis.

8. Body mass index (BMI) ≥40 kg/m2.

9. Medical conditions whose symptoms and effects could alter protein catabolism and/or
IgG utilization (e.g. protein-losing enteropathies, nephrotic syndrome).

10. Known IgA deficiency with antibodies to IgA.

11. History of hypersensitivity, anaphylaxis or severe systemic response to
immuno-globulin, blood or plasma derived products, or any component of Gamunex.

12. Known blood hyperviscosity, or other hypercoagulable states.

13. Use of IgG products within six months prior to enrolment.

14. Use of other blood or plasma-derived products within three months prior to enrollment.

15. Patients with a history of drug or alcohol abuse within the past five years prior to
enrollment.

16. Patients unable or unwilling to understand or comply with the study protocol

17. Participating in another interventional clinical study with investigational treatment
within three months prior to enrollment.

18. Women who are breast feeding, pregnant, or planning to become pregnant, or are
unwilling to use an effective birth control method (such as implants, injectable,
combined oral contraceptives, some intrauterine devices (IUDs), sexual abstinence or
vasectomized partner) while on study.