Evaluation of Nicotinamide Riboside in Prevention of Small Fiber Axon Degeneration and Promotion of Nerve Regeneration
Phase: PHASE2
Conditions: Small Fiber Neuropathy
Sponsor: Johns Hopkins University

Evaluation of Nicotinamide Riboside in Prevention of Small Fiber Axon Degeneration and 
Promotion of Nerve Regeneration  
 
NCT03912220 
 
Study Protocol including statistical analysis 
 
Document Date: 01/16/2020 

 
Date: March 25, 2019    
Principal Investigator: Ahmet Hoke 
Application Number: IRB00210072 
JHMIRB eFormA  01 
Version 3 Dated:   06/2007 
 
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1. 
Abstract 
Small fiber neuropathy (SFN) is a type of peripheral neuropathy that affects the small umyelinated 
fibers, including both somatic innervation of the skin and autonomic nerves. Although diabetes and 
prediabetes are the two most common causes, up to 50% of all SFN remain idiopathic. Currently 
there is no effective treatment that prevents it or reverses it through regeneration of nerve fibers.  
 
Recent advances in understanding the molecular machinery that mediates Wallerian degeneration 
(i.e. degeneration of nerve fibers after physical transection) showed that key players in this 
pathway (e.g. NMNAT2, Sarm1) and NAD+ metabolites play a similar role in degeneration of 
axons in a distal-to-proximal manner seen in many peripheral neuropathies including SFN. Pre-
clinical studies have shown that rapid depletion of NAD initiates a cascade of molecular events 
that leads to axon degeneration and that supplementation of a NAD precursor, nicotinamide 
riboside (NR) can prevent this degeneration. 
 
In this study we plan to evaluate the ability of NR to prevent degeneration of small somatic sensory 
axons innervating the epidermis as well as its ability to promote regeneration of these same fibers 
in a human experimental model of nerve degeneration and regeneration. This experimental human 
model has been used previously to evaluate the rate of nerve degeneration and regeneration in 
several peripheral neuropathies and in healthy subjects.  
 
Since NR is available as a nutritional supplement, if successful, this research can lead to 
development of a therapy for a variety of peripheral neuropathies very rapidly.  
 
 
2. 
Objectives (include all primary and secondary objectives) 
We propose to use an established model of capsaicin-induced axonal degeneration and regeneration 
to assess the potential of nicotinamide riboside (NR) to delay small unmyelinated nerve fiber 
degeneration as well as to promote regeneration. The study will test two hypotheses: 
(1) 
NR-treatment will reduce capsaicin-induced axonal degeneration in the epidermis in healthy 
controls. 
(2) 
NR-treatment will enhance axonal regeneration after capsaicin-induced epidermal 
denervation in healthy controls.  
 

 
Date: March 25, 2019    
Principal Investigator: Ahmet Hoke 
Application Number: IRB00210072 
JHMIRB eFormA  01 
Version 3 Dated:   06/2007 
 
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3. 
Background 
Small fiber neuropathy (SFN) manifests in a variety of different diseases and often results in 
symptoms of burning pain, shooting pain, allodynia, and hyperesthesia (Tavee and Zhou, 2009).  
Although strength remains preserved in patients with SFN, the pain and paresthesia’s are often 
disabling.  Diabetes mellitus (DM) and impaired glucose tolerance (IGT) in combination with 
metabolic disease are the most common identified causes of SFN (Hovaguimian and Gibbons, 
2011). In these cases, besides strict glucose control, no other treatment option has demonstrated the 
ability to slow or prevent axon loss in people with diabetic patients with peripheral neuropathy. 
 
Pathologically, the peripheral nerve damage in patients with SFN affects predominantly or 
exclusively the small myelinated (Aδ) fibers or unmyelinated C fibers.  Many small fiber 
neuropathy patients test normally on conventional electrophysiological tests because 
intraepidermal nerve fiber function is not assessed by routine nerve conduction studies.   Thus, in 
many patients, the only objective evidence of neuropathy is by skin biopsy determining the 
intraepidermal nerve fiber density (IENFD) in the collected skin tissue samples (Holland et al., 
1998),   
 
The capsaicin cream is an FDA approved medication available over the counter for treatment of 
various conditions including arthritis related joint pain and post herpetic neuralgia (Fernandes et 
al., 2016).  It is the active ingredient in hot chili peppers and has been shown to bind vanilloid 
receptors on C- and A-delta nerve fibers leading to calcium entry and subsequent axonal 
degeneration (Marsh et al., 1987; Pini et al., 1990).   The application of over-the-counter strength 
capsaicin cream (0.1%) for 48 hours leads to loss of intraepidermal nerve fibers mimicking the 
changes seen in small fiber neuropathies (Simone et al., 1998; Nolano et al., 1999). Associated 
with the loss of intraepidermal nerve fibers is a decrease in sensation in the area of the patch. Over 
weeks to months, the fibers slowly regenerate, repopulating the treated area (Polydefkis et al., 
2004; Hahn et al., 2007).  This regenerative response is associated with improved sensory function 
as well.  
 
Nicotinamide riboside (NR) is a pyridine-nucleoside form of vitamin B3 that functions as a 
precursor to nicotinamide adenine dinucleotide or NAD+.   Studies in mice have shown that 
boosting the levels of NAD+ can produce multiple health benefits, including reducing nerve 
damage (Trammell et al., 2016a; Hamity et al., 2017). In humans, the levels of NAD+ diminish 
with age and it has been suggested that loss of this metabolite may play a role in age-related health 
decline (Johnson and Imai, 2018).  NR is FDA approved as a dietary supplement and can be 
purchased over the counter.   
 
4. 
Study Procedures 
a. Study design: 
This is a randomized double-blinded study to evaluate the effects of NR on experimental axon 
degeneration and regeneration. After the initial screening (visit 1) is completed, the patients will 
undergo a skin biopsy and be randomized to either the study drug or placebo and will be 
instructed to take it for a week prior to visit 2. Based on existing pharmacokinetic studies, this 
should be sufficient to raise the plasma NAD levels at the time of experimental denervation of 
the skin. At visit 2, patients will undergo two baseline skin biopsies and application of the 
capsaicin patch for 48 hours and will be instructed to continue the study drug. At visit 3 (48 
hours after visit 2), capsaicin patch will be removed, and a repeat skin biopsy will be done to 
evaluate the degree of epidermal denervation. Patients will be instructed to continue the study 
drug for another 3 months and will undergo repeat skin biopsies at 2 months (visit 4) and 3 

 
Date: March 25, 2019    
Principal Investigator: Ahmet Hoke 
Application Number: IRB00210072 
JHMIRB eFormA  01 
Version 3 Dated:   06/2007 
 
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months (visit 5). Blood samples will also be drawn at each visit to measure NAD levels to 
confirm compliance and to correlate with degree of epidermal innervation. Figure 1 depicts a 
schema of visits and timelines.  
 
 
 
b. Study duration and number of study visits required of research participants. 
As outlined above, there will be a total of 5 visits over 3 and ½ months.  
 
c. Blinding, including justification for blinding or not blinding the trial, if applicable. 
The study will be done in a blinded manner where the clinical evaluation and the 
histopathological evaluation of degeneration and regeneration will be done by different teams. 
Patients will be randomized and given unique patient identifiers by the research coordinators. 
The staff at the cutaneous nerve laboratory carrying out the histopathological evaluation will not 
know the identities of the patients or the samples. At the end of the study, the code will be 
broken and the PI will have access to the histopathological evaluations and patient identities to 
carry out the statistical analysis.  
 
d. Justification of why participants will not receive routine care or will have current therapy 
stopped. 
The patients will continue with their current routine care. They will not be asked to stop any 
medication or care. 
 
e. Justification for inclusion of a placebo or non-treatment group. 
Since human nerves degenerate and regenerate at different rates, in order to find out if NR has 
any therapeutic value, we do need to include a placebo control group. 
 
f. Definition of treatment failure or participant removal criteria. 
No participant will be removed from the study. Even if the treatment does not lead to faster 
nerve regeneration, previous research has shown that after topical capsaicin, epidermis fully 
reinnervates within 6 months. We will examine whether NR can speed this regeneration. 
 
 
Figure 1: Study Timeline
Visit 1: 
Screening
History
NRO exam
Blood tests
Skin bx
Visit 2: 
Baseline
2 Skin bxs
Caps. patch
Blood tests
1wk
Visit 3: 
Degen. 
Eval.
Skin bx
Blood tests
2d
Visit 4: 
Regen. 
Eval.
Skin bx
Blood tests
Visit 5: 
Regen. 
Eval.
Skin bx
Blood tests
2mo
1mo
Study drug or placebo

 
Date: March 25, 2019    
Principal Investigator: Ahmet Hoke 
Application Number: IRB00210072 
JHMIRB eFormA  01 
Version 3 Dated:   06/2007 
 
Page 4 of 7 
 
g. Description of what happens to participants receiving therapy when study ends or if a 
participant’s participation in the study ends prematurely. 
Once the study is completed, the participants will continue with their regular life and medical 
care. If a participant leaves the study early, the impact on epidermal reinnervation is minimal as 
it will regenerate.  
 
5. 
Inclusion/Exclusion Criteria 
 
Study will be conducted in healthy adult patients aged 18-65 without any symptoms, signs or 
risk factors of peripheral neuropathy.  
Inclusion criteria 
• Age: 18-65 
• BMI<32 
• Normal neurological examination defined as NIS<2 (Neuropathy Impairment Score) 
Exclusion criteria 
• History of peripheral neuropathy 
• Any peripheral neuropathy risk factor including diabetes, Vitamin B12 deficiency, HIV-
infection, chronic kidney or hepatic disease, hypothyroidism, chemotherapy or other 
know neurotoxic exposure. 
• Pregnancy 
• Abnormal Labs: HIV, B12, HgA1c, Thyroid Stimulating Hormone (TSH), Complete 
Blood Count (CBC), Comprehensive Metabolic Panel (CMP) 
 
6. 
Drugs/ Substances/ Devices 
a. The rationale for choosing the drug and dose or for choosing the device to be used. 
As outlined in background section NR is commercially available as a nutritional supplement and 
has been evaluated in humans in a Phase 1 pharmacokinetic study (Trammell et al., 2016b). It is 
safe at the doses used in that study (100 mg, 300 mg and 1000 mg) over the course of 36 days 
with no significant side effects except 2 patients reporting flushing sensation. Since NR is able 
to elevate the NAD levels in plasma, we expect that this correlates with elevated tissue levels of 
NAD and able to prevent distal axonal degeneration of small unmyelinated fibers induced by 
capsaicin.  
 
b. Justification and safety information if FDA approved drugs will be administered for non-FDA 
approved indications or if doses or routes of administration or participant populations are 
changed. 
NR is available over the counter as a nutritional supplement as a form of vitamin B3 and is sold 
under various brand names including Tru Niagen at a dose of 300 mg per capsule.  It is FDA 
approved as a nutritional supplement and recommended daily dose is 15 mg. However, based on 
the study by Trammell and colleagues, effect of NR on NAD metabolism was best observed at 
the highest dose of 1000 mg/day. There were no significant side effects or toxicity at that dose 
over 36 days of observation. Furthermore, a more recent clinical trial of NR in obese men 
looked at the effects of NR on insulin sensitivity over 12 weeks and utilized a dose of 1000 mg 
twice a day without any significant side effects or drop out from the study (Dollerup et al., 
2018). In this study there were increases in multiple NAD metabolites in the serum and urine 
with this dose.  Given that both studies did not observe any side effects or toxicity doses above 
1000 mg a day, and that the study by Dollerup and colleagues showed increases in NAD 
metabolites, we plan to use 1000 mg orally (four 250mg capsules) twice a day for convenience 

 
Date: March 25, 2019    
Principal Investigator: Ahmet Hoke 
Application Number: IRB00210072 
JHMIRB eFormA  01 
Version 3 Dated:   06/2007 
 
Page 5 of 7 
 
of dosing using the commercially available NR.  The placebo capsules will be prepared by 
ChromaDex who is also supplying the study drug.  
 
c. Justification and safety information if non-FDA approved drugs without an IND will be 
administered.  
Not applicable 
 
7. 
Study Statistics 
 
a. Primary outcome variable. 
We are testing whether NR will reduce axonal degeneration as well as promote regeneration. 
The primary outcome will the measurement of epidermal nerve fiber counts. 
 
b. Secondary outcome variables. 
Plasma NAD levels will be measured and correlated with primary outcome measure 
 
c. Statistical plan including sample size justification and interim data analysis. 
Aim 1 focuses on the ability of NR to reduce or prevent nerve fiber degeneration in the 
capsaicin model. From past studies, we know that following topical capsaicin application, the 
epidermis is nearly completely denervated. A previous study of 66 healthy control subjects, the 
baseline intraepidermal nerve fiber density was 22.7 + 10.1 fibers/mm (Polydefkis et al., 2006).  
Following 2 days of topical capsaicin application, the post-capsaicin IENFD was 0.25 + 0.04 
fibers/mm (nearly 99% reduction in nerve fiber density). 
 
We expect a very similar study subject profile in the current study. If that is true, 20 
subjects/arm will have a power of 0.8 to detect a difference in post-capsaicin epidermal nerve 
fiber density between NR and placebo of as low as 0.035 fibers/mm. If our subjects show more 
variability (standard deviation of 0.06 instead of 0.04) we would still have a power of 80% to 
detect a difference of 0.055 fibers/mm. Therefore, we are confident that a sample of 20 subjects/ 
group is sufficient to determine whether NR decreases axonal degeneration in our model. 
 
Aim 2 focuses on the potential for NR to promote IENFD regrowth. Following denervation with 
topical capsaicin, epidermal nerve fibers re-innervate the epidermis in a predictable fashion.  
Biopsies taken at two and three months following denervation have higher IENFD, the rate of 
regrowth is determined by calculating the slope of the line of IEND against time. Across several 
studies, this rate of nerve fiber regrowth has been 0.18 + 0.08 fibers/mm/day (Polydefkis et al., 
2004).  A sample of 20 subjects/group will have a power of 0.8 to detect a 40% or greater 
change in nerve fiber regeneration. We will have a power of 0.6 to detect a 30% improvement in 
regeneration. 
 
d. Early stopping rules. 
The study will be terminated early if the subjects experience any significant side effects. 
NR is produced as a supplement by a number of different manufacturers. There have been no 
side effects reported. Additionally, it was well tolerated in several published studies. Therefore 
we do not anticipate any toxicity. If a subject complains of side effects, the potential for any 
causation will be reviewed by Drs. Hoke and Polydefkis and reported to the IRB. 
 
 
8. 
Risks 

 
Date: March 25, 2019    
Principal Investigator: Ahmet Hoke 
Application Number: IRB00210072 
JHMIRB eFormA  01 
Version 3 Dated:   06/2007 
 
Page 6 of 7 
 
a. Medical risks, listing all procedures, their major and minor risks and expected frequency. 
 
The capsaicin denervation model and other study procedures have been successfully performed 
in numerous Johns Hopkins IRB-approved studies ( including as part of six industry-sponsored 
multicenter clinical trials with over 600 subjects total. Therefore, we do not anticipate any 
complications. 
 
Neurological exam:  There are no risks associated with a neurological examination.  
 
Capsaicin cream: Capsaicin is the active ingredient in hot peppers and may cause a local 
burning sensation to the area that it is applied.  The degree of burning is generally less than mild 
sunburn.  The affected area will become less sensitive to sensory stimuli due to local nerve fiber 
degeneration.  With time the area should return to normal or near normal with subsequent nerve 
regeneration and reinnervation of the skin. We have obtained IRB approval for similar studies in 
the past (RPN00-10-25-01, RPN 99-11-02-01, NA_00010088 (multicenter trial), WIRB Pr. No.:  
20060008 (multicenter trial)) and have a FDA exemption letter for the use of topical capsaicin. 
The study participants may use over-the-counter, non-steroidal pain medications to manage any 
pain associated with the use of capsaicin cream.  
 
Skin biopsy testing requires taking a 3mm-punch biopsy.  The affected areas are anesthetized 
with subcutaneous 1% lidocaine with epinephrine, and the site will be sterilely dressed after the 
procedure.  No sutures are involved.  The patients will receive instructions how to care for each 
biopsy site after the procedure. The risk of infection is estimated at 1:500 and is likely less in 
healthy subjects.  Punch skin biopsy may result in a small scar that generally fades by one year.   
 
b. Steps taken to minimize the risks. 
The skin biopsies will be done under sterile conditions. Patients will be given clear instructions 
on how to care for the biopsy sites.  
 
c. Plan for reporting unanticipated problems or study deviations. 
If the patients experience any signs of infection at the site of biopsies, they will be asked to call 
the study coordinator and/or principal investigator. They will be seen in the clinic and 
appropriate medical care will be provided. Similarly, if the patients experience any side effects 
from the study drug, they will be asked to call the study coordinator and/or the principal 
investigator and report it.  
 
d. Legal risks such as the risks that would be associated with breach of confidentiality. 
In order to preserve participant confidentiality, all study participant records will be stored in a 
locked file cabinet located in the study coordinator’s office. All subjects will be given a study-
specific unique identifying number and this will be used to label study documents. Data 
spreadsheets will use deidentified subject study numbers and will be password protected and 
stored on the study coordinator’s computer which is backed up regularly. 
 
e. Financial risks to the participants. 
There is no cost to participate in the study.  
 
 
9. 
Benefits 

 
Date: March 25, 2019    
Principal Investigator: Ahmet Hoke 
Application Number: IRB00210072 
JHMIRB eFormA  01 
Version 3 Dated:   06/2007 
 
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There is no direct benefit to subjects. We are testing the potential benefit of NR on human 
nerve degeneration and regeneration. 
 
 
10. 
Payment and Remuneration 
There will be no cost to study subjects to participate. Subjects will be paid $100/session for 
each study visit ($500 total) plus $100 if they complete all 5 visits of the study.  Each 
subject will be paid $300 after the 3rd visit and the remaining $300 at the completion of the 
5th visit.  If subjects decide not to continue with the study, they will be paid for the sessions 
they completed but they will not be eligible to receive the study completion bonus of $100.  
 
 
11. 
Costs 
a. 
There is no cost to participate in the study. 
 
 
12. 
References 
 
 
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Hamity MV, White SR, Walder RY, Schmidt MS, Brenner C, Hammond DL (2017) Nicotinamide riboside, a form of vitamin 
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