Studio di sospensione di fase 2, randomizzato, controllato con placebo, in doppio cieco, con arruolamento arricchito volto a valutare l’efficacia e la sicurezza di BIIB074 nel trattamento del dolore manifestato da soggetti con neuropatia delle piccole fibre confermata, idiopatica o associata a diabete mellito

Drug: BIIB074;Drug: Placebo

Key Inclusion Criteria:

1. This study will be conducted in subjects who have had a diagnosis of at least probable
SFN, length-dependent distribution, for 6 months and =10 years prior to screening,
defined as a history of the symptoms and clinical signs based on discussions at the
ACTTION CONCEPPT meeting on diagnosis of SFN, Washington, DC March 2018, and confirmed
by intraepidermal nerve fiber density (IENFD) values, and weekly mean average daily
pain (ADP) score of =5 and =9 on an 11-point Pain Intensity Numeric Rating Scale
(PI-NRS) over the last 7 days of prior to the Screening visit.

2. In addition to these criteria, subjects with diabetes will be required to have HbA1c
=11%, treated with oral hypoglycemics and/or subcutaneous insulin or diet, no evidence
of ulcers, advanced retinopathy (defined as greater than State 3 [moderate
non-proliferative diabetic retinopathy]) (DCCT/EDIC Research Group 2017), severe
nephropathy, or clinically significant obstructive atherosclerotic disease or current
class IV heart failure to be eligible for the study.

Key Exclusion Criteria:

1. Previous exposure to BIIB074 (formerly known as CNV1014802 or GSK1014802).

2. Use of capsaicin patch within 3 months prior to Screening.

3. Unable or unwilling to discontinue concomitant medications for SFN pain prior to Day
1.

4. Unable or unwilling to comply with the prohibited concomitant medication restrictions,
including but not limited to UDP-glucuronosyltransferase (UGT) inducers and
inhibitors, monoamine oxidase inhibitors (MAOIs), and Nav blockers.

5. Use of over-the-counter medications, vitamin and mineral supplements, herbal remedies
(including St. John's wort), dietary supplements, or foods (including grapefruit
juice) that affect and UGTs.

6. Unable or unwilling to discontinue medications that are P-glycoprotein substrates with
a narrow therapeutic index, including but not limited to digoxin.

7. History of hemophilia or Von Willebrand's disease, or use of anticoagulants that may
result in bleeding risk during the skin biopsy.

8. Any contraindication, as determined by the Investigator, to performing a skin biopsy
for intraepidermal nerve fiber analysis.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.