Efficacy, Tolerability, and Safety of NXN-462 in Patients With Post-Herpetic Neuralgia

NXN-462 is designed to target the nitric oxide synthase system (NOS), specifically the
neuronal NOS (nNOS) isoform. By design, NXN-462 is a potent inhibitor of nNOS with good
affinity, and has little or no affinity for a range of G protein-coupled receptors, ion
channels, and enzymes. NXN-462 is being developed as an oral therapy for the treatment of
neuropathic pain syndromes, including PHN. This drug design strategy provides a new
therapeutic paradigm for the treatment of chronic neuropathic pain.

Inclusion Criteria:

- Male, or a non-pregnant, non-lactating female 18 years or older

- Have voluntarily provided written informed consent

- able to speak, read, write, and understand English

- clinical diagnosis of PHN for a minimum of 6 months

- pain intensity score of ≥3 on a 0-10 Numerical Rating Scale (NRS) at the Screening
Visit

- generally in good health (other than PHN) at Screening

Exclusion Criteria:

- Are pregnant and/or lactating

- Diagnosis of any chronic pain syndrome that would interfere with the assessment of
PHN

- evidence of multiple causes of neuropathic pain,e.g.lumbar radiculopathy in the
lumbosacral area

- Have had neuroablation or neurosurgical intervention for PHN

- Have been taking opioid analgesics for >5 days/week

- Have received nerve block or intrathecal analgesia within 6 weeks of the study

- History of significant gastrointestinal disease, liver disease, renal disease,
endocrine disease, or cardiovascular disease

- clinically significant abnormal clinical laboratory test results or vital signs

- Are immunocompromised or immunosuppressed for any reason

- History of alcohol or other substance abuse (not including nicotine or tobacco)
within 5 years

- Significant psychiatric disorder which requires drug treatment (except depression or
anxiety treated with Selective Serotonin Re-uptake Inhibitors)

- Have received an investigational drug or have used an investigational device within
30 days of Screening.

- Have previously been randomized to this study