Efficacy and Safety Study of Z160 in Subjects With Postherpetic Neuralgia

Inclusion Criteria:

- Provide written informed consent.

- Either sex but must be aged >=18 years.

- Diagnosis of PHN as defined by the presence of pain in the area affected by herpes
zoster >=6 months after the herpes zoster skin rash has healed.

- Pain score over the last week of >=3 and <=8 on the PI-NRS

- If female, the subject must be postmenopausal , surgically sterilized for >=3 months
before the screening visit, or agree to use 2 reliable methods of contraception if of
childbearing potential. If male, the subject must agree to use condoms.

- Willing and able to comply with all study procedures.

Exclusion Criteria:

- Severe pain caused by diseases other than PHN.

- Neurolytic or neurosurgical therapy for PHN within 6 months of screening (subjects
who received a spinal cord stimulator implant at least 6 months before screening are
eligible, but the settings need to remain stable during the double blind study period
without use of a magnet).

- History of seizure, excluding pediatric febrile seizures, or currently has seizures.

- Stroke or transient ischemic attack (TIA) <=6 months before the screening visit.

- History of or a current diagnosis of schizophrenia or bipolar disorder.

- Major depressive disorder or generalized anxiety disorder <=6 months before the
screening visit. Subjects who are on stable doses of selective serotonin uptake
inhibitors (SSRIs) for depression (other than major depressive disorder) are eligible
for the study.

- Clinically significant alcohol or substance dependency <=1 year before the screening
visit

- Imminent risk of suicide (positive response to question 4 or 5 on the C-SSRS) or had
a suicide attempt within 6 months before the screening visit.

- Clinically significant conditions that, in the investigator's opinion, may interfere
with the study procedures or compromise the subject's safety.

- Malignancy (other than nonmetastatic basal or squamous cell carcinoma of the skin or
carcinoma in situ of other organs that was surgically removed >1 year before
screening and has not recurred).

- Condition that is known to interfere with the absorption, distribution, metabolism,
or excretion of drugs.

- Illness within 30 days before screening.

- History of hypersensitivity to calcium channel blockers.

- Multiple drug allergies

- Opioids (at doses exceeding the equivalent of 15 mg of oral morphine) or a high-dose
capsaicin patch (Qutenza) <=30 days before the screening visit.

- Moderate or strong cytochrome P450 inducer within 30 days before the screening visit.

- Digoxin or prohibited medications that cannot be discontinued before randomization.

- Other exclusions apply.