Phase 2a, Exploratory Study to Evaluate the Safety, Efficacy, Tolerability and Pharmacokinetics of XPF-002 in Patients With Primary/Inherited Erythromelalgia

Inclusion Criteria: * Must have a Body Mass Index (BMI) of 18-40 kg/m2 (inclusive) * Have primary or inherited erythromelalgia (IEM) * Experience flares of pain in your feet or hands caused by erythromelalgia * Be generally healthy (apart from your pain) * Stop taking your usual pain medications and certain other medications for up to 11.5 weeks * Not be pregnant or breast-feeding * Must be able and willing to provide informed consent and willing to comply with all study procedures and restrictions Exclusion Criteria: * Must not be in constant pain (must not continually be in moderate pain, 3/10 or more) * Coexistent source of pain from other conditions that may interfere with the study interpretation * HIV, Hepatitis B or C * Treatment for significant depression within 6 months of Screening * Not willing to use adequate contraception * Alcoholism, alcohol or substance abuse * Presence or history of major psychiatric disturbance * Any other condition or finding that may pose undue risk for participation * Use of any other investigational drug in the 30 days prior to dosing * Donation or loss of whole blood or plasma prior to dosing as follows: 50 mL to 499 mL within 30 days, or more than 499 mL within 56 days * Employee or relative of an employee who is directly involved in the study