This is a clinical study for adult subjects with Post Traumatic Stress Disorder.

Open label clinical study to evaluate the efficacy of PRX-03140 in reducing PTSD symptoms

Inclusion Criteria:

1. Male and female subjects between ages 18-55
2. The subject has signed and dated the written informed consent to participate in the study
3. The subject is able to understand and comply with written and verbal protocol requirements, instructions, and protocol-stated restrictions
4. The subject meets criteria for PTSD as defined by the DSM-IV-TR
5. Stable use of clinically prescribed medications
6. Subject able to complete baseline, 4 weeks, and 12 week psychological and cognitive evaluation
7. Female subjects - not surgically sterile (hysterectomy, bilateral oophorectomy, or bilateral tubal ligation) for at least 6 months or at least 2 years postmenopausal - must agree to utilize one of the following forms of contraception, if sexually active with a male partner, from screening through completion of the study. Approved forms of contraception are abstinence, hormonal (oral, implant, transdermal, vaginal, or injection) in use at least 3 consecutive months prior to the first dose of study medication, double barrier (condom with spermicide; diaphragm with spermicide), intrauterine device (IUD), or vasectomized partner (6 months minimum since vasectomy).

Exclusion Criteria:

1. Actively alcohol or drug dependent as defined by DSM-IV-TR Criteria
2. Patient actively suicidal within last 12-months or with current suicidal ideation
3. History of schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, learning disability, stroke, multiple sclerosis or seizure disorder by interview
4. Participation in a clinical drug research study within the past 30 days
5. Subject currently taking any SSRI or anti-depressant medication.
6. Pregnant or breastfeeding females
7. Subjects will be excluded based on lab values, ECG findings, or physical findings that the Investigators deems exclusionary.