Stopped early due to inadequate separation on primary efficacy endpoint at Week 12 according to Interim Analysis conducted on the first 274 (50%) patients.

This is a 12-week, multicenter, randomized, double-blind, placebo-controlled, fixed-dose study that will investigate the efficacy and safety of 5.6 mg TNX-102 SL (2 x 2.8 mg tablets)-a sublingual formulation of cyclobenzaprine. Following successful screening and randomization, eligible patients will have a telephonic visit at week 2 and then return regularly to the study clinic for monthly visits for assessments of efficacy and safety.

Inclusion Criteria:

• Male or female between 18 and 75 years of age, who have served in any branch of the military.
• Diagnosed with current PTSD as determined by the Clinician-Administered PTSD Scale (CAPS-5) for DSM-5.
• Index trauma(s) resulting in PTSD must meet DSM-5 criterion A for PTSD as described in CAPS-5, have occurred in 2001 or later, be military service related.
• Willing to refrain from use of all other formulations of cyclobenzaprine.
• Willing and able to refrain from antidepressants and other excluded medications.
• Capable of reading and understanding English and able to provide written informed consent.
• If female, either not of childbearing potential or practicing a medically acceptable method of birth control throughout the study.
• Willing and able to comply with all protocol-specified requirements.

Exclusion Criteria:

• Increased risk of suicide, based on the investigator's judgment that is of a severity that is not appropriate for outpatient management, or that warrants additional therapy excluded by the protocol.
• Significant (e.g., moderate or severe) comorbid traumatic brain injury (TBI) by history.
• Severe depressive symptoms at screening or baseline.
• Clinically significant laboratory abnormalities based on screening laboratory tests and/or medical history in the investigator's opinion.
• Use of antidepressant medication within 2 months of baseline.
• Female patients who are pregnant or lactating.
• History of serotonin syndrome, severe allergic reaction or bronchospasm or known hypersensitivity to cyclobenzaprine or the excipients.
• Seizure disorder.
• Patients with a body mass index (BMI) > 45.
• Has received any other investigational drug within 30 days before Screening.
• Previous participation in any other study with TNX-102 SL.
• Family member of investigative staff.