The study was stopped due to business reasons.

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, at the time of signing ICF, inclusive.
• Diagnosed with current (past month) PTSD as determined by the MINI 7.0.2 Module H (PTSD).
• Index trauma(s) resulting in PTSD must meet DSM-5 Criterion A for PTSD as described in the CAPS 5, must have occurred within 9 years of Screening Visit 1, and must have occurred when the participant was ≥18 years of age.
• Willing and able to withdraw and refrain from opioids for the course of the study.
• Willing to refrain from use of all other formulations of cyclobenzaprine for the course of the study.
• Willing and able to refrain from antidepressants and other excluded medications.
• Capable of reading and understanding English and able to provide written informed consent to participate.
• Willing to comply with the requirements and restrictions listed in the informed consent form (ICF) and in the protocol.
• If female, either not of childbearing potential or practicing a medically acceptable method of birth control throughout the study.
• Body mass index (BMI) within the range 17.5 - 35 kg/m^2 (inclusive).

Exclusion Criteria:

• Current or ongoing exposure to the trauma that resulted in the PTSD (ie, non-work-related trauma such as ongoing domestic abuse).
• 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 (eg, 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 participants who are pregnant or lactating.
• History of serotonin syndrome, severe allergic reaction or bronchospasm or known hypersensitivity to cyclobenzaprine or the excipients in TNX-102 SL or placebo formulations.
• Seizure disorder.
• Current moderate or severe sleep apnea not well controlled by positive airway pressure (PAP) or oral (mouthpiece) devices.
• Has received any other investigational drug within 90 days before Screening or has taken cyclobenzaprine within 21 days of the Randomization visit.
• Previous participation in any other study with TNX-102 SL.
• Family member of investigative staff.