This is an extension study of participants who previously completed a Transcend-sponsored clinical trial evaluating TSND-201 as a treatment for PTSD.

Participants will be followed for up to 52 weeks. During the 52 week period, PTSD symptoms and safety will be assessed monthly.

Participants' PTSD symptoms will be assessed at each observational visit and if criteria for Relapse has been met, participants may be eligible to receive a course of TSND-201 treatment.

Inclusion Criteria:

• Participation in and successful completion of a prior Transcend-sponsored clinical trial with TSND-201.
• Agree to not participate in any other interventional clinical trials for the duration of this study.
• Willing and able to provide informed consent.

Exclusion Criteria:

• Had significant deviation(s)/non-compliance in parent study in the opinion of the Investigator which would deem them unsuitable for participation.
• Change or development of any physical or psychological finding that would make participant unsuitable for study.