Selected Inclusion Criteria:  Ability to give informed consent. ECOG performance status ≤ 2 A histologically confirmed diagnosis, per the WHO 2016 classification, of any PTCL or CTCL subtype listed in the protocol. Relapsed or refractory disease. Refractory disease is defined as progression during treatment or recurrent/progressive disease within 6 months of completing a treatment regimen that achieved either stable disease or a PR/CR. Relapsed disease is defined as progression or recurrence at least 6 months after a prior documented response (PR or CR). Adequate organ and hematopoietic function as defined in the protocol. Ability to take oral medication without crushing, dissolving or chewing tablets. In the investigator's opinion, the patient has the ability to communicate satisfactorily with the investigator and the study team, to participate fully in the study, comply with all requirements, and has an anticipated life expectancy of at least 3 months.  Selected Exclusion Criteria:  History of, or a concurrent, clinically significant illness, medical condition or laboratory abnormality that, in the investigator's opinion, could affect the conduct of the study Pregnant or breast feeding women Unwilling or unable to use a medically acceptable form of contraception during the time of participation in the trial (sexual abstinence is permissible) unless documented successful vasectomy, hysterectomy, bilateral oophorectomy or post-menopausal for at least 2 years.  Uncontrolled current illness, including, but not limited to the following:  Ongoing or active infections requiring intravenous antimicrobials Symptomatic congestive heart failure (CHF) defined as NYHA class II, III or IV (Appendix II), or ejection fraction <45% in any patient. Unstable angina pectoris within 6 months of study enrollment Unstable cardiac arrhythmia History of myocardial infarction, stroke or intracranial hemorrhage within 6 months prior to enrollment Moderate to severe hepatic impairment (Child-Pugh class B or C). Psychiatric illness or social situations that would limit compliance with study requirements. Known HIV infection Known Hepatitis B or Hepatitis C infection Recent (within 21 days of initiation of therapy, day 1) major surgery Less than 14 days have elapsed since last radiation therapy or chemotherapy treatment or patient has not recovered from all clinically significant treatmentrelated toxicity; less than 90 days have passed since date of autologous stem cell transplant and patient has not recovered to ≤grade 1 toxicity related to this procedure. Use of systemic steroids at a dose equivalent to >10 mg/day of prednisone Prior treatment with pacritinib Requires anticoagulation with heparin, warfarin or equivalent Vit K antagonist History of significant bleeding (≥ Grade 2 by CTCAE), bleeding diatheses, or bleeding complications within the past 6 months. Treatment with potent CYP450 inducers and strong CYP3A4 inhibitors (See Appendix IV), for which no alternative is available. Treatment with strong CYP450 inducers or strong CYP3A4 inhibitors within 2 weeks of initiation of therapy, day 1. Concurrent administration of QTc prolonging agents. Significant QTc prolonging agents must be stopped within 5 half-lives of day 1. Any gastrointestinal or metabolic condition that could interfere with the absorption of oral medication. Prior allogeneic stem cell transplant.