Long-Term Safety of ARQ-151 Cream in Adult Subjects With Chronic Plaque Psoriasis

Inclusion Criteria: 1. Participants legally competent to sign and give informed consent 2. Males and females ages 18 years and older 3. Subjects with chronic plaque psoriasis who met eligibility criteria for ARQ-151-201, successfully completed ARQ-151-201 through Week 12, and are able to enroll into this long-term safety study on the Week 12 visit of the previous study (ARQ-151-201). 4. Females of childbearing potential (FOCBP) must have a negative urine pregnancy test at all study visits. In addition, sexually active FOCBP must agree to use at least one form of highly effective contraception throughout the trial. Highly effective forms of contraception include: oral/implant/injectable/transdermal contraceptives, intrauterine device, or partner's vasectomy. If barrier methods are used (e.g., condom with spermicide, diaphragm with spermicide), then 2 forms of conception are required. The use of abstinence as a contraceptive measure is acceptable as long as this is a consistent part of a lifestyle choice and a backup method has been identified if the subject becomes sexually active. 5. Post-menopausal women with spontaneous amenorrhea for at least 12 months or have undergone surgical sterilization (permanent sterilization methods include hysterectomy, bilateral oophorectomy, hysteroscopic sterilization, bilateral tubal ligation or bilateral salpingectomy). Exclusion Criteria: 1. Subjects who experienced an ARQ-151 treatment-related AE or a serious AE (SAE) that precluded further treatment with ARQ-151 cream in Study ARQ-151-201. 2. Subjects that use any Excluded Medications and Treatments 3. Current diagnosis of guttate, erythrodermic/exfoliative, palmoplantar, or pustular psoriasis. 4. Subjects who cannot discontinue the use of strong P-450 cytochrome inhibitors e.g., indinavir, nelfinavir, ritonavir, clarithromycin, itraconazole, ketoconazole, nefazodone, saquinavir, suboxone and telithromycin during the study period. 5. Subjects who cannot discontinue the use of strong P-450 cytochrome inducers e.g., efavirenz, nevirapine, glucocorticoids, barbiturates (including phenobarbital), phenytoin, and rifampin during the study period. 6. Known or suspected: * severe renal insufficiency or severe hepatic disorders * hypersensitivity to component(s) of the investigational products * history of severe depression, suicidal ideation 7. Females who are pregnant, wishing to become pregnant during the study, or are breast-feeding. 8. Subjects with any serious medical condition or laboratory abnormality that would prevent study participation or place the subject at significant risk, as determined by the Investigator. 9. Subjects with a history of chronic alcohol or drug abuse within 6 months of initiation of study medication. 10. Current or a history of cancer within 5 years with the exception of fully treated skin basal cell carcinoma, cutaneous squamous cell carcinoma or carcinoma in situ of the cervix. 11. Subjects who are unable to communicate, read or understand the local language, or who display another condition, which in the Investigator's opinion, makes them unsuitable for clinical study participation.