This study is to evaluate the safety and efficacy of a topical lotion when applied once daily to adult participants with moderate to severe plaque psoriasis (defined as an Investigator's Global Assessment [IGA] score of 3 or 4).

The objective of the study is to evaluate the safety and efficacy of topical IDP-122 Lotion when applied once daily to adult participants with moderate to severe plaque psoriasis. The intent of the study is specifically to evaluate the safety and efficacy of a once daily application of IDP-122 Lotion in comparison with vehicle.

Inclusion Criteria:

• Male or female, of any race, at least 18 years of age (inclusive).
• Freely provides both verbal and written informed consent.
• Has an area of plaque psoriasis appropriate for topical treatment that covers a body surface area (BSA) of at least 3%, but no more than 12%. The face, scalp, palms, soles, axillae, and intertriginous areas are to be excluded in this calculation.
• Is willing and able to avoid prolonged exposure of the treatment area to ultraviolet radiation (natural and artificial) for the duration of the study.
• Has a clinical diagnosis of psoriasis at the Baseline visit with an IGA score of 3 or 4. (The face, scalp, palms, soles, axillae and intertriginous areas are to be excluded in this assessment).

Exclusion Criteria:

• Has spontaneously improving or rapidly deteriorating plaque psoriasis or pustular psoriasis, as determined by the Investigator.
• Presents with psoriasis that was treated with prescription medication and failed to respond to treatment, even partially or temporarily, as determined by the Investigator.
• Presents with any concurrent skin condition that could interfere with the evaluation of the treatment areas, as determined by the Investigator.
• Is pregnant, nursing an infant, or planning a pregnancy during the study period.
• Has received treatment with any investigational drug or device within 60 days or 5 drug half-lives (whichever is longer) prior to the Baseline visit or is concurrently participating in another clinical study with an investigational drug or device.