• Added only CCR4-positive subjects and the most common PTCL subtypes who expressed the CCR4 target excluding those with indolent disease and/or lower CCR4 expression; • Excluded subjects with a history of moderate or severe psoriasis or with psoriasis associated with systemic symptoms or with a 1st degree relative with history of psoriasis that required medical intervention; • Allowed subjects with known bone marrow involvement to participate if their platelet count was ≥75,000 and allowed for laboratory retesting if the criteria for hematologic, hepatic, and renal function were not met; • Specified that safety surveillance would be performed on a regular basis by the Sponsor and independent therapeutic experts and extended the safety monitoring period from 30 to 90 days after the last dose of study medication; • The subject was required to use contraception for 3 months after the last dose of study drug; • Provided guidelines for documenting and treating a treatment-emergent skin rash; • Incorporated the mSWAT for subjects with skin disease with the IWG response criteria (definitions added) for assessment of global response; • Included the assessment of AEs from the time of informed consent rather than after the first dose of study drug; • Allowed subjects to continue monthly treatment with mogamulizumab, at the discretion of the investigator, beyond CR; • Updated the guidelines for the treatment of hypersensitivity-like reactions; • Allowed skin biopsies for CCR4 expression in subjects with skin disease.

• To modify the Inclusion/Exclusion Criteria; • To increase the number of sites; • To specify the permissible dosing interval for mogamulizumab; • To allow subjects with PD in one disease compartment to continue treatment for a period of up to 8 weeks and allow additional time for the demonstration of an objective response; • To allow subjects who experienced a CR to continue to be treated for a period of 12 months or until progression, whichever occurred first; • To clarify the guidance for the treatment of hypersensitivity-like reactions; • To remove clinical laboratory assessments (i.e., CD4 and CD8 cell counts) not necessary for the conduct of this study. • To lengthen the Screening period; • To clarify the acceptable age of archived lymph node or skin biopsy sample (i.e., collected within 3 months Pretreatment) and to allocate a portion of the sample collected to test a second method of CCR4 analysis in order to establish compatibility between the tests; • To clarify that the SWAT must be performed for all subjects; • To clarify that certain body weight changes requires dose adjustment and to describe the storage conditions of the reconstituted drug product; • To specify that in this study, disease progression and lymphopenia should not be considered adverse events.