Phase 4 is not blinded.
https://www.fda.gov/media/75398/download
Quote:We recommend that any part of the interim report to the DMC that includes comparative effectiveness and safety data presented by study group, whether coded or completely unblinded, be available only to DMC members during the course of the trial, including any follow-up period—that is, until the trial is completed and the blind is broken for the sponsor and investigators. If interim reports are shared with the sponsor, it may become impossible for the sponsor to make potentially warranted changes in the trial design or analysis plan in an unbiased manner (see Section 6.3). Even aggregate data on safety and efficacy may be informative; these data may be needed for some trial management functions (e.g., sample size adjustments, centralized endpoint assessment), but are best limited to those who cannot otherwise carry out their trial management responsibilities.
In many cases, the DMC receives reports in two parts: an "open" section, which presents data only in aggregate and focuses on trial conduct issues such as accrual and dropout rates, timeliness of data submission, eligibility rates and reasons for ineligibility; and a "closed" section, in which the comparative outcome data are presented. The open section of these reports is usually provided to sponsors, who
may convey any relevant information in these reports to investigators, IRBs, and other interested parties, as the data presented in the "open" section are not likely to bias the future conduct of the trial and are often important for improving trial
A sponsor’s decision to establish an independent DMC does not preclude interaction of the sponsor with the DMC. Sponsor involvement in an open part of the DMC meeting, during which data such as enrollment, compliance, and event rates may be viewed in
aggregate but not separately by study arm
https://www.fda.gov/media/75398/download
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