Q: What is the next status after "Editor assigned" and "Under review" for the journal JPET?

The status “Under review” implies that your manuscript has cleared the initial editorial screening and has been sent for peer review. The peer review process usually takes a long time as reviewers are busy researchers themselves. Therefore, it is quite natural for the status of your manuscript to remain “Under review” for quite several weeks or even a few months.

Once the review is completed, your manuscript will be sent back to the journal editor and the status will change to "With Editor" or "Required reviews completed." This means that the reviews have come back to the editor and he/she will now take a decision on your manuscript. If the editor is not satisfied with the review then he/she may send your manuscript for an additional review and the status will then change back to “under review.” If the reviews are satisfactory, the status will change to "Decision in process" which is the final stage before you receive the decision. 

Related reading:

• What does a status change from "under review" to "under editor evaluation" and back to "under review" mean?
• Why did the status change from "Under Review" to "Ready for Decision" and then back to "Under review"?