Should a program I have not finished yet be mentioned in the SOP?
If the experience was positive for you in some way, then sure, you can talk about it.  For example, perhaps it gave you a greater appreciation for what research entails, or the scientific method, or it made you excited to get to school every day, etc. etc.

If you only have one sentence about it, then don't include it in the essay.  You can always mention it briefly somewhere else in the application.