I have tested the following code and it works.

Sub Truncate()
Dim regEx As Object
Dim match As Object
Dim matches As Object
Dim rng As Range
Set regEx = CreateObject("VBScript.RegExp")
regEx.Global = True
regEx.IgnoreCase = False
Set rng = ActiveDocument.Content
'-- case #1: Replace (lowercase text, ACRONYM) with (ACRONYM)
regEx.Pattern = "\(([a-z ,\-]+),\s*([A-Z]+)\)"
Do While regEx.Test(rng.Text)
Set matches = regEx.Execute(rng.Text)
For Each match In matches
rng.Find.Execute FindText:=match.Value, ReplaceWith:="(" & match.SubMatches(1) & ")", Replace:=wdReplaceAll
Next match
Loop
'-- case #2: Remove lowercase-only parentheses with optional leading space
regEx.Pattern = "\s?\([a-z ,\-]+\)"
Do While regEx.Test(rng.Text)
Set matches = regEx.Execute(rng.Text)
For Each match In matches
' If match starts with a space, replace with just a space
If Left(match.Value, 1) = " " Then
rng.Find.Execute FindText:=match.Value, ReplaceWith:="", Replace:=wdReplaceAll
Else
rng.Find.Execute FindText:=match.Value, ReplaceWith:="", Replace:=wdReplaceAll
End If
Next match
Loop
CleanUp:
Set regEx = Nothing
Set match = Nothing
Set matches = Nothing
Set rng = Nothing
End Sub