How to Truncate the combination of string and numerical?

In a module, a line item is list formatted and the data displayed is in the form "String1:String2 Numerical code". How to truncate the data and display the string1 only in the same line item?

Example:  "ABCD:efgh 12345" (say) is displayed in the list formatted line item. Then, how to display only ABCD in the same line item?