GREP at the begining with any Letter

Hello,

I try to remove the comma in an Index Reference,  always at the beginning of the paragraph, followed by the letter g

INCORRECT:

Human, g

human, g

CORRECT:

Human g

human g

But is not working:

replaceTextUsingGREP ("((\^\[\\l\\u\]\*\?)$)(, g)","$1 g");
function replaceTextUsingGREP (input, output) { 
    app.findGrepPreferences = app.changeGrepPreferences = NothingEnum.nothing; 
    app.findGrepPreferences.findWhat = input;
    app.changeGrepPreferences.changeTo = output;
    //app.activeDocument.changeGrep(); 
    var changedResults = app.activeDocument.changeGrep();
    app.findGrepPreferences = app.changeGrepPreferences = NothingEnum.nothing; 
}

Please, do you know what is wrong?

Thanks so much.