Unable to parse JSON response body in JavaScript

I am trying to parse the below response body that I received from my http request.

callback({"processingDurationMillis":29,"authorisedAPI":true,"success":true,"airline":null,"errorMessage":null,"distance":"4,128.4","units":"km"})

I need help in accessing the distance field in the body, but first I am unable to change this JSON into a JS object.

Here's what I'm doing

response = HTTP.call('GET', URL,function(err,result){
        console.log(result.content);
        data = JSON.parse(result.content);

        var extractedData = data['distanceResponse'];
        console.log(extractedData);
    });

I'm able to log result.content but nothing after. Please help? Thanks much appreciated!

via Chebli Mohamed