How can I remove last * from each “organisations”: value from the string without using JSON.parse() and remove last , from [] using javascript?

let abc = '[{"userid":"88623619","organisations":"Imperial College London*Imperial College Healthcare NHS Trust*Imperial College Healthcare NHS Trust*Imperial College Healthcare NHS Trust*Milton Keynes Hospital NHS Foundation Trust*","oversightGroupRole":"Chair","oversightGroupMemberName":"Dr Ahmed Ahmed","oversightGroupType":"Steering Committee"},{"userid":"88624025","organisations":"Bangor University*Barnet, Enfield and Haringey Mental Health NHS Trust*Cambridge University Hospitals NHS Foundation Trust*","oversightGroupRole":"Public Member","oversightGroupMemberName":"Professor b b","oversightGroupType":"Advisory Group"},{"userid":"88623985","organisations":"Aberdeen And District Fibromyalgia Support Group*Additive Design Ltd*Altnagelvin Area Hospital*Ataxia UK*Tameside Hospital NHS Foundation Trust*","oversightGroupRole":"Chair","oversightGroupMemberName":"Chief TestTestRr TestTestRr","oversightGroupType":"Data Monitoring Committee"},]';

the Desried Result is

abc = '[{"userid":"88623619","organisations":"Imperial College London*Imperial College Healthcare NHS Trust*Imperial College Healthcare NHS Trust*Imperial College Healthcare NHS Trust*Milton Keynes Hospital NHS Foundation Trust","oversightGroupRole":"Chair","oversightGroupMemberName":"Dr Ahmed Ahmed","oversightGroupType":"Steering Committee"},{"userid":"88624025","organisations":"Bangor University*Barnet, Enfield and Haringey Mental Health NHS Trust*Cambridge University Hospitals NHS Foundation Trust","oversightGroupRole":"Public Member","oversightGroupMemberName":"Professor b b","oversightGroupType":"Advisory Group"},{"userid":"88623985","organisations":"Aberdeen And District Fibromyalgia Support Group*Additive Design Ltd*Altnagelvin Area Hospital*Ataxia UK*Tameside Hospital NHS Foundation Trust","oversightGroupRole":"Chair","oversightGroupMemberName":"Chief TestTestRr TestTestRr","oversightGroupType":"Data Monitoring Committee"},]';

My Code which is not working:

let abc = '[{"userid":"88623619","organisations":"Imperial College London*Imperial College Healthcare NHS Trust*Imperial College Healthcare NHS Trust*Imperial College Healthcare NHS Trust*Milton Keynes Hospital NHS Foundation Trust*","oversightGroupRole":"Chair","oversightGroupMemberName":"Dr Ahmed Ahmed","oversightGroupType":"Steering Committee"},{"userid":"88624025","organisations":"Bangor University*Barnet, Enfield and Haringey Mental Health NHS Trust*Cambridge University Hospitals NHS Foundation Trust*","oversightGroupRole":"Public Member","oversightGroupMemberName":"Professor b b","oversightGroupType":"Advisory Group"},{"userid":"88623985","organisations":"Aberdeen And District Fibromyalgia Support Group*Additive Design Ltd*Altnagelvin Area Hospital*Ataxia UK*Tameside Hospital NHS Foundation Trust*","oversightGroupRole":"Chair","oversightGroupMemberName":"Chief TestTestRr TestTestRr","oversightGroupType":"Data Monitoring Committee"},]';

    abc = abc.replace(/,(?=[^,]*$)/, '');

    let startIndex = 0;
    while ((startIndex = abc.indexOf('"organisations":', startIndex)) !== -1) {    
        let endIndex = abc.indexOf('*', startIndex + '"organisations":'.length);
        if (endIndex !== -1) {       
            abc = abc.slice(0, endIndex) + abc.slice(endIndex + 1);
        }
        startIndex += '"organisations":'.length;
    }

    console.log(abc);