Clinical results In antiretroviral naive patients Study 138 is an international randomised, open-label, multicenter, prospective trial of 883 antiretroviral treatment naïve patients comparing REYATAZ/ ritonavir (300 mg/ 100 mg once daily) to lopinavir/ ritonavir (400 mg/ 100 mg twice daily), each in combination with fixed dose tenofovir/ emtricitabine (300 mg/ 200 mg tablets once daily).