Background: This study aims to determine the factors affecting HBV DNA suppression in chronic hepatitis B patients with tenofovir disoproxil fumarate (TDF). Methods: A case-control was carried out from October 2021 to August 2022 on 182 chronic hepatitis B patients who had TDF therapy regularly for 24 weeks at H. Adam Malik and USU Hospitals in Medan, Indonesia. The history of the samples was obtained, followed by physical examination, and blood collection. CTLA-4 polymorphism examination was carried out using real-time PCR, while the serum CTLA-4 levels were assessed with ELISA. Results: The CTLA-4 -1661G>A polymorphism, genotype GG+AG, increased 1.52 times risk of not achieving HBV DNA suppression to TDF compared to genotype AA (p=0.041). High CTLA-4 levels increased 2.28 times risk, high HBV DNA levels increased 2.09 times risk, low ALT levels increased 1.95 times risk of not achieving HBV DNA suppression (p= 0.009, 0.026, 0.036, respectively). There was no relationship between gender, age, ethnicity, obesity, baseline AST, HBeAg, genotype, liver fibrosis and HBV DNA suppression after 24 weeks of treatment (p>0.05). Conclusions: The levels of CTLA-4, HBV DNA, ALT, and CTLA-4 -1661G>A polymorphism have a potential relationship with the suppression of HBV DNA in chronic hepatitis B patients with TDF.
