Resmetirom Indication Clarification: Approved for NASH Fibrosis, Not Hepatitis B Cirrhosis

　　Resmetirom is a selective thyroid hormone receptor-beta(THR-β)agonist whose primary approved indication worldwide is for the treatment of adults with non-cirrhotic non-alcoholic steatohepatitis(NASH),now also referred to as metabolic dysfunction-associated steatohepatitis(MASH),accompanied by moderate-to-severe liver fibrosis at stages F2 to F3.The drug exerts its therapeutic effect by activating hepatic THR-βreceptors,thereby modulating lipid metabolism,reducing hepatic fat accumulation,and improving fibrotic progression.Its molecular target and therapeutic rationale are entirely centered on metabolic liver disease.It is critical to emphasize that resmetirom is not an antiviral agent against hepatitis B virus(HBV);it does not suppress HBV replication and must never be used as a substitute for any established antiviral therapy for chronic hepatitis B.

　　From a pathophysiological perspective,chronic hepatitis B is a viral liver disease caused by persistent HBV infection,with its core pathological process involving continuous viral replication within hepatocytes and the resultant immune-mediated liver injury.In contrast,NASH/MASH,the condition targeted by resmetirom,falls within the spectrum of metabolic diseases,driven primarily by insulin resistance,dysregulated lipid metabolism,and chronic inflammation.The etiology,pathological mechanisms,and therapeutic targets of these two conditions are fundamentally distinct.Therefore,characterizing resmetirom as a treatment for hepatitis B is scientifically untenable.Even in patients who concurrently harbor HBV infection and fatty liver disease,each condition must be managed according to its respective clinical guidelines;resmetirom should never be regarded as a therapeutic intervention for hepatitis B itself.

　　Regarding the scope of approved indications,resmetirom is strictly limited to patients with non-cirrhotic NASH/MASH who have been assessed as having F2 or F3 stage liver fibrosis.Patients who have already progressed to the cirrhotic stage(F4)fall outside the approved patient population.Consequently,a diagnosis of HBV-related cirrhosis does not qualify a patient for resmetirom therapy.Clinicians must not extrapolate the drug's efficacy in NASH-related fibrosis to HBV-related cirrhosis or other forms of end-stage liver disease.For all patients who have advanced to cirrhosis,regardless of underlying etiology,management should follow established cirrhosis treatment guidelines.

　　In real-world clinical practice,some patients present with overlapping liver pathologies,including concurrent HBV infection,fatty liver,and liver fibrosis.In such complex scenarios,it becomes even more imperative to clearly delineate the therapeutic objectives of each medication.Resmetirom's designated role remains that of a metabolic intervention for NASH/MASH with F2–F3 fibrosis,not a dedicated treatment for HBV-related cirrhosis.If clinicians consider using resmetirom to address the steatohepatitis component in patients with coexisting HBV,this decision must be made only after ensuring that HBV is adequately controlled with standard antiviral therapy,and following comprehensive specialist evaluation.Under no circumstances should resmetirom replace or lead to discontinuation of guideline-directed antiviral treatment for hepatitis B.

　　In summary,resmetirom's approved indication is explicitly defined as adult non-cirrhotic NASH/MASH with F2–F3 liver fibrosis,intended to be used in conjunction with lifestyle modifications including dietary adjustment and exercise.This drug belongs to an entirely separate therapeutic paradigm from hepatitis B antiviral therapy;it neither controls HBV infection nor treats HBV-related cirrhosis.Accurately understanding the indication boundaries and mechanism of action of resmetirom is essential for ensuring medication safety and achieving precision treatment.