[NA Eun-kyung, Edaily Reporter] Celltrion is launching a Phase 4 clinical trial in the United States to establish clinical evidence supporting a 240 mg high-dose regimen of its autoimmune disease treatment Zymfentra, also known as infliximab.

The company announced Tuesday that it had submitted an Investigational New Drug (IND) application to the U.S. Food and Drug Administration (FDA) for a Phase 4 trial of the 240 mg Zymfentra regimen.

The trial will enroll 447 patients with Crohn’s disease and ulcerative colitis at 55 sites across the United States. It will compare a high-dose intravenous formulation of infliximab with a 240 mg dose of Zymfentra to evaluate whether the Zymfentra regimen is non-inferior.

Through this trial, Celltrion aims to establish clinical evidence supporting the 240 mg dose and expand treatment options in the U.S., where prescriptions currently focus on the 120 mg dose. The company plans to give physicians greater flexibility to select a dosage based on a patient’s condition and disease severity.

Zymfentra is the subcutaneous formulation of Celltrion’s infliximab biosimilar, Remsima. It received FDA approval in 2023 through the new drug application pathway and is currently marketed in the U.S. for the treatment of adults with Crohn’s disease and ulcerative colitis.

Celltrion has already utilized higher-dose regimens of Remsima SC in Europe. According to the company, Remsima SC held approximately a 32% market share in the five major European markets—known as the EU5—in the first quarter of this year. Celltrion initiated the U.S. trial as part of an effort to apply the dose-adjustment strategy used in Europe to the U.S. market.

The company is also seeking to expand Zymfentra’s indications. Celltrion is conducting a global clinical trial to add rheumatoid arthritis to Zymfentra’s U.S. indications, which are currently limited to inflammatory bowel disease. If approved for the additional indication, Zymfentra could reach a broader pool of potential patients.

U.S. sales of Zymfentra are also on the rise. Sales reached 99.5 billion won ($73.8 million) in the first half of this year, a 176.4% increase from the same period a year earlier. Celltrion stated that Zymfentra has secured insurance coverage for more than 90% of insured patients in the U.S. and is sold through the company’s direct sales network.

Once it obtains clinical data supporting the 240 mg regimen, Celltrion plans to pursue a U.S. prescribing strategy offering both 120 mg and 240 mg doses. Along with the planned expansion into rheumatoid arthritis, the company aims to broaden Zymfentra’s prescribing base in the U.S.

“This trial is designed to broaden Zymfentra’s dosing options based on patients’ conditions,” a Celltrion official said. “We will secure clinical data supporting the higher dose and expand Zymfentra’s prescribing base in the U.S. by broadening its indications.”